Ansys Icepak Tutorials

ANSYS Icepak Tutorials

ANSYS, Inc. Southpointe 275 Technology Drive Canonsburg, PA 15317 [email protected] http://www.ansys.com (T) 724-746-3304 (F) 724-514-9494

Release 14.0 November 2011 ANSYS, Inc. is certified to ISO 9001:2008.

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Table of Contents 1. Using This Manual ................................................................................................................................... 1 1.1. What's In This Manual ........................................................................................................................ 1 1.2. How To Use This Manual .................................................................................................................... 1 1.2.1. For the Beginner ...................................................................................................................... 1 1.2.2. For the Experienced User .......................................................................................................... 1 1.3.Typographical Conventions Used In This Manual ................................................................................ 1 1.4. Mouse Conventions Used In This Manual ........................................................................................... 2 1.5. When To Call Your ANSYS Icepak Support Engineer ............................................................................ 2 2. Finned Heat Sink ..................................................................................................................................... 3 2.1. Introduction ..................................................................................................................................... 3 2.2. Prerequisites ..................................................................................................................................... 3 2.3. Problem Description ......................................................................................................................... 3 2.4. Step 1: Create a New Project .............................................................................................................. 4 2.5. Step 2: Build the Model ..................................................................................................................... 5 2.6. Step 3: Generate a Mesh .................................................................................................................. 18 2.7. Step 4: Physical and Numerical Settings ........................................................................................... 23 2.8. Step 5: Save the Model .................................................................................................................... 25 2.9. Step 6: Calculate a Solution ............................................................................................................. 25 2.10. Step 7: Examine the Results ........................................................................................................... 27 2.11. Step 8: Summary ........................................................................................................................... 35 2.12. Step 9: Additional Exercise ............................................................................................................. 36 3. RF Amplifier ........................................................................................................................................... 37 3.1. Introduction ................................................................................................................................... 37 3.2. Prerequisites ................................................................................................................................... 37 3.3. Problem Description ....................................................................................................................... 37 3.4. Step 1: Create a New Project ............................................................................................................ 38 3.5. Step 2: Build the Model ................................................................................................................... 39 3.6. Step 3: Create Assemblies ................................................................................................................ 53 3.7. Step 4: Generate a Mesh .................................................................................................................. 55 3.8. Step 5: Physical and Numerical Settings ........................................................................................... 58 3.9. Step 6: Save the Model .................................................................................................................... 61 3.10. Step 7: Calculate a Solution ........................................................................................................... 61 3.11. Step 8: Examine the Results ........................................................................................................... 63 3.12. Step 9: Summary ........................................................................................................................... 70 4. Use of Parameterization to Optimize Fan Location .............................................................................. 71 4.1. Introduction ................................................................................................................................... 71 4.2. Prerequisites ................................................................................................................................... 71 4.3. Problem Description ....................................................................................................................... 71 4.4. Step 1: Create a New Project ............................................................................................................ 72 4.5. Step 2: Build the Model ................................................................................................................... 72 4.6. Step 3: Creating Separately Meshed Assemblies ............................................................................... 83 4.7. Step 4: Generate a Mesh .................................................................................................................. 84 4.8. Step 5: Setting up the Multiple Trials ................................................................................................ 84 4.9. Step 6: Creating Monitor Points ....................................................................................................... 86 4.10. Step 7: Physical and Numerical Setting ........................................................................................... 87 4.11. Step 8: Save the Model .................................................................................................................. 88 4.12. Step 9: Calculate a Solution ........................................................................................................... 89 4.13. Step 10: Examine the Results ......................................................................................................... 90 4.14. Step 11: Reports ............................................................................................................................ 93 4.15. Step 12: Summary ......................................................................................................................... 93 Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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ANSYS Icepak Tutorials 4.16. Step 13: Additional Exercise to Model Higher Altitude Effect ........................................................... 93 5. Cold-Plate Model with Non-Conformal Meshing .................................................................................. 97 5.1. Introduction ................................................................................................................................... 97 5.2. Prerequisites ................................................................................................................................... 97 5.3. Problem Description ....................................................................................................................... 97 5.4. Step 1: Create a New Project ............................................................................................................ 97 5.5. Step 2: Build the Model ................................................................................................................... 97 5.6. Step 3: Create a Separately Meshed Assembly ................................................................................ 101 5.7. Step 4: Generate a Mesh ................................................................................................................ 102 5.8. Step 5: Physical and Numerical Settings ......................................................................................... 103 5.9. Step 6: Save the Model .................................................................................................................. 105 5.10. Step 7: Calculate a Solution .......................................................................................................... 105 5.11. Step 8: Examine the Results ......................................................................................................... 105 5.12. Step 9: Summary ......................................................................................................................... 106 5.13. Step 10: Additional Exercise ......................................................................................................... 106 6. Heat-Pipe Modeling and Nested Non-Conformal Meshing ................................................................ 107 6.1. Introduction ................................................................................................................................. 107 6.2. Prerequisites ................................................................................................................................. 107 6.3. Problem Description ..................................................................................................................... 107 6.4. Step 1: Create a New Project .......................................................................................................... 108 6.5. Step 2: Build the Model ................................................................................................................. 109 6.6. Step 3: Create Nested Non-conformal Mesh Using Assemblies ........................................................ 113 6.7. Step 4: Generate a Mesh ................................................................................................................ 115 6.8. Step 5: Physical and Numerical Settings ......................................................................................... 115 6.9. Step 6: Save the Model .................................................................................................................. 116 6.10. Step 7: Calculate a Solution .......................................................................................................... 117 6.11. Step 8: Examine the Results ......................................................................................................... 117 6.12. Step 9: Summary ......................................................................................................................... 119 7. Non-Conformal Mesh .......................................................................................................................... 121 7.1. Introduction ................................................................................................................................. 121 7.2. Prerequisites ................................................................................................................................. 121 7.3. Problem Description ..................................................................................................................... 121 7.4. Step 1: Create a New Project .......................................................................................................... 122 7.5. Step 2: Build the Model ................................................................................................................. 122 7.6. Step 3: Generate a Conformal Mesh ............................................................................................... 124 7.7. Step 4: Physical and Numerical Settings ......................................................................................... 125 7.8. Step 5: Save the Model .................................................................................................................. 126 7.9. Step 6: Calculate a Solution ........................................................................................................... 126 7.10. Step 7: Examine the Results ......................................................................................................... 126 7.11. Step 8: Add an Assembly to the Model ......................................................................................... 127 7.12. Step 9: Generate a Non-conformal Mesh ...................................................................................... 129 7.13. Step 10: Save the Model .............................................................................................................. 130 7.14. Step 11: Calculate a Solution ........................................................................................................ 130 7.15. Step 12: Examine the Results ....................................................................................................... 131 7.16. Step 13: Summary ....................................................................................................................... 131 8. Mesh and Model Enhancement Exercise ............................................................................................. 133 8.1. Objective ...................................................................................................................................... 133 8.2. Prerequisites ................................................................................................................................. 133 8.3. Skills Covered ............................................................................................................................... 133 8.4. Training Method Used ................................................................................................................... 133 8.5. Loading the Model ........................................................................................................................ 133 8.6. A 15 Minute Exploration ................................................................................................................ 133

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Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

ANSYS Icepak Tutorials 8.7. Step-by-Step Approach ................................................................................................................. 134 8.8. Modification 1: Non-Conformal Mesh of the Heat Sink and Components ........................................ 135 8.9. Modification 2: Resolution of Thin Conducting Plate Intersecting Non-Conformal Region ................ 137 8.10. Modification 3: Non-Conformal Mesh for the hi-flux-comps Cluster .............................................. 137 8.11. Modification 4: A Super Assembly... .............................................................................................. 138 8.12. Modification 5: A Simplification Based on Magnitudes of Resistances... ......................................... 140 8.13. Modification 6: A Classic Case for Thin Conducting Plate... ............................................................ 140 8.14. Conclusion .................................................................................................................................. 141 9. Loss Coefficient for a Hexa-Grille ........................................................................................................ 143 9.1. Introduction ................................................................................................................................. 143 9.2. Prerequisites ................................................................................................................................. 143 9.3. Problem Description ..................................................................................................................... 143 9.4. Step 1: Create a New Project .......................................................................................................... 144 9.5. Step 2: Build the Model ................................................................................................................. 144 9.6. Step 3: Define Parameters and Trials ............................................................................................... 146 9.7. Step 4: Generate a Mesh ................................................................................................................ 153 9.8. Step 5: Physical and Numerical Settings ......................................................................................... 154 9.9. Step 6: Save the Model .................................................................................................................. 155 9.10. Step 7: Calculate a Solution .......................................................................................................... 155 9.11. Step 8: Examine the Results ......................................................................................................... 155 9.12. Step 9: Summary ......................................................................................................................... 156 10. Inline or Staggered Heat Sink ........................................................................................................... 157 10.1. Introduction ............................................................................................................................... 157 10.2. Prerequisites ............................................................................................................................... 157 10.3. Problem Description ................................................................................................................... 157 10.4. Step 1: Create a New Project ........................................................................................................ 158 10.5. Step 2: Build the Model ................................................................................................................ 159 10.6. Step 3: Define Design Variables .................................................................................................... 160 10.7. Step 4: Define Parametric Runs and Assign Primary Functions ...................................................... 162 10.8. Step 5: Generate a Mesh .............................................................................................................. 165 10.9. Step 6: Physical and Numerical Settings ....................................................................................... 166 10.10. Step 7: Save the Model .............................................................................................................. 166 10.11. Step 8: Define Monitor Points ..................................................................................................... 166 10.12. Step 9: Calculate a Solution ........................................................................................................ 166 10.13. Step 10: Examine the Results ...................................................................................................... 167 10.14. Step 11: Summary ..................................................................................................................... 172 11. Minimizing Thermal Resistance ........................................................................................................ 173 11.1. Introduction ............................................................................................................................... 173 11.2. Prerequisites ............................................................................................................................... 173 11.3. Problem Description ................................................................................................................... 173 11.4. Step 1: Create a New Project ........................................................................................................ 174 11.5. Step 2: Build the Model ................................................................................................................ 174 11.6. Step 3: Define Design Variables .................................................................................................... 175 11.7. Step 4: Generate a Mesh .............................................................................................................. 177 11.8. Step 5: Physical and Numerical Settings ....................................................................................... 178 11.9. Step 6: Save the Model ................................................................................................................ 178 11.10. Step 7: Define Primary, Compound, and Objective Functions ....................................................... 178 11.11. Step 8: Calculate a Solution ........................................................................................................ 180 11.12. Step 9: Examine the Results ....................................................................................................... 181 11.13. Step 10: Summary ..................................................................................................................... 182 11.14. Step 11: Additional Exercise ....................................................................................................... 182 12. Radiation Modeling .......................................................................................................................... 185 Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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ANSYS Icepak Tutorials 12.1. Introduction ............................................................................................................................... 185 12.2. Prerequisites ............................................................................................................................... 185 12.3. Problem Description ................................................................................................................... 185 12.4. Step 1: Create a New Project ........................................................................................................ 185 12.5. Step 2: Build the Model ................................................................................................................ 185 12.6. Step 3: Generate a Mesh .............................................................................................................. 191 12.7. Step 4: Physical and Numerical Settings ....................................................................................... 193 12.8. Step 5: Solving the Model Without Radiation ................................................................................ 193 12.9. Step 6: Save the Model ................................................................................................................ 196 12.10. Step 7: Calculate a Solution- No Radiation .................................................................................. 196 12.11. Step 8: Surface to Surface (S2S) Radiation Model ........................................................................ 196 12.12. Step 9: Discrete Ordinates (DO) Radiation Model ........................................................................ 197 12.13. Step 10: Ray Tracing Radiation Model ......................................................................................... 197 12.14. Step 11: Examine the Results ...................................................................................................... 197 12.15. Step 12: Summary ..................................................................................................................... 200 13. Transient Simulation ......................................................................................................................... 201 13.1. Introduction ............................................................................................................................... 201 13.2. Prerequisites ............................................................................................................................... 201 13.3. Problem Description ................................................................................................................... 201 13.4. Step 1: Create a New Project ........................................................................................................ 201 13.5. Step 2: Build the Model ................................................................................................................ 202 13.6. Step 4: Generate a Mesh .............................................................................................................. 206 13.7. Step 5: Physical and Numerical Settings ....................................................................................... 206 13.8. Step 6: Save the Model ................................................................................................................ 207 13.9. Step 7: Calculate a Solution .......................................................................................................... 207 13.10. Step 8: Generate a Summary Report ........................................................................................... 207 13.11. Step 9: Examine the Results ....................................................................................................... 208 13.12. Step 10: Examine Transient Results in CFD Post ........................................................................... 210 13.13. Step 10: Summary ..................................................................................................................... 215 14. Zoom-In Modeling in ANSYS Workbench .......................................................................................... 217 14.1. Introduction ............................................................................................................................... 217 14.2. Prerequisites ............................................................................................................................... 217 14.3. Problem Description ................................................................................................................... 217 14.4. Step 1: Create a New Project ........................................................................................................ 218 14.5. Step 2: Build the Model ................................................................................................................ 219 14.6. Step 3: Generate a Mesh .............................................................................................................. 220 14.7. Step 4: Physical and Numerical Settings ....................................................................................... 221 14.8. Step 5: Save the Model ................................................................................................................ 222 14.9. Step 6: Calculate a Solution .......................................................................................................... 222 14.10. Step 7: Examine the Results ....................................................................................................... 222 14.11. Step 8: Create a Zoom-In Model ................................................................................................. 224 14.12. Step 9: Edit the Zoom-in Model .................................................................................................. 226 14.13. Step 10: Mesh the Zoom-In Model ............................................................................................. 228 14.14. Step 11: Zoom-In Physical and Numerical Settings ...................................................................... 229 14.15. Step 12: Examine the Zoom-in Results ........................................................................................ 229 14.16. Step 13: Summary ..................................................................................................................... 231 14.17. Step 14: Additional Exercise 1 .................................................................................................... 231 14.18. Step 15: Additional Exercise 2 .................................................................................................... 232 15. IDF Import ......................................................................................................................................... 235 15.1. Introduction ............................................................................................................................... 235 15.2. Prerequisites ............................................................................................................................... 235 15.3. Problem Description ................................................................................................................... 235

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ANSYS Icepak Tutorials 15.4. Step 1: Create a New Project ........................................................................................................ 235 15.5. Step 2: Build the Model ................................................................................................................ 236 15.6. Step 3: Component Filtration Alternatives .................................................................................... 240 15.7. Step 4: Component Models Alternatives ...................................................................................... 241 15.8. Step 5: Summary ......................................................................................................................... 242 16. Modeling CAD Geometry .................................................................................................................. 245 16.1. Introduction ............................................................................................................................... 245 16.2. Prerequisites ............................................................................................................................... 245 16.3. Problem Description ................................................................................................................... 245 16.4. Step 1: Creating a New Project ..................................................................................................... 246 16.5. Step 2: Build the Model ................................................................................................................ 247 16.6. Step 3: Generate a Mesh .............................................................................................................. 255 16.7. Step 4: Physical and Numerical Settings ....................................................................................... 258 16.8. Step 5: Save the Model ................................................................................................................ 261 16.9. Step 6: Calculate a Solution .......................................................................................................... 262 16.10. Step 7: Examine the Results ....................................................................................................... 263 16.11. Step 8: Summary ....................................................................................................................... 265 17. Trace Layer Import for Printed Circuit Boards ................................................................................... 267 17.1. Introduction ............................................................................................................................... 267 17.2. Prerequisites ............................................................................................................................... 267 17.3. Problem Description ................................................................................................................... 268 17.4. Step 1: Create a New Project ........................................................................................................ 268 17.5. Step 2: Build the Model ................................................................................................................ 268 17.6. Conduction Only Model (PCB Without the Components) .............................................................. 276 17.7. Step 1: Generate a Mesh .............................................................................................................. 276 17.8. Step 2: Set Physical and Numerical Values .................................................................................... 277 17.9. Step 3: Save the Model ................................................................................................................ 277 17.10. Step 4: Calculate a Solution ........................................................................................................ 277 17.11. Step 5: Examine the Results ....................................................................................................... 278 17.12. PCB With the Actual Components Under Forced Convection ...................................................... 279 17.13. Step 1: Generate a Mesh ............................................................................................................ 279 17.14. Step 2: Set Physical and Numerical Values .................................................................................. 280 17.15. Step 3: Calculate a Solution ........................................................................................................ 280 17.16. Step 4: Examine the Results ....................................................................................................... 280 17.17. Using the Model Layers Separately Option ................................................................................. 281 17.18. Summary .................................................................................................................................. 282 17.19. Additional Exercise 1 ................................................................................................................. 282 17.20. Additional Exercise 2 ................................................................................................................. 282 18. Joule/Trace Heating .......................................................................................................................... 283 18.1. Introduction ............................................................................................................................... 283 18.2. Prerequisites ............................................................................................................................... 283 18.3. Problem Description ................................................................................................................... 283 18.4. Step 1: Create a New Project ........................................................................................................ 283 18.5. Step 2: Build the Model ................................................................................................................ 284 18.6. Step 3: Generate a Mesh .............................................................................................................. 289 18.7. Step 4: Physical and Numerical Settings ....................................................................................... 290 18.8. Step 5: Save the Model ................................................................................................................ 291 18.9. Step 6: Calculate a Solution .......................................................................................................... 291 18.10. Step 7: Examine the Results ....................................................................................................... 291 18.11. Step 8: Summary ....................................................................................................................... 294 19. Microelectronics Packages - Compact models .................................................................................. 295 19.1. Introduction ............................................................................................................................... 295 Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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ANSYS Icepak Tutorials 19.2. Prerequisites ............................................................................................................................... 295 19.3. Problem Description ................................................................................................................... 295 19.4. Step 1: Create a New Project ........................................................................................................ 296 19.5. Step 2: Build the Model ................................................................................................................ 296 19.6. Step 3: Generate a Mesh .............................................................................................................. 305 19.7. Step 4: Physical and Numerical Settings ....................................................................................... 306 19.8. Step 5: Save the Model ................................................................................................................ 307 19.9. Step 6: Calculate a Solution .......................................................................................................... 307 19.10. Step 7: Examine the Results ....................................................................................................... 309 19.11. Step 8: Summary ....................................................................................................................... 310 19.12. Step 9: Additional Exercise ......................................................................................................... 310 20. Multi-Level Meshing .......................................................................................................................... 311 20.1. Objective .................................................................................................................................... 311 20.2. Prerequisites ............................................................................................................................... 311 20.3. Skills Covered .............................................................................................................................. 311 20.4. Training Method Used ................................................................................................................. 311 20.5. Loading the Model ...................................................................................................................... 311 20.6. Step-by-Step Approach ............................................................................................................... 311 20.7. Modification 1: Multi-Level Meshing of the Fan_Guide ................................................................. 314 20.8. Modification 2: Multi-Level Mesh of the Sheetmetal_hs_assy.1 ..................................................... 315 20.9. Generate a Mesh ......................................................................................................................... 316 20.10. Conclusion ................................................................................................................................ 319 21. Characterizing a BGA-package by Utilizing ECAD Files .................................................................... 321 21.1. Introduction ............................................................................................................................... 321 21.2. Prerequisites ............................................................................................................................... 321 21.3. Problem Description ................................................................................................................... 321 21.4. Step 1: Create a New Project ........................................................................................................ 321 21.5. Step 2: Build the Model ................................................................................................................ 321 21.6. Step 3: Generate a Mesh .............................................................................................................. 325 21.7. Step 4: Physical and Numerical Settings ....................................................................................... 326 21.8. Step 5: Save the Model ................................................................................................................ 327 21.9. Step 6: Calculate a Solution .......................................................................................................... 327 21.10. Step 7: Examine the Results ....................................................................................................... 327 21.11. Step 8: Summary ....................................................................................................................... 329 22. Zero Slack with Non-Conformal Meshing ......................................................................................... 331 22.1. Introduction ............................................................................................................................... 331 22.2. Prerequisites ............................................................................................................................... 331 22.3. Problem Description ................................................................................................................... 331 22.4. Step 1: Create a New Project ........................................................................................................ 333 22.5. Step 2: Default Units .................................................................................................................... 333 22.6. Step 3: Build the Model ................................................................................................................ 333 22.7. Step 4: Import Traces ................................................................................................................... 333 22.8. Step 5: Add Slack Values .............................................................................................................. 334 22.9. Step 6: Generate Mesh (with Slack Values) .................................................................................... 335 22.10. Step 7: Zero Slack ...................................................................................................................... 336 22.11. Step 8: Generate Mesh (with Zero Slack) ..................................................................................... 337 22.12. Step 9: Physical and Numerical Settings ..................................................................................... 337 22.13. Step 10: Save the Model ............................................................................................................. 338 22.14. Step 11: Calculate a Solution ...................................................................................................... 338 22.15. Step 12: Examine the Results ...................................................................................................... 338 22.16. Step 13: Summary ..................................................................................................................... 338 23. ANSYS Icepak - ANSYS Workbench IntegrationTutorial ................................................................... 339

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ANSYS Icepak Tutorials 23.1. Introduction ............................................................................................................................... 339 23.2. Prerequisites ............................................................................................................................... 339 23.3. Problem Description ................................................................................................................... 339 23.4. Step 1: Create a New Project ........................................................................................................ 340 23.5. Step 2: Build the Model ................................................................................................................ 341 23.6. Step 3: Generate a Mesh .............................................................................................................. 344 23.7. Step 4: Physical and Numerical Settings ....................................................................................... 346 23.8. Step 5: Save the Model ................................................................................................................ 346 23.9. Step 6: Calculate a Solution .......................................................................................................... 346 23.10. Step 7: Examine the Results with CFD-Post ................................................................................. 347 23.11. Step 8: Thermo-Mechanical Structural Analysis ........................................................................... 349 23.12. Step 9: Summary ....................................................................................................................... 349 24. Postprocessing Using ANSYS CFD-Post ............................................................................................ 351 24.1. Introduction ............................................................................................................................... 351 24.2. Prerequisites ............................................................................................................................... 351 24.3. Problem Description ................................................................................................................... 352 24.4. Step 1: Create a New Project ........................................................................................................ 352 24.5. Step 2: Parametric Trials and Solver Settings ................................................................................. 354 24.6. Step 3: Calculate a Solution .......................................................................................................... 355 24.7. Step 4: Postprocessing Using ANSYS CFD-Post ............................................................................. 355 24.8. Step 5: Comparison Study ............................................................................................................ 378 24.9. Step 6: Summary ......................................................................................................................... 383 25. High Density Datacenter Cooling ..................................................................................................... 385 25.1. Introduction ............................................................................................................................... 385 25.2. Prerequisites ............................................................................................................................... 385 25.3. Problem Description ................................................................................................................... 385 25.4. Step 1: Create a New Project ........................................................................................................ 386 25.5. Step 2: Set Preferences ................................................................................................................ 387 25.6. Step 3: Build the Model ................................................................................................................ 388 25.7. Step 4: Generate a Mesh .............................................................................................................. 413 25.8. Step 5: Create Monitor Points ....................................................................................................... 413 25.9. Step 6: Physical and Numerical Settings ....................................................................................... 414 25.10. Step 7: Save the Model .............................................................................................................. 415 25.11. Step 8: Calculate a Solution ........................................................................................................ 415 25.12. Step 9: Examine the Results ....................................................................................................... 417 25.13. Step 10: Additional Exercise: Visualize and analyze the results in ANSYS CFD-Post ........................ 424 25.14. Step 11: Summary ..................................................................................................................... 424 26. Design Modeler - Electronics ............................................................................................................ 425 26.1. Introduction ............................................................................................................................... 425 26.2. Prerequisites ............................................................................................................................... 425 26.3. Problem Description ................................................................................................................... 425 26.4. Step 1: Create a New Project ........................................................................................................ 425 26.5. Step 2: Build the Model ................................................................................................................ 426 26.6. Step 3: Add Shortcuts to the Toolbar ............................................................................................ 427 26.7. Step 4: Edit the Model for ANSYS Icepak ....................................................................................... 428 26.8. Step 5: Opening the Model in ANSYS Icepak ................................................................................. 445 26.9. Step 6: Summary ......................................................................................................................... 447 Index ........................................................................................................................................................ 449


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Chapter 1: Using This Manual 1.1. What's In This Manual This manual contains tutorials that teach you how to use ANSYS Icepak to solve different types of problems. In each tutorial, features related to problem setup and postprocessing are demonstrated. The tutorial "Finned Heat Sink" provides detailed instructions designed to introduce the beginner to ANSYS Icepak. This tutorial provides explicit instructions for all steps in the problem setup, solution, and postprocessing. The remaining tutorials assume that you have read or solved the tutorial "Finned Heat Sink", or that you are already familiar with ANSYS Icepak and its interface. In these tutorials, some steps will not be shown explicitly. The input files are available in the installation area and available for download on the ANSYS Customer Portal.

1.2. How To Use This Manual Depending on your familiarity with computational fluid dynamics and ANSYS Icepak, you can use this tutorial guide in a variety of ways: 1.2.1. For the Beginner 1.2.2. For the Experienced User

1.2.1. For the Beginner If you are a beginning user of ANSYS Icepak, you should first read and solve the tutorial "Finned Heat Sink", in order to familiarize yourself with the interface and with basic setup and solution procedures. You may then want to try a tutorial that demonstrates features that you are going to use in your application. For example, if you are planning to solve a problem involving radiation, you should look at the tutorial "Radiation Modeling". You may want to refer to other tutorials for instructions on using specific features, such as grouping objects, even if the problem solved in the tutorial is not of particular interest to you.

1.2.2. For the Experienced User If you are an experienced ANSYS Icepak user, you can read and/or solve the tutorial(s) that demonstrate features that you are going to use in your application. For example, if you are planning to solve a problem involving radiation, you should look at the tutorial "Radiation Modeling". You may want to refer to other tutorials for instructions on using specific features, such as grouping objects, even if the problem solved in the tutorial is not of particular interest to you.

1.3. Typographical Conventions Used In This Manual Several typographical conventions are used in this manual's text to facilitate your learning process. •

Different type styles are used to indicate graphical user interface menu items and text inputs that you enter (e.g., Open project panel, enter the name projectname). Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

1

Chapter 1: Using This Manual •

A mini flow chart is used to indicate the menu selections that lead you to a specific panel. For example, Model → Generate mesh indicates that the Generate mesh option can be selected from the Model menu at the top of the ANSYS Icepak main window. The arrow points from a specific menu toward the item you should select from that menu.

•

A mini flow chart is also used to indicate the list tree selections that lead you to a specific panel or operation. For example, Problem setup →

Basic parameters

indicates that the Basic parameters item can be selected from the Problem setup node in the Model manager window •

Pictures of toolbar buttons are also used to indicate the button that will lead you to a specific panel. indicates that you will need to click on this button (in this case, to open the Walls For example, panel) in the toolbar.

1.4. Mouse Conventions Used In This Manual The default mouse buttons used to manipulate your model in the graphics window are described in Manipulating Graphics With the Mouse in the Icepak User's Guide. Although you can change the mouse controls in ANSYS Icepak to suit your preferences, this manual assumes that you are using the default settings for the mouse controls. If you change the default mouse controls, you will need to use the mouse buttons you have specified instead of the mouse buttons that the manual tells you to use.

1.5. When To Call Your ANSYS Icepak Support Engineer The ANSYS Icepak support engineers can help you to plan your modeling projects and to overcome any difficulties you encounter while using ANSYS Icepak. If you encounter difficulties we invite you to call your support engineer for assistance. However, there are a few things that we encourage you to do before calling: 1.

Read the section(s) of the manual containing information on the options you are trying to use.

2.

Recall the exact steps you were following that led up to and caused the problem.

3.

Write down the exact error message that appeared, if any.

4.

For particularly difficult problems, package up the project in which the problem occurred (see Packing and Unpacking Model Files in the Icepak User's Guide for instructions) and send it to your support engineer. This is the best source that we can use to reproduce the problem and thereby help to identify the cause.

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Chapter 2: Finned Heat Sink 2.1. Introduction This tutorial demonstrates how to model a finned heat sink using ANSYS Icepak. In this tutorial you will learn how to: •

Create a new project.

•

Create blocks, openings, fans, sources, and plates.

•

Include effects of turbulence in the simulation.

•

Calculate a solution.

•

Examine contours and vectors on object faces and on cross-sections of the model.

2.2. Prerequisites This tutorial assumes that you have little to no experience with ANSYS Icepak and so each step will be explicitly described.

2.3. Problem Description The cabinet contains an array of five high-power devices, a backing plate, ten fins, three fans, and a free opening, as shown in Figure 2.1 (p. 4). The fins and backing plate are constructed of extruded aluminum. Each fan has a total volume flow rate of 18 cfm and each source dissipates power at the rate of 33 W. According to the design objective, the base of the devices should not exceed 65°C when the fins are swept with air at an ambient temperature of 20°C.


3

Chapter 2: Finned Heat Sink

Figure 2.1 Problem Specification

2.4. Step 1: Create a New Project 1.

Start ANSYS Icepak, as described in Starting ANSYS Icepak in the Icepak User's Guide. When ANSYS Icepak starts, the Welcome to Icepak panel opens automatically.

2.

Click New in the Welcome to Icepak panel to start a new ANSYS Icepak project. The New project panel appears.

4


Step 2: Build the Model

3.

Specify a name for your project and click Create. ANSYS Icepak creates a default cabinet with the dimensions 1 m × 1 m × 1 m, and displays the cabinet in the graphics window.

Note You can rotate the cabinet around a central point using the left mouse button, or you can translate it to any point on the screen using the middle mouse button. You can zoom into and out from the cabinet using the right mouse button. To restore the cabinet to its default orientation, select Home position in the Orient menu.

2.5. Step 2: Build the Model To build the model, you will first resize the cabinet to its proper size. Then you will create the backing plate and opening, followed by the elements that will be duplicated (i.e., the fans, fins, and devices). 1.

Resize the default cabinet in the Cabinet panel. Model →

Cabinet


5


Extra You can also open the Cabinet panel by selecting the Cabinet item in the Model manager window and then clicking the Edit object button ( ) in the Object modification toolbar. Resizing of the cabinet object can also be done in the geometry window in the lower right hand corner of the GUI. a.

In the Cabinet panel, click the Geometry tab.

b.

Under Location, enter the following coordinates: xS

0

xE

0.075

yS

0

yE

0.25

zS

0

zE

0.356

c.

Click Done to resize the cabinet and close the panel.

d.

In the Orient menu, select Scale to fit to scale the view of the cabinet to fit the graphics window.

Extra You can also scale the view by clicking the Scale to fit button (

6

).



Extra After selecting the object to be edited in the model tree, there are several ways you can open the Edit panel: •

2.

Double-click on the object in the model tree, or –

Type Ctrl+e, or

–

Right-click the object in the model tree and scroll to Edit object, or

–

Click the Edit button in the object geometry window, or

–

Click the Edit icon (

) in the model toolbar.

Create the backing plate. The backing plate is 0.006 m thick and divides the cabinet into two regions: the device side (where the high-power devices are contained in a housing) and the fin side (where the fins dissipate heat generated by the devices). The backing plate is represented in the model by a solid prism block.

Extra Blocks allow six-sided control for meshing and thermal specifications, whereas plates allow for only two-sided control. a.

Click the Create blocks button (

) to create a new block.

ANSYS Icepak creates a new solid prism block in the center of the cabinet. You need to change the size of the block. b.

Click the Edit object button (

c.

Click the Geometry tab.

d.

Enter the following coordinates for the block:

) to open the Blocks panel.

xS

0

xE

0.006

yS

0

yE

0.25

zS

0

zE

0.356


7


e. 3.

Click Done to modify the block and close the panel.

Create the free opening on the fin side of the backing plate. a.

Click the Create openings button (

) to create a new opening.

ANSYS Icepak creates a free rectangular opening lying in the x-y plane in the center of the cabinet. You need to change the size of the opening.

8

b.


c.


d.

Enter the following coordinates for the opening:

) to open the Openings panel.

xS

0.006

xE

0.075

yS

0

yE

0.25

zS

0.356

zE

—



e. 4.

Click Done to modify the opening and close the panel.

Create the first fan. Each fan is physically identical to the others, except with respect to its location on the cabinet wall. To create the set of three fans, you will build a single fan as a template, and then create two copies, each with a specified offset in the y direction. a.

) to create a new fan.

Click the Create fans button (

ANSYS Icepak creates a free circular fan lying in the x - y plane in the center of the cabinet. You need to change the size of the fan and specify its mass flow rate. b.

Click the Edit object (

c.


d.

Enter the following coordinates for the fan:

e.

) to open the Fans panel.

xC

0.04

yC

0.0475

zC

0

Enter 0.03 for the external radius (Radius), and 0.01 for the internal radius (Int Radius).


9


f.

Click the Properties tab.

g.

Keep the default Fan type of intake.

h.

Under the Fan flow tab, select Fixed and Volumetric. Enter a volume flow rate of 18 cfm.

Note Make sure to update the units to cfm by clicking on the triangle button and selecting cfm from the drop-down list.

10



i. 5.

Click Done to modify the fan and close the panel.

Copy the first fan (fan.1) to create the second and third fans (fan.1.1 and fan.1.2). a.

In the graphics display window, select fan.1 using the Shift key and right mouse button.

b.

In the object context menu, select Copy and the Copy fan fan.1 panel opens.

c.

Enter 2 as the Number of copies.

d.

Enable the Translate option and specify a Y offset of 0.0775 m.


11


e.

Click Apply. ANSYS Icepak makes two copies of the original fan, each offset by 0.0775 m in the y direction from the previous one.

6.

Create the first high-power device. Like the fans, each device is physically identical to the others, except with respect to its location in the cabinet. To create the set of five devices, you will build a single rectangular planar source as a template, and then create four copies, each with a specified offset in the y direction. a.

Click the Create sources button (

) to create a source.

ANSYS Icepak creates a free rectangular source in the center of the cabinet. You need to change the geometry and size of the source and specify its heat source parameters.

Note For planar objects, select the desired plane first, then enter the coordinates.

12

b.


c.


d.

Keep the default selection of Rectangular.

e.

In the Plane drop-down list, select Y-Z.

f.

Enter the following coordinates for the source:

) to open the Sources panel.

xS

0

xE

—

yS

0.0315

yE

0.0385


Step 2: Build the Model zS

0.1805

zE

g.


h.

Under Thermal specification, set the Total power to 33 W.

0.2005


13


i. 7.

8.

Click Done to modify the source and close the panel.

Copy the first device (source.1) to create the other four devices (source.1.1, source.1.2, source.1.3, and source.1.4). a.

In the Model manager window, select the source.1 item under the Model node.

b.

Click the Copy object button (

c.

Follow the same instructions that you used above to copy the fans, using a Y offset of 0.045 m to create 4 copies.

).

Create the first fin. Like the fans and devices, each fin is physically identical to the others, except with respect to its location in the cabinet. To create the array of ten fins, you will build a single rectangular plate as a template, and then create nine copies, each with a specified offset in the y direction. a.

Click the Create plates button (

) to create a plate.

ANSYS Icepak creates a free rectangular plate in the x-y plane in the center of the cabinet. You need to change the orientation and size of the plate and specify its thermal parameters.

14

b.


c.


d.

In the Plane drop-down list, select X-Z.

e.

Enter the following coordinates for the plate:

) to open the Plates panel.


Step 2: Build the Model xS

0.006

xE

0.075

yS

0.0125

yE

—

zS

0.05

zE

0.331

f.


g.

Under Thermal model, select Conducting thick from the drop-down menu.

h.

Set the Thickness to 0.0025 m.

i.

Keep default as the Solid material.

Note Since the default solid material is extruded aluminum, you need not specify the material explicitly here.


15


j. 9.

Click Done to modify the plate and close the panel.

Copy the first fin (plate.1) to create the other nine fins (plate.1.1, plate.1.2, ..., plate.1.9). a.

In the Model manager window, select the plate.1 item under the Model node.

b.

Click the Copy object button (

c.

Follow the same instructions that you used above to copy the fans, using a Y offset of 0.025 m to create 9 copies.

).

The completed model will look like Figure 2.2 (p. 17), which is shown in the Isometric view (available in the Orient menu or by clicking the Isometric view button (

)).

Note You can remove the object names by clicking the Display object names button (

16


).


Figure 2.2 Completed Model for the Finned Heat Sink

10. Check the model to be sure that there are no problems (e.g., objects that are too close together to allow for proper mesh generation). Model → Check model

Note You can also click the Check model button (

) to check the model.

Note ANSYS Icepak should report in the Message window that 0 problems were found. 11. Check the definition of the modeling objects to ensure that you specified them properly. View → Summary (HTML) The HTML version of the summary displays in your web browser. The summary displays a list of all the objects in the model and all the parameters that have been set for each object. You can view the detailed version of the summary by clicking the appropriate object names or property specifications. If you notice any incorrect specifications, you can return to the appropriate modeling object panel and change the settings in the same way that you originally entered them.


17


2.6. Step 3: Generate a Mesh You will generate the mesh in two steps. First you will create a coarse mesh and examine it to determine where further mesh refinement is required. Then you will refine the mesh based on your observations of the coarse mesh.

Extra For more information on how to refine a mesh locally, refer to Refining the Mesh Locally in the Icepak User's Guide. Model → Generate mesh

Extra You can also generate a mesh by clicking the Generate mesh button ( Mesh control panel. 1.

), which opens the

Generate a coarse (minimum-count) mesh. a.

In the Mesh control panel, select Coarse in the Mesh parameters drop-down list. ANSYS Icepak updates the panel with the default meshing parameters for a coarse (minimumcount) mesh, shown in the panel below.

18

b.

Set the Mesh units and all the Minimum gap units to mm.

c.

Set the Minimum gap to 1 mm for X, Y, and Z.

d.

Set the Max X size to 3.5, the Max Y size to 12.5, and the Max Z size to 17.5.


Step 3: Generate a Mesh

e.

Click the Generate button to generate the coarse mesh.

Note If the Allow minimum gap changes option is unchecked under the Misc tab, ANSYS Icepak will inform you that your minimum object separation is more than 10% of the smallest size object in the model . You can stop the meshing process, ignore the warning, or allow ANSYS Icepak to correct the values. f.

2.

If this warning appears, click Change value and mesh in the Minimum separation in x and Minimum separation in y panels to accept the recommended changes to your model and continue generating the mesh.

Examine the coarse mesh on a cross-section of the model. a.

Click the Display tab. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

19

Chapter 2: Finned Heat Sink b.

Turn on the Cut plane option.

c.

In the Set position drop-down list, select X plane through center.

d.

Turn on the Display mesh option. The mesh display plane is perpendicular to the fins, and aligned with the devices, as shown in Figure 2.3 (p. 21).

Note The number of elements may vary slightly on different machines.

20



Figure 2.3 Coarse Mesh on the y-z Plane

e.

Use the slider bar to move the plane cut through the model. See Figure 2.4 (p. 22) to examine a close-up view of the coarse mesh.

Note You can change the mesh color using the Surface mesh color and the Plane mesh color options. The mesh elements near the fins are too large to sufficiently resolve the problem physics. In the next step, you will generate a finer mesh. 3.

Generate a finer mesh. a.

Click the Settings tab.

b.

Under Global, select Normal in the Mesh parameters drop-down list. ANSYS Icepak updates the panel with the default meshing parameters and Minimum gap values for a “normal" (i.e., finer than coarse) mesh.

4.

Click the Generate button in the Mesh control panel to generate the finer mesh.

5.

Examine the new mesh. The graphics display updates automatically to show the new mesh. Click the Display tab and use slider bar to advance the plane cut and view the mesh throughout the model.


21


Figure 2.4 Fine and Coarse Mesh on the y-z Plane

6.

22

Turn off the mesh display. a.

Click the Display tab in the Mesh control panel.

b.

Deselect the Display mesh option.

c.

Click Close to close the Mesh control panel.


Step 4: Physical and Numerical Settings

Note After deselecting the Display mesh option and closing the Mesh control panel, you can display the mesh on selected objects by using the context menu in the graphics display window. To display the context menu, hold down the Shift key and press the right mouse button anywhere in the graphics window, but not on an object. Select Display mesh and select the object you want it displayed on.

Figure 2.5 Display mesh option

2.7. Step 4: Physical and Numerical Settings Before starting the solver, you will first review estimates of the Reynolds and Peclet numbers to check that the proper flow regime is being modeled. 1.

Check the values of the Reynolds and Peclet numbers. Solution settings →

Basic settings


23


a.

Click the Reset button. Reset calculates the Reynolds and Peclet numbers.

b.

Check the values printed to the Message window. The Reynolds and Peclet numbers are approximately 13,000 and 9,000, respectively, so the flow is turbulent. ANSYS Icepak will recommend setting the flow regime to turbulent.

Note These values are only estimates, based on the current model setup. Actual values may vary, and may need to be verified, depending on your design. c. 2.

Click Accept to save the solver settings.

Enable turbulence modeling. Problem setup →

24

Basic parameters

a.

In the Basic parameters panel, select Turbulent as the Flow regime.

b.

Keep the default Zero equation turbulence model.

a.

Turn radiation off by clicking Off under Radiation.


Step 6: Calculate a Solution

b.

Click Accept to save the new settings.

2.8. Step 5: Save the Model ANSYS Icepak automatically saves the model for you before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the job you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your job file when it saves the model.) File → Save project

Note Alternatively, you can click the

button in the File commands toolbar.

2.9. Step 6: Calculate a Solution 1.

Start the calculation. Solve → Run solution

Note You can click the Run solution button (

) in the Model and solve toolbar.


25


2.

Keep the default settings in the Solve panel.

3.

Click Start solution to start the solver.

Note There are no universal metrics for judging convergence, a good indicator is when the solution no longer changes with more iterations and when the residuals have decreased to a certain degree. The default criterion is that each residual will be reduced to a value − − of less than except the energy residual, for which the default criterion is . It is a good idea to judge convergence not only by examining residuals levels, but also by monitoring relevant integrated quantities. ANSYS Icepak begins to calculate a solution for the model, and a separate window opens where the solver prints the numerical values of the residuals. ANSYS Icepak also opens the Solution residuals graphics display and control window, where it displays the convergence history for the calculation. Upon completion of the calculation, your residual plot will look something like Figure 2.6 (p. 27). You can zoom in the residual plot by using the left mouse.

Note The actual values of the residuals may differ slightly on different machines, so your plot may not look exactly the same as Figure 2.6 (p. 27).

26


Step 7: Examine the Results

Figure 2.6 Residuals

4.

Click Done in the Solution residuals window to close it.

2.10. Step 7: Examine the Results ANSYS Icepak provides a number of ways to view and examine the solution results, including: •

plane-cut views

•

object-face views

The following steps illustrate how to generate and display each view. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

27


Note The objective of this exercise is to determine whether the air flow and heat transfer associated with the heat sink (fans and fins) are sufficient to maintain device temperatures below 65°C. You can accomplish this by creating different plane cuts and monitoring the velocity vector and temperature on it. Plane-cut views allow you to observe the variation in a solution variable across the surface of a plane. You will use the Plane cut panel to view the direction and magnitude of velocity across a horizontal plane. 1.

To open the Plane cut panel, select Plane cut in the Post menu.

Extra You can also open the Plane cut panel by clicking the Plane cut button ( 2.

).

Display velocity vectors on a plane cut on the fin side of the enclosure. Post → Plane cut a.

In the Name field, enter the name cut-velocity.

b.


Tip Click the triangle button located next to the Set position text field to open the drop-down list.

28

c.

Turn on the Show vectors option.

d.

Click Create.

e.

In the Orient menu, select Orient positive X.


Step 7: Examine the Results This orients the model as shown in Figure 2.7 (p. 29). You can see that the maximum velocity occurs at the fan blades. The lowest velocity occurs between the top fin and the adjacent cabinet wall, and between the bottom fin and the adjacent cabinet wall.

Extra You can also select the positive button (

orientation by clicking the Orient positive X

).

Figure 2.7 Velocity Vectors on the Fin Side of the Enclosure

f.

In the Plane cut panel, turn off the Active option. This temporarily removes the velocity vector display from the graphics window, so that you can more easily view the next postprocessing object.

Note You can later open the Inactive folder in the model tree and locate cut_velocity. cut_velocity can be either deleted or reactivated by dragging it to Trash or to the Post-processing folder, as well as with the right-click dialog. 3.

Display contours of temperature on the fin side of the enclosure. a.

Click New in the Plane cut panel.

b.

In the Name field, enter the name cut-temperature.

c.


d.

Turn on the Show contours option and click Parameters. The Plane cut contours panel opens.


29

Chapter 2: Finned Heat Sink e.

Keep the default selection of Temperature.

f.

For Shading options, keep the default selection of Banded.

g.

For Color levels, select Calculated and then select This object from the drop-down list.

h.

Click Apply. ANSYS Icepak computes the color range for the display based on the range of temperatures on this plane cut.

i.

Click Done to save the new settings, close the panel, and update the graphics display. The graphics display updates to show the temperature contour plot. The actual values of temperature may slightly differ on different systems. You can use the scroll bar to change the x-location of the plane cut. In addition, the plane cut can be dragged through the model when you press the Shift key and hold down the middle mouse button on the plane. Ensure you click the edge of the plane cut so as to not move any objects. Figure 2.8 (p. 31) shows that heat conducts through the fins from the sources in both directions.

30



Figure 2.8 Temperature Contours on the Fin Side of the Enclosure

j. 4.

In the Plane cut panel, turn off the Active option.

Display velocity vectors superimposed with pressure contours. a.

Click New in the Plane cut panel.

b.

In the Name field, enter the name cut-prvelocity.

c.


d.

Specify the display of velocity vectors. i.

Turn on the Show vectors option and click Parameters. The Plane cut vectors panel opens.

e.

ii.

Select Fixed from the Color by drop-down list.

iii.

Click on the square next to Fixed color and select black from the color palette.

iv.

Click Done to close the panel.

Specify the display of contours of pressure. i.

Turn on the Show contours option and click Parameters. The Plane cut contours panel opens.

ii.

In the Plane cut contours panel, select Pressure in the Contours of drop-down list.

iii.


iv.


v.

Click Done to save the new settings, close the panel, and update the graphics display. The graphics display updates to show the pressure contour plot superimposed on the velocity vector plot. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

31

Chapter 2: Finned Heat Sink Figure 2.9 (p. 32) shows isolated regions of high pressure immediately downstream of the fans, including local maxima at the upstream tips of the fins.

Figure 2.9 Pressure Contours and Velocity Vectors on the Fin Side of the Enclosure

f. 5.

In the Plane cut panel, turn off the Active option.

Display contours of temperature on all five high-power devices. An object-face view allows you to examine the distribution of a solution variable on one or more faces of an object in the model. To generate an object-face view, you must select the object and specify both the variable to be displayed (e.g., temperature) and the attributes of the view (e.g., shading type). You will use the Object face panel to create a solid-band object-face view of temperature on all five high-power devices and on the backing plate. a.

To open the Object face panel, select Object face in the Post menu. Post → Object face

Extra You can also open the Object face panel by clicking the Object face button (

32

).

b.

In the Name field, enter the name face-tempsource.

c.

In the Object drop-down list, click source.1, hold down the Shift key, and click source.1.4 to select all the sources, and click the Accept button.

d.

Turn on the Show contours option.



e.

Click Parameters next to the Show contours option. The Object face contours panel opens.

f.

In the Object face contours panel, keep the default selection of Temperature in the Contours of drop-down list.

g.


h.


i.

Click Done to save the new settings, close the panel, and update the graphics display. The graphics display updates to show the temperature contours on the sources.

j.

Use your right mouse button to zoom in and look more closely at each source. Figure 2.10 (p. 34) shows a view with the temperature contours on all five sources. The temperature distributions are similar for all sources: warm in the center and decreasing in tem-


33

Chapter 2: Finned Heat Sink perature toward the edges of the source. Temperature distributions on the top and bottom sources are similar to each other, as are distributions on the two remaining sources.

Note To view the temperature contours on an individual source, hold down the Shift key and drag a box around a source object using the left mouse button. The source object will show as highlighted in the Model manager window. Right click the source object to display the context menu and select Create>Object face(s)>Separate. The Object face panel is displayed for that particular object. Change the settings to match the ones used above for all source objects and click Create.

Figure 2.10 Temperature Contours on the Five Devices

k. 6.

In the Object face panel, turn off the Active option.

Display line contours of temperature on the backing plate. a.

Click New in the Object face panel.

b.

In the Name field, enter the name face-tempblock.

c.

In the Object drop-down list, select block.1 and click Accept.

d.

Turn on the Show contours option and click Parameters. The Object face contours panel opens.

34

e.

In the Object face contours panel, keep the default selection of Temperature in the Contours of drop-down list.

f.

For Contour options, deselect Solid fill and select Line.

g.

For Level spacing, select Fixed and set the Number of contour lines to 200.

h.

For Color levels, select Calculated and then select This object from the drop down list. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 8: Summary i.

Click Done to save the new settings, close the panel, and update the graphics display. The graphics display updates to show the temperature contours on the block. Figure 2.11 (p. 35) shows that most of the heat is confined to the region near the sources. The maximum temperature occurs near the middle three sources.

Figure 2.11 Temperature Contours on the Backing Plate

j. 7.

Click Done in the Object face panel to close the panel.

Save the post-processing objects created. a.

Select Save post objects to file in the Post menu.

b.

Click on Save in the File selection window that opens. Upon saving the project, all objects created during post-processing are saved within a post_objects file for future retrieval.

Note ANSYS Icepak does not automatically save the post-processing objects created in the current session. When you exit ANSYS Icepak, they are deleted unless they are saved using the above steps.

2.11. Step 8: Summary In this tutorial, you set up and solved a model in order to determine the ability of the specified heat sink to maintain source temperatures below 65 °C. Postprocessing results show that the maximum source temperature is about 60 °C, indicating that the heat sink provides adequate cooling for the sources.


35


2.12. Step 9: Additional Exercise To determine the effectiveness of the heat sink under conditions involving the failure of the middle fan, deactivate or edit fan.1.1, go to the Properties tab and turn on Failed under the Options tab, assign a free-area ratio of 0.3, and click Done. Next, remesh the model, solve it again using a different solution ID, and examine the new results.

Note When you are finished examining the results, you can end the ANSYS Icepak session by clicking Quit in the File menu. File → Quit

36


Chapter 3: RF Amplifier 3.1. Introduction This tutorial demonstrates how to model an RF Amplifier using ANSYS Icepak. In this tutorial you will learn how to: •

Create a new project.

•

Create openings, fans, sources, enclosure, PCB, heat sink and walls.

•

Use non-conformal meshing.

•

Include effects of gravity and turbulence in the simulation.

•

Calculate a solution.

•


3.2. Prerequisites This tutorial assumes that you have little experience with ANSYS Icepak, but that you are generally familiar with the interface. If you are not, please review Sample Session in the Icepak User's Guide.

3.3. Problem Description RF Amplifiers are typically sealed enclosures that are placed within larger systems. They present a challenge from the thermal management perspective because no direct exchange of air exists between the interior of the amplifier and the ambient. The common method of cooling such subsystems is to mount a large heat sink on the amplifier housing that cools all the devices within the enclosure. A simplified version of an RF amplifier (Figure 3.1 (p. 38)) will serve as the model for this tutorial. There will be free convection inside the amplifier and forced convection in the external domain.


37

Chapter 3: RF Amplifier

Figure 3.1 Schematic of the RF Amplifier


Start ANSYS Icepak, as described in Chapter 1 of the User's Guide. When ANSYS Icepak starts, the Welcome to Icepak panel opens automatically.

2.


38



3.

Specify the name amplifier for your project and click Create. ANSYS Icepak creates a default cabinet with the dimensions 1 m × 1 m × 1 m, and displays the cabinet in the graphics window.


3.5. Step 2: Build the Model To build the model, you will first resize the cabinet to its proper size. Then you will create the amplifier housing, devices (heat sources), PCB, heatsink, fan and other geometrical objects. 1.

Resize the default cabinet and create an opening on one side of the cabinet. Model →

Cabinet

Select the cabinet in the Model tree and specify the following in the object geometry window:


39


Extra After selecting the object to be edited in the model tree, there are several ways you can open the Edit panel: •

Double-click on the object in the model tree, or –

Type Ctrl+e, or

–

Right-click the object in the model tree and scroll to Edit object, or

–

Click the Edit button in the object geometry window, or

–

Click the Edit object icon (

) in the model toolbar

Figure 3.2 The Cabinet Geometry Tab Panel

One side of this cabinet has an opening. Assign Properties on this boundary, in the Properties tab of the Cabinet object panel (Figure 3.3 (p. 41)):

40

a.

Change the Max y Wall type to be an Opening.

b.

Click Done to accept the inputs and close the panel.



Figure 3.3 The Cabinet Boundary Panel

2.

Create the Y and Z faces of the amplifier housing as an enclosure using the enclosure object. Click on the Create enclosures icon ( and dimensions:

) in the model toolbar, then specify the following Name

In the Properties tab specify the followings: a.

Change the Boundary type to Open for Min X and Max X. For others, retain the boundary type as Thin.

b.

Specify the Solid material as Polystyrene-rigid-R12.

Tip You have to scroll down the list to find this material. c.

Click Done.


41


Figure 3.4 The Enclosure Panel

3.

Create the Xmin face of the amplifier housing as a wall. The wall covers the Xmin side of the enclosure.

4.

Click on the Create walls icon (

) in the model toolbar to create a new wall.

In the object edit window, name the wall Xmin and change the plane to Y-Z.

Note While we will use the align tools to place the wall at the desired locations, we could also specify the dimensions/locations of the wall in the Geometry tab and achieve the same result. However, the align tools are faster, and thus are the recommended method. To start the process, left-click Morph Edges icon ( by-step procedure described below:

42

) in the model toolbar. Now, follow the step-

a.

Select the Zmax edge of the wall (Figure 3.5 (p. 43)) by left mouse clicking it in the graphical window. Notice that it turns red to indicate that it has been selected.

b.

Click the middle mouse button to accept this edge.

c.

Select the lower Zmax edge of the enclosure (Figure 3.5 (p. 43)) with the left mouse button. Notice that it turns yellow to indicate that it has been selected.



Figure 3.5 Schematic Showing Edge Identities for Alignment

d.

Click the middle mouse button to accept the transformation. The wall Xmin should have now been moved and resized. Now the wall should extend to the entire Xmin side of the enclosure.

To specify the remaining wall dimension, stay in the match edge mode and complete the following steps: a.

Click the Zmin edge of the wall with the left mouse button. Be sure that it (and not the enclosure edge) is highlighted in red. By repeatedly clicking the left mouse button, ANSYS Icepak cycles through all possible edges.

b.

Click the middle mouse button to accept.

c.

Using the left mouse button, click the lower Zmin edge of the enclosure.

d.

Click the middle mouse button to accept. The wall should now form the Xmin face of the enclosure.

e.

Click the right mouse button to exit the Match edge mode.

The resulting model is shown in Figure 3.6 (p. 44) with shading to highlight new definitions. Shading is available under the Info tab in most panels.


43


Figure 3.6 Geometry with Wall

Double-click on the newly created wall object (Xmin) in the model tree to open the Walls panel. Now specify the following properties to the wall in the Properties tab. a.

Specify a Wall thickness of 1 mm (0.001 m).

b.

Specify the Solid material as Polystyrene-rigid-R12 under Plastics.

c.

Specify the External conditions as Heat transfer coefficient and click the Edit button. The Wall external thermal conditions panel opens.

44


Step 2: Build the Model i.

Select Heat transfer coefficient in the External conditions drop-down list and press Edit. The Wall external thermal conditions panel opens.

ii.

Set the Heat transfer coeff to 5 W/K-

iii.

Click Done to close the Wall external thermal conditions panel.

iv.

Click Done to close Walls panel (Figure 3.7 (p. 45))

.

Figure 3.7 The Walls Panel

5.

Create the PCB. The PCB will cover the Xmax side of the enclosure. a.

Click on the Create printed circuit boards icon ( double click on the PCB object in the Model tree.

b.

Specify the following in the geometry window:

c.

Specify the Trace layer type as Detailed and input the parameters under Trace layer parameters (make sure that you enter both columns) in the Properties tab as shown in Figure 3.8 (p. 46). There are four internal layers.

) in the Model toolbar to create a PCB and

Please notice that the Effective conductivity in plane and normal directions are updated when you click on the Update button (Figure 3.8 (p. 46)).


45


Figure 3.8 The Printed circuit boards Panel

d. 6.

Click Done to close the Printed circuit boards panel.

Create the devices as 2D sources. There are 12 devices on the bottom side of the PCB. Theses devices are created as 2D sources. The following steps show you how to create one and then use the copy utility to create the remaining 11 sources.

46

a.

Click on the Create sources icon ( ) in the model toolbar to create a source and double click on the source object in the model tree.

b.

Specify the following name, dimensions, and properties to the source.



c.

In the Properties tab, specify the Total power as 7 W (Figure 3.9 (p. 47)) and click Done.

Figure 3.9 The Sources Panel

d.

Create the other devices (sources) object by creating two copies of the device and translating it to z= 0.055 m. Please follow the steps below for copying the source object. i.

Right mouse click on the source object and choose the Copy option.

ii.

Specify the Number of copies as 2.

iii.

Turn on the Translate option.

iv.

Specify the Z offset to 0.055 m.

v.

Click Apply to copy the object.


47


Figure 3.10 The Copy source device Panel

e.

Similarly, create the other devices (sources) object by copying the sources created in the previous steps. i.

Left mouse click and select device, then while holding down the Ctrl key, select device.1, and device.2. Right mouse click and choose the Copy option.

ii.

Specify the Number of copies as 3.

iii.

Turn on the Translate option.

iv.

Specify the Y offset to 0.064 m.

v.

Click Apply to copy the object.

Note Following these two copy actions, you should now have 12 sources (Figure 3.11 (p. 49)) in a four rows by three columns pattern.

48



Figure 3.11 Geometry with Devices

7.

Create the heat sink. The extruded fin heat sink with the flow in the y direction will be created to remove the heat from the PCB. a.

Click on the Create heat sinks icon ( ) in the Model toolbar to create a heat sink and double click on the heat sink object in the model tree. Specify the following dimensions in the geometry window.


49


b.

In the heat sink object panel, select the Geometry tab, and specify a Base height of 0.004 m and an Overall height of 0.04 m.

c.

Specify the properties of the heat sink as shown in Figure 3.12 (p. 50) below. Note that we are not changing parameters in the Flow/thermal data, Pressure loss, or Interface tabs.

Figure 3.12 The Heat sinks Panel

d. 8.

Click Done to close the Heat sinks panel.

Create the fan. For this model, we will make use of ANSYS Icepak's fan library and search tool. a.

Select the Library tab in the model manager window(Figure 3.13 (p. 51)).

b.

Right-click on Libraries in the model tree and choose Search fans. The Search fan library dialog appears.

50

i.

In the Physical tab, deactivate the Min fan size and enter 80 mm for the Max fan size.

ii.

Select the Thermal/flow tab, enable the Min flow rate option and specify a Min flow rate of 80 cfm. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.


Note The minimum flow rate used in the search criteria implies the minimum free flow of the fans. iii.

Click on the Search button.

Note ANSYS Icepak lists all the fans in its libraries that satisfy these conditions. c.

Select the fan called delta.FFB0812_24EHE in the Name column by clicking on it with the left mouse button.

d.

Click Create to load the fan into the model.

Figure 3.13 Search Fan library Panel

e.

Now, we need to specify the location of the fan created in the previous steps. Resize the fan geometry based on the Figure 3.14 (p. 52) (note X-Z plane).


51


Figure 3.14 The Fans Panel

The final geometry should look like Figure 3.15 (p. 53).

52


Step 3: Create Assemblies

Figure 3.15 The Final Geometry

f.

Check the definition of the modeling objects to ensure that you specified them properly. View → Summary (HTML)

Note The HTML version of the summary displays in your web browser. The summary displays a list of all the objects in the model and all the parameters that have been set for each object. You can view the detailed version of the summary by clicking the appropriate object names or property specifications. If you notice any incorrect specifications, you can return to the appropriate modeling object panel and change the settings in the same way that you originally entered them.

3.6. Step 3: Create Assemblies For both organizational purposes and to have a finer mesh in the fan and enclosure, we will create two assemblies. The first assembly will consist of the RF amplifier and heat sink; the second assembly will consist only of the fan.


53

Chapter 3: RF Amplifier 1.

2.

54

To create the amplifier assembly: a.

Select the positive X view by either using the icon in the shortcut menu or simply press Shift+X and then Shift+S to fit to scale the view in the graphics window.

b.

While pressing Shift, drag a bounding box around the amplifier using the left mouse button. Release the mouse button and notice that all of the objects forming the amplifier and heat sink have been selected in the model tree.

c.

Right-click on the highlighted enclosure (Housing) in the model tree and select Create and then Assembly from the list. All of the selected objects have now been added to the assembly.

d.

In the Object geometry window, rename the assembly “assembly.1" to amplifier and click Apply.

Create a new assembly for the fan object: a.

Click on the Create assemblies icon (

b.

In the Model tree, use the left mouse button to drag the fan, delta.FFB0812_24EHE, into the new assembly to add it to this assembly.

c.

In the Object geometry window, rename this assembly as fan and click Apply.

) in the model toolbar to create a new assembly.



Figure 3.16 Two Assemblies

3.7. Step 4: Generate a Mesh Before generating a mesh, we will specify the slack values for the assemblies. Slack values represent a finite offset from an object to a non-conformal mesh boundary and are required when meshing assemblies separately. 1.

Edit both assemblies (right-click the assembly name in the model toolbar and select Edit), then select the Meshing tab. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

55


Toggle on Mesh separately and then specify the slack values indicated in the following table. Make sure you remember to add slack values to both assemblies.

Table 3.1 Slack Values for the Amplifier and Fan Name

Min X

Min Y

Min Z

Max X

Max Y

Max Z

Amplifier

0

0.02

0.01

0

0.05

0.01

Fan

0.01

0

0.01

0.01

0.05

0.01

Figure 3.17 Fan Assemblies Panel

3.

To create the mesh, go to Model → Generate Mesh. The Mesh control panel (Figure 3.18 (p. 57)) appears. The Mesh control panel can also be opened by clicking on the Generate mesh icon ( the shortcut menu.

56


) in


Figure 3.18 The Mesh control Panel

4.

As a first step, generate a coarse mesh by choosing Coarse in the Mesh parameters drop-down list in the Global tab, as shown in Figure 3.18 (p. 57). Click Generate to create a mesh.

Note If you have unchecked Allow minimum gap changes in the Misc tab, the Minimum separation warning will appear. This warning message appears when the minimum gap specified is more than 10% of the smallest sized object in the model. Please select Change value and mesh if the warning message pops up. 5.

To view the mesh, display a plane-cut view through the center of the cabinet, perpendicular to the fins (y-z plane).

6.

To create a plane-cut, follow these steps: a.

Click on the Display tab at the top of the Mesh control panel.

b.

Toggle on Display mesh and Cut plane.

c.

Under Plane location, set position to X plane through center in the drop-down list.

d.

Press Shift+X to orient to the positive X direction and view the newly created plane cut.

e.

Move the plane using the slider bar to see different views.

Make sure that the amplifier assembly is expanded and inspect the cells adjacent to the heat sink fins. Notice that the resolution is coarse (Figure 3.19 (p. 58)), with only a couple of cells between fins. As flow passes between the fins, boundary layers will grow and their degree of resolution Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

57

Chapter 3: RF Amplifier will dictate the accuracy of the simulation. It is advisable to have at least three to four cells between fins to adequately resolve the growth of boundary layers. Better resolution is achieved by refining the mesh. 7.

Choose Normal in the Mesh parameters drop-down list in the Settings tab. Click Generate and inspect the resulting mesh. Note that the number of cells between adjacent fins have increased (Figure 3.19 (p. 58)), providing better resolution of the boundary layers. You can display the mesh on selected objects or the cut plane by using the context menu in the graphics display window. To display the context menu, hold down the Shift key and press the right mouse button anywhere in the graphics display window. Select Display mesh or Display cut plane mesh in the context menu and the mesh will be displayed on selected objects or the cut plane will be displayed. It is also a good practice to select the Quality tab and review the Face Alignment, Quality, Volume, and Skewness. The histograms show the figure of merit (Face Alignment, Quality Ratio, Volume or Skewness) versus number of cells. By clicking on the bars that form the histogram, the particular cells with that value of quality are displayed in the graphics window.

Figure 3.19 Coarse and Fine Mesh

8.

Once you have explored the mesh quality, click Close to dismiss the Mesh control dialog box.

3.8. Step 5: Physical and Numerical Settings Before starting the solver, you will first review estimates of the Reynolds and Peclet numbers to check that the proper flow regime is being modeled. 1.

58

Check the values of the Reynolds and Peclet numbers.


Step 5: Physical and Numerical Settings Solution settings →

Basic settings

a.

Click the Reset button.

b.

Check the values printed to the Message window. The Reynolds and Peclet numbers are approximately 56282.6 and 39876.6 respectively, so the flow is turbulent. ANSYS Icepak recommends setting the flow regime to turbulent.

Note These values are only estimates, based on the current model setup. Actual values may vary, and may need to be verified, depending on your design. c. 2.

Click Accept to save the solver settings.

Enable turbulence modeling. Problem setup →

Basic parameters

a.

In the Basic parameters panel, select Turbulent as the Flow regime and keep the default Zero equation turbulence model.

b.

Turn on the Gravity vector option and make sure that gravity in the y-direction is -9.8 m/

Note Specifying gravity is important for the natural convection inside the RF amplifier. c.

Turn off radiation.

d.

Click Accept to save the new setting.

The panel appears as shown in Figure 3.20 (p. 60).


59


Figure 3.20 Basic parameters Panel

3.

Return to the Basic settings panel, specify the number of iterations as 300, click Reset and then Accept again.

4.

Set up the temperature limits for all the sources. Model → Power and temperature limits a.

Enter a new value of 60°C for Default temperature limit.

b.

Click on All to default.

c.

Click Apply and then click Accept to close the panel.

Note The default temperature limit is used during postprocessing to identify components that exceed their limits or components that are close to this limit. This value is not used to solve the problem.

60



3.9. Step 6: Save the Model ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the job you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your job file when it saves the model.) File → Save project

Note You can click the save button (

) in the File commands toolbar.


Create monitors.

Note It is good practice to monitor the solution progress for certain objects. Dragging the object in the model tree and placing it in the Points folder can accomplish this. a.

Drag device.2 and cabinet_default_side_maxY into the Points folder.

b.

Right mouse click on the cabinet_default_side_maxY in the Points folder.

c.

Select Edit and deselect temperature and activate Velocity (Figure 3.21 (p. 61)).

d.

Click Accept to accept the modifications and to dismiss the per-object's Modify point panel.

Figure 3.21 The Modify point Panel


61


Start the calculation. Solve → Run solution

Note Alternatively, you can click on the Run solution icon ( toolbar to display the Run solution panel.

) in the model and solve

a.

Enable Write overview of results when finished in the Results tab.

b.

Click on the Start solution button to start the solver. While iterating the solution, windows will appear showing convergence history, Figure 3.22 (p. 62) and Figure 3.23 (p. 63).

Figure 3.22 Convergence Plot

62



Figure 3.23 Monitor Plot

3.11. Step 8: Examine the Results Once the model has converged (Figure 3.22 (p. 62) and Figure 3.23 (p. 63)), ANSYS Icepak automatically generates a solution overview report. This report contains detailed information, such as object-based mass and volumetric flow rates, fan operating points, heat flows for objects with specified power, heat flows for objects that communicate with the ambient, maximum temperatures, and overall balances. Please carefully review the solution overview and note that the solution satisfies conservation of mass and energy (scroll to the bottom of the report). Also note the fan operating point. The solution overview is automatically saved and can be reopened from Report → Solution overview → Create. 1.

Compare the object temperature values for all sources with the temperature limits assigned. Post → Power and Temperature values The Power and temperature limit setup window appears. a.

Click Show too hot. The Power and Temperature limit setup show the default temperature limit and the resulting maximum temperature value for each source next to them. If an assembly is expanded in the model tree and if the resulting temperature of any object exceeds the temperature limit specified, ANSYS Icepak shows all the critical objects in red color.

b. 2.

Click Accept to close the dialog box.

Create object faces.

Note Ensure that the amplifier and fan assemblies are expanded, so that the fins are visible. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

63

Chapter 3: RF Amplifier a.

Press Shift+Z to orient the view in the positive Z direction.

b.

To create an object face, click the Object face icon (

c.

In the Object drop down list, specify heatsink.1 as the object and click Accept.

d.

Select Show contours and click the Parameters button (adjacent to show contours) to access the Object face contours edit dialog box.

e.

) in the shortcut toolbar.

i.

Select This object in the drop-box adjacent to Calculated to use the object-based range.

ii.

Click Done to close the Object face contours panel.

Click Done to close the Object face panel.

Note You can also create contours on heatsink.1 by selecting this object in the Model manager window and click the right mouse button to display the context menu. Select Create>Object face(s)>Separate and the Object face panel will appear. The Object face panel is displayed for that particular object.

Figure 3.24 Object Face Panel

Note Using the mouse, rotate the heat sink to examine the surface temperature distribution. Notice that the location of the devices is clearly discernible on the bottom of the heat sink. Also note that the devices get progressively hotter in the flow direction (Figure 3.25 (p. 65)).

64



Figure 3.25 Temperature Contours on the Face

Note Notice that face.1 has now appeared in the model tree in the Post processing folder. Right mouse click on face.1 and note that you can deactivate, edit, and delete it. You can move face.1 into the Inactive folder to deactivate it. Face.1 can be either deleted or reactivated by dragging it to Trash or to the Postprocessing folder, as well as with the right mouse click dialog. 3.

Create plane cuts. ) in the shortcut toolbar.

a.

To create a plane cut, click the Plane cut icon (

b.

Select the Set position as Point and normal and select Show vectors, as shown in the panel below. Enter PX, PY, and PZ, as well as NX, NY, and NZ according to Figure 3.26 (p. 66).


65


Figure 3.26 Plane Cut

c.

Click the Parameters button adjacent to Show vectors.

d.

Select Uniform in Display options group box and specify value as 5000. The Uniform option for the velocity will put the vectors uniformly in the 5000 data points.

e.

Select This object in the drop-box adjacent to Calculated and click Done to close the panel.

The vector plots are shown in the graphics window (Figure 3.27 (p. 67)).

66



Figure 3.27 Velocity Vectors on the Mid X Plane

Note Examining the vector plot, we can see that the flow pattern is symmetric, with two large recirculating zones adjacent to the fan. Zoom into the region directly in front of the fan and notice that two smaller recirculating zones exist in front of the hub. These local effects can be important when objects are close to the hub region.

Note You can move a plane cut through a model by pressing the Shift key, holding down the middle mouse button on the edge of a vector and dragging the plane cut through the model in the graphics display window. 4.

Create isosurfaces. a.

Click the Isosurface icon (



67

Chapter 3: RF Amplifier b.

Specify Temperature as the Variable, input a Value of 55°C, and select Show contours and click Parameters. In the Isosurface contours panel, select Smooth for Shading options and This object in the drop-box adjacent to Calculated. Click Done.

c.

Click Update in the Isosurface panel and notice that an isosurface has been placed around all of the sources, indicating that they have temperatures in excess of 55°C (Figure 3.28 (p. 68)).

Figure 3.28 Isosurface of Temperature 55°C

68

d.

Now, change the Variable to Speed and input a Value of 4. Click Update. Notice that the regions with velocities in excess of 4 m/s are now displayed (Figure 3.29 (p. 69)).

e.

Once you have examined the isosurface, delete or deactivate it using one of the previously described methods.



Figure 3.29 Isosurface of Speed 4 m/s

5.

Create variation plots. a.

Click the Variation plot icon (


Note Before creating the variation plots, please ensure that the amplifier assembly is expanded, so that the fins are visible. Next, press Shift+Z to orient the view in the positive Z direction. b.

Within the variation plot dialog box, complete the following: i.

Specify the Variable as UY.

ii.

Click the From screen button.

iii.

Click the left mouse button on the center on the heat sink fins.

iv.

Click Create.

c.

An xy-plot of UY velocity versus z-coordinate should now be visible. Toggle on the Symbols button and notice that the velocity profile across the solution domain is now represented with dots at the postprocessing locations. Notice that ANSYS Icepak has created a line that is colored locally according to the UY velocity magnitude.

d.

Save the xy-plot. i.

Click the Save button at the bottom of the Variation of UY plot window.

ii.

Enter a file name in the resulting Save curve dialog box.

iii.

Click Save to save the file in the model folder.


69


3.12. Step 9: Summary In this tutorial, you have learned about the usage of enclosure, PCB, source and heat sink objects. The use of ANSYS Icepak's fan library and search tool has been explained. Meshing of assemblies and postprocessing features in ANSYS Icepak were also explained.

70


Chapter 4: Use of Parameterization to Optimize Fan Location 4.1. Introduction The purpose of this tutorial is to demonstrate the following ANSYS Icepak features with the help of a small system level model. In this tutorial you will learn how to: •

Use network blocks as one way of modeling packages.

•

Specify contact resistance using side specifications of a block object.

•

Define a variable as a parameter and solve the parametric trials.

•

Specify fan curves.

•

Use local coordinate systems.

•

Generate a summary report for multiple solutions.

4.2. Prerequisites This tutorial assumes that you have little experience with ANSYS Icepak, but that you are generally familiar with the interface. If you are not, please review Sample Session in the Icepak User's Guide and the tutorial "Finned Heat Sink" of this guide as some of the steps that were discussed in these tutorials will not be repeated here.

4.3. Problem Description The system level model consists of a series of IC chips on a PCB. A fan is used for forced convection cooling of the power dissipating devices. A bonded fin extruded heat sink with eight 0.008 m thick fins is attached to the IC chips. The fan flow rate is defined by a nonlinear fan curve. The system also consists of a perforated thin grille. A study is carried out for the optimum location of the fan by using the parameterization feature in ANSYS Icepak.


71

Chapter 4: Use of Parameterization to Optimize Fan Location

Figure 4.1 Schematic of the Geometry



2.

Click New in the Welcome to Icepak panel to start a new ANSYS Icepak project.

3.

Specify a name for your project (i.e., fan_locations) and click Create. ANSYS Icepak creates a default cabinet with the dimensions 1 m × 1 m × 1 m, and displays the cabinet in the graphics window. This cabinet will be modified in the next section.

4.5. Step 2: Build the Model 1.

Resize the default cabinet. The cabinet forms the boundary of your computational model. Press the isometric view icon ( ) for a 3D view. Select Cabinet in the Model manager window and enter the location values as shown in the panel below. The geometry window can be found in the lower right hand corner of the GUI.

72



Extra The previous tutorial showed you how to enter these values in the Cabinet panel. 2.

Create the Fan. Click on the Create fans icon ( ) in the object toolbar next to the model tree to create a 2D intake circular fan on one side of the cabinet. Change the plane to yz and enter the location values shown in the geometry window below:

•

Defining a parameter for multiple trials. One of the objectives of this exercise is to parameterize the location of the fan. To create a parametric variable in ANSYS Icepak, input a $ sign followed by the variable name. Thus, to create the parametric variable “zc,” type $zc in the zC box in addition to the other location values, and click Apply. When ANSYS Icepak asks you for an initial value of “zc", enter an initial value of 0.1, and click Done.

Figure 4.2 The Param value Panel

We will now set the physical properties that will define the fan behavior: a.

Edit the fan object and go to Properties tab.

b.

In the Properties tab, retain the selection of Intake for Fan type and select Non-linear in the Fan flow tab.

c.

Enter the characteristic curve by clicking on the Edit button and selecting Text Editor in the dropdown list in the Non-linear curve group box.


73


Figure 4.3 The Fans Panel (Properties Tab)

d.

First change the units of the volume flow rate and pressure according to the units in Table 4.1: Values for the Curve Specification Panel (p. 74) and enter the values in pairs with a space between them in the Curve specification panel.

Table 4.1 Values for the Curve Specification Panel

74

Volume Flow (CFM)

Pressure (in_water)

0

0.42

20

0.28

40

0.2

60

0.14

80

0.04

90

0.0

e.

Click Accept to close the form.

f.

Select the Edit button again in the Non-linear curve group box and click on Graph Editor in the drop-down list to view the fan curve (Figure 4.4 (p. 75) ).



Figure 4.4 The Fan Curve Panel

g.

Click Done to close the Fan curve panel.

h.

In the Properties tab, give the fan an RPM of 4000 in the Swirl tab, located next to the Fan flow tab.

i.

In the Properties tab, give the fan an Operating RPM of 2000 in the Options tab, located next to the Swirl tab.

Note The fan curve defined originally for RPM=4000 will be automatically scaled according to the fan laws for the new operating RPM=2000. The swirl RPM(4000) can also be used to compute the swirl factor. j.

Click Update and Done to close the fan window.

Now the model looks as shown in Figure 4.5 (p. 76).


75


Figure 4.5 Model with Fan

Extra The shading of the fan object can be changed by changing the Shading option under the Info tab to change the shading of just that object, or by leaving it as default and changing the default shading option by going to View → Default shading to change the shading of all objects that have default shading selected. 3.

Set up a Grille. a.

Click on the Create grille icon ( ) for creating a new grille, set its plane to yz. Then, using the morph faces option move the grille to the max-X face of the cabinet. Step by step instructions on how to use the morph faces option is presented in the graphics display window after clicking the icon ( ) or you can also resize the grille as shown in the panel:

b.

We will now define properties for the grill by clicking the Properties tab.

Note This is a 50% open perforated thin grille.

76

i.

Under velocity loss coefficient, retain the default selection of Automatic.

ii.

Specify a Free area ratio of 0.5.


Step 2: Build the Model iii.

Retain Perforated thin vent for the Resistance type.

iv.

Click Update and then Done to close the panel.

For more details on loss coefficient data, please refer to Handbook of Hydraulic Resistance, by I. E. Idelchick. The model looks as shown in Figure 4.6 (p. 77).

Figure 4.6 Model with Fan and Grill

4.

Set up a wall.

Note The model includes a 0.01 m thick PCB that touches and covers the entire min-Y floor of the cabinet. The PCB is exposed to the outside with a known heat flux of 20 W/m2. In order to take in consideration the heat flux, we will use a wall object to simulate the PCB. a.

Click on the Create walls icon ( ) to create a new wall. We will define the geometry and physical parameters for the wall object: i.

Make the plane xz.

ii.

Use the morph faces icon ( ) from the model toolbar so that the wall object covers the entire min-Y floor of the cabinet.

iii.

Edit the Wall object and go to Properties tab.


77

Chapter 4: Use of Parameterization to Optimize Fan Location iv.

In the Material group box, set the Wall thickness to 0.01 m and the Solid material to FR4.

v.

In the Thermal specification group box, specify a Heat flux of 20 W/m2.

vi.

Click Update and then Done to close the panel.

After creating the wall, the model looks as shown in Figure 4.7 (p. 78).

Figure 4.7 Model with Wall Added

5.

Create blocks. In this step, we will create several types of blocks to represent different physics. •

Creation of Solid Blocks Now, we will create four blocks that dissipate 5 W each and have a contact resistance of 0.005 C/W on their bottom faces.

78

a.

Create a new block ( ) , and retain the type as solid and geometry as Prism. Enter the location values shown in the panel below:

b.

Edit the block and specify the following in the Properties tab:


Step 2: Build the Model i.

In the Surface specification group box, click on the Individual sides check box and click Edit (Figure 4.8 (p. 79)). A.

Select MinY and toggle on Thermal properties and Resistance.

B.

Under Thermal condition, retain the selection of Fixed heat and Total power of 0 W.

C.

Select Thermal resistance from the drop-down menu next to Resistance.

D.

Set Thermal resistance to 0.005 C/W and click Accept.

E.

Click Accept to close the panel.

Figure 4.8 The Individual side specification

c.

ii.

In the Thermal specification group box in the Properties tab, retain the selection of default for Solid Material (you can also select Al-Extruded which is the default).

iii.

Set Total Power to 5 W.

iv.

Click Update and Done to close the panel.

Next, make three copies of this block with an X offset of 0.08 m.

Extra The previous tutorial showed you how to make a copy of an object.


79


Figure 4.9 Creation of Solid Blocks

•

Creation of Network blocks Let us now create four IC chips in the form of network blocks. To create a network block, we will create a Block object and change the block type to Network in the Properties tab. Each network block will have junction-to-board, junction-to-case, and junction-to-sides thermal resistances. The values of these resistances are known a priori. a.

Add a new block, and position it as shown in the panel below:

b.

Edit the block to change the properties of this block; –

Ensure that the Block type is set to Network.

–

Toggle on Star Network. → Enter the Network parameters as shown in Figure 4.10 (p. 81).

80



Figure 4.10 The Properties Panel

c. •

Now make three copies of this network block with an X offset of 0.08 m. This finishes the creation of the network blocks.

Creation of a Hollow Block

Note Finally, to cut out a section of the cabinet from the computational domain, we can create a hollow block. This represents a region that does not affect heat transfer, but alters the flow patterns. a.

Create a new Block; make sure it is a hollow.

b.

In the Geometry tab, create a new Local coord system.

c.

Select Create new from the Local coord system: drop-down list.

d.

Enter X offset = 0.1, Y offset = 0, Z offset = 0.

e.

Click Accept. This is just to demonstrate the use of local coordinate system.

f.

Further, size the block as follows:


81


6.

Now we will create the detailed heat sink. The heat sink base acts as a heat spreader for all the chips. a.

Click on the Create heat sinks icon ( in the following table:

) and edit it, entering its location and properties as shown

Table 4.2 Heatsink Properties Geometry Plane:

xz

xS/xE:

0.02/0.34

yS/yE:

0.03/—

zS/zE:

0.1/0.23

Base height:

0.01 m

Overall height:

0.06 m

Properties Type:

Detailed

Flow Direction:

X

Detailed Fin type:

Bonded fin

Fin setup Fin spec:

Count/thickness

Count:

8

Thickness:

0.008 m

Flow/thermal data Fin material:

default

Base material:

Cu-Pure

Interface

b.

82

Fin bonding:

Click the Edit button

Effective thickness:

0.0002 m

Solid material:

default

Click Update and Done. This completes the model building process. The complete model should look like that shown in Figure 4.11 (p. 83).


Step 3: Creating Separately Meshed Assemblies

Figure 4.11 Final Model

4.6. Step 3: Creating Separately Meshed Assemblies One of the key aspects of modeling is to use an adequate mesh for the model. We need to have a fine mesh in the areas where temperature gradients are high or flow is turning. Having a too coarse of a mesh will not give you accurate results and at the same time, too fine a mesh may lead to longer run times. The best option is to explore the model carefully and look for opportunities to reduce mesh counts in the areas where the gradients are not steep. Creating non-conformal assemblies gives required accuracy along with reduced mesh count. Select set of objects to create assemblies. Also decide suitable slack values for assembly bounding box. Your selection can be reviewed in the section below where we will create non-conformal meshed assemblies. We will now create two non-conformal meshed assemblies. 1.

To create the first assembly, first highlight all the blocks (except the hollow block) and the heat sink object in the model tree, then right-click on them and choose Create and then Assembly.

2.

Right-click and select Rename from the menu. Rename the assembly, as Heatsink-packages-asy.

3.

To build the “bounding box" for the assembly called Heatsink-packages-asy, double-click on it to edit the assembly.

4.

In the Meshing tab of the Assemblies panel, toggle on Mesh separately, and then set the Slack parameters as the following:

Table 4.3 Slack Values for Heatsink-packages-asy Assembly Min X

0.005 m

Max X

0.015 m


83

Chapter 4: Use of Parameterization to Optimize Fan Location Min Y

0.005 m

Max Y

0.005 m

Min Z

0.005 m

Max Z

0.005 m

Note •

5.

Note that for the Heatsink-packages-asy, we have set a bounding box that is 0.005 m bigger than the assembly at five sides except Max X where the slack is defined higher (0.015 m) to capture the wake region of the flow.

Click Update and Done to complete the bounding box specifications for the assembly. Following the same procedure above, create one more assembly for the fan object (name it Fanasy). Use the following table to assign the Slack values for the Fan-asy assembly.

Table 4.4 Slack Values for Fan-asy Assembly Min X

0m

Max X

0.005 m

Min Y

0.002 m

Max Y

0.002 m

Min Z

0.002 m

Max Z

0.002 m

4.7. Step 4: Generate a Mesh To generate the mesh: 1.

Open the Mesh control panel, keep the default values for the mesh settings and ensure that Mesh assemblies separately is on.

2.

Click Generate. You will get a warning about minimum separation if the Allow minimum gap changes option is unchecked in the Misc tab.

Extra This warning appears because the Minimum gap (separation) which is like a tolerance setting for the mesher is larger than 10% of the smallest feature in the model. When there are objects smaller than the mesher tolerance, those objects will not be meshed correctly. To avoid this we use the change value and mesh option which modifies the minimum gap to 10% of the smallest object. This option is used for this particular tutorial and may not be applicable all the time. As separation setting is a useful tool designed to avoid unnecessary mesh due to inadvertent misalignments in the model (without modifying the geometry), we may use other options suitable to the model. 3.

Click on Change value and mesh.

4.

Examine the mesh by taking plane cuts; examine Face alignment and Quality ratio.

5.

Go to the Mesh control panel, click on the Display and Quality tabs to examine the mesh.

4.8. Step 5: Setting up the Multiple Trials Before we start solving the model, we will set up the parametric trials for the fan location parameter “zc". 84


Step 5: Setting up the Multiple Trials 1.

Go to the Solve menu and select Define trials. a.

The Parameters and optimization panel pops up.

b.

Toggle on Parametric trials in the Setup tab.

c.

Select the Design variables tab and next to Discrete values, type 0.165 following 0.1, separated by a space as shown in the Figure 4.12 (p. 85):

Figure 4.12 The Parameters and optimization Panel- Design variables tab

d.

Click Apply.

Note After the first trial has been completed, ANSYS Icepak has the options of starting the following trial(s) from the default initial conditions specified in Problem setup panel, or from the solution(s) of the trial run(s) that have completed.


85

Chapter 4: Use of Parameterization to Optimize Fan Location For this model, next go to the Trials tab and ensure the Restart ID is blank for the 2nd trial as shown in Figure 4.13 (p. 86). This instructs ANSYS Icepak to start the 2nd run from the default initial conditions. 2.

Click on Reset button and select Values to use the base names for trial naming.

Figure 4.13 The Parameters and optimization Panel- Trials tab

3.

Click Done to close the Parameters and optimization panel.

4.9. Step 6: Creating Monitor Points Create two monitor points by dragging and dropping (block.1 and grille.1) into the Points folder to monitor the velocity in the grille and the temperature in one of the solid blocks. The variables to be monitored can be easily changed by selecting them in the Monitor points panel.

86


Step 7: Physical and Numerical Setting

Figure 4.14 The Modify point Panel

4.10. Step 7: Physical and Numerical Setting Set up the basic problem parameters to solve the flow and energy equations, and use the Zero equation turbulence model. Since natural convection is not involved, there is no need to turn on the Gravity vector. Problem setup →

Basic parameters


87


Figure 4.15 The Basic parameters Panel

Solution settings →

Basic settings

Enter 200 in the Number of iterations field in the Basic settings panel.

Figure 4.16 The Basic settings Panel

4.11. Step 8: Save the Model ANSYS Icepak saves the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the job you saved and continue your analysis in a future ANSYS

88


Step 9: Calculate a Solution Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your job file when it saves the model.) File → Save project Alternatively, click the save button (

) in the file commands toolbar.

4.12. Step 9: Calculate a Solution The Solve panel is used for single trials only; therefore, the solution can only be calculated from the Parameters and optimization panel. Open the Parameters and optimization panel and click Run to calculate a solution for both trials.

Figure 4.17 The Parameters and optimization Panel- Trials tab


89


4.13. Step 10: Examine the Results Once the solutions are done, click on the Post menu and select Load solution ID. Select the solution that corresponds to the first (parametric) run, i.e., zc = 0.1. If you want to view objects inside the assemblies, you can open all the model nodes by right mouse clicking Model in the Model manager window and selecting Expand all. Use the various postprocessing features available in ANSYS Icepak to display your solution. A description of how to generate plane cut and object face views can be found in Step 7: Examine the Results of the Finned Heat Sink tutorial. In particular, use the following views: 1.

Plane cut panel to display the velocity vectors on a plane through the cabinet

Figure 4.18 Trial 1 Vector Plots at Constant Z Plane Cut

90



Figure 4.19 Trial 2 Vector Plots at Constant Z Plane Cut

Important To view the 2nd parametric run, click on the Post menu and select Load solution ID. Select the solution that corresponds to the second parametric run, i.e., zc = 0.165. The graphics display window updates automatically. 2.

Object face panel to display temperature contours on wall.1 and on all blocks


91


Figure 4.20 Trial 1 Temperature Contours on Blocks and PCB (wall.1)

Figure 4.21 Trial 2 Temperature Contours on Blocks and PCB (wall.1)

3.

Object face panel to display temperature contours on the faces of the PCB (wall.1) and on all blocks

4.

Surface probe panel to display the temperature values at a particular point

92


Step 13: Additional Exercise to Model Higher Altitude Effect Examine the solution sets of both runs. You will find that, in the second run, the maximum temperature is lower than in the first run and that the network blocks are the hottest objects inside the cabinet. The second trial has the fan located at zC= 0.165 which is closer to the heat sink location. This increases the flow velocity over the heat sinks and thus increases the convective heat transfer coefficient, which leads to more heat transfer from the fins (blocks) and thus reduces the maximum temperature.

4.14. Step 11: Reports 1.

Overview Report At the end of the runs, ANSYS Icepak automatically displays an overview report because you selected Write overview of results when finished in the Solve panel. This report has: •

fan operating point

•

volume flow rate through the grille

•

heat flow from the chips

•

network junction temperatures

•

heat flows for the wall and the grille.

Examine these results. Go to the Report menu and then select Solution overview and click on View to display the desired overview report. 2.

Summary Report You can also create a single summary report containing the results of all the trial runs completed. Go to the Solve menu and select Define report. In the Define summary report panel, under ID pattern, enter the default filter, "*", which picks all the available solution IDs. Press new and hold down Ctrl and select block.1, block.1.1., block.2, block.2.1, and block.3 from the drop-down menu under Objects, and then press Write. Verify that the second trial gives lower temperatures.

4.15. Step 12: Summary In this tutorial, you learned how to set up and solve parametric trials, specify fan curves and create a new local coordinate system. The use of network blocks to model packages has been demonstrated as well as how to specify contact resistance using side specifications of a block object. You also learned how to generate a summary report for multiple solutions.

4.16. Step 13: Additional Exercise to Model Higher Altitude Effect The final model can also be used to model the effects of higher altitudes. In order to model this correctly, new air properties at the particular altitude need to be defined and assigned to the default fluid. The density of air is the most affected property and gets lower as you go higher in altitude. The data for air properties at a different altitude is presented in many handbooks and may even include temperature change affect with it. For an altitude of 3000 m, we can select the available library material Air@3000m. Please note that a custom material having any properties can be created and stored in the material library to use in any project.


93


Then, select Problem setup → Basic Parameters and assign the new air material to the default fluid.

In addition, in the Fan flow section of the Fans Properties tab, all the defined fan curves need to be modified by multiplying the existing data with the ratio of densities (the density of air at 3000 m / the density of air at 0 m), which in this case is smaller than 1. Finally, the model is ready to be run to account for the effects of higher altitude.

94


Step 13: Additional Exercise to Model Higher Altitude Effect


95

96


Chapter 5: Cold-Plate Model with Non-Conformal Meshing 5.1. Introduction This tutorial demonstrates how to model a cold-plate using ANSYS Icepak. In this tutorial you will learn how to: •

Use the priorities of different objects to model complex shapes in ANSYS Icepak.

•

Use multiple fluids in a model.

5.2. Prerequisites This tutorial assumes that you have reviewed Sample Session in the Icepak User's Guide and Tutorials "Finned Heat Sink" and "RF Amplifier" of this guide.

5.3. Problem Description The model consists of a cold-plate, where the cold-plate fluid is transporting a significant fraction of the heat from two plates mounted on either side of it. The natural convection in the external air is also instrumental in some heat transfer. The model setup is shown in Figure 5.1 (p. 101). The objective of this exercise is to illustrate the use of two different fluids in ANSYS Icepak. The model includes two heated plates, cooled by water circulating inside the cold-plate cavity, as well as by air driven by natural convection externally. Separately meshed assemblies will be employed to reduce the overall mesh count in the domain. The model will be constructed using the default metric unit system.

5.4. Step 1: Create a New Project Create a new project called cold-plate.

5.5. Step 2: Build the Model Construct the cabinet and all the other objects according to the following specifications. Note that during the model building, you may use the alignment tools. Please remember that you can align the face, edge and vertex of one object with another. For example, you could align the bottom face of the cylinders to the cabinet (see Figure 5.1 (p. 101)). You may also use the align tools to create the openings on the cold-plate inlet and outlet regions. •

Cabinet Enter the following start and end locations for the cabinet

Table 5.1 Cabinet Start and End Values xS

0.0 m

xE

0.4 m


97

Chapter 5: Cold-Plate Model with Non-Conformal Meshing

•

yS

0.0 m

yE

0.3 m

zS

0.0 m

zE

0.2 m

Blocks Create a solid block, block.1, and a fluid block, block.2 with the following specifications. The table below also gives the geometrical region where block.2 is located to have the material properties of the fluid.

Table 5.2 block.1 and block.2 Specifications block.1

xS

0.05 m

xE

0.35 m

Geometry: Prism

yS

0.08 m

yE

0.22 m

Block type: Solid

zS

0.07 m

zE

0.13 m

block.2

xS

0.06 m

xE

0.34 m

Geometry: Prism

yS

0.09 m

yE

0.21 m

Block type: Fluid

zS

0.08 m

zE

0.12 m

Solid material: Al-Extruded

Fluid material: Water (@280K) Because block.2 is being created after block.1, it will have a higher relative meshing priority.

Note Because Al-Extruded is set as the Default solid in the Defaults tab of the Basic parameters panel, you can then leave the material selection as default while creating the object instead of selecting the material each time when an object is being created. Next, we will create some cylindrical blocks. While editing cylindrical blocks, first select the block shape as cylinder, then select the desired plane and finally enter the dimensions.

Table 5.3 Cylindrical Block Specifications Object

xC

yC

zC

Height

Radius

IRadius

Specifications

block.3

0.1 m

0.0 m

0.1 m

0.09 m

0.015 m

0.0 m

Block type: Solid

Geometry: Cylinder

Solid material: Al-Extruded

Plane: X-Z block.4

0.3 m

0.0 m

0.1 m

0.09 m

0.015 m

0.0 m

Geometry: Cylinder

Block type:Solid Solid material: Al-Extruded

Plane: X-Z block.5

98

0.1 m

0.0 m

0.1 m

0.09 m

0.01 m

0.0 m

Block type: Fluid


Step 2: Build the Model Object

xC

yC

zC

Height

Radius

IRadius

Geometry: Cylinder

Specifications Fluid material: Water(@280K)

Plane: X-Z block.6

0.3 m

0.0 m

0.1 m

0.09 m

0.01 m

0.0 m

Block type: Fluid

Geometry: Cylinder

Fluid Material: Water(@280K)

Plane: X-Z Because the fluid blocks, block.5 and block.6, are created after the solid blocks, they will have higher relative meshing priorities.

Note An alternative way to build the cylinders would be to create the solid block, block.3, and then the fluid block, block.5, group these together, and then copy them with an offset of 0.2 in the x direction. Note that the naming of the cylinders will not be consistent with the tutorial. However, you could rename the objects to their corresponding names in the tutorial by right mouse clicking each copied object in the Model tree and selecting Rename. •

Plates

Table 5.4 Plate Specifications Object

Specifications

plate.1

xS

0.07 m

xE

0.33 m

Solid material:

Geometry: Rectangular

yS

0.1 m

yE

0.2 m

Al-Extruded

Plane: X-Y

zS

0.06 m

zE

—

Power: 200W

plate.2

xS

0.07 m

xE

0.33 m

Solid material:


yS

0.1 m

yE

0.2 m

Al-Extruded

Plane: X-Y

zS

0.13 m

zE

—

Power: 200W

Thermal model: Conducting thick: 0.01 m

Thermal model: Conducting thick: 0.01 m

Note Note: An alternative way to create plate.2 would be to copy plate.1 with a Z offset of 0.07m. •

Openings


99

Chapter 5: Cold-Plate Model with Non-Conformal Meshing The openings at the liquid inflow and outflow regions of the cold-plate are

Table 5.5 Opening Specifications Object

xC

yC

zC

Radius

opening.1 (outlet opening)

0.1 m

0m

0.1 m

0.01 m

0.3 m

0m

0.1 m

0.01 m

Specifications

Type: Free Geometry: Circular Plane: X-Z opening.2 (inlet opening)

Y velocity = 0.2 m/s

Type: Free Geometry: Circular Plane: X-Z

Note You could also have made a copy of outlet opening (opening.1) with an X offset of 0.2 to create inlet opening (opening.2). The openings at the cabinet boundary for external air natural convection are

Table 5.6 Openings at Cabinet Boundary Specifications Object opening.3

xS

0.4 m

xE

—

Type: Free

yS

0.0 m

yE

0.3 m


zS

0.2 m

zE

0.0 m

opening.4

xS

0.0 m

xE

—

Type: Free

yS

0.0 m

yE

0.3 m


zS

0.2 m

zE

0.0 m

Plane:Y-Z

Plane:Y-Z

Note Instead of creating the openings, opening.3 and opening.4 above, you could have edited the cabinet and changed the wall type on these two faces to openings. The final model should appear similar to the drawing shown in Figure 5.1 (p. 101).

100


Step 3: Create a Separately Meshed Assembly

Figure 5.1 The cold-plate Model

Note Figure 5.1 (p. 101) has changed the opacity, shading and color of some objects to make the objects easier to see.

5.6. Step 3: Create a Separately Meshed Assembly To create a separately meshed assembly, highlight all the objects in the model tree other than the cabinet, opening.3, and opening.4. Right mouse click on them and choose Create and then Assembly. To enable separate meshing for the assembly, double-click on assembly.1 to edit the assembly. Under the Meshing tab, toggle on the Mesh separately button and then enter the slack values as follows:

Table 5.7 Slack Values for Mesh Assembly Min X

0.01 m

Max X

0.01 m

Min Y

0.0 m

Max Y

0.01 m

Min Z

0.01 m

Max Z

0.01 m

The bounding box of the assembly is larger than the original assembly by 0.01 m on five sides. The slack value for the min Y side of the assembly is set to be 0 m, since the min Y side of the assembly is at the bottom surface of the cabinet. Click Update and Done to complete editing the separately meshed assembly.


101


5.7. Step 4: Generate a Mesh Open the Mesh control panel, make sure that the Mesh assemblies separately option is toggled on and Normal mesh is selected for Mesh parameters. Change the Max size ratio to 4 and keep the other global default mesh settings. The mesh needs to be refined for the inner prismatic fluid block (block.2). In the Misc tab, make sure Allow minimum gap changes is checked. Then toggle on Object params and click Edit in the Local tab. Choose block.2 and check Use per-object parameters and enter 30, 16, and 10 respectively for the X, Y and Z counts for the mesh in the fluid block, as shown in the following figure. Click Done to close the Per-object meshing parameters panel.

Click Generate to mesh the model. Visualize the mesh at plane cuts and surface displays from the Display tab. 102



5.8. Step 5: Physical and Numerical Settings A calculation of the Reynolds number shows that the problem is turbulent. To set up turbulent flow, go to Problem setup → Basic parameters and choose the Zero equation turbulence model for the Flow regime in the General setup tab. Gravity acts in the negative x direction in this problem. To setup the effects of gravity, toggle on the Gravity vector in the General setup tab. Enter the new values for the gravity vector as x = -9.80665, y = 0 and z = 0. Now go to the Transient setup tab and set an initial X velocity of 0.005 m/s in the x direction. Accept all other defaults in the Basic parameters panel. These are shown in Figure 5.2 (p. 103).

Figure 5.2 Switching on Gravity and Turbulent Flow

Note For steady state natural convection cases, setting a small initial velocity opposite to the gravity vector direction is advised as this assists with the initial convergence of the model. For cases where there is no forced convection, clicking on Reset in the Solution settings → Basic settings menu automatically sets a small initial velocity in the direction opposite to the gravity vector. This may not be necessary in this model though, because the flow will be forced through the cold plate. We will have mixed convection (forced + natural) heat transfer mode.


103


Figure 5.3 Basic and Advanced Solver Settings

Select the Basic settings panel from the Solution settings branch of the tree and set the Number of iterations to 300. Go to Advanced settings and make sure Under-relaxation factors for Pressure, Momentum, and Temperature are 0.3, 0.7, and 1.0, respectively. Change the Stabilization under Joule heating potential to BCGSTAB, and select Double for the Precision drop-down list. The recommended basic settings and advanced solver setup for this model are shown in Figure 5.3 (p. 104). Add three monitor points to the Points folder, one to monitor the velocity at the center of the opening.1 (outlet opening), and two to monitor the temperature at the center of block.2 and plate.2, respectively. The easiest way to create them is to select the objects from the Model tree and then drag them to the Points folder of the tree. ANSYS Icepak will then automatically monitor values at the centers of these objects. The default setting is to monitor Temperature. To change this, double click on the object under the Points folder, and choose which variables to monitor at that location.

104



5.9. Step 6: Save the Model ANSYS Icepak automatically saves the model for you before it starts the calculation, but it is a good idea to save the model after the model building and meshing is complete. File → Save project Alternatively, click the save button (

) in the file commands toolbar.

5.10. Step 7: Calculate a Solution Select the Solve menu and click on Run solution. In the Solve panel, under the Results tab toggle on Write overview of results when finished, and then click Start solution.

5.11. Step 8: Examine the Results Please review the solution overview report created to ensure that mass (volume) flow rate and energy balances are satisfied. To postprocess the results, create the following object face and plane cut objects:

Table 5.8 Object Face and Plane Cut Specifications Object

Specifications/Display Attributes

Description

face.1

Object: all blocks (select the blocks using Object-face view of temperature on all the blocks. the Ctrl key or the Shift key and the left What is the maximum temperature? mouse button) Show contours/Parameters Contours of: Temperature Contours options: Solid fill and Smooth Color levels: Calculated/Global limits

cut.1

Set position: Z plane through center Show vectors/ Parameters Color by: Velocity Magnitude

Observation: Water is circulating through the internal channel, providing most of the cooling for the model. On the outside, air flows over the system by natural convection.

Color levels: Calculated/Global limits face.2

Objects: opening.1 (outlet) and opening.2 (inlet) Show particle traces/ Parameters

Observe the flow pattern from inlet opening to outlet opening passing through the cold plate. Animate the particle traces.

Variable: Speed Display options: Uniform: 30 Particle options: Keep all the defaults Style: Dye trace (Width = 1) and Particles (Radius = 2) Color levels: Calculated/ This Object cut.2

Set position: X plane through center Show particle traces/ Parameters

Observe the flow pattern in (+) X direction. Animate the particle traces.


105

Chapter 5: Cold-Plate Model with Non-Conformal Meshing Variable: Speed Display options: Uniform: 30 Particle options: Keep all the defaults Style: Dye trace (Width = 1) and Particles (Radius = 2) Color levels: Calculated/ This Object cut.3

Set position: Y plane through center Show contours of Temperature.

Due to the nature of the problem, the temperature distribution should be symmetric around the central xy plane. Please verify this in the solution.

You can save the postprocessing objects that you just created by clicking Save post objects to file option in the Post menu. ANSYS Icepak will save these objects under the file named post_objects in the Icepak project folder. If you do not save them at this stage, they will not be automatically saved for future retrieval when you end the current ANSYS Icepak session.

5.12. Step 9: Summary In this problem, we modeled a cold-plate that included two heat plates cooled by water circulating inside the cold-plate cavity as well as air driven by natural convection externally. This exercise also demonstrated how to use the priorities of different objects to model complex shapes in ANSYS Icepak and the use of multiple fluids in a model.

5.13. Step 10: Additional Exercise To see the cooling capacity (effectiveness) of water, you may run the same model by replacing the fluid properties (of the fluid blocks) by Glycol, i.e., make all the fluid blocks air blocks. You should see a significant increase in the maximum temperature.

106


Chapter 6: Heat-Pipe Modeling and Nested Non-Conformal Meshing 6.1. Introduction This tutorial demonstrates how to model simple heat pipes and an active heat sink using ANSYS Icepak. In this tutorial, you will learn how to: •

Create orthotropic solid materials.

•

Use those materials to simulate a heat-pipe in a system.

•

Use of copy mirror and copy translate functions.

•

Create nested non-conformal assemblies.

6.2. Prerequisites This tutorial assumes that you have little experience with ANSYS Icepak, but that you are generally familiar with the interface. If you are not, please review Sample Session in the Icepak User's Guide and the tutorial "Finned Heat Sink" of this guide. Some steps in the setup and solution procedure will not be shown explicitly.

6.3. Problem Description Heat pipes are used to transport heat from a heat source area (where there is limited space for heat dissipation) to a place where it is dissipated. The objective of this exercise is not to model the detailed physics inside a heat pipe. Instead, we will model a heat pipe by using a series of cylindrical solid blocks that connect the heat source to an air-cooled heat sink. These blocks will have an orthotropic conductivity with very large conductivity in the pipe axis direction where the heat is carried away. The model will be constructed using the default metric unit system. We will also make use of nested non-conformal meshing using assemblies to reduce the cell count in the model.


107

Chapter 6: Heat-Pipe Modeling and Nested Non-Conformal Meshing

Figure 6.1 Heat-pipe Tutorial Base Model


Copy the file ICEPAK_ROOT/tutorials/heat-pipe/heat-pipe-nested-NC.tzr to your working directory. You must replace by the full path name of the directory where ANSYS Icepak is installed on your computer system.

2.

Start ANSYS Icepak, as described in Starting ANSYS Icepak in the Icepak User's Guide.

Note ANSYS Icepak can be started in ANSYS Workbench using the import .tzr feature or it can be opened as a stand-alone product.

108


Step 2: Build the Model 3.

Click Unpack in the Welcome to Icepak panel.

4.

In the File selection panel, select the packed project file heat-pipe-nested-NC.tzr and click Open.

5.

In the Location for the unpacked project file selection dialog, select a directory where you would like to place the packed project file, enter a project name in the New project text field then click Unpack.

6.5. Step 2: Build the Model Note In ANSYS Icepak, the packed file feature compresses a model to the files needed to build, mesh and run the model (job, model and problem files). In many of the tutorials, part of the model is already created and packed to speed up the learning process. The model originally has three blocks and only block.1 has an assigned power (25 W). The model also has one fan and one grille. Next, we will build a heat sink in the area of the fan, grille and the heat pipe system to connect block.1 to the heat sink. 1.

Create materials utilizing ANSYS Icepak's orthotropic material conductivity feature. The idea is to have a material that has very high conductivity in the pipe heat removal directions but normal conductivity in the other directions. •

Click on the material icon (

•

Click on the material name with the right mouse button and select Edit or double click the material name to open the Edit panel.

•

Go to the Properties tab and make sure to toggle on Material type to be Solid and set the Conductivity type to be Orthotropic from the drop-down list.

•

Deselect the Edit check box next to conductivity and create the following materials with orthotropic conductivity properties using the template in Figure 6.2 (p. 110).

) in the object toolbar for each new material to be created.


109


Figure 6.2 Orthotropic Material Properties

Table 6.1 Orthotropic Properties Name

Nominal Conductivity

Orthotropic multiplier

material.1

20000

X=1

Y = 0.005

Z = 0.005

material.2

20000

X = 0.005

Y=1

Z = 0.005

material.3

20000

X=1

Y=1

Z = 0.005

The above materials have the so-called orthotropic conductivity, which is not uniform in all three directions. The effective conductivity in each direction is equal to the Nominal conductivity multiplied by the orthotropic multiplier in that direction. 2.

After creating these heat pipe materials, we build the heat pipe made of cylindrical blocks and square joints. •

Create five block objects.

•

Use the values in the following table (be sure to note the geometry)

Table 6.2 Block Specifications Object

Geometry

xC

yC

zC

Height

Radius

IRadius

Specifications

pipe1

Shape: Cylinder

0.05 m

0.11 m

0.1 m

0.245 m

0.01 m

0.0 m

Type: Solid

Plane: Y-Z

110


Solid material: material.1

Step 2: Build the Model Object

Geometry

xC

yC

zC

Height

Radius

IRadius

Specifications

pipe2

Shape: Cylinder

0.325 m

0.365 m

0.1 m

0.267 m

0.01 m

0.0 m

Type: Solid

Plane: Y-Z pipe3


Shape: Cylinder

0.31 m

0.125 m

0.1 m

0.225 m

0.01 m

0.0 m

Plane: X-Z

Type: Solid


Object

Geometry

xS

yS

zS

xE

yE

zE

Specifications

Joint1

Shape: Prism

0.295 m

0.095 m

0.085 m

0.325 m

0.125 m

0.115 m

Type: Solid Solid material: material.3

Joint2

Shape: Prism

0.295 m

0.35 m

0.085 m

0.325 m

0.38 m

0.115 m

Type: Solid Solid material: material.3

Note You can use the Copy object function to speed up the creation of the remaining objects after pipe1 and joint1 are created. However, the names will not be the same as the tutorial. To rename an object, right mouse click the object in the Model tree and click Rename. 3.

Next, we will also build the heat sink using block objects. •

Build the base and one pin according to the following

Table 6.3 Base and Pin Specifications Object

Geometry

Base Shape: Prism

xS

yS

zS

xE

yE

zE

Properties

0.42 m

0.35 m

0.05 m

0.592 m

0.38 m

0.15 m

Block type: Solid Solid material: default

Object

Geometry

xC

yC

zC

Height

Radius / Radius 2

Int radius / Int radius 2

Properties

Pin

Shape: Cylinder,

0.44 m

0.38 m

0.067 m

0.04 m

0.01 m / 0.006 m

0m/0 m

Block type: Solid


111

Chapter 6: Heat-Pipe Modeling and Nested Non-Conformal Meshing Plane: XZ

Solid material: default

Non-uniform radius Note that the non-uniform radius option is in the Geometry tab as shown below and that the Plane option is X-Z (Figure 6.3 (p. 112)).

Figure 6.3 Non-uniform Cylinder

112

•

Make two copies of Pin with an offset of 0.033 m in the Z direction (i.e., Number of copies= 2, Translate with Z offset = 0.033 m).

•

Highlight the three tapered fins (Pin, Pin.1 and Pin.2), make four copies of this highlighted group with an offset of 0.033 m in the X direction (i.e., Number of copies = 4, Translate with X offset = 0.033 m).


Step 3: Create Nested Non-conformal Mesh Using Assemblies •

Group all the pins by highlighting them in the model tree, click on the right mouse and select Copy and finally make one copy as follows: Number of copies = 1, Translate with Y offset = -0.03, Mirror with Plane: XZ and About: Low end. The final model should appear as shown in Figure 6.4 (p. 113).

Figure 6.4 Model with Heat Pipe and Heat Sink

6.6. Step 3: Create Nested Non-conformal Mesh Using Assemblies In this exercise, our goal is to reduce the overall cell count to a reasonable level while retaining a good cell resolution within the model, especially where the velocity and temperature gradients are higher. 1.

Create three individual assemblies (one for the heat sink and the base, the second one for the vent, and the last one for the fan). Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

113

Chapter 6: Heat-Pipe Modeling and Nested Non-Conformal Meshing a.

Highlight all the pins and the base in the model tree.

b.

Right mouse click and select Create then Assembly.

c.

Rename the assembly as Heatsink-asy.

d.

Double click on the assembly to open the Edit panel.

e.

Under the Meshing tab, toggle on the Mesh separately button.

f.

Set the slack to the following values:

Table 6.4 Slack Values for Heatsink-asy Min X

0.005 m

Max X

0.005 m

Min Y

0.005 m

Max Y

0.005 m

Min Z

0.015 m

Max Z

0.005 m

Note For the Heatsink-asy, we have set a bounding box that is 0.005 m bigger than the assembly at five sides except Min Z where the slack is defined higher (0.015m) to capture the wake region of the flow. g.

Click Update and Done.

h.

Following the same procedure above, create two more assemblies; one for vent.1 (name it Ventasy) and one for the fan (name it Fan-asy).

i.

Use the following tables to assign slack values for Vent-asy and Fan-asy assemblies, respectively.

Table 6.5 Slack Values for Vent-asy Min X

0.01 m

Max X

0.01 m

Min Y

0.01 m

Max Y

0.01 m

Min Z

0.01 m

Max Z

0m

Table 6.6 Slack Values for Fan-asy

2.

Min X

0.01 m

Max X

0.01 m

Min Y

0.01 m

Max Y

0.01 m

Min Z

0m

Max Z

0.01 m

Put the previously created assemblies into an outer assembly covering all. a.

Highlight all the three assemblies above and click the right mouse button.

b.

Select Create assembly.

c.

Rename this main assembly HS-vent-fan-asy.

d.

Assign the following slack values to the assembly.

Table 6.7 Slack Values for HS-vent-fan-asy Min X 114

0.02 m

Max X

0.02 m


Step 5: Physical and Numerical Settings Min Y

0.02 m

Max Y

0.02 m

Min Z

0m

Max Z

0m

6.7. Step 4: Generate a Mesh 1.

Go to Model → Generate Mesh or use the toolbar shortcut (

2.

In the Mesh control panel, specify a global maximum element size of 0.025 m in all three directions (Max X size = Max Y size = Max Z size = 0.025).

3.

Verify that the Coarse option is selected next to Mesh parameters and change the Max size ratio from 10 to 5.

4.

Make sure that Mesh assemblies separately button is toggled on.

5.

Under the Options tab, set the Init element height to 0.003.

6.

Click Generate. Visualize the mesh by making plane cuts and surface displays under the Display tab, especially between the heat sink pins and on the surface of the fan and grille objects. The meshing panel should look like the one in Figure 6.5 (p. 115) when finished:

) to open the Mesh control panel.

Figure 6.5 Mesh control Panel

6.8. Step 5: Physical and Numerical Settings 1.

Go to Problem setup → Basic parameters. In the General setup tab, change the Flow regime to be Turbulent and keep the default selection of Zero equation.


115

Chapter 6: Heat-Pipe Modeling and Nested Non-Conformal Meshing 2.

Go to the Transient setup tab and set the initial condition for the velocity in the z-direction to be -0.1 m/s to achieve faster convergence (If there is an initial guess at the start of the solution there is a lesser chance of large initial velocities in the first iteration). These two steps are shown in Figure 6.6 (p. 116). Click Accept for these changes to take effect.

Figure 6.6 Turbulent Flow and Initial Z-Velocity

3.

Under Solution settings → 6.7 (p. 116)).

Basic settings, set the Number of iterations to 200 (Figure

Figure 6.7 Basic settings Panel

4.

Click Accept.

6.9. Step 6: Save the Model ANSYS Icepak automatically saves the model for you before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save project 116




2.

Add in two monitor points, one to monitor velocity at the center of vent.1, and one to monitor the temperature at the center of the block.1. a.

Select vent.1 and block.1 from the list and then drag them to the Points branch of the tree. (Alternatively, one can create monitor points by simply selecting these objects in the model tree, clicking on the right mouse button and selecting Create and then Monitor point.)

b.

Because ANSYS Icepak will by default monitor the temperature at the centroid or center of these objects, double-click on vent.1 under the monitor Points branch.

c.

Select velocity as the variable to monitor and deselect temperature.

d.

Accept the change.

Go to Solve → Run solution or click on the shortcut button ( solution.

). Start the solver by clicking Start

6.11. Step 8: Examine the Results To postprocess results for this exercise, create the following object-face and plane-cut views:


Specifications

Description

face.1

Object: all blocks

Object-face view of temperature on all the blocks.

(Choose using Ctrl and Shift keys and left mouse button)

Observations: The view shows the flow of heat from the heated block (block1.) to the air-cooled heat sink.

Show contours Parameters Contours of: Temperature Contours options: Solid fill/ Smooth Color levels: Calculated/ Global limits cut.1

Plane location: Set position: Y plane through center Scroll up to about 0.8 Show vectors Parameters

Plane cut (x-z) view of the velocity vectors through the center of the fan. Observations: The view shows air flowing from the grill to the fan, passing through the fins of the heat sink.

Color by: Velocity magnitude face.1 and cut.1 should look similar to Figure 6.8 (p. 118) and Figure 6.9 (p. 119) that follow.


117


Figure 6.8 face.1 (Temperature Contour -all blocks)

118


Step 9: Summary

Figure 6.9 cut.1 (Velocity Vectors through Fan)

6.12. Step 9: Summary In this problem, we have modeled a simplified heat pipe using cylindrical solid blocks of orthotropic conductivity. The exercise also demonstrated the application of copy and mirror features as well as the use of nested non-conformal meshing using assemblies in ANSYS Icepak.


119

120


Chapter 7: Non-Conformal Mesh 7.1. Introduction This tutorial compares the effects of using a conformal mesh versus a non-conformal mesh in a simple pin-fin heat sink problem. In this tutorial, you will learn how to: •

Generate a non-conformal mesh and related parameters such as bounding box, slacks etc.

•

Understand the effects of non-conformal mesh on total mesh counts and on results.

•

Generate and compare summary reports.

•

Apply non-conformal rules and restrictions.

7.2. Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS Icepak and that you have solved Sample Session in the Icepak User's Guide and the tutorial "Finned Heat Sink". Some steps in the setup and solution procedure will not be shown explicitly.

7.3. Problem Description The model consists of a pin-fin heat sink composed of aluminum, which is in contact with a source dissipating 10 W, as shown in Figure 7.1 (p. 122). The source-heatsink assembly sits in the middle of a wind tunnel with a wind speed of 1.0 m/s. The ambient temperature is 20°C. The flow regime is turbulent. The objective of this exercise is to become familiar with the non-conformal meshing methodology and its application. The solution results of conformal and non-conformal mesh will be examined and compared. In ANSYS Icepak, assemblies of objects can be meshed separately. A region can be defined around a particular assembly and this region can be meshed independently of the mesh outside this region. This allows a fine mesh to be confined in a particular region of interest and it helps to reduce overall mesh count without sacrificing the accuracy of the results.


121

Chapter 7: Non-Conformal Mesh


7.4. Step 1: Create a New Project Open a new project and name it non-conformal.

7.5. Step 2: Build the Model •

Cabinet Enter the following start and end locations for the Cabinet. xS

0.3 m

xE

0.7 m

yS

0.5 m

yE

0.7 m

zS

0.0 m

zE

1.0 m

–

Opening on Cabinet Boundaries Open the Cabinet object panel. In the Properties tab, change Wall type of Min z to Opening. Click Edit to open the Openings panel. In the Properties tab of the Openings panel, enter 1 m/s for the Z velocity and keep Temperature as ambient (which is 20°C).

–

Grille on Cabinet Boundaries Under the Properties tab of the Cabinet panel, change the wall type of Max z to Grille. Click Edit to open the Grille panel. In the Properties tab of the Grille panel, change the free area ratio to 0.8 and leave the other default property specifications.

122



Figure 7.2 Grille Properties Specifications

•

Source Create a source using the following dimensions: Object

•

Specification

source.1

xS = 0.48 m

xE = 0.52 m


yS = 0.52 m

yE = —

Plane: X-Z

zS = 0.48 m

zE = 0.52 m

Total power: 30 W

Heat sink Now, create a heat sink with the following geometrical and physical properties. Tab

Settings

Geometry

Plane: X-Z Start/end xS = 0.46 m, xE = 0.54 m yS = 0.50 m, yE = — zS = 0.40 m, zE = 0.6 m Base height: 0.02 m Overall height: 0.1 m

Properties

Type: Detailed Flow direction: Z Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

123

Chapter 7: Non-Conformal Mesh Detailed fin type: Cross cut extrusion Fin setup/Fin spec: Count/thickness Count: 8 in Z-dir and 8 in X-dir Thickness: 0.01 m in Z-dir and 0.004 m in X-dir Flow/thermal data: default base and pin material The screen shots of the heatsink panel is shown in Figure 7.3 (p. 124).

Figure 7.3 Heat sink Properties

7.6. Step 3: Generate a Conformal Mesh Generate a conformal mesh for the model. 1.

Open the Mesh control panel using Model → Generate mesh. a.

In the Mesh control panel, set the Max element size for X to 0.02 m, for Y to 0.01 m, and for Z to 0.05 m.

b.

Under the Global tab, make sure that Normal is selected next to Mesh parameters.

c.

Under the Misc tab, make sure Allow minimum gap changes is checked.

d.

Click Generate.

Note The minimum gap for X, Y, Z might adjust to 10% of the minimum dimension in respective directions. Make a note of the number of elements, the minimum face alignment and the aspect ratio. 2.

124

Examine the mesh. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 4: Physical and Numerical Settings a.

Click the Display tab.

b.


c.

In the Set position drop-down list, select Y plane through center.

d.

Turn on the Display mesh option.

Note The mesh display plane is an x-z plane cut through the center of the cabinet as shown in Figure 7.4 (p. 125). Note the clustered mesh lines extending from the heat sink all the way across the domain in both the x and z directions. The total number of cells is about 144000.

Figure 7.4 Conformal Mesh, Central Y Plane

3.



b.


7.7. Step 4: Physical and Numerical Settings Before starting the solver, you first review estimates of the Reynolds and Peclet numbers to check that the proper flow regime is being modeled. Solution settings →

Basic settings


125

Chapter 7: Non-Conformal Mesh Click Reset in the Basic settings panel. Check the values printed to the Message window. The Reynolds and Peclet numbers are approximately 12600 and 8900, respectively, so the flow is turbulent. To set up turbulent flow, go to Problem setup → Basic parameters and choose the Zero equation turbulence model under the General setup tab. Click Accept to accept the new solver settings. Basic settings and set the Number of iterations to 300. Go to AdGo to Solution settings → vanced settings and specify Under-relaxation factors for Pressure, Momentum, and Temperature as 0.7, 0.3, and 1.0 respectively. Define a monitor point by dragging the source object (source.1) into the Points folder. This creates a monitor point for temperature of the object, which can be used to judge convergence.

7.8. Step 5: Save the Model ANSYS Icepak saves the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) before the solution. The model can be saved using File → Save project.

7.9. Step 6: Calculate a Solution Start the calculation by clicking on Solve → Run solution. Specify “conformal" as the ID. Click Start solution to start the solver.

7.10. Step 7: Examine the Results In this step, you will examine the maximum temperature using ANSYS Icepak's summary reporting tool. Report → Summary report 1.

126

Define a report that will display temperature data for the source and the heat sink. a.

In the Define summary report panel, click New.

b.

In the Objects drop-down list, select heatsink.1 and click Accept.

c.

In the Value drop-down list, select Temperature.

d.

Repeat steps (a) through (c) for source.1.


Step 8: Add an Assembly to the Model

e.

Click Write to generate a summary report.

ANSYS Icepak opens the Report summary data panel, where minimum, maximum, and mean temperatures for the heat sink and source are displayed. Note that the maximum temperature is about 36.7° C.

2.

Click Done to close the Report summary data panel.

3.

Click Close to close the Define summary report panel.

7.11. Step 8: Add an Assembly to the Model You will now create an assembly out of the source and heat sink objects. The assembly will be meshed separately from the rest of the model.

Note Because you are changing the current model, thereby invalidating the post-processing data that has been loaded from the previous steps, you will need to generate a mesh (a nonconformal mesh) and calculate the solution again which is shown in steps 9 through 11.


127

Chapter 7: Non-Conformal Mesh 1.

2.

Create an assembly consisting of the source and the heat sink objects. a.

Click the Create assemblies button ( ) to create a new assembly. This creates an assembly node in the Model manager window under the Model node.

b.

Select the source.1 item under the Model node in the Model manager window, hold down the Ctrl key, and then select the heatsink.1 item.

c.

Hold down the left mouse button, drag both highlighted items into the assembly.1 node of the tree, then release the left mouse button.

Edit the assembly and define its bounding box. ) to open

a.

Select the assembly.1 node in the Model tree, and then click the Edit object button ( the Assemblies panel.

b.

Click the Meshing tab.

c.

Turn on the Mesh separately option and enter the Slack parameters shown in Figure 7.5 (p. 128).

Figure 7.5 Slack Values and Mesh Controls in the Separately Mesh Assembly

This creates a bounding box region that is 0.05 m larger than the assembly on four sides. Since Min Y is already at the bottom of the cabinet, no slack value can be provided for it. A larger slack value of 0.15 m has been provided in the Max Z direction to resolve the wake region. Not that a smaller Max X and Max Z grid size has been specified within the assembly compared to the global max grid size. This helps to refine the mesh within the separately meshed assembly. 128


Step 9: Generate a Non-conformal Mesh d.

Click Done to set the properties of the assembly and close the panel. The new model is shown in Figure 7.6 (p. 129).

Figure 7.6 The Source and Heat Sink in a Separately Meshed Assembly

7.12. Step 9: Generate a Non-conformal Mesh assembly.1 will be meshed separately when the mesh is generated. The non-conformal mesh will limit the clustering to a region inside a bounding box slightly larger than the source-heatsink assembly. 1.

Generate a non-conformal mesh for the model. Model → Generate mesh a.

In the Mesh control panel, keep the Max element size for X set to 0.02 m, for Y set to 0.01 m, and for Z set to 0.05 m.

b.

Under the Global tab, make sure the Mesh assemblies separately option is checked.

c.

Click Generate to create the mesh.

Note Make a note of the number of elements, the minimum face alignment, and the aspect ratio. 2.

Examine the mesh. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

129

Chapter 7: Non-Conformal Mesh a.


b.


c.


d.

Turn on the Display mesh option. The mesh display plane is an - plane cut through the center of the cabinet as shown in Figure 7.7 (p. 130). Note the clustered mesh lines extending from the heat sink all the way across the domain in both the and directions only within the bounds of the assembly. The total number of cells is about 107000.

Figure 7.7 Non-conformal Mesh

3.



b.


7.13. Step 10: Save the Model ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save project

7.14. Step 11: Calculate a Solution 1. 130

Retain the same Number of iterations (300) in the Basic settings panel. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 13: Summary 2.

Start the Solution. Solve → Run solution a.

Specify non-conformal as the solution ID.

b.

Click Start solution to start the solver.

Note The monitor point that you already created is automatically used for the new solution. The solution converges after about 175 iterations. Note, however, that the exact number of iterations required for convergence may vary on different computers.

7.15. Step 12: Examine the Results In this step, you will examine the maximum and minimum temperatures of the source and heat sink in the new version of the model. Report → Summary report 1.

Define a report that displays temperature data for the assembly. a.

Retain the same temperature report of the source and the heat sink, as used in the version without the assembly.

b.

Click Write to generate a summary report. Note that the maximum temperature is about 35.8° C, representing a temperature rise of about 15.8° C from the ambient temperature of 20° C. The maximum temperature is very close to that obtained in the version with conformal mesh.

2.


3.


7.16. Step 13: Summary In this tutorial, you generated both a conformal and a non-conformal mesh for a simple source-heatsink geometry and compared the two sets of results. The comparison found an approximate 20 percent reduction in the number of cells for the non-conformal mesh with a negligible change in the temperature data.


131

132


Chapter 8: Mesh and Model Enhancement Exercise 8.1. Objective The objective of this exercise is to lead you through the decision making process that's involved in improving a model. The inferences from the exercise should help you make appropriate modeling choices during your next thermal modeling project.

8.2. Prerequisites The trainee should be familiar with: •

ANSYS Icepak modeling objects

•

Basics of meshing

•

Non-conformal meshing

8.3. Skills Covered •

Choice of thin vs. thick objects

•

Basic meshing techniques

•


•

Use of object separation setting

8.4. Training Method Used A troubleshooting approach is used in this tutorial. A model with potential for improvement is provided. You will be given 15 minutes to try your hand at improving the model (note: you are not expected to complete all the improvements in this short time). This will help you familiarize yourself with the issues associated with the model. Then, an approach for improving the model is delineated in the form of step-by-step hints. Feel free to explore the software interface, collaborate with another trainee, or ask the instructor.

8.5. Loading the Model •

Unpack and load the model named meshing-tutorial-start.tzr.

•

Rename it to any other name of your choice.

8.6. A 15 Minute Exploration Without making any changes, the model results in about 750,000 cells. It is possible to reduce this mesh significantly without compromising accuracy. You are allowed to modify, delete, or add objects as long as the physics being modeled stays unchanged. You may want to refer to the power and material specifications to justify model changes. Non-conformal meshing is one of the techniques that will help you accomplish this task. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

133

Chapter 8: Mesh and Model Enhancement Exercise Work with this model for as long as you prefer within the allocated 15 minutes and STOP. Proceed to the next set of instructions.

Hint Start by generating the mesh without any changes. View mesh cut planes at various orientations and locations to identify root causes that result in unnecessary mesh clusters in noncritical regions. Then modify the model in order to tackle the issues you notice.

8.7. Step-by-Step Approach •

Save the model you have been working on to another name. (You may be revisiting this model to compare notes with the suggested approach)

•

Reload the model you had unpacked earlier (“meshing-tutorial-start").

•

Save it to another name of your choice.

•

Generate mesh without modifying the model. You will see a mesh count of about 750,000 cells.

Note Ensure the meshing type is Mesher-HD. •

Create mesh cut planes in different orientations to identify the root cause for such a high mesh count. One such cut plane (Z plane through center set position) is shown in Figure 8.1 (p. 135).

•

Figure 8.1 (p. 135) shows that the high mesh count is due to grid bleeding from the heat sink and the components cooled by it.

Note What feature in ANSYS Icepak allows you to avoid grid bleeding?

134


Modification 1: Non-Conformal Mesh of the Heat Sink and Components

Figure 8.1 A Mesh Cut Plane View of the Given Model When Meshed Without Modifications

8.8. Modification 1: Non-Conformal Mesh of the Heat Sink and Components 1.

Create an assembly containing the heat sink and the components cooled by it (green colored objects). Name it HS-asy.


135

Chapter 8: Mesh and Model Enhancement Exercise

Tip

2.

•

Shift + left mouse click and draw a window around the group of objects you would like to assemble.

•

You can make the mesh and some objects invisible to select the heat sink objects.

•

You can also select the objects in the Model manager window by left mouse clicking heatsink.1 and then Shift + left mouse clicking HS_component.

We will test two non-conformal assembly options: a regular non-conformal assembly (with slack values) and a zero slack non-conformal assembly.

Regular non-conformal assembly a.

Activate Mesh separately under the Meshing tab of the Assemblies panel for this assembly (HSasy) and specify appropriate slack values (we recommend 1 mm on all sides). While specifying slack values, make sure that you are not violating any of the rules regarding non-conformal meshing.

Note It is recommended to use the Case check macro to ensure a thin conducting plate is not intersecting a non-conformal assembly. In the Macros menu, select Case check> Automatic Case Check Tool. Click the Apply button for the following options: Assembly intersection check and Thin Conducting Plate and Assembly Intersections. If there is an intersecting plate, the slack value should be changed to get rid of this error. b.

Generate the mesh again.

c.

Observe the decrease in element count with every modification you make. The mesh count should be around 315,000 cells.

Zero slack non-conformal assembly a.

Open the HS-asy edit panel and change the slack values on all sides to zero.

b.


c.

Display the mesh at some selected planes to observe mesh in the domain.

d.

Display the mesh on Mask.1. Note that the mesh fully exists for the plate, even though it is intersecting with a face of the assembly.

e.

Observe the reduction in the mesh count; the mesh count should be about 260,000 cells.

Note Zero slack non-conformal assembly resulted in fewer mesh count than the regular nonconformal assembly intersecting thin conducting plate. This limitation will be resolved in the next step.

136


Modification 3: Non-Conformal Mesh for the hi-flux-comps Cluster

8.9. Modification 2: Resolution of Thin Conducting Plate Intersecting Non-Conformal Region •

Question the choice of using the thin conducting plate object type for the plate object (Mask.1). –

What is the thickness of the mask plate?

–

What is the conductivity of the solid material assigned to this plate?

–

Find out the thickness and conductivity of the PCB on which the thin plate is lying.

–

Based on the above information, do you think that the mask object is a significant spreader of heat compared to the PCB? → The mask is not a significant heat spreader, however it tends to impede heat flow across it. Hence, we cannot completely ignore it. → In fact, there are two mask plates modeled as thin conducting plates in this model (one for each PCB). → Change the plate type of both mask plates to Contact Resistance while maintaining the same thickness (0.00001 m). This way you maintain the thermal resistance in the normal direction while ignoring the heat spreading laterally.

•

Regenerate the mesh or load the existing one (the mesh is still the same as there is no change in geometry).

•

View cut planes of the mesh to see if you have any more unnecessary mesh clusters. Figure 8.2 (p. 137) shows one such cut plane. –

This time the unwanted grids are from the clusters of components called “hi-flux-comp" (red colored objects).

Figure 8.2 Mesh Bleeding After 1 Non-Conformal Region

8.10. Modification 3: Non-Conformal Mesh for the hi-flux-comps Cluster 1.

Create a non-conformal mesh around the cluster of components called “hi-flux-comps".


137

Chapter 8: Mesh and Model Enhancement Exercise Even though you are only interested in isolating the “hi-flux-comps", there are two cylindrical objects very close to it. You have two choices. •

Avoid the cylinders by using zero slack value. This may be too small and create a small gap between the interface and the cylinders, which is not desirable.

•

Include the cylinders to the assembly. This is the suggested approach.

2.

Create a zero slack non-conformal assembly that includes the hi-flux-comps, Tabs, Dies, and adjacent cylinders. Note that the Tabs and Dies are contained within the hi-flux-comps.

3.


4.

Repeat cut plane viewing. Figure 8.3 (p. 138) shows a cut plane view after creating the two separate mesh regions.

Figure 8.3 Mesh Bleeding from the Boards

8.11. Modification 4: A Super Assembly... •

The mesh bleeding you see in Figure 8.3 (p. 138) can be tackled by creating a separately meshed assembly of the entire enclosure object (the blue box). In order to see the effect of zero slack non-conformal assemblies, you may want to try meshing the model once with zero slack assembly, and then with slack values for the non-conformal assembly.

•

The resultant mesh cut plane is shown in Figure 8.4 (p. 139).

138


Modification 4: A Super Assembly...

Figure 8.4 Cut Plane View of Recursive Embedded Mesh

•

This method of creating a super assembly containing sub-non-conformal assemblies is called “nested non-conformal meshing" or “recursive embedded meshing".

•

Revisiting the Separation Setting By default, ANSYS Icepak's accepts all minimum gap changes. We shall revisit these changes now. –

In the Mesh control panel, set all the Minimum gap settings to 0.0001 m.

–

In the Misc tab, uncheck Allow minimum gap changes.

–

Generate the mesh.

–

The pop-up message as shown in Figure 8.5 (p. 139) will appear.

Figure 8.5 Separation Warning

–

This warning appears because the separation (think of it as a tolerance setting for the mesher) distance is larger than 10% of the smallest feature in the model.

–

When there are objects smaller than the mesher tolerance, those objects will not be meshed correctly.

–

However, note that the separation setting is a useful tool designed to avoid unnecessary meshes due to inadvertent misalignments in the model (without modifying the geometry).

–

Look for the name of the object featured in the warning and its dimension.

–

Why should you model an object that's 0.1 mm in thickness? Is it likely to improve the accuracy of your results? Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

139

Chapter 8: Mesh and Model Enhancement Exercise –

Do not accept the suggested change to the separation settings.

8.12. Modification 5: A Simplification Based on Magnitudes of Resistances... •

From the name of the object, one can infer that the warning is regarding an air gap under one of the components, which is modeled as a thick plate.

•

There is a reason for not using contact resistance type plate to model the Airgap. –

Two thin objects cannot overlap. If the Airgap was modeled as contact resistance plate, the underlying mask may not be meshed in the region common to the Mask and the Airgap. → What is the Mask thickness and conductivity? → What is the Airgap thickness and conductivity? → The purpose for modeling these two objects is to capture their insulating effects. → How does the resistance (thickness/conductivity) of the mask compare to that of the Airgap? → Does the mask contribute significantly to the overall (sum) of the two resistances? → Can you justify suppressing the mask under the air gap by making the Airgap a contact resistance plate? → When you make the Airgap a contact resistance plate, make sure that the Effective thickness is the same (1e-4 m). → Also make sure the Airgap has higher priority over the Mask object. •

You can do this by editing the plate object and changing the Priority setting under the Info tab. (Larger priority number means higher priority. Objects with higher priority are listed lower in the Model manager window).

•


•

This time you will see another separation warning about the AL-spreader. Again, do not accept the changes.

8.13. Modification 6: A Classic Case for Thin Conducting Plate... •

Since a contact resistance plate will not model the in-plane spreading of heat, we can't use it here. Thin conducting plate models conduction in the normal as well as the planar direction. At the same time the thin conducting plate will not generate slender cells. The decrease in thickness due to a thin plate approximation of the Al-spreader is negligible.

•

140

Generate the mesh one more time. You will see the separation warning again - this time about the die objects which are 0.0004 m. –

These objects are power generating components, which are already thin conducting plates. The warning is about the width of the packages.

–

The surface area of the dies is a critical parameter affecting the temperature prediction for the component. This cannot be simplified.

–

Hence accept the suggested change in separation setting. The resultant mesh count will be significantly less than what we got without any changes to the given model.


Conclusion

Note It is also possible to use a separation distance larger than the recommended 10% value. Values of up to 50% (of the smallest dimension) may be used in cases where reducing the mesh count is critical. •

You will now get a separation warning about the tabs. We cannot change the geometry of the tabs, so accept the suggested change in separation settings again.

•

Here are some suggested qualities of meshes: –

The size of the first cells from critical heat dissipating surfaces should be less than 1 mm for a 1st cut analysis. → View mesh cut plane on the wall of the enclosure object, the PCB and the critical heat generating components to see if you are fulfilling the above requirement. → Use the Object params control to request mesh refinement near all the important surfaces mentioned above.

– •

Generate the mesh to see if your request is being honored.

Finally, a comparison... For comparison purposes, deactivate the Mesh assemblies separately option in the Mesh control panel and generate the mesh. The difference between the mesh with this check button active and inactive is the effect of non-conformal meshing.

•

STOP: Solution and post processing are beyond the scope of this exercise. Please compare the suggested approach with the approach you were attempting during the initial 15 minute period of this tutorial.

8.14. Conclusion A model with room for improvement is provided. Using approximate object choices and meshing strategies, the model and the mesh were improved. The approach delineated in this exercise can help reduce significant run time without compromising the physics being modeled.


141

142


Chapter 9: Loss Coefficient for a Hexa-Grille 9.1. Introduction This tutorial demonstrates how to define trials, run parametric solutions, and post-process the results. Often, there is a need to calculate the loss coefficient of grilles that have certain hole patterns. The purpose of the problem is to determine the minor loss coefficient of a grille that has hexagonal holes. In this tutorial you will learn how to: •

Define a parameter to optimize the design.

•

Define trials.

•

Define primary and compound functions that you want to report.

•

Calculate parametric solutions.

•

Report and plot parametric results.

9.2. Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS Icepak and that you have solved or read the tutorial "Finned Heat Sink". Some steps in the setup and solution procedure will not be shown explicitly.

9.3. Problem Description The model includes a cabinet that is 160 mm in length with inlet and outlet openings at the two ends (with cross sectional area of 7.363 mm x 12.7 mm), and four symmetry walls at the other sides. The model also includes a part of the hexa-grille placed at the center of the channel in the streamwise direction, as shown in Figure 9.1 (p. 144). The grille has one full hexagonal hole at the center and four quarter hexagonal holes placed around it. This pattern was selected because it forms a periodic region and is sufficient to calculate the loss coefficient. The solution obtained from this run can be replicated to form the solution for the entire domain.


143

Chapter 9: Loss Coefficient for a Hexa-Grille



Copy ICEPAK_ROOT/tutorials/loss-coefficient/loss-coefficient.tzr to your working directory. Replace ICEPAK_ROOT by the full path name of the directory where ANSYS Icepak is installed on your computer system.

2.


3.

Click Unpack in the Welcome to Icepak panel. The File selection panel appears.

4.

In the File selection panel, select the packed project file loss-coefficient.tzr and click Open. The Location for the unpacked project file selection dialog appears.

5.

In the Location for the unpacked project file selection dialog, select a directory where you would like to place the packed project file, enter a project name in the New project text field, then click Unpack.

9.5. Step 2: Build the Model This tutorial uses an existing model. ANSYS Icepak displays the model in the graphics window, as shown in Figure 9.2 (p. 145).

144



Figure 9.2 Loaded Model

Save the problem to a new project file. This enables you to expand on the problem without affecting the original file. File → Save project as 1.

In the Project text box, enter the name loss-coefficient-new.

2.

Click Save.


145


9.6. Step 3: Define Parameters and Trials You will first define a parameter and trials according to the parameter. Next, you will define a summary report, then primary and compound functions to be reported. 1.

Define a velocity parameter at the inlet opening in terms of the Reynolds number (

).

Note The velocity at the inlet opening in terms of the Reynolds number (), which is customarily used in loss-coefficient plots in lieu of velocity, is calculated as = ∗ , where the kinematic viscosity ν = 1.5843e-5 kg/m.s, and the hydraulic diameter of the duct Dh = 9.322e-3 m.

146

a.

Select the inlet opening, cabinet_default_side_minx, in the Model manager window, and then click the Edit object button ( ) to open the Openings panel.

b.


c.

Select X Velocity and set the value to $Re*1.5843e-5/9.322e-3.


Step 3: Define Parameters and Trials

2.

d.

Click Done to set the properties of the opening. This opens the Param value panel.

e.

Set the Initial value of Re to 10, and click Done to close both the Param value and the Openings panels.

Define six trials according to the different values of the Reynolds number. Solve → Define trials a.

In the Parameters and optimization panel, make sure Parametric trials and All combinations are enabled in the Setup tab.

b.

Click on the Design variables tab, enter the following values for the Reynolds number in the box next to Discrete values: 10 50 100 500 1000 1750. Click Apply to accept the changes.


147


148



Note Parameters values can also be exported/imported by clicking the Export or Import button in the Setup tab of the Parameters and optimization panel. Clicking Export or Import opens a file selection dialog box and overrides any existing data.

c.

Click the Trials tab to review the trials. Make sure the Trials across top option at the bottom of the tab is disabled, and click Reset to select Values instead of Numbered in order to use the base names as values.


149


d. 3.


Define the report that displays average velocity and pressure data at the inlet and outlet openings. Solve → Define report

Note The loss coefficient is obtained by dividing the total pressure differential through the domain by the average dynamic pressure,

150

=

− − −

.

a.

In the Define summary report panel, click New.

b.

In the Objects drop-down list, select cabinet_default_side_maxx and click Accept.

c.

In the Value drop-downlist, select UX.

d.

Repeat steps (a) and (b), then select Pressure in the Value drop-down list.

e.

Repeat steps (a) through (d) for cabinet_default_side_minx.



f. 4.

Click the Close button to accept the settings and close the panel.

Set the parametric trials and define primary and compound functions. Solve → Run optimization a.

In the Parameters and optimization panel, click the Setup tab.

b.

Verify that the Parametric trials and All combinations options are turned on.

c.

Click the Functions tab.

d.

Define four primary functions (Pstat_in, Pstat_out, Uave_in, and Uave_out).

Note These functions represent static pressures and velocities at the inlet and outlet, respectively. i.

Under Primary functions, click the New button to open the Define primary function panel.

ii.

In the Define primary function panel, enter Pstat_in for the Function name.

iii.

Select Report summary from the Function type drop-down list and cabinet_default_side_minx Pressure from the Item drop-down list and retain the selection of Max.

iv.

Click Accept to accept the changes and close the panel.


151


v.

Repeat steps (i) through (iv) for the following three functions: Function name

Function type

Item

Max/Mean

Pstat_out

Report summary

cabinet_default_side_maxx Pressure

Max

Uave_in

Report summary

cabinet_default_side_minx UX

Mean

Uave_out

Report summary

cabinet_default_side_maxx UX

Mean

Important All function names are case-sensitive. 5.

152

Define five compound functions (Pdyn_in, Pdyn_out, Ptot_in, Ptot_out, and Kfact). a.

Under Compound functions, click the New button to open the Define compound function panel.

b.

In the Define compound function panel, enter Pdyn_in for the Function name.

c.

Next to Definition enter 0.5*1.1614*$Uave_in*$Uave_in.

d.

Click Accept to accept the changes and close the panel.

e.

Repeat steps (a) through (d) for the following four functions: Function name

Definition

Pdyn_out

0.5*1.1614*$Uave_out*$Uave_out



6.

Ptot_in

$Pstat_in+$Pdyn_in

Ptot_out

$Pstat_out+$Pdyn_out

Kfact

($Ptot_in-$Ptot_out)/$Pdyn_out


9.7. Step 4: Generate a Mesh For this model, you will generate the mesh in just one step. The resulting mesh will be sufficiently fine near object faces to resolve the flow physics properly. Model → Generate Mesh 1.

2.

Generate the mesh for the model. a.

Keep all the defaults in the Mesh control panel.

b.

Click Generate in the Mesh control panel to generate the mesh.

Examine the mesh. a.


b.


c.


d.

Turn on the Display mesh option. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

153


Note The mesh display plane is an - plane cut through the center of the cabinet as shown in Figure 9.3 (p. 154).

Figure 9.3 Mesh on the x-z Plane

3.

Deselect the Display mesh option to turn off the mesh display.

4.



Confirm that only the flow solution is to be obtained, and the flow regime is set to laminar. Problem setup →

2.

a.

Keep the default selection of Flow(velocity/pressure) under Variables solved.

b.

Keep the default selection of Laminar for the Flow regime.

c.


Increase the Number of iterations to 500. Solution settings →

3.

Basic settings

a.

Enter 500 in the Number of iterations field.

b.

Click Accept in the Basic settings panel.

Confirm under-relaxation factors are correct. Solution settings →

154

Basic parameters

Advanced settings


Step 8: Examine the Results The Advanced solver setup panel opens. a.

Confirm that the Under-relaxation factor for Pressure is 0.7 and for Momentum is 0.3.

b.

Click Accept in the Advanced solver setup panel.

9.9. Step 6: Save the Model ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the project you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your project file when it saves the model.) File → Save project

9.10. Step 7: Calculate a Solution Start the calculation. 1.

Solve → Run optimization

Note button in the Model and solve toolbar to display Alternatively, you can click the the Parameters and optimization panel. 2.

Make sure Allow fast trials (single .cas file) is unchecked in the Setup tab.

3.

Click Run in the Parameters and optimization panel.

9.11. Step 8: Examine the Results As ANSYS Icepak starts performing the trials, the Parametric trials panel opens, displaying all the function values defined a priori, as well as parameters and running times for each trial. The Parametric trials can also be opened by selecting Show optimization/param results from the Report menu. Report → Show optimization/param results

Plot the loss coefficient, Kfact, against the Reynolds number, Re. 1.

In the Parametric trials panel, click the Plot button to open the Selection panel. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

155

Chapter 9: Loss Coefficient for a Hexa-Grille 2.

In the Selection panel, select Re as the

axis variable, and click Okay.

3.

In another Selection panel, which automatically opens up, select Kfact as the y axis variable, and click Accept. This displays the plot Kfact vs Re, as shown in Figure 9.4 (p. 156)

Figure 9.4 Kfact vs Re Plot

9.12. Step 9: Summary In this tutorial, you used the parameterization tool to calculate the loss coefficient of a grille for different values of Reynolds number (Re). You also defined other functions (e.g., static pressure and velocities at the inlet and outlet) that were reported for different Reynolds numbers. The results show that as Re increases, the loss coefficient decreases.

156


Chapter 10: Inline or Staggered Heat Sink 10.1. Introduction This tutorial demonstrates how to use the check-box (boolean) parameter control for design variables, and how to assign primary functions, in order to determine whether an inline or a staggered pin fin heat sink performs better in a single model. The resulting maximum temperature on the package will be compared. Non-conformal meshing will also be employed to reduce the cell count, required memory, and run time. In addition, particle traces passing a non-conformally meshed assembly will be presented during the post-processing of the results. In this tutorial you will learn how to: •

Define a check-box parameter (design variable).

•

Define different values for a design variable.

•

Run and report parametric trials.

•

Clip a plane cut to align it with the sides of a heat sink assembly.

•

Display particle traces coming from the fan and the opening.

10.2. Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS Icepak and that you have solved or read Tutorial Finned Heat Sink (p. 3). Some steps in the setup and solution procedure will not be shown explicitly.

10.3. Problem Description The model includes the package assembly, containing a BGA package object (compact conduction model), inline or staggered assemblies consisting of the respective heat sink objects, PCB object, spreader plate, a fan at the exit, and an opening at the inlet of the wind tunnel. The model geometry is shown in Figure 10.1 (p. 158).


157

Chapter 10: Inline or Staggered Heat Sink



Copy the file ICEPAK_ROOT /tutorials/heat_sink/heat_sink2b.tzr to your working directory. You must replace ICEPAK_ROOT by the full path name of the directory where ANSYS Icepak is installed on your computer system.

2.

Start ANSYS Icepak, as described in Section 1.5 of the User's Guide.

Note When ANSYS Icepak starts, the Welcome to Icepak panel will open automatically. 3.

158




Note The File selection panel will appear. 4.

In the File selection panel, select the packed project file heat-sink2b.tzr and click Open.

Note The Location for the unpacked project file selection dialog will appear. 5.


10.5. Step 2: Build the Model Note This tutorial uses an existing model. ANSYS Icepak will display the heat sink model in the graphics window. To view all components, expand all the assemblies of the model in the Model manager window.

Note You can rotate the cabinet around a central point using the left mouse button, or you can translate it to any point on the screen using the middle mouse button. You can zoom into and out from the cabinet using the right mouse button. To restore the cabinet to its default orientation, select Home position from the Orient menu. Save the problem to a new project file.

Note This will allow you to expand on the problem without affecting the original file. File → Save project as •

In the Project name text box, enter the name heat-sink-new.

•

Click Save.


159


10.6. Step 3: Define Design Variables Note For both heat sinks, you will define the HeatSink parameter, which will activate/deactivate heat sinks parametrically. 1.

Define the HeatSink parameter for the Inline heat sink. a.

160

Select the Inline assembly in the Model manager window, and then click the Edit object button ( ) to open the Assemblies panel.


Step 3: Define Design Variables

b.

Right-click the Active check box to open the Active parameter panel.

c.

Select ON if variable is equal to this object's name.

d.

Enter $HeatSink in the Variable text box.

Caution Note that all function names are case sensitive.

e.

Click Accept in the Active parameter panel to accept the changes and close the panel.

f.

Click Update in the Assemblies panel to open the Param value panel.


161

Chapter 10: Inline or Staggered Heat Sink g.

In the Param value panel, enter Staggered for the Initial value of HeatSink, and click Done to close the panel.

Note The word Active in the Assemblies panel became green. Also, note that the Inline assembly in the Model manager window is moved to the Inactive node. h. 2.

Click Done in the Assemblies panel to close the panel.

Define the HeatSink parameter for the Staggered heat sink. a.

Repeat above steps for the Staggered assembly.

Note You will not have to specify the initial value again.

10.7. Step 4: Define Parametric Runs and Assign Primary Functions You will first define values for your design variable. Next, you will review parametric trials and define primary functions to be calculated and reported. Solve → Run optimization

Extra Alternatively, you can click the 1.

162

button.

Define parameter values. a.

In the Parameters and optimization panel, click the Design variables tab.

b.

Next to Discrete values, after "Staggered" type in "Inline". Make sure to separate the two with a space.

c.

Click Apply to accept the changes.


Step 4: Define Parametric Runs and Assign Primary Functions

2.

Review trials. a.

Click the Trials tab.

b.

Make sure that the Order for Staggered is 1, and for Inline is 2.

c.

Select tr_HeatSink_Staggered as the Restart ID for the tr_HeatSink_Inline trial as shown in the image below.


163


3.

164

Define a primary function. a.

Click the Functions tab.

b.

Click the New button in the Primary functions group box.



c.

In the Define primary function panel, enter Tmax next to Function name.

d.

In the Value drop-down list, select Maximum temperature of objects.

e.

In the Object drop-down list, select the 700_BGA_40X40_5peripheral_p1.50 object in the Package assembly, and click Accept.

f.

In the Define primary function panel, click Accept to save the changes and close the panel.

g.

Click Done in the Parameters and optimization panel to close the panel.

10.8. Step 5: Generate a Mesh For this model, you will not generate a mesh in advance. Meshing will be automatically performed for each design trial during the parametric trials. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

165

Chapter 10: Inline or Staggered Heat Sink Model → Generate Mesh 1.

Make sure that the Mesh type is Hexa unstructured.

2.

In the Global tab, make sure that the Mesh assemblies separately option is turned on.

3.

Keep all other defaults in the Mesh control panel.

4.

Click Close in the Mesh control panel to close the panel.

10.9. Step 6: Physical and Numerical Settings Define basic parameters. Solution settings →

Basic settings

•

Set the Number of iterations to 300.

•

Click Accept in the Basic settings panel to accept the settings and close the panel.


10.11. Step 8: Define Monitor Points It is always a good approach to define monitor points before starting to run a simulation. In this model, a temperature monitor point was already defined by dragging the BGA package object into the Points node in the Model manager window. A velocity monitor point was also defined by dragging the Xmax opening object into the Points node and selecting Velocity and unchecking Temperature from the Modify points panel. In addition to the residual plot, the monitor plot will display temperature at the center of the BGA package object during the solution process and provide an indication of convergence.


Open the Parameters and optimization panel, if it is not already opened. Solve → Run optimization

Note You can click the

button in the Model and solve toolbar.

2.

Click the Setup tab, and make sure that options Parametric trials and All combinations are selected. Deselect Allow fast trials (single .cas file).

3.

Click Run in the Parameters and optimization panel, to start the calculations.

166



Note As ANSYS Icepak starts calculating solutions for the model, the Solution residuals window, displaying convergence history, and the Temperature Point monitors window will open. Also, the Parametric trials panel will open displaying the function values, as well as parameters and running times for both trials, as shown in Figure 10.2 (p. 167). The Parametric trials can also be opened by selecting Show optimization/param results from the Report menu.

Figure 10.2 The Parametric trials Panel

10.13. Step 10: Examine the Results The results from tr_HeatSink_Inline will be examined in this section. 1.

In the Orient menu, select Orient negative Z.

2.

Display velocity vectors on a plane cut at the exit region of the heat sink. Post → Plane cut

Extra You can also open the Plane cut panel by clicking the

button.

a.

In the Name field, enter the name cut_velocity.

b.

In the Set position drop-down list, select Vertical - screen select.

c.

Select a point in the graphics window between the fan and the heat sink assembly.

d.

Turn on the Show vectors option, and click Parameters to open the Plane cut vectors panel.

e.

In the Plane cut vectors panel, in the Color levels group box, select This object from the Calculated drop-down list.

f.

Check Project to plane.


167


g.

Click Done in the Plane cut vectors panel to accept the changes and close the panel.

h.

In the Orient menu, select Isometric view.

Note The graphics window will be updated, as shown in Figure 10.3 (p. 168)

Figure 10.3 Velocity Vectors at the Exit Region of the Heat Sink

3.

168

Move this plane cut through the model. a.

Hold down the Shift key, press and hold down the middle mouse button on the edge of a vector.

b.

Drag the plane cut through the model in the graphics display window.



4.

Clip the plane cut to align it with the sides of the heat sink assembly. a.

In the Orient menu, first select Orient positive X, then Scale to fit.

b.

Unexpand the Inline assembly node in the Model manager window if it was expanded in order to see the edges of the assembly in the graphics window.

c.

In the Plane cut panel (that was already opened), select Enable clipping, then click Max Y in the orange region under Clip to box.

d.

Click the top edge of the assembly in the graphics window.

e.

In the Plane cut panel, click Min Z in the orange region under Clip to box.

f.

Click the left edge of the assembly in the graphics window.

g.

In the Plane cut panel, click Max Z in the orange region under Clip to box.

h.

Click the right edge of the assembly in the graphics window.

i.

Click the Update button.

Note The graphics window will be updated, as shown in Figure 10.4 (p. 170)


169


Figure 10.4 Clipped Plane Cut

5.

Display particle traces in a forward direction. a.


b.

In the Plane cut panel, unselect Show vectors and Enable clipping and select Show particle traces.

c.

Click Parameters next to Show particle traces to open the Plane cut particles panel.

d.

Select Speed from the Variable drop-down list.

e.

In the Display options group box, keep the default selection of Uniform, and enter 50.

f.

In the Style group box, keep the default selection of Dye trace and select Particles with Radius 2.

g.

In the Color levels group box, select This object from the Calculated drop-down list.

h.

Click Done to update the graphics window.

Note The graphics window will display the particle traces in the forward direction, as shown in Figure 10.5 (p. 171)

170



Figure 10.5 Forward Particle Traces

6.

Display particle traces at the opening (Xmax). a.

In the Orient menu, select Orient negative Z.

b.

In the Plane cut panel, deselect Active and click New.

c.

In the Name field, enter the name opening-velocity.

d.

In the Set position drop-down list, select Vertical - screen select.

e.

Select a point in the graphics window near the opening (Xmax). This point will should be around 0.814 on the slider bar.

f.

Turn on the Show particle traces option, and click Parameters to open the Plane cut particles panel.

g.

Select Speed from the Variable drop-down list.

h.

In the display options group box, keep the default selection of Uniform, and enter 50.

i.

In the Style group box, keep the default selection of Dye trace and select Particles with Radius 2.

j.

In the Color levels group box, select This object from the Calculated drop-down list.

k.

Click Done in the Plane cut particles and Plane cut panels to close the panels and update the graphics window.

l.



171


Figure 10.6 Opening particle traces

10.14. Step 11: Summary In this tutorial, you used the optimization tool to determine whether an inline or a staggered pin fin heat sink performs better in a single model. The resulting maximum temperature on the package was found to be higher in the case of the staggered heat sink.

172


Chapter 11: Minimizing Thermal Resistance 11.1. Introduction Heat sink optimization is crucial in a variety of industrial applications. Usually, the challenge is to minimize the thermal resistance (or to maximize the heat transfer) and the amount of material used for the heat sink. The objective of this tutorial is to minimize the thermal resistance for the big heat sink, while keeping the maximum temperature in the entire system below 70°C and ensuring that the total mass of the heat sinks does not exceed 0.326 kg. In this tutorial you will learn how to: •

Set up an optimization problem.

•

Define design variables.

•

Define primary, compound, and objective functions.


11.3. Problem Description The model comprises an FR-4 board (FR-4.1) of 20.32 cm × 30.48 cm and 1.59 mm thick with several components placed on the board (Figure 11.1 (p. 174)). Two grilles are placed at the upstream and downstream of the board with the free flow area ratios of 60% and 50%, respectively. There are also two components (block.1.3 and block.1.3.1) dissipating 5 W each. There is a CPU (block.1) dissipating 50W and a heat sink (heatsink_small) is placed on the top of it. Between the heat sink and the CPU, there is a thermal interface material (TIM_1) with a thermal conductivity of W/mK. These components and three small power caps (power_cap_1.1, power_cap_1.1.1 and power_cap_1.1.2), dissipating 1 W each, form a non-conformal assembly (hs_assembly_1). On the other side of the board, there are eight chips, dissipating 20 W each, and a parallel plate heat sink (heatsink_big) is placed on the top of the chips. Similar to the case of the small heat sink, there is a thermal interface material (TIM_2.1 and TIM_2.1.1) between the large heat sink and the chips with the same thermal conductivity. These components together form a non-conformal assembly (hs_assembly_2).


173

Chapter 11: Minimizing Thermal Resistance



Copy ICEPAK_ROOT/tutorials/optimization/optimization.tzr to your working directory. Replace ICEPAK_ROOT by the full path name of the directory where ANSYS Icepak is installed on your computer system.

2.


3.


4.

In the File selection panel, select the packed project file optimization.tzr and click Open. The Location for the unpacked project file selection dialog appears.

5.


11.5. Step 2: Build the Model This tutorial uses an existing model. ANSYS Icepak will display the model in the graphics window. To view all components, expand all the assemblies of the model in the Model manager window. 174


Step 3: Define Design Variables

Note You can rotate the cabinet around a central point using the left mouse button, or you can translate it to any point on the screen using the middle mouse button. You can zoom into and out from the cabinet using the right mouse button. To restore the cabinet to its default orientation, select Home position from the Orient menu. Save the problem to a new project file (this enables you to expand on the problem without affecting the original file). File → Save project as 1.

In the Project name text box, enter the name optimization-new.

2.

Click Save.

11.6. Step 3: Define Design Variables The large heat sink needs to be optimized in terms of the number of fins and fin thickness. Therefore, you will define the following design variables for the large heat sink: fin count (in the range from 2 to 18) and fin thickness (in the range from 0.254 mm to 2.032 mm). 1.

Define the finCount and finThick design variables for the heatsink_big and specify their initial values. a.

Expand the hs_assembly_2 node in the Model manager window.

b.

Select the heatsink_big in the Model manager window and click the Edit object button ( to open the Heat sinks panel.

c.


d.

Under the Fin setup tab, type $finCount next to Count, and press Enter on the keyboard to open the Param value panel.

)

Important All function names are case-sensitive. e.

In the Param value panel, enter 12 for the Initial value of finCount, and click Done to close the panel.

f.

In the Heat sinks panel, under the Fin setup tab, type $finThick next to Thickness, and press Enter on the keyboard to open the Param value panel.

g.

In the Param value panel, enter 0.762 for the Initial value of finThick, and click Done to close the panel.


175


h. 2.

Click Done in the Heat sinks panel to close the panel.

Specify the constraint values for the design variables. Solve → Run optimization

Extra Alternatively, you can click the a.

176

button.

Turn on the Optimization option in the Setup tab. Then click on the Design variables tab.



The design variables that you had defined will be listed in the panel, and their initial values will be shown in the Base value text box. b.

Select finCount from the list, then enter 2 for the Min value constraint, 18 for the Max value constraint.

c.

Select Allow only multiples, keep the default value of 1, and click Apply.

d.

Select finThick from the list, then enter 0.254 for the Min value constraint, 2.032 for the Max value constraint, and click Apply.

e.

Make sure Allow only multiples is only activated for finCount, not finThick.

f.


11.7. Step 4: Generate a Mesh For this model, you will not generate a mesh in advance. Meshing will be automatically performed for each design trial during parametric trials. Model → Generate Mesh. 1.

Make sure that the Mesh type is Mesher-HD and the Mesh assemblies separately option is turned on.

2.

Make sure the Allow minimum gap changes is enabled in the Misc tab.

3.

Click Close in the Mesh control panel to close the panel. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

177


11.8. Step 5: Physical and Numerical Settings Problem setup →

Basic parameters

1.

Keep all the defaults in the Basic parameters panel.

2.

Click Accept in the Basic parameters panel to accept the settings and close the panel.


Basic Settings

1.

Make sure Number of iterations is 125.

2.

Make sure the convergence criteria for Flow is 0.001, and for Energy is 1e-7.

3.

Click Accept to close the Basic settings panel.

11.9. Step 6: Save the Model ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the project you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your project file when it saves the model.)

11.10. Step 7: Define Primary, Compound, and Objective Functions Note The objective of this tutorial is to minimize the thermal resistance of the heat sink while keeping the maximum temperature for the entire system below 70°C and ensuring that the total mass of the heat sinks does not exceed 0.326 kg. Therefore, you will define the following primary functions: thermal resistance for the large heat sink (bighsrth), mass of the large heat sink (bighsms), mass of the small heat sink (smlhsms), and global maximum temperature of 70°C (mxtmp). You will also define a compound function, the total mass of the heat sinks of 0.326 kg (totalmass). For the objective function, you will minimize the thermal resistance of the large heat sink (bighsrth). 1.

Go to Solve → Run optimization to open the Parameters and optimization panel.

2.

In the Functions tab, define four primary functions. a.

Define the thermal resistance function for the large heat sink (bighsrth). i.

178

Click the New button under Primary functions.


Step 7: Define Primary, Compound, and Objective Functions

b.

ii.

In the Define primary function panel, enter bighsrth next to Function name.

iii.

In the Function type drop-down list, keep the default selection of Global value.

iv.

In the Value drop-down list, select Thermal resistance of heatsink.

v.

In the Object drop-down list, select the heatsink_big object under hs_assembly_2, and click Accept.

vi.

In the Define primary function panel, click Accept to save the changes and close the panel.

Define the mass function for the large heat sink (bighsms). i.

c.

Define the mass function for the small heat sink (smlhsms). i.

d.

3.

4.

Repeat step (a) for the bighsms as the Function name, Global value as the Function type, Mass of objects as the Value, and heatsink_big as the Object. Repeat step (a) for the smlhsms as the Function name, Global value as the Function type, Mass of objects as the Value, and heatsink_small as the Object.

Define a constraint function as the global maximum temperature of 70°C (mxtmp). i.

Click the New button under Primary functions.

ii.

In the Define primary function panel, enter mxtmp next to Function name.

iii.

In the Function type drop-down list, keep the default selection of Global value.

iv.

In the Value drop-down list, keep the default selection of Global maximum temperature.

v.

Select Constraint and keep the default selection of Max value.

vi.

Enter 70 in the text entry field and click Accept to save the changes and close the panel.

Define a compound function. a.

Under Compound functions, click the New button to open the Define compound function panel.

b.

In the Define compound function panel, enter totalmass for the Function name.

c.

Next to Definition enter $bighsms+$smlhsms.

d.

Select Constraint and keep the default selection of Max value.

e.

Enter 0.326 in the text entry field and click Accept to save the changes and close the panel.

Define an objective function. a.

In the Parameters and optimization panel, select bighsrth from the Objective function dropdown list.

b.

Keep the default selection of Minimize value.


179



Open the Parameters and optimization panel, if it is not already opened. Solve → Run optimization

Note Alternatively, you can click the 2.

button in the Model and solve toolbar.

Set up the optimization process. a.

In the Parameters and optimization panel, click the Setup tab.

b.

Verify that the Optimization option is turned on, and keep all the defaults for this option.

c.

Deselect Allow fast trials (single .cas file).

Note Due to the geometry change based on the fin thickness and fin count, the fast trials option is not possible in this problem.

180


Step 9: Examine the Results d.

3.

Select Sequential solution of flow and energy equations.

Click Run in the Parameters and optimization panel to start the calculations.

11.12. Step 9: Examine the Results As ANSYS Icepak starts calculating solutions for the model, the Optimization run window opens and ANSYS Icepak displays the function values, design variables, and the running times for each optimization iteration. In addition, the function values and design variables are plotted versus iteration number, as shown in Figure 11.2 (p. 182).


181


Figure 11.2 The Optimization run Panel

Note Each iteration takes three trials.

11.13. Step 10: Summary In this tutorial, you used the optimization tool to minimize the thermal resistance for the big heat sink. The results show that ANSYS Icepak predicts the best (optimized) case has a fin count of 18 and a fin thickness of 0.56 mm. In this case, the maximum temperature for the entire system is determined to be 69.21°C (with the constraint of 70°C) while the total mass is 0.3245 kg (with the constraint of 0.326 kg). The objective function (thermal resistance) is predicted as 0.2421°C/W.

11.14. Step 11: Additional Exercise You can also try to optimize the fin count and the fin thickness of both heat sinks and the free flow area ratios of the inlet and exit grilles. A sample case may be as follows: •

•

182

Design variables –

Fin count for the large heat sink: 2-20

–

Fin thickness for the large heat sink: 0.254-2.032mm

–

Fin count for the small heat sink: 2-12

–

Fin thickness for the small heat sink: 0.254-2.032 mm

–

Free flow area ratio of the inlet grille: 30-80%

–

Free flow area ratio of the exit grille: 30-80%

Primary functions Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 11: Additional Exercise

•

–

Thermal resistance for the large heat sink (bighsrth)

–

Mass of the large heat sink (bighsms)

–

Mass of the small heat sink (smlhsms)

–

Maximum temperature for the entire system: 70°C (mxtmp)

Compound function –

•

Total mass of the heat sinks: 0.45 kg (totalmass)

Objective function –

Minimize the large heat sink thermal resistance (bighsrth)


183

184


Chapter 12: Radiation Modeling 12.1. Introduction This tutorial demonstrates how to model radiation in ANSYS Icepak. In this tutorial, you will learn how to include the effects of radiation in a free convection environment with surface-to-surface (S2S), discrete ordinates (DO) and ray tracing radiation models.

12.2. Prerequisites This tutorial assumes that you have worked on Sample Session in the Icepak User's Guide and the tutorials "Finned Heat Sink" and "RF Amplifier" in this guide.

12.3. Problem Description Radiation heat transfer becomes significant at high temperatures and is typically more important for natural convection problems as compared to forced convection problems in electronics cooling applications. ANSYS Icepak provides three different models to solve for radiation effects: surface to surface (S2S) model, discrete ordinates (DO) model and ray tracing model. This tutorial involves a source with a heat sink placed on a printed circuit board (PCB) and is being cooled with natural convection. We will first solve the model without radiation, then use the surface to surface model followed by the discrete ordinates and the ray tracing models and lastly compare the results of all these four cases.

12.4. Step 1: Create a New Project Open a new project and name it hsink-rad.


Open the Cabinet panel by double clicking the Cabinet object in the Model manager window. In the Geometry tab, enable the Fix values option to make sure the values stay the same as we use different units. Change all the units from m to mm. Then, input the following dimensions in the Geometry tab of the Cabinet panel (Figure 12.1 (p. 186)).


185

Chapter 12: Radiation Modeling

Figure 12.1 Dimensions of the Cabinet and the Boundary Condition Specifications

2.

In the Properties tab of the Cabinet panel, define all the sides of the cabinet as shown above. The min y and max y sides are defined as openings while all the remaining sides are stationary walls.

3.

Click Done to close the Cabinet panel.

4.

The printed circuit board (PCB), heat sink base and the fins of the heat sink will be constructed using the block object in ANSYS Icepak.

5.

Create the PCB.

186

a.

First, create a block and rename it as PCB in the Info tab of the Blocks panel.

b.

Specify the dimensions of the block in the Geometry tab as shown below in Figure 12.2 (p. 187).



Figure 12.2 Dimensions of the PCB

c. 6.

Click Done to close the Blocks panel.

Create a new material and assign it to the PCB. a.

Right-click the Model node and select Create object and then Material. A new node called Materials will open.

b.

Expand the Materials node until you reach material.1. Double click material.1 to open the Materials panel.

c.

In the Properties tab of the Materials panel, choose Orthotropic from the Conductivity type drop-down list. i.

7.

Enter 40, 40, and 0.4 W/m-K for the X, Y, and Z directions, respectively.

d.

Click Done to close the Materials panel.

e.

In the Model manager window, double click the PCB object we created to open the Blocks panel again.

f.

In the Properties tab of the Blocks panel, pick material.1 from the Solid material drop-down list.

g.


Create the heat sink base. a.

Create a new block and rename it as hs-base in the Info tab of the Blocks panel.

b.

Specify the dimensions of the block in the Geometry tab as shown below in Figure 12.3 (p. 188). Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

187


Figure 12.3 Dimensions of the hs-base

c. 8.


Create the fins. a.

Create a new block and rename it as hs-fin.1.1 in the Info tab of the Blocks panel.

b.

Specify the dimensions of the block in the Geometry tab as shown below in Figure 12.4 (p. 189).

Note The units depicted in Figure 12.7 (p. 192) are in mm and m.

188



Figure 12.4 Heat Sink Fin Dimensions

9.

c.

Leave all the other properties as their default values. Click Done to close the Blocks panel.

d.

To complete the creation of the remaining fins we will use a copy procedure. i.

Right click the hs-fin1.1 object in the Model manager window and select Copy. The Copy block hs-fin.1.1 panel opens.

ii.

Set Number of copies to 8.

iii.

Check the Translate option and set the X, Y and Z offset to 15, 0, and 0 mm respectively.

iv.

Click Apply to close the Copy block hs-fin.1.1 panel and create the new fins.

Create a 75W 2D source. a.

Create a source using the Create sources button in the model toolbar.

b.

In the Sources panel, specify the geometry and properties of the source according to Figure 12.5 (p. 190).

c.

Click Done to close the Sources panel and complete the creation of the model.


189


Figure 12.5 Source at the Bottom on the Heat Sink

Tip Alternatively, you can use the snapping tool from the object geometry area to snap the source dimensions to those of the min z side of the hs-base block object.

The final model should appear as shown in Figure 12.6 (p. 191).

190



Figure 12.6 Schematic of the Model

12.6. Step 3: Generate a Mesh In order to generate a fine mesh on the heat sink and the neighboring regions while retaining a coarser mesh in the remaining part of the model, we create a non-conformal assembly enclosing all the objects created and specify separate meshing parameters for this assembly. 1.

Choose the source (source.1), base of the heat sink (hs-base), and all the fins (hs-fin1.1.x) in the Model tree together and right mouse click to and select Create and then Assembly.

2.

Double click assembly.1 in the model tree to open the Assemblies panel. a.

In the Meshing tab, click on the Mesh separately button, and specify the slack values as well as the max sizes in each of the coordinate directions for the assembly as depicted in Figure 12.7 (p. 192).

b.

This will refine the mesh within the assembly and also prevent the increase in the overall mesh count by confining the fine mesh to within the assembly object.


191


Note The units depicted in Figure 12.7 (p. 192) are in mm and m.

Figure 12.7 Meshing Parameters for assembly.1

c. 3.

192

Click Done to close the Assemblies panel.

Once the assembly creation is complete, open the Mesh control panel by pressing the Generate mesh button. a.

Change the Mesh units to mm.

b.

Input the Max element size specifications according to Figure 12.8 (p. 193).


Step 5: Solving the Model Without Radiation

Figure 12.8 Global Mesh Control Parameters

c.

Keep all other parameters as their default values.

d.

Make sure Allow minimum gap changes is checked under the Misc tab.

e.

Press Generate to create the mesh.

f.

You can view the mesh using the Cut plane and Surface options available in the Display tab.

g.

Once you have finished viewing the mesh, make sure you uncheck Display mesh in the Display tab, and click Close to close the Mesh control panel.

12.7. Step 4: Physical and Numerical Settings Once the model is meshed, we will solve it for different situations, i.e. with radiation off followed by including the effects of radiation using both the view factor method as well as the discrete ordinates and ray tracing methods available in ANSYS Icepak 13 or later.

12.8. Step 5: Solving the Model Without Radiation 1.

Go to a.

Problem setup →

Basic parameters.

Under the General setup tab(Figure 12.9 (p. 194)) i.

Make sure that solution for both the Flow and Temperature is switched on.

ii.

Because this is a natural convection problem turn on the Gravity vector option.

iii.

Choose Turbulent under the Flow regime group box and use the default option of Zero equation.


193

Chapter 12: Radiation Modeling iv.

Make sure that the Radiation option is turned Off.

Figure 12.9 Basic Parameters

b.

Under the Defaults tab i.

c.

In the Ambient conditions group box, set the Temperature and the Radiation temp to 40°C.

Under the Transient setup tab. i.

Enter a small velocity value for the Y velocity such as 0.01 m/s.

Note In free convection flow problems, setting a small initial velocity opposite to the gravity vector direction is suggested. ii. d. 2.

3.

194

Retain the defaults for all other settings in the Basic parameters panel.

Press Accept to close the Basic parameters panel.

Go to


Basic settings.

a.

Set the Number of iterations to 400

b.

Make sure the Flow is 0.001 and the Energy is 1e-7 in the Convergence criteria group box.

c.

Click Accept to close the Basic settings panel.

Go to


Advanced settings.


Step 5: Solving the Model Without Radiation a.

In the Advanced solver setup panel specify the Under-relaxation parameters of 0.7 and 0.3 for Pressure and Momentum, respectively.

b.

Select Double from the precision drop-down list at the bottom of the panel (Figure 12.10 (p. 195)).

Figure 12.10 Solution Settings

c.

Keep all other default options in the Advanced solver setup panel.

d.

Press Accept to close the Advanced solver setup panel.


195


12.9. Step 6: Save the Model ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save project

12.10. Step 7: Calculate a Solution- No Radiation 1.

Go to Solve → Run solution to bring up the Solve panel. a.

Enter norad as the solution ID.

b.

Click on Start solution at the bottom of the panel.

c.

Once the solution residuals have converged you can post process the results using plane cuts and object faces. Note the maximum value of temperature for comparison with successive runs wherein radiative heat transfer will be enabled in the model.

Note You can check the maximum temperatures of each object by going to Report → Solution overview → Create.

12.11. Step 8: Surface to Surface (S2S) Radiation Model 1.

2.

Go to

Basic parameters.

a.

In the Basic parameters panel, select On in the Radiation group box.

b.

Make sure the Surface to surface radiation model is enabled.

c.

Click Accept to close the Basic parameters panel.

To model radiation effects go to Model → Radiation form factors or use the radiation icon ( open up the Form factors panel.

) to

a.

Under Participating objects, select all objects by clicking All and leave all other settings to their default values.

b.

Press Compute to calculate the view factors.

c.

196

Problem setup →

i.

You can display the view factors calculated by clicking each participating object listed under Display object values.

ii.

After reviewing the view factors, select Don't recompute.

iii.

The settings for the view factor calculations setup are shown in Figure 12.11 (p. 197).

Press Close to close the Form factors panel.



Figure 12.11 Enabling Radiation in ANSYS Icepak Model

3.

Go to Solve → Run solution and start the solver with S2S as the solution ID.

4.

Once the solution residuals have converged, make note of the maximum temperature.

12.12. Step 9: Discrete Ordinates (DO) Radiation Model Next, we will run the discrete ordinates radiation model. 1.

Go to

Problem setup →

Basic parameters.

a.

Enable the Discrete ordinates radiation model option in the Radiation group box.

b.

Press Accept to close the Radiation panel.

2.

Start the solution again with DO as the solution ID.

3.


12.13. Step 10: Ray Tracing Radiation Model Next, we will run the ray tracing radiation model. 1.

Go to

Problem setup →

Basic parameters.

a.

Enable the Ray tracing radiation model option in the Radiation group box.

b.

Press Accept to close the Radiation panel.

2.

Start the solution again with Ray as the solution ID.

3.


12.14. Step 11: Examine the Results Compare the maximum temperature between the runs where radiative heat transfer was enabled versus the runs where it was not. You can clearly see that radiation is important in this model and there is a significant difference in the maximum temperature in the field with and without radiation. Further,


197

Chapter 12: Radiation Modeling there is reasonable agreement in the plane cut post processing objects obtained using the different radiation models. Figure 12.12 (p. 199) compares the temperature fields for all the four cases.

198



Figure 12.12 Plane cuts on the z = 20 mm plane for (a) Radiation disabled (b) S2S radiation model (c) Discrete ordinates radiation model and (d) ray tracing radiation model

Table 12.1 Maximum Source Temperature for Different Models No radiation

82.59°C

Surface to surface

75.08°C Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

199

Chapter 12: Radiation Modeling Discrete ordinates

76.38°C

Ray tracing

75.63°C

Note The actual values may differ slightly on different machines, so your values may not look exactly the same. In most models, the use of the surface to surface (view factors) model is strongly recommended. The discrete ordinates model should be used only for very complex geometries where there are many surfaces and computation of the view factors can become extremely computationally expensive. This is also true when there are CAD objects present in the ANSYS Icepak model. The ray tracing model is also for complex geometries and for objects that have large temperature variations.

12.15. Step 12: Summary In this problem we demonstrated how to model radiation in ANSYS Icepak. We first solved the model without radiation and then used the surface-to-surface model followed by the discrete ordinates and ray tracing methods and lastly compared the results of all four cases.

200


Chapter 13: Transient Simulation 13.1. Introduction The purpose of this exercise is to demonstrate how to model and post-process transient problems. In this tutorial, you will learn how to: •

Define a transient problem

•

Specify time-dependent parameters for objects

•

Group and copy modeling objects

•

Examine the results of a transient simulation, including animating results over time

13.2. Prerequisites This tutorial assumes that you have worked on Sample Session in the Icepak User's Guide and the first two ANSYS Icepak tutorials of this guide.

13.3. Problem Description The model involves a natural convection cooled heat sink and four heat sources attached to the bottom of the heat sink. The power dissipated by each of the four sources varies with time and peaks at 100 W.


Create a new project called transient.

2.

From Problem setup → Basic parameters, go to the Transient setup tab, select Transient under the Time variation group box. Then enter the Start and End times as 0 and 20 seconds, respectively.

3.

Click on Edit parameters and set the Time step increment to 1 s and the Solution save interval to 1. Click Accept in the Transient parameters panel and then the Basic parameters panel to save the new time parameters.


201

Chapter 13: Transient Simulation

Figure 13.1 Setting up the Model as Transient

13.5. Step 2: Build the Model Construct the model according to the following specifications. The final model is shown in Figure 13.4 (p. 206). •

Cabinet xS

0.05 m

xE

0.35 m

yS

0.1 m

yE

0.55 m

zS

0.05 m

zE

0.25 m

Open the Cabinet object panel, go to the Properties tab, under Wall type, change Min y and Max y to Opening. Press Done and then Shift+I for an isometric view. •

Plate Object

Specification

plate.1

xS = 0.1 m

xE = 0.3 m

Solid material:

Geometry:

yS = 0.2 m

yE = 0.4 m

default

Rectangular

zS = 0.12 m

Plane: X-Y

(Al-Extruded) Thermal model: Conducting thick: 10 mm

202


Step 2: Build the Model •

Blocks Object

xC

yC

zC

Height

Radius

IRadius

Specification

block.1

0.15 m

0.25 m

0.13 m

0.06 m

0.02m

0.0

Block type:

Geometry:

Solid

Cylinder

Radius2

IRadius2

Solid material:

Plane: X-Y

0.012m

0.0

default

Nonuniform radius

(Al-Extruded)

Make two copies of the tapered fin (block.1), offset by 0.05 m in the X direction (i.e., Number of copies = 2, and Translate with X offset = 0.05 m). Select all three tapered fins, and make two copies of this group with an offset of 0.05 m in the Y direction (i.e., Number of copies = 2, and Translate with Y offset = 0.05 m). Remember to right mouse click on the icon in the Model tree to copy objects. These tapered cones model a heat sink with tapered cone fins. •

Sources The four sources have a peak power of 100 Watts each with a cycle time of 20 seconds. The variation of power is according to the following exponential curve, and is the time. Object

= × , where and are constant,

Specification

source.1

xS = 0.12 m

xE = 0.18 m


yS = 0.22 m

yE = 0.28 m

Plane: X-Y

zS = 0.12 m

Total power = 100 W

Create a source (source.1) per the specification in the table above. In the Properties tab of the Sources panel, toggle on Transient, click Edit, and enter 0 for Start time and 20 for End time. To specify the variation curve, click on Exponential and set a = 0.025 and b = 100. Click Update and Done, in the Transient power panel, and then the Sources panel.


203


Figure 13.2 Defining Transient Power for the Sources

Now make one copy of source.1 with an offset of 0.1 m in the X-direction. Select source.1 and source.1.1, then make one copy of these two sources with an offset of 0.1 m in the Y-direction to complete the construction of the sources. Basic To view the time-dependent power specified for the sources, go to Problem setup → parameters. Select the Transient setup tab and click on View (next to Edit parameters) near the top of this panel. This displays the time variation of the power specified using sources.

204



Figure 13.3 Viewing the Variation of Power on the Sources with Time

A time dependent power profile such as a piecewise linear curve can also be imported/exported by clicking Load All/Save All in the Transient panel. Clicking Load All will open the Load all curves file selection dialog box and override any existing data. Select the CSV file containing the curve data and click Open. The final model should appear as that shown in Figure 13.4 (p. 206).


205


Figure 13.4 Schematic of the Model

13.6. Step 4: Generate a Mesh To generate a mesh for this model, go to Model → Generate mesh and specify a global maximum element size of 0.02 m in the x, y and z directions in the Max element size group box. Across from Mesh parameters, select Normal and keep the default global mesh settings parameters. Then go to the Options tab and select Init element height and enter 0.005. Then click Generate to create the mesh. Once the mesh is generated, display and examine the mesh from the Display tab. Remember to uncheck the Display mesh option when you are done examining the mesh.

Note The Init element height feature can be used in a relatively simple model as this one. It is not recommended to be used for complex models as this can create very large mesh count.

13.7. Step 5: Physical and Numerical Settings The transient settings for this model were defined at the initial stages of model building. This is required as assigning transient power to the sources require the problem as transient a priori. Go to

Problem setup →

Basic parameters. In the General setup tab, ensure Laminar is set for

Flow regime, and toggle on the default Gravity vector (i.e., X = 0, Y = -9.80665 m/s2, Z = 0). In the Transient setup tab, give a small initial (global) velocity of 0.001 m/s in the Y direction. Accept the changes made and exit this window.

206


Step 8: Generate a Summary Report Go to Solution settings → Basic settings and click on Reset to examine the estimated Rayleigh Advanced settings and set the Under-relaxation number. Then go to Solution settings → factors to 0.7 for Pressure and 0.3 for Momentum. Press Accept to close the panel. In the Basic settings panel, set Iterations/ timestep to 100. The number of iterations per time-step should be sufficient for the solution to converge at each time-step. Press Accept to close the panel.


Create a point monitor to monitor the temperature change with time by dragging and dropping source.1 into the Points folder in the Model tree.

13.8. Step 6: Save the Model ANSYS Icepak automatically saves the model for you before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save project

13.9. Step 7: Calculate a Solution Go to Solve → Run solution. In the Results tab, click Write overview of results when finished and click Start solution.

13.10. Step 8: Generate a Summary Report Go to Solve menu and select Define report. In the Define summary report panel, enable Specified. Select All times in the Report time group box. Select New, hold down the Shift key and select all blocks in the Objects drop down list. Click Accept. Click Write to display the Report summary data panel shown in Figure 13.6 (p. 208)


207


Figure 13.6 Define summary report Panel

13.11. Step 9: Examine the Results Results of transient runs can be displayed in still images or animations. To display still images, you can choose to display at a given time or a given time-step. To do so, after creating post objects in the same manner as in a steady state run, you can go to Post → Transient settings or click the transient settings icon ( ) to open the Post-processing time panel. To display at a given time-step, you can toggle on Time step, and click Forward or Backward to step through the time steps. To display at a given time, you can toggle on Time value, fill in the time to begin the display and the time Increment, and select Forward or Backward. To view these images in this model, create the following post-processing objects:


Specifications

Description

face.1

Object: all blocks and plate.1

Observations: The view shows the temperature distribution on the faces of all the blocks and the base plate. The transport of thermal energy from the sources to the fins of the heatsink can be clearly observed.

Show contours/Parameters

208


Step 9: Examine the Results Object

Specifications

Description

Contours of: Temperature Contours options: Solid fill Shading options: Smooth Color levels: Calculated/Global limits Post → Transient settings: Time step: 1 or Time value: 0 Forward or Backward cut.1

Set position: Z plane through center

Observation: The view shows air flowing from one opening to the other. Also notice that the velocity distribution changes with time.

Show vectors/Parameters Color by: Velocity magnitude Transient: Same as the above To animate the above post objects, go to Post → Transient settings to open the Post-processing time panel. Click on Animate to open the Transient animation window. To animate the current display on screen, click on Animate in the Transient animation panel. The animation can be played once, from the start time to end-time, or in the Loop mode. In addition to animating the display in screen, you can also write the animation to a file in MPEG, GIF, and some other neutral formats to be saved and played back later using a third party software. To do that, go to Post → Transient settings, then click Animate to open the Transient animation panel. Toggle on Write to file, then click Write to open the Save animation panel. Pick a file format, give it a file name, and then Save. This sequence saves the entire display area with no scaling. Alternatively, you can click on the Options tab in the Save animation panel and modify the Scale factor in the Save animation options panel. Also available in Save animation options panel is Print region. Choose the default Full screen or Mouse selection. Choosing Mouse selection allows one to draw a rubber band and select only a part of the screen. To do so, choose Mouse selection, specify the file type and file name, then click on Save in the Save animation panel. With the cursor showing a square and the red prompt at the bottom of the screen, draw a rectangular region with the left mouse to save it to the animation file. You can examine how a variable changes over time at selected points using the History plot panel. To open this panel, select History plot in the Post menu or click (

) in the Postprocessing toolbar.

In the History plot panel, enter 20 seconds for End time, click the Add point button and select source.1 for the point. Click the Create button to display the plot shown in Figure 13.7 (p. 210).


209


Figure 13.7 History plot

13.12. Step 10: Examine Transient Results in CFD Post You can also postprocess results using tools in ANSYS CFD-Post. Go to the Post menu in Icepak and select Write CFD Post File. Enabling this option writes out a data file (filename.cfd.dat) that can be loaded into CFD-Post. To launch CFD Post for a Windows system, click Start>All Programs>ANSYS 14.0>Fluid Dynamics>CFD Post 14.0 or for a Linux system you can access CFD Post using ~ansys_inc/v140/CFD-Post/bin/cfdpost. In CFD Post, select Load Results... in the File menu to display the Load Results File dialog box. Select the filename.cfd.dat file that corresponds to the transient solution.

210


Step 10: Examine Transient Results in CFD Post

Figure 13.8 Results in CFD Post

Once the results have been loaded into CFD-Post, there are several options to view and analyze a transient solution. 1.

Display time history similar to what is displayed in Icepak. a.

Go to Insert → Text

b.

Enter the text, “Auto Annotation”.

c.

In the Definition tab of the Details view, enter “Time”.

d.

Enable the Embed Auto Annotation option.

e.

In the Type drop-down list, select Timestep.

f.

Click Apply.


211


Figure 13.9 Details of Auto Annotation

2.

212

Create a contour. a.

Go to Insert → Contour and create a new contour named TemperatureContours.

b.

Update the settings for the Geometry tab of the Details view for TemperatureContours as shown in Figure 13.10 (p. 213) and click Apply to create the contour (Figure 13.11 (p. 214).


Step 10: Examine Transient Results in CFD Post

Figure 13.10 Details of TemperatureContours


213


Figure 13.11 TemperatureContours Display

3.

Display temperature at different time steps. a.

214

) to display the Timestep Selector panel. Double click a Click the timestep selector icon ( timestep to view the corresponding temperatures. See Figure 13.12 (p. 215) for details.


Step 10: Summary

Figure 13.12 Timestep Selector Panel

Additional options that are available in CFD-Post can be found in "Postprocessing Using ANSYS CFDPost".

13.13. Step 10: Summary In this tutorial, you set up and solved a transient model and used the animation technique to examine the results over time. Results were also examined in CFD-Post.


215

216


Chapter 14: Zoom-In Modeling in ANSYS Workbench 14.1. Introduction This tutorial demonstrates how to create and modify a zoom-in model (system sub-model) in ANSYS Icepak. You will begin in ANSYS Workbench and drag an Icepak template into the Project Schematic. An Icepak .tzr file is imported, the model is modified and solved according to the instructions in the tutorial. The project will also include postprocessing results in CFD-Post. In this tutorial, you will learn how to: •

Create an ANSYS Icepak analysis in ANSYS Workbench

•

Create a zoom-in model from a solved system level model

•

Run that model with more detail added

•

Merge the detailed system level model back into the system level model

•

Postprocess results in CFD-Post

14.2. Prerequisites This tutorial assumes that you have little experience with ANSYS Icepak and ANSYS Workbench, but that you are generally familiar with the interface. If you are not, please review Sample Session in the Icepak User's Guide and the tutorial "ANSYS Icepak - ANSYS Workbench IntegrationTutorial" of this guide.

14.3. Problem Description The objective of this exercise is to become familiar with ANSYS Icepak's zoom-in-model capabilities. Detailed systems can sometimes be solved first with reasonable simplifications, and then have more detailed sub-models run from boundary conditions created from the region in question. For example, multiple packages can be simplified as one plate with the total power of all packages. A system level model can be solved, and a sub-region can be created with the velocities and temperatures from the system level model and have more detail on the board in question. In this tutorial, you will run a simplified system level model of a slotted chassis, learn how to create an ANSYS Icepak zoom-in model, run that model and then merge the detailed section back into the original system.


217

Chapter 14: Zoom-In Modeling in ANSYS Workbench



218

Start ANSYS Workbench.



Figure 14.2 ANSYS Workbench

2.

Copy ICEPAK_ROOT/tutorials/rack/rack.tzr to your working directory. You must replace ICEPAK_ROOT by the full path name of the directory where ANSYS Icepak is installed on your computer system.

3.

Drag an Icepak template from the Toolbox into the Project Schematic.

4.

Right mouse click the Icepak Setup cell and select Import Icepak Project From .tzr.

5.

Select Browse... and the File selection panel appears. Select the packed project file rack.tzr and click Open.

6.

The CAD model appears in the graphics display window. Click the isometric toolbar icon ( the isometric view of the model.

) to display

14.5. Step 2: Build the Model Note Look at the specifications of the different components. The model has 10 pairs of plates (Figure 14.1 (p. 218)). If you examine any pair of plates, plate.1.x represents the PCB and plate.2.x represents the components on that PCB. In real life each PCB would have many components mounted on it. We are simplifying the model by representing the components with a single plate. The thickness of these plates equals the average height of the components. All the PCBs have the same configuration and the same components. The total power of the components in each PCB is 30 W, so each of the plates (plate.2.x) are 30 W. Save the problem to a new project file. This will allow you to expand on the problem without affecting the original file. File → Save project


219

Chapter 14: Zoom-In Modeling in ANSYS Workbench 1.

In the Project text box, enter the name rack-new.

2.

Click Save.

Note ANSYS Workbench will close Icepak to save the model, you will need to launch Icepak again to continue.

14.6. Step 3: Generate a Mesh For this model, you will generate the mesh in just one step. You will specify object-specific meshing parameters to ensure that the resulting mesh is sufficiently fine near object faces to resolve the flow physics properly. 1.

Go to Model → Generate Mesh or use the toolbar shortcut (

2.

In the Mesh control panel, make sure Hexa unstructured is selected as the Mesh type.

3.

Set the Max element size for X, Y, and Z to 0.03 m if not already set.

4.

Select the Normal option next to Mesh parameters.

5.

In the Local tab, select Edit next to Object params (Figure 14.3 (p. 221)). Verify that the individual localized mesh settings for the following objects are:

) to open the Mesh control panel.

Object type

Object name

Parameter

Requested Value

Openings

All openings

Y count

10

Plates

All plates

Low end height

0.003

High end height

0.003

Y count

4

Block

block.3

Note You can also set mesh parameters by right clicking object in the Model tree and selecting Edit mesh parameters.

220



Figure 14.3 Object Parameters in the Mesh control Panel

6.

Press Done to close the Per-object meshing parameters panel.

7.

In the Settings tab of the Mesh control panel, Generate the mesh and then display and check the mesh quality from the Display tab. Uncheck the Display mesh option when you are done.


Go to Solution settings → Basic settings and Solution settings → , and verify that the following values are set for each variable:


Advanced settings

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Chapter 14: Zoom-In Modeling in ANSYS Workbench 2.

Go to Problem setup → Basic parameters and make sure the Flow regime is Turbulent and the turbulence model is Zero equation under the General setup tab. Press Accept to close the panel.

3.

Now add two temperature point monitors for plate2.1 and plate2.2 into the Points folder to observe the progress of the solution at the center of the objects. To do this, highlight both objects in the Model tree using the Ctrl key and the left mouse button, and then drag objects into the Points folder. The default setting for a monitor point is temperature so nothing else has to be done.

14.8. Step 5: Save the Model ANSYS Icepak saves the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the project you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your project file when it saves the model.) File → Save project


Go to Solve → Run solution menu and turn on Sequential solution of flow and energy equations in the General setup tab.

Note When gravity is not turned on in the solution, you have the opportunity to reduce solve time if desired by selecting this option. Since there are no buoyancy effects, there is no longer a coupling of the Navier-Stokes and energy equations. Thus, you can completely converge the flow equations and then use that value in the energy equation instead of solving both on every iteration. 2.

Click Start solution to run the solver.

14.10. Step 7: Examine the Results 1.

After the solution has converged, create the following post processing objects: Object

Specifications

Description

face.1

Object: plate2.2

Object-face view of temperature on plate2.2

Show contours/Parameters

Observation(s): Note the min & max temperatures and the temperature distribution.

Contours of: Temperature Contours options: Solid fill Shading options: Banded Contour levels: Level spacing: Fixed/ Number = 20 Calculated: This object face.2 222

Object: all fans

Objects-face showing the flow pattern.


Step 7: Examine the Results Object

Specifications

Description

Show particle traces/Parameters

Observation(s): Animate the particle traces. If you want to see motion from start to end, turn off particles and animate the traces.

Variable: Speed Display options: Uniform = 50 Style: Dye trace and Particles cut.1

Plane location:

Plane cut (x-y) view of the velocity vectors in the z plane.

Set position: Z plane through center

Observation(s): Flow patterns (especially around the plates)

Show vectors cut.2

Plane location:

Plane cut (y-z) view of the velocity vectors in the x plane.

Set position: X plane through center

Observation(s): Flow patterns (especially around the plates)

Show vectors face.1 and cut.1 should look similar to Figure 14.4 (p. 223) and Figure 14.5 (p. 224).

Figure 14.4 face.1 (Plate2.2 Temperature)


223


Figure 14.5 cut.1 (Z-Plane Through Center Velocity)

2.

Finally, save all the postprocessing objects created. Go to Post → Save post objects to file. Save it with default file name post_objects to be used in future.

14.11. Step 8: Create a Zoom-In Model With a solution obtained for the main model, we can now zoom-in around one pair of PCB-components plates, namely plate.1.2 and plate.2.2. 1.

Go to Post → Create zoom-in model. The Zoom-in modeling panel appears. The boundaries for the zoom-in also appear in the ANSYS Icepak main window as a bold white box. By default this zoomin box is coincidental with the cabinet.

2.

Resize this box by entering the values shown in Figure 14.6 (p. 225) into the zoom-in window. Be sure to change Max Y to an outflow and Min Z and Max Z to walls. (Please note that the zoom-in box now surrounds plate.1.2 and plate.2.2 and includes portions of some on the remaining system level model objects (Figure 14.7 (p. 226)).) There needs to be one outflow to compensate for slight differences in flow with a pressure differential. The wall objects are created since the entire face on that side is created in a solid or on a solid surface.

224


Step 8: Create a Zoom-In Model

Note The coordinates for each of the zoom-in boundaries can also be specified by clicking the Select button to the right of the appropriate text entry box and clicking the left mouse button on the desired point in the graphics display window. You may want to orient your view depending upon the coordinate being selected to ensure a more accurate selection. The boundaries of the zoom-in model will be displayed in the graphics window as you update them.

Figure 14.6 The Zoom-in modeling setup Panel

3.

Click on Accept to create the zoom-in model. Since many of the parts in the zoom-in model extend out of the zoom-in box, a warning message window should appear listing a set of objects that lie outside.

4.

In the Objects overlapping dialog box, click the Resize button to resize these parts to fit into the zoom-in model. ANSYS Icepak writes out a zoom-in model called rack-new.zoom_in. ANSYS Icepak reports on the operations to construct the model and creates the profiles in the ANSYS Icepak messages window.


225


Figure 14.7 Zoom in Box

14.12. Step 9: Edit the Zoom-in Model 1.

Set up a new Icepak template in same ANSYS Workbench project. Then link a Results cell to this Icepak component. The Results cell should link to the Icepak Solution cell.

2.

Right mouse click the Icepak Setup cell and select Import Icepak Project

3.

In the file selection dialog, select the zoom-in model called rack-new.zoom_in. (It will be in the same location as the folder for the system level model.) In the system level model we used a single conducting

226


Step 9: Edit the Zoom-in Model thick plate to represent the components. We can now replace the plate.2.2 by the individual components. 4.

Double click plate.2.2 to open the Plates panel and make the following changes: Field

Value

Info Name

Chip

Geometry Specify by

Start / length

YL

0.05 m

ZL

-0.05 m

Properties Power 5.

3.0 W

Create nine additional components in an array. a.

Right mouse click Chip and select Copy.

b.

Create two copies of Chip with an Z-offset of -0.065 m.

c.

Select and highlight all three Chip plates in the Model tree.

d.

Make three copies of the three plates with an Y-offset set to 0.07 m in the same way you copied the singe chip.

e.

View the geometry in isometric view (Shift+I).

f.

Delete two of the components to form the pattern shown in Figure 14.8 (p. 228).


227


Figure 14.8 Schematic of the Completed Zoom-in Model

14.13. Step 10: Mesh the Zoom-In Model 1.

Go to Model → Generate mesh, and set the Mesh type to Hexa unstructured and the Mesh parameters to Coarse.

2.

In the Local tab, turn off the Object params.

3.

In the Global tab, enter the following global mesh settings:

Table 14.1 Global Settings for Zoom-in Model Max element size for X:

0.003 m

Max element size for Y:

0.02 m

Max element size for Z:

0.02 m

Min elements in gap

2

Min elements on edge

1

Max size ratio

3

The meshing panel should now look like Figure 14.9 (p. 229).

228


Step 12: Examine the Zoom-in Results

Figure 14.9 Zoom-in Mesh control Panel

4.

Generate the mesh and then display and check the mesh quality from the Display tab. Make sure to uncheck the Display mesh option when you are done.

14.14. Step 11: Zoom-In Physical and Numerical Settings 1.

Drag and drop the two chips in the corners of the top row (chip.5 and chip2.3) into the Points folder in the Model tree to monitor the temperature at the centers of these two chips.

2.

Delete the monitor point plate.2.2 brought in from the system level model (it no longer exists as an object).

3.

Go to

4.

Solve the model by selecting Solve → Run solution and by clicking on Start solution under the General setup tab.


Basic settings to change the maximum number of iterations to 300.

14.15. Step 12: Examine the Zoom-in Results After the solution has converged, create the following postprocessing objects and compare the results with the system level models. Object

Specifications

Description

face.1

Object: all chips

Object-face view of temperature on all chips

Show contours/ Parameters

Observation(s): Note the min & max temperatures and the temperature distribution.


229

Chapter 14: Zoom-In Modeling in ANSYS Workbench Object

Specifications

Description

Contours of: Temperature Contours options: Solid fill Shading options: Smooth Calculated: This object face.2

Object: side_opening.miny

Object-face showing the flow pattern

Show particle traces/ Parameters

Observation(s): Note the flow pattern on both sides of plate1.2 and over the components. Animate the particle traces.

Variable: Speed Particle options Start time: 0; End time: 1 Display options: Uniform = 100 Style: Dye trace and Particles

Figure 14.10 (p. 231) shows the two object faces at the same time.

230


Step 14: Additional Exercise 1

Figure 14.10 face.1 and face.2

14.16. Step 13: Summary If we were to model all the components in the system level model, we could have ended up with a cell count of about 10 times the size of the zoom-in model. The simplifications at the system-level enabled us to quickly solve the system level model. The zoom-in model showed us the temperature variation at the card level, which was essential to identify the correct locations of the hot spots.

14.17. Step 14: Additional Exercise 1 Set up this problem in a Workbench based Icepak project. Then set up another Icepak component in the same Workbench project schematic and replace the PCB plate with a detailed PCB object and postprocess the results in CFD Post.


231

Chapter 14: Zoom-In Modeling in ANSYS Workbench You can then perform a comparison study in CFD Post by setting up a third Icepak component. This time duplicate the first Icepak component and link this component to the available Results component. Post process the results in CFD Post and compare them to the results containing the PCB plate object.

14.18. Step 15: Additional Exercise 2 Additional exercise may be performed to create a non-conformal mesh assembly surrounding the details of the third PCB in the main model. Then, the results obtained using non-conformal meshed assembly may be compared to the results obtained using the main model with the conformal mesh and to the ones from the zoom_in approach with conformal mesh. 1.

Save the rack-new.zoom_in model with a new model name such as rack.zoom_in_merge.

2.

Delete all the components within the model except all the plates which represents the PCB and the chips and re-save the model. (This version has all the unnecessary components for the system merge removed.)

3.

Open the main model rack.

4.

Save it as rack-merge-NC.

5.

Use File → Merge Project to import rack.zoom_in_merge into this model with all the details of chips.

6.

Deactivate the old components residing where the merged components are ( plate.1.2 and plate.2.2).

7.

Create a non-conformal assembly containing all the chips and the board. It is suggested a slack value of 3-5 mm in all directions for the assembly is a good value to start without violating any of the rules.

8.

Finally, mesh and run the model with a different solution ID and compare the results to the previously obtained ones. Verify that the results are very comparable. Figure 14.11 (p. 233) shows a temperature comparison between the zoom-in model and the system level model with a non-conformal assembly. While the temperatures are slightly different, the overall distribution (hot spots) stay the same.

232


Step 15: Additional Exercise 2

Figure 14.11 Temperature Comparison: Zoom-in vs. System with Non-conformal assembly


233

234


Chapter 15: IDF Import 15.1. Introduction This tutorial demonstrates the “IDF" import capability of ANSYS Icepak. In this tutorial, you will learn how to: •

Import IDF files.

•

Apply the various options offered in ANSYS Icepak's IDF import capability.

15.2. Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS Icepak and that you have solved or read the tutorial "Finned Heat Sink". If you have not, please review Sample Session in the Icepak User's Guide.

15.3. Problem Description Intermediate Data Format (IDF) is a data exchange specification between ECAD and MCAD for the design and analysis of printed circuit boards. An IDF CAD model is generated by software such as Mentor Graphics. Typical IDF models include a board file and a library file. The board file includes board layout (board dimension and shape, location of the components), and the library file includes component information (size, power dissipation, junction to case and junction to board thermal resistance, etc.). ANSYS Icepak's IDF import utility is designed to convert the IDF CAD data into an ANSYS Icepak model automatically. ANSYS Icepak imports the geometry as well as parameters such as power and material property based on the availability of such information. This tutorial does not involve generating a mesh, calculating a solution or examining results. These steps will not be shown in this tutorial.


Start ANSYS Icepak, as described in Starting ANSYS Icepak on a Linux System and Starting ANSYS Icepak on a Windows System of the User's Guide. When ANSYS Icepak starts, the Welcome to Icepak panel opens automatically.

2.

Click New in the Welcome to Icepak panel to start a new ANSYS Icepak project. The New project panel appears. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

235

Chapter 15: IDF Import 3.

Specify a name for your project. a.

In the Project name text box, enter the name idf-demo.

b.

Click Create.

15.5. Step 2: Build the Model To build the model, you will first import the board layout. The board and the associated library files have to be chosen at this step. File → Import → IDF file

Figure 15.1 IDF Import Menu

1.

In the IDF import panel, click the Browse button next to the Board file (ascii) field and select the file (brd_board.emn). Board files have the extension “*.emn" or “*.brd". Note that the library file (brd_board.emp) gets loaded automatically. Specify Project Name as tutorials/idf_import (Figure 15.2 (p. 236)).

Figure 15.2 IDF import Panel - Load files

2.

236

Click Next and go on to the Layout options section (Figure 15.3 (p. 237)). Retain all default settings:


Step 2: Build the Model •

Import type as Detail

•

Board plane as XY - this is always detected automatically

•

Board shape as Rectangular

•

Board properties - Click Edit button to access the Board properties where you can enter details such as number of trace layers, coverage and layer thickness etc. Layer properties refer to the average properties of all internal layers. In this example, examine the defaults, and click Cancel to close the Board properties panel.

Note More advanced PCB models are covered in the introductory tutorial, "RF Amplifier", and application tutorial, Trace Layer Import for Printed Circuit Boards (p. 267) located in this guide. •

Drilled holes are for positioning purposes and usually are not thermally important. During the import, they can be ignored. By default, ANSYS Icepak leaves import drilled holes unchecked under Detailed options.

•

Enable Make all components rectangular under Detailed options to convert all polygonal components to prisms.

Figure 15.3 IDF import Panel - Layout options

3.

Click Next to go to the Component filters section (Figure 15.4 (p. 238)). Components can be filtered either by size and power or by component type. For now, select Filter by component type and Import all components. The other options will be explained in more detail at the end of the tutorial.


237

Chapter 15: IDF Import

Figure 15.4 IDF import Panel - Component figures

4.

Click Next to go to the Component models section (Figure 15.5 (p. 238)).

5.

Select Model all components as and keep the default settings. The option Choose specific component model will be discussed later in the tutorial.

Figure 15.5 IDF import Panel - Component models

6.

238

Click on Next to go to the Miscellaneous options section (Figure 15.6 (p. 239)). Select Append Part Name to Reference Designator under the Naming conventions group box.



Figure 15.6 IDF import Panel - Miscellaneous options

7.

Click Finish to complete the import.

8.

Examine the imported model (Figure 15.7 (p. 240)). Observe: •

the different types of blocks

•

the material properties of the PCB block, which is called BOARD_OUTLINE.1

•

the power and resistance values of the network blocks, if any.

Note that: •

The components form into groups according to types automatically

•

You can use the edit function under groups to change properties for all the components in the same group at one time

•

You should check message windows for missing properties.

Figure 15.7 (p. 240) shows ANSYS Icepak model with components modeled as 3D objects (solid blocks or two-resistor network blocks). Appropriate boundary conditions need to be applied before starting thermal analysis. In addition, you can review power values by selecting the Power and temperature limit option in the Model menu.


239


Figure 15.7 IDF Imported Model with All Components

15.6. Step 3: Component Filtration Alternatives 1.

If Filter by size/power is chosen (Figure 15.8 (p. 240)), the size filter and/or power filter may be specified. Only those components that are either larger than the specified size filter, or dissipate more than the specified power filter, are imported. If these fields are ignored, all components are imported.

Figure 15.8 IDF Import Panel - Components filters: Filter by size/power

2.

240

If Filter by component type is chosen (Figure 15.9 (p. 241)), the required components can be selected through the Component selection panel (Figure 15.10 (p. 241)); otherwise all the components are included. The Component selection panel contains reference designators for all components.


Step 4: Component Models Alternatives

Figure 15.9 IDF Import Panel - Component filters: Filter by component type

After clicking Choose, you can choose individual components from the panel in the figure below:

Figure 15.10 Component selection Panel

15.7. Step 4: Component Models Alternatives 1.

The Model all components as option is available through both filtration mechanisms.

2.

The Choose specific component model option is available when filtering by component type. ANSYS Icepak allows the component property to be added if no thermal information is available from the IDF file (IDF 2.0), or modify properties if it is available (IDF 3.0).

3.

Under Choose specific component model, properties of required components can be loaded from an existing file using the Load data from file option. The format for the file is: Reference designator

Power (W)

Rjc (C/W)

Rjb (C/W)

Figure 15.11 (p. 242) shows a sample file. Objects not present in the file are imported with data already present in the IDF file, or as solid blocks with no power specification.


241


Figure 15.11 Set Component Property Using File

4.

Component properties may also be edited manually by selecting the Specify values for individual component types option. The components to be imported are listed under Selected components. The component name is composed of the type and name and the number of copies, followed by a more descriptive part name (Figure 15.12 (p. 242)). To manually set the component property, you can select the component in the Selected components list. Multiple selections can be made with Ctrl + left mouse or Shift + left mouse. Then, you can choose the model type: Two-resistor (Rjc-Rjb), 3d blocks, or 2d sources, and specify power. For a two-resistor model, Rjc and Rjb values need to be specified as well. After inputting your specifications, you can click Apply to complete the modification.

Figure 15.12 Manual Selection of Component Models

15.8. Step 5: Summary IDF import capability of ANSYS Icepak was used to import a board level model with all components. It was observed that the board properties and component properties (where specified) were automatically

242


Step 5: Summary updated in the ANSYS Icepak model. Components filtration and modeling alternatives that are available in the IDF import mechanism, were also discussed.


243

244


Chapter 16: Modeling CAD Geometry 16.1. Introduction Complex geometries are common in today's electronics cooling applications. Examples include complex enclosure shapes, heat sink fins, louvers, etc. Proper accounting of the geometry of these objects is important for accurate prediction of flow and heat transfer. Modeling of these complex geometries is possible by using the direct CAD modeling feature in ANSYS Icepak. The hex-dominant mesher is used to create an unstructured mesh for these complex shapes. This tutorial demonstrates how to use the hex-dominant mesher to create an unstructured mesh for complex shapes in ANSYS Icepak. In this tutorial you will learn how to: •

Use a CAD object and create an unstructured mesh using the hex-dominant mesher.

•

Solve for flow and heat transfer in a model.

•


16.2. Prerequisites This tutorial assumes that you have little experience with ANSYS Icepak, but that you are generally familiar with the interface. If you are not, please review Sample Session in the Icepak User's Guide.

16.3. Problem Description The cabinet contains a heat sink 1 with extruded fins having aerofoil cross section, mounted on a block with a heat source placed between them. These objects are placed in a wind tunnel setup as shown in Figure 16.1 (p. 246).

1

The heat sink used for this sample problem was obtained from the company Alpha, www.alphanovatech.com/cindexe.html#w. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

245

Chapter 16: Modeling CAD Geometry

Figure 16.1 Wind Tunnel Model with Heatsink Modeled as CAD Block

16.4. Step 1: Creating a New Project 1.


2.


246



3.


In the Project name text box, enter the name shapes.

b.

Click Create.

Note ANSYS Icepak creates a default cabinet with the dimensions 1 m × 1 m × 1 m and displays the cabinet in the graphics window.

16.5. Step 2: Build the Model To build the model, you will first create the CAD block representing the heat sink. You will need to import the required CAD file into ANSYS Icepak. ANSYS Icepak can import CAD files in step and IGES formats. 1.

Import the IGES/Step file into ANSYS Icepak a.

Go to Model → CAD data.

b.

Select Load in the CAD data panel and click on Load IGES/Step file.

c.

Select w35-20.stp in the File selection panel and click Open.


247


d. 2.

248

The CAD model appears in the graphics display window.

In the CAD data panel, select the surfaces to be used to create the CAD block. a.

In the Creation mode section of the CAD data panel, ensure Selected is enabled.

b.

Select Use CAD surfaces directly.

c.

In the Create object section, select Blocks.

d.

Drag a rectangular region around the displayed CAD model to select the surfaces to be used to create the CAD block. Clicking on the middle mouse button creates the block (e.g., F_4074 or similar name) which can be used in the ANSYS Icepak model. In the CAD data panel, under Families, click None to hide all CAD lines and surfaces.



e. 3.

Close the CAD data panel.

Resize the default cabinet in the Cabinet panel. Model →

Cabinet

a.

In the Cabinet object panel, click the Geometry tab.

b.

Under Location, enter the Start/end coordinates shown in Table 16.1: Coordinates for the Cabinet (p. 249) :

Important Note that the dimensions are in mm.

Table 16.1 Coordinates for the Cabinet xS

-100 mm

xE

150 mm

yS

-5 mm

yE

20 mm

zS

-25 mm

zE

25 mm

c.

Click Update to resize the cabinet.

d.

In the Orient menu, select Isometric view to scale and orient the view of the cabinet to fit the graphics window (Figure 16.2 (p. 250)).


249


Figure 16.2 Creating the Heat Sink CAD Block From a CAD File

4.

250

Edit the cabinet properties to specify the Min x and Max x sides as openings. a.

Select Opening from the drop-down menu under Wall type for Min x and Max x.

b.

Select Edit to display the Openings object panel for Min x and specify the


velocity to be 5 m/s.


c. 5.

Press Done in the Openings object panel and then the Cabinet object panel to apply the changes and close the panels.

Create a block at the base of the heat sink. a.


) to create a new block.

ANSYS Icepak creates a new solid prism block in the center of the cabinet. You need to change the size of the block. b.


c.


d.

Enter the Start/end coordinates for the Prism block as shown in Table 16.2: Coordinates for the Block (p. 252).

) to open the Blocks panel.


251



Table 16.2 Coordinates for the Block xS

-30 mm

xE

30 mm

yS

-5 mm

yE

0 mm

zS

-25 mm

zE

25 mm

The block touches the cabinet in the Min y direction, and the heat sink in Max y. The Min z and Max z sides of the block touch the cabinet.

6.

e.

In the Properties tab, select Solid for the Block type if not already selected. Under Thermal specification, keep default as the Solid material. Because the default solid material is extruded aluminum, you need not specify the material explicitly here.

f.

Click Done to modify the block and close the panel.

Create a source between the base block and the heat sink. ) to create a source.

a.

Click the Create sources button (

b.

Edit the source Geometry with the Start/end dimensions given in Table 16.3: Coordinates for the Source (p. 252).


Table 16.3 Coordinates for the Source

c.

252

Shape

Rectangular

Plane

X-Z

xS

-10 mm

xE

10 mm

yS

0

yE

—

zS

10 mm

zE

-10 mm

Edit the source Properties and specify a Total power of 50.0 Watts.



d.

Click Done to modify the source property and close the panel.

Note We will allow heat transfer from the base of the metal block by creating a wall, wall.1 on the Min y side of the block and the cabinet boundary. 7.

Create a wall at the base of the metal block. a.

Edit the wall Geometry with Start/end dimensions given in Table 16.4: Coordinates for the Wall (p. 253).


Table 16.4 Coordinates for the Wall Shape

Rectangular

Plane

X-Z

xS

-30 mm

xE

30 mm

yS

-5 mm

yE

—

zS

-25 mm

zE

25 mm


253

Chapter 16: Modeling CAD Geometry b.

Edit the wall Properties to specify the boundary conditions of the wall. i.

Select Heat transfer coefficient from the External conditions drop-down list.

ii.

Press Edit to open the Wall thermal conditions panel.

iii.

Select Heat transfer coeff in the Thermal conditions group box.

iv.

Input a Heat transfer coeff of 10 W/km2 and keep the default selection of Constant in the Heat transfer coefficient group box. The Reference temperature is ambient.

Figure 16.3 Specifying Boundary Condition for the Wall

v.

Press Done in the Wall external thermal conditions panel and then the Walls object panel to apply the changes close the panels.

The final model should correspond to the one shown in Figure 16.1 (p. 246).

254




In order to properly mesh the heat sink, a fine mesh needs to be used in that region. To reduce the overall mesh count, the finely meshed region should be secluded using a separately meshed assembly. a.

Choose the heat sink (F_4074 or similar name) and source.1 from the Model tree and create an assembly called assembly.1.

b.

The meshing parameters for this assembly are shown in Figure 16.4 (p. 255).



Note The slacks in the Min Z and Max Z directions are specified by snapping with the cabinet boundary in the respective directions. Note the use of Max element size in each direction to control the mesh refinement in the assembly. c.

Press Done to close the Assemblies panel. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

255

Chapter 16: Modeling CAD Geometry 2.

Another separately meshed assembly, assembly.2 is created with assembly.1 to enable a smooth transition of the fine mesh in assembly.1 to the relatively coarse mesh in the outer regions of the model. a.

Choose assembly.1, block.1 and wall.1 from the Model tree and create assembly.2.

b.

The meshing parameters for this assembly are shown in Figure 16.5 (p. 256).



Note There is a larger max grid size in this assembly compared to assembly.1. c. 3.

Go to Model → Generate mesh. a.

256

Press Done to close the Assemblies panel. Keep the default selection of Mesher-HD for the Mesh type and input the settings shown in Figure 16.6 (p. 257) below. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.



Figure 16.6 Mesh control Panel Inputs

Note When meshing models containing CAD blocks, you could select Hexa unstructured or Hexa cartesian for the global Mesh type, but only Mesher-HD should be used to mesh CAD blocks. Therefore, you must create assemblies with Mesher-HD as the Mesh type around all the CAD blocks. b. 4.


The surface mesh on the heat sink and the mesh on the center “y" plane is shown in Figure 16.7 (p. 258). The relatively coarse mesh in the overall cabinet, the intermediate mesh in assembly.2 and the fine mesh in assembly.1 is clearly seen in the central “y" plane view of the mesh as shown in Figure 16.8 (p. 258).


257


Figure 16.7 Mesh Near Heat Sink

Figure 16.8 Y-Plane View of Mesh


Go to a.

Problem setup →

Basic parameters.

In the General Setup tab, make sure that both the flow and the temperature fields are switched on.

Note This is a forced convection problem; therefore the natural convection as well as radiation effects can be ignored.

258


Step 4: Physical and Numerical Settings b.

Switch off the Radiation and make sure Gravity vector is unchecked.

c.

Choose Turbulent and then Zero equation in the Flow regime group box.

Note The problem being dominated by forced convection, a sequential solution of flow and energy equation shall be used. d. 2.

Press Accept to save the settings and close the panel.

Under Solution settings → Basic settings, specify the number of iterations to 300, the Flow convergence to 0.001 and the Energy convergence to 1e-14, as shown in Figure 16.9 (p. 260), and press Accept to save the settings and close the panel.


259



3.

Stringent energy convergence criterion is required when the energy equation is solved separately. Go to

Advanced settings.

a.

Make sure that the Under-relaxation parameters for Pressure and Momentum are 0.3 and 0.7 respectively.

b.

Input the following for Temperature in the Linear solver group box:

c.

260


i.

Choose W from the Type drop-down list.

ii.

Enter 1e-6 for the Termination criterion and the Residual reduction tolerance.

Change Precision to Double.


Step 5: Save the Model

Figure 16.10 Advanced solver setup Panel

Note These settings are used for separate solution of the energy equation d.

Press Accept to save the changes and close the panel.

16.8. Step 5: Save the Model ANSYS Icepak saves the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the job you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your job file when it saves the model.) File → Save project

Note You can click the save project button (



261



Go to Solve → Run solution to display the Solve panel. a.

Enable Sequential solution of flow and energy equations.

b.

Click Start solution to start the solver. ANSYS Icepak begins to calculate a solution for the model, and a separate window opens where the solver prints the numerical values of the residuals. ANSYS Icepak also opens the Solution residuals graphics display and control window, where it displays the convergence history for the calculation.

Note The actual values of the residuals may differ slightly on different machines, so your plot may not look exactly the same as Figure 16.11 (p. 262).

Figure 16.11 Residuals

c. 262

Click Done in the Solution residuals window to close the panel. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.


16.10. Step 7: Examine the Results The distribution of the different quantities on the CAD heat sink can be visualized using the object face option, as in any other ANSYS Icepak object. 1.

Click the Object face button (

) under the Postprocessing toolbar.

a.

Choose the CAD block from the Object drop-down list

b.

Click on Show contours and then Parameters to open the Object face contours panel.

c.

Keep the default selection of Temperature in the Contours of drop-down list.

d.

Keep the default selection of Solid fill in the Contours of group box.

e.

Select Smooth in the Shading options group box.

f.

Keep the default selection of Calculated in the Color levels group box and choose This object from the drop-down list.

Figure 16.12 Post Object Face Settings for CAD Block

g.

Press Done in the Object face contours panel and then in the Object face panel to close the panels and view the postprocessing object. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

263

Chapter 16: Modeling CAD Geometry This maps the color range to the temperature distribution on the heat sink. The temperature on a given point can be seen using the surface probe tool. Figure 16.13 (p. 264) shows the temperature distribution on the heat sink.

Figure 16.13 Temperature Distribution on the Heat Sink

2.

Right click face.1 in the Model tree and deselect Active to deactivate the postprocessing object.

3.

Click the Plane cut button (

) under the Postprocessing toolbar.

a.

Select Y plane through center from the Set position drop-down list.

b.

Select Show vectors option.

c.

Click Create and Done. Zoom in to display more details.

The velocity field around the heat sinks fins, visualized on the central y -plane, is shown in Figure 16.14 (p. 265).

264


Step 8: Summary

Figure 16.14 Velocity Field Around the Heat Sinks Fins

16.11. Step 8: Summary In this tutorial, you imported a CAD object and set up a problem. You then created an unstructured mesh using the hex-dominant mesher. This forced convection problem was solved for flow and heat transfer and the results were examined on object faces and cut planes in the model.


265

266


Chapter 17: Trace Layer Import for Printed Circuit Boards 17.1. Introduction A printed circuit board (PCB) is generally a multi-layered board made of dielectric material and several layers of copper traces. From the thermal modeling point of view, a PCB may be treated as a homogeneous material with bi-directional thermal conductivity, i.e. thermal conductivity value is different in the normal-to-plane direction than that of the in-plane direction. This approach is reasonable as long as the trace distribution is more-or-less uniform in any given layer. However, with the continuing challenges to increase product functionality while decreasing product size, designers are compelled to place more and more functionality on individual PCB's. As PCB's become more densely populated, their trace layers are becoming more non-uniform and it is prudent to use locally varying thermal conductivity information on the board. PCBs often have large copper spread in the power and ground planes, this along with the presence of vias (especially thermal vias) can be effectively used by the designer to spread heat from the package. A detailed conductivity map of the pcb is required to simulate heat transfer, which is possible in Ansys Icepak using the trace feature. Conducting a computational heat transfer simulation for each individual layer is costly and impractical for a system level model. In ANSYS Icepak, it is possible to import trace layout of the board and compute locally varying orthotropic conductivity (kx, ky, and kz) on the board using a profile mesh size. The supported file formats are (1) MCM, BRD and TCB files and (created using Cadence, Synopsys, Zuken, and Mentor), (2) ANF files and (3) ODB++ files. Ansoftlinks installation and licensing is required to create ANF files to be read by Icepak. Icepak can read ODB++ files, but an Ansoftlinks license is required. To import MCM/BRD files, Cadence Allegro must be installed. In this tutorial, we will show : •

How to import trace layout of a typical PCB in TCB format and solve two sample cases based on the trace layout information.

•

How to use Model layers separately option for better accuracy.

•

How to import Gerber format layer and via files.



267

Chapter 17: Trace Layer Import for Printed Circuit Boards

17.3. Problem Description A PCB board, library files and traces are imported to create the model. The model is first solved for conduction only, without the components and then solved using the actual components with forced convection.



2.


3.


In the Project name text box, enter the name trace-import.

b.

Click Create.

17.5. Step 2: Build the Model To build the model, you will first import the board layout. The board and the associated library files have to be chosen at this step and the trace file can be imported later. File → Import → IDF file 1.

In the IDF import panel, select the board (A1.bdf ). You can keep the default project name A1, specify the model directory using Browse and click on Next. The associated library files are imported automatically.

2.

268

Select Next to see your Layout options. Keep Detail for the Import type, XY for the board plane and Rectangular for the board shape.



Note Because we import the trace information later, we do not need to edit the board properties at this time. 3.

Select Next to see the Component filtering options. Ensure Import all components is selected.

Note You can filter certain components at this step by their size and power information, i.e. you can ignore the small components or the ones dissipating low power. We will import all of the components in this tutorial. 4.

Select Next to see the Component models section. Select Model all components as. Keep the default selection of 3d blocks and the default Cutoff height for modeling components as 3d blocks.


269


Note If you have thin components on your board, they can be modeled as 2D sources. In this tutorial, we would like to model all the components as rectangular blocks. 5.

270

Click Next to go to the Miscellaneous options section where you can specify the naming and monitor options. Keep the default options and click Finish to start importing the files. This will take some time depending on the speed of your machine.



You have learned how to import board and library files, and in general you can import any IDF file by using the procedure above. The next step in building the model is to import the trace files. A pre-built board model named “A11" (see Figure 17.1 (p. 271)) will be used to demonstrate the trace file import. This pre-built model was extracted from the previous board file (A11.brd), a number of small components were removed and a non-conformal assembly was formed.

Figure 17.1 A11 Board Layout

a.

Unpack A11.tzr file to your desktop and name the project “A11".


271


Note As mentioned earlier, the trace file (.brd, .tcb, .mcm, .anf, or .odb++) can either be imported during the IDF file import or the trace layout information can be assigned to the board after importing the IDF file. b.

Right click BOARD_OUTLINE.1 in the Model manager window and click Edit to display the Blocks object panel. To import the trace layout, follow the procedures below. i.

In the Geometry tab, select ASCII TCB from the Import ECAD file drop down list (Figure 17.2 (p. 272)).

Figure 17.2 Blocks [BOARD_OUTLINE.1] Panel

ii.

Select A1.tcb from the Trace file panel. This process may take a few minutes depending on the speed of your computer.

iii.

Once the import process is completed, you can edit the layer information in the Board layer and via information panel (Figure 17.3 (p. 273)). The number of layers in the board will automatically be imported to ANSYS Icepak and you will have to enter the thickness of each layer and the material type. In this tutorial, the metal layers are pure Cu and the dielectric layers are FR-4.

272


Step 2: Build the Model iv.

Enter the layer thickness as shown in Table 17.1: Thickness Information on the Board (Layer 1: Top, Layer 7: Bottom layers) (p. 273) and choose 100 rows and columns.

Table 17.1 Thickness Information on the Board (Layer 1: Top, Layer 7: Bottom layers) Layer

Thickness (mm)

Layer 1

0.04

Layer 2

0.45364

Layer 3

0.062

Layer 4

0.467

Layer 5

0.055

Layer 6

0.442

Layer 7

0.045

Figure 17.3 Importing Trace Layout and Editing Layer Information

v.

By default, layers are lumped for each sub-grid, therefore, the Model layers separately option is off. They can also be modeled separately, which will be discussed later when the Model layers separately option is used. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

273

Chapter 17: Trace Layer Import for Printed Circuit Boards vi.

Via information (e.g., material, plating thickness, filled/un-filled, via diameter etc.) is imported automatically (Figure 17.4 (p. 274)), keep the default settings.

Figure 17.4 Vias Information

vii. Click Accept to save your settings.

Note The background mesh matrix (rows and columns) is used to compute the orthotropic conductivity on the board. The rows represent the division of the board in the y-direction, the columns represent the division of the board in the x-direction and the size field determines the divisions of the board and indicates the grid size in each direction. The values of k, kx, ky, and kz on each cell are determined by the local trace density and the direction. ANSYS Icepak does not include the trace geometry in the physical model; however, the locally varying orthotropic conductivity is mapped from the background mesh to the physical model mesh. Once the trace file is imported and assigned to the board geometry, the trace layers are associated with the board and are moved (in translation and/or rotation) with the board object.

274


Step 2: Build the Model viii. Press Done to close the Blocks object panel. ix.

Right click on the object BOARD_OUTLINE.1 and go to Traces from the menu.

Note You can view the traces in three different ways, i.e. single color, color by layer, or color by trace. Each of the trace layers can be viewed separately by switching the visible option on or off in the layers part of the panel. (Figure 17.5 (p. 275)).

Figure 17.5 Displaying Traces on the Board

x.

Select color by trace; the board traces are as shown in Figure 17.6 (p. 276).


275


Figure 17.6 Trace Layout on the PCB with the Color by trace Option

17.6. Conduction Only Model (PCB Without the Components) Follow these steps for a conduction-only model:

17.7. Step 1: Generate a Mesh You will generate a mesh for each sample problem. First we will consider a board without any components. 1.

Make all objects (including the openings) inactive except the BOARD_OUTLINE.1 object.

2.

Select the cabinet and select Autoscale from the Edit window to make the size of the board and the cabinet the same.

3.

Go to the Properties tab of the Cabinet object panel, and select Wall from the Min z and Max z dropdown lists.

4.

Press Edit next to Min z to open the Walls object panel.

5.

276

a.

In the Properties tab, select Temperature from the External conditions drop-down list, and keep the ambient temperature (20°C).

b.

Press Done to close the panel.

Press Edit next to Max z to open the Walls object panel. a.

In the Properties tab, specify a Heat flux of 50000 W/m2 in the Thermal specification group box.

b.




Note The rest of the sides are insulated. The board will be simulated using a conductiononly model. 6.

Press Done to close the Cabinet panel.

7.

Go to Model → Generate mesh to open the Mesh control panel.

8.

a.

Make sure the Mesh type is Mesher-HD.

b.

Specify a Max element size for X, Y, and Z as 5, 3, and 0.05 mm respectively, and a Minimum gap of 1 mm in all three directions.

c.

Keep all other defaults and click Generate.

Once the mesh has been created, Close the Mesh control panel.

17.8. Step 2: Set Physical and Numerical Values 1.

2.

3.

Go to

Problem setup →

Basic parameters.

a.

Since this is a conduction only model, toggle off the Flow option in the General setup tab.

b.

Make sure Radiation is off and keep all other default values.

c.

Press Accept to close the Basic parameters panel.

Go to


Basic settings.

a.

Keep the default Number of iterations and set the Convergence criteria for Energy to 1e-12.

b.


Go to a.


Advanced settings.

Input the following for Temperature in the Linear solver group box: i.

Choose W cycle from the Type drop-down list.

ii.

Enter 1e-6 for both the Termination criterion and Residual reduction tolerance.

b.

Select Double for the solver Precision.

c.


17.9. Step 3: Save the Model ANSYS Icepak saves the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save project

17.10. Step 4: Calculate a Solution Go to Solve → Run solution or click on the shortcut button ( solution.

). Start the solver by clicking Start


277



Once the model has converged, Activate cut.1 if not already activated.

2.

Edit cut.1 and make sure that Point and normal is the Set position.

3.

Make sure that PX, PY, PZ are 0, 0, and 0.78232, respectively and the NX, NY, and NZ are 0, 0, and 1, respectively.

4.

Press Done and view the model.

The mid-plane temperature distribution shows that the high temperature regions occur at the no-trace areas and low temperature regions occur at areas with a high trace concentration. This is expected as the copper content is directly proportional to the trace concentration. It is worth noting that if a compact or detailed PCB were used in lieu of the traced PCB, one would obtain a fixed temperature for the entire mid-plane and this fixed temperature would be different from the average temperature of the traced PCB on the same plane.

Figure 17.7 Temperature Distribution on the PCB (mid-plane)

Note The spatially varying non-uniform conductivity of the board can also be viewed during post processing. The conductivities in the three direction K_X, K_Y, and K_Z are available as postprocessing variables with plane cuts and object faces. Figure 17.8 (p. 279) plots kx at the board mid-plane by selecting K_X from the Contours of drop-down list from Plane cut contours panel of the cut.1 object. In the present case, because we chose not to model the layers separately, there will be no variation of the conductivities in the board-normal direction.

278



Figure 17.8 K_X Distribution on the PCB (mid-plane)

17.12. PCB With the Actual Components Under Forced Convection Follow these steps for a model that has components:


In order to put the actual components back into the model, highlight all the components under the Inactive folder and drag them back into the Model folder. Highlight the two wall objects created for the “conduction only" model and drag them into the Inactive folder.

2.

Click on the Cabinet and Autoscale it from the Edit window.

3.

If not already defined, assign an X Velocity of -1.5 m/s in the Properties tab of the Openings panel for the Max x side of the cabinet (the minus sign shows that the flow is in the negative x direction).


279

Chapter 17: Trace Layer Import for Printed Circuit Boards While not shown here, the trace import feature has a number of advantages on the meshing side. It should be remembered that detailed PCB's cannot intersect non-conformal assemblies; however, there is no such limitation for block objects. Since a PCB is represented as a block in the case of importing traces, non-conformal assemblies can intersect it. 4.

Open the Mesh control panel and choose X, Y, Z sizes as 9.5, 7, and 0.7 mm respectively.

5.

Keep all other defaults and Generate the mesh.

17.14. Step 2: Set Physical and Numerical Values 1.

Since we now have forced convection, go to Problem Setup → Basic parameters toggle on the Flow button. Keep and choose Turbulent and Zero equation for the flow regime and press Accept to close the panel.

2.

Basic settings and make sure the Number of iterations is 300 and Go to Solution settings → that the Convergence criteria are the same as the last mode, and press Accept to close the panel.

3.

Keep the same Advanced settings as the previous case.

17.15. Step 3: Calculate a Solution Click Solve → Run Solution to display the Solve panel. Enter a different solution id for the forced convection model (i.e., A11-conv). Enable Sequential solution of flow and energy equations and click Start solution.

17.16. Step 4: Examine the Results To display contours of temperature on the board, follow the procedures below. 1.

Once the model has converged, deactivate cut.1 and go to Post → Object Face.

2.

Select BOARD_OUTLINE.1 from the Object drop-down list, and deselect all the options except Max Z in the Object sides group box.

3.

Turn on the show contours and click on Parameters button.

4.

Keep the default selection of Temperature.

5.

For Color levels, select This object from the drop-down list.

6.

Press Done in the Object face contours panel and then the Object face panel to view the postprocessing object. This shows the temperature distribution at the top of the surface of the board (Figure 17.9 (p. 281)). There are two hot spots underneath the high heat flux components.

280


Using the Model Layers Separately Option

Figure 17.9 Top Surface Temperature Distribution: PCB With Imported Traces (100 x 100) in Forced Convection

7.

Deactivate the face.1 postprocessing object.

17.17. Using the Model Layers Separately Option Next we revisit the conduction only model. This time all the metal layers will be modeled separately and not lumped together in the thickness direction. 1.

Go to the Post → Load solution ID.

2.

Select the solution ID corresponding to the model which has just the PCB without any components.

3.

Deactivate all postprocessing objects if any are active.

4.

Display the Board layer and via information panel by selecting Trace layers and vias from the Geometry tab of the Blocks panel for the BOARD_OUTLINE.1 object.

5.

Check the Model layers separately box and press Accept to close the panel.

6.

Press Done to close the Blocks panel.

Note •

The Model layers separately option automatically creates contact resistance plates in the plane of the board at the start and end locations of each metal layer. These dummy plates have zero thermal resistance and their sole purpose is to ensure proper mesh resolution within the board. Figure 17.10 (p. 282) shows the plates created for the tracing layers on this board.

•

To model each of the layers separately we need to ensure that there is at least one cell across each of the metal and dielectric layers at the correct locations in the board-normal direction.


281


Figure 17.10 Contact Resistance Plates for Meshing the Individual Layers Separately

7.

Now the model can be meshed again same mesh settings as earlier except for the Minimum gap in the Z direction, which should be set to 0.25 mm to account for the contact resistance plates, and solved with the exact same boundary conditions. The temperature distribution and conductivity profiles on the board can be viewed again during post processing to examine the effect of modeling the layers separately as compared to the previous case.

17.18. Summary In this tutorial, you imported the board layout and trace files. Then you simulated the board using a conduction only model. Postprocessing this model showed high temperature regions occurring at the no-trace areas and low temperature regions occurring at areas with a high trace concentration. Then you simulated the board with the components put back into the model and simulated under forced convection. Then you simulated the conduction using the Model layers separately option.

17.19. Additional Exercise 1 Using this model, you can determine the joule/trace heating of the imported traces. This problem is described in Tutorial "Joule/Trace Heating".

17.20. Additional Exercise 2 Create a model with a detailed package with thermal solder balls. Place it on a board modeled without and with separate meshing of the layers and check the difference of temperature distribution.

282


Chapter 18: Joule/Trace Heating 18.1. Introduction In Tutorial Trace Layer Import for Printed Circuit Boards (p. 267), you learned how to import a trace layout of a typical PCB using TCB format and also learned how to model the trace layers separately for better modeling accuracy. In this tutorial, you will learn how to model resistive heating or joule heating of the imported traces in the PCB. Since PCB traces have electrical resistance, they will heat up as current flows through them. Modeling this phenomenon will provide us with an accurate prediction of the temperature distribution in the PCB, which can be important, for example, in evaluating the performance of the cooling system.

18.2. Prerequisites This tutorial assumes that you have completed Tutorial Trace Layer Import for Printed Circuit Boards (p. 267) of this guide. This same model is used to determine the joule/trace heating capability in ANSYS Icepak.

18.3. Problem Description The model in Tutorial Trace Layer Import for Printed Circuit Boards (p. 267) contains imported traces and will be used in this tutorial. You will determine the joule/trace heating capacity of the traces.


Start ANSYS Icepak, as described in Chapter 1 of the User's Guide.

Note When ANSYS Icepak starts, the Welcome to Icepak panel will open automatically. 2.

Click Unpack in the Welcome to Icepak panel to start a new ANSYS Icepak project.

Note The File selection panel will appear. 3.

In the File selection panel, select the packed project file joule-heating.tzr and click Open.

Note The project file can be found in your installation directory at ICEPAK_ROOT/tutorials/joule-heating/joule-heating.tzr.


283

Chapter 18: Joule/Trace Heating 4.

In the Location for the unpacked project panel, select a directory where you would like to place the packed project file, enter a project name in the New Project text field, and click Unpack.

18.5. Step 2: Build the Model This tutorial uses an existing model. Since the traces are already imported in the model, you will work directly on the Joule heating capability in ANSYS Icepak. 1.

Select BOARD_OUTLINE.1 from the Model tree and open the Blocks panel. a.

In the Geometry tab, click on the Edit button next to Model trace heating. The Trace heating panel opens. i.

In the drop-down list under Layers, select INT1_3. The list below Display traces shows available traces. You can filter the traces to view by setting an Area filter (the default in ANSYS Icepak is 20% of the Largest trace area) and clicking the Filter button. In this example, use an Area filter of 17890 mm2, as this will only show the significant traces.

Note The Trace heating panel lists the traces in each layer in order of descending area, see Figure 18.1 (p. 285). ii.

284

Before you create a solid trace of Trace 1_1724, you need to modify the Max angle filter and the Min length filter to ignore the fine details in the trace geometry and reduce the mesh count. If not already selected, select Trace 1_1724 and set the Max angle filter to 135 and the Min length filter to 1.0 mm.



Figure 18.1 Trace Heating Panel Selection and Options

iii.

Click on the Create solid trace button. ANSYS Icepak will create a polygonal solid block named BOARD_OUTLINE.layer-3-trace-1_1724 that contains the trace information. (The actual name may vary). Click Done to close the Trace heating panel.

Note You can try reducing the Area filter to 1000 mm2 to check how many traces appear. We are interested in the second largest trace, trace 1_1724. b. 2.

Click Done in the Blocks panel to close the panel and view the model.

Select the polygonal trace from the Model tree and open the Blocks panel. a.

In the Geometry tab of the Blocks panel, make sure there are around 60 vertices for the trace, as shown in Figure 18.2 (p. 286). Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

285

Chapter 18: Joule/Trace Heating

Figure 18.2 Polygonal Trace Block

b.

Go to the Properties tab. i.

286

Make sure that the Solid material is tr_1_1724_sol_mat and then select Edit definition in the drop-down list. A.

The Materials panel opens.

B.

Make sure the Properties tab of the Materials panel looks like Figure 18.3 (p. 287).

C.

Press Done to close the Materials panel.



Figure 18.3 Trace Materials Panel Properties Tab

ii.

In order to activate Joule heating of the trace, press the Edit button for the Joule option. The Joule heating power panel opens. A.

For the first boundary condition in the Boundary conditions group box, set Side to side1, Boundary type to current, and specify the Current to 25 Amps.

B.

For the second boundary condition, set Side to side42, Boundary type to voltage, and the Voltage to 0 V.


287


Figure 18.4 Boundary conditions for the Trace Block

Note Current conservation needs to be manually inspected by the user.

288



Figure 18.5 Entry and Exit Sides for the Trace Block

Note The side numbers are estimates as they may be slightly different for each model. C.

Press Done in the Joule heating power panel and then the Blocks panel to close the panels and view the model.


Create a non-conformal assembly for the trace. a.

Right click the BOARD_OUTLINE.1.layer-3-trace-1_1724 object and go to Create and then Assembly.

b.

Double click the assembly you created to open the Assemblies panel. i.

In the Meshing tab, select Mesh separately and input the Slack settings, Mesh type, Max element size, and Min gap settings as shown in Figure 18.6 (p. 290).


289


Figure 18.6 Mesh Settings for the Trace Board

Note Ensure Mesh type is Mesher-HD. c. 2.

Press Done to close the Assemblies panel.

Go to Model → Generate mesh to open the Mesh control panel. a.

Make sure the Mesh type is Mesher-HD.

b.

Keep the global settings under the Max element size group box as 9, 5, and 0.75 mm, for X, Y, and Z respectively.

c.

Set the Minimum gap as 0.75, 0.45, and 0.035 mm for X, Y, and Z, respectively.

d.

Generate the mesh.

e.

Check the mesh quality for the trace and the overall model from the Display and Quality tabs.


Double click the cabinet_default_side_maxx object in the Model tree to open the Openings panel. a.

290

In the Properties tab, make sure the X Velocity is -1.5 m/s. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 7: Examine the Results b. 2.

3.

4.


Go to

Problem setup →

Basic parameters.

a.

Since this is a forced convection problem, ensure that the Flow is toggled on and that Turbulent is selected under Flow regime. Select Zero equation as the turbulence model.

b.

Press Accept to close the panel.

Go to


Basic settings.

a.

Make sure the Convergence criteria for Flow is 0.001.

b.

Set the Number of iterations to 200 and the Convergence criteria for Energy and Joule heating to 1e-8.

c.


Go to a.


Advanced settings.


Choose W cycle from the Type drop-down list.

ii.


b.

Make sure the Precision for the solver is Double.

c.


18.8. Step 5: Save the Model ANSYS Icepak will save the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save Project


Click Solve → Run Solution.

2.

Click Start solution.

18.10. Step 7: Examine the Results Once the model has converged, create an object face. 1.

Select the trace and show the temperature contours. a.

Go to Post → Object face.

b.

In the Object drop-down list, select the trace (BOARD_OUTLINE.1.layer-3-trace-1_1724).

c.

Select Show contours and click Parameters. In the Object face contours panel, select Temperature in the Contours of drop-down list and select This object next to Calculated in the Color levels group box. Click Apply.

d.

Observe the trend of the temperature contour and how it varies from one side to other, and compare the maximum temperature for the cases with and without trace modeling (Figure 18.7 (p. 292)).


291


Figure 18.7 Trace Temperature Contours with Forced Convection

2.

292

Now plot the electric potential of the same trace, Figure 18.8 (p. 293).



Figure 18.8 Trace Electric Potential Contours with Forced Convection

a.

Click on Parameters to open the Object face contours panel.

b.

Select Electric Potential from the Contours of drop-down list and press Apply.

c.

Observe the contours. •

Do you observe any similarity between the temperature and the electric potential contours? Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

293

Chapter 18: Joule/Trace Heating • d.

The temperature contours are closely related to the electric potential contours, which is a direct result of joule heating of the trace.

Press Done in the Object face contours and Object face panels to close the panels.

18.11. Step 8: Summary Tutorial Trace Layer Import for Printed Circuit Boards (p. 267) is utilized to model the joule heating capability of a trace.

294


Chapter 19: Microelectronics Packages - Compact models 19.1. Introduction This tutorial is a case study of a board design. A card supplier is making two package type changes to an existing commercial board. The objective of the thermal simulation project is to see if the selected new packages are likely to function without overheating. In the event of over heating, what kind of thermal management should be recommended? In this tutorial, you will learn how to: •

Perform a board level simulation with appropriate package models.

•

Determine if the selected new packages can function without overheating.

19.2. Prerequisites This tutorial assumes that you have worked on Sample Session in the Icepak User's Guide and the first two ANSYS Icepak tutorials of this guide.

19.3. Problem Description A designer is to select packages for a new design at the drawing board level. Available information about the board and packages is given. Determine cooling solutions in the event there is overheating.



295

Chapter 19: Microelectronics Packages - Compact models


Copy the file ICEPAK_ROOT/tutorials/compact-package/compact-package-modeling.tzr to your working directory. You must replace ICEPAK_ROOT by the full path name of the directory where ANSYS Icepak is installed on your computer system.

2.


3.


4.

In the File selection panel, select the packed project file compact-package-modeling.tzr and click Open.

5.

In the Location for the unpacked project file selection dialog, select a directory where you would like to place the packed project file, enter a project name (i.e., test-1) in the New project text field then click Unpack.

19.5. Step 2: Build the Model This tutorial uses an existing model. ANSYS Icepak will display the model in the graphics window as shown in Figure 19.2 (p. 297). Available information about the board and packages is shown in Table 19.1: Available Details for Objects in the Model (p. 297) and Table 19.2: Available Information for 400 PBGA (p. 298).

296



Figure 19.2 Layout of the board to be analyzed

Table 19.1 Available Details for Objects in the Model Object

# of Occurrences in model

Available information

Power (w)

PCB

1

1.6 mm thick, FR4 Material, six 1 oz. layers of Copper, 30% coverage for all layers

0

Heat Spreader for TO-220 packages

3

Extruded Aluminum

0

TO-220 Packages

9

DIP

6

None

0.5

400 PBGA (new package type to the existing board)

6

See Table 19.2: Available Information for 400 PBGA

2.0

232 PQFP (new package type to the existing board)

2

232 leads, 40 mm X 40 mm Footprint, 2 mm height

3.5

= 2.5° C/W


1.5

297


Note An ounce of Copper is actually the thickness of 1 ounce/sq.ft of plane copper sheet. Using copper density this translates to a thickness of 0.035 mm.

Table 19.2 Available Information for 400 PBGA Feature

Size (mm)

Overall package

26 x 26 x 2.15

Material/ConOther info ductivity (W/mK)

Where to input this info? Dimensions tab

Mold compound

0.8

Die/Mold tab

Die

18 x 18 x 0.4

Silicon material

Die/Mold tab

Die Flag

18 x 18 x 0.035 (equivalent)

80.0 (effective)

Die/Mold tab

Die Attach

0.05 mm thick

Not mentioned

Die/Mold tab

Substrate

0.4 mm thick

FR4

Substrate tab

Substrate traces

0.035 mm thick

Copper

4 layers, top and bottom 30% coverage intermediate layers are 100% (plane layers)

Substrate tab

Vias

Unknown

Not mentioned

Number of vias unknown

Substrate tab (use 0 for vias)

Solder Balls

Standard

Solder

20 x 20 count, full array

Solder tab

Wire Bonds

Not mentioned

Usually Gold

1.

Die/Mold tab

Create the PCB ). Then edit the Create a PCB object by clicking on the Create printed circuit boards button ( PCB by clicking the Edit object button ( ) while the PCB object is selected in the Model tree. Enter the following in the Geometry tab: Object type

Name

Shape/Type/Plane

Global Coordinates (m) XS— YS— ZS— XE— YE— ZE

PCB

2.

298

pcb.1

XZ

0.0 — 0.0 — 0.0— 0.25— NA— 0.2

a.

Go to the Properties tab. Enter the PCB thickness of 1.6 mm for Substrate thickness.

b.

Change the default unit from micron to Cu-oz/ft2 for high and low surface thickness and for internal layer thickness under Trace layer parameters section.

Material information for the PCB is in Table 19.1: Available Details for Objects in the Model (p. 297). This information can be entered for the selected PCB object as shown in Figure 19.3 (p. 299).



Figure 19.3 PCB Edit Form with input based on PCB information in the Table with Model Object Details above

Now, you should see the PCB object overlapping the block called PCB. There is no more need for this block.

Note You recreated the PCB object geometry using coordinates of the imported PCB block. 3.

Deactivate the block named “PCB".

4.

Heat spreader for TO-220 devices a.

5.

Since default solid material happens to be extruded aluminum, all three spreaders should have come into the model with correct material specification. Check this information by editing the objects.

Modeling Packages This model has four different types of objects. Based on available information and our objectives, we shall use different compact package modeling capabilities in ANSYS Icepak. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

299

Chapter 19: Microelectronics Packages - Compact models a.

TO220 Type Packages i.

There are 9 TO-220 device blocks. Select them all at once by drawing a “window" with Shift+left mouse (see Figure 19.4 (p. 300)). Press Shift+I for an isometric view. Simultaneous selection can also be done in the Model manager window, press the Ctrl key and left mouse click to select objects.

Figure 19.4 Window Selecting Multiple Objects for Simultaneous Edit

ii.

You should see all TO-220 devices highlighted in the tree. Please note that only TO-220 objects should be selected. If you see other objects highlighted (such as the Spreader objects), please deselect them by holding down the Ctrl key and left mouse clicking them in the tree. You can simultaneously edit all of the remaining objects at once by clicking your right mouse on any one of the selected TO-220 objects in the tree. A.

Select Network for the Block type.

B.

Keep the default selection of Two Resistor for the Network type.

C.

In order to assign the resistance, we need to identify a reference side. This is the purpose of “board side" input. We want the resistance to be applied from Junction to the side in contact with the spreader (Max Z side). We can accomplish this in two ways: •

Designate Min Z side as the Board side and assign the supplier provided resistance value (2.5 C/W from Table 19.1: Available Details for Objects in the Model (p. 297)) to Rjc. OR

•

300

Designate Max Z side as the Board side and assign the supplier provided resistance value to Rjb. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.


Note Zero resistance means that there would not be any link and the resistance values are infinite. D.

Input 1.5 W for the Junction power.

Figure 19.5 TO-220 Properties Tab

iii. b.

Click Done to finish the operation.

DIP type packages i.

As we did before for the TO_220 objects, select all the DIP objects and simultaneously edit them.

ii.

Use default solid material (any material will work because we are not interested in DIP temperature). A.

Input 0.5 W in the Total Power field.

B.

Click Done


301


Note Dip is the package type for which we have the least information. So we are left with two options: •

Try to get information from supplier. OR

•

Perform a tentative simulation with available information. The options are considered along with the following facts: –

The DIPs constitute a lower heat flux than the other components in the board.

–

This is an existing design in which the DIPs have been known to run well below their specified temperature even at max power.

Based on the above reasoning, it is easier to perform a tentative simulation with the available power information than to obtain the information from the supplier. In this context the purpose of the DIP package modeling is to appropriately account for air and PCB heating due to flow over the DIPs. Accurate prediction of the DIP temperature is not an objective. c.

PQFP package modeling Internal details are unavailable for the PQFP type package. But based on the exterior details such as lead count, foot print size, and package height information, it is possible to construct a compact model of a typical package for screening analysis. i.

Go to the Libraries node by clicking the Library tab in the Model manager window. Then right-click Libraries and select Search packages.

Note A package may also be created using either IC package macros or a package object.) ii.

In the Search package library panel enter all known information about the package (Table 19.1: Available Details for Objects in the Model (p. 297)) as search criteria. Clicking the Search button should return 1 the closest matching packages from the library. Pick the package that is most similar in description to the 232-lead PQFP information available and select Create. Figure 19.6 (p. 303) depicts the package search procedure.

1

If search does not return a relevant package, click on the package object icon to create a new package object. After entering the few known values, you may enter reasonable values or leave the remaining parameters as defaults.

302



Figure 19.6 Package Search Procedure

iii.

Go back to the Project tab and edit the created package object. Make sure that: •

The Package type is QFP.

•

The Package thickness is 2.0 mm.

•

The Model type is Compact Conduction Model (CCM).

•

The Symmetry is Full.


303


Note CCM is a compact model based on geometric simplifications that still preserve the original heat transfer pathways of the package. It has been demonstrated 2

that CCM is fairly accurate and boundary condition independent. Other options under Model type are: •

To model the package in full detail. This option is meant for package level modeling. Using this in board or system design will unduly complicate the simulation.

•

To characterize Junction-to-case and Junction-to-board network resistances for a two resistance compact model. We will be doing this for the PBGA package.

iv.

Select the Die/Mold tab. (The Substrate and Solder tabs show blank interface since QFP type packages do not have solder or substrate). Enter 3.5 W for Power.

v.

Use all other defaults under Die/Mold tab. Click Done to close the tab.

vi.

The package created is in an arbitrary location. You may use the Align face centers button ( ) to position the base center of the created package object with that of the 232PQFP block. The dimensions of the package should match the dimensions of the 232PQFP block:

vii. There is no more need for the 232PQFP block. Deactivate it. viii. There is another “232PQFP" block (232PQFP.1). Create a copy of the first package object and align with the remaining “232PQFP" block. Then, deactivate the second “232PQFP" block (232PQFP.1). The dimensions of the second package should be:

d.

PBGA package modeling We have fairly comprehensive information about the PBGA type package from the supplier (see Table 19.2: Available Information for 400 PBGA (p. 298)). Using this information we can construct a CCM or characterize to determine Θjc and Θjb to model it as a 2-resistor network model as shown here: i.

Select all the blocks named 400-PBGA and edit all of them simultaneously. A.

Select Network as the Block type and Two resistor as the Network type.

B.

Set the board side as Min Y.

2

Karimanal, K.V. and Refai-Ahmed, G., “Validation of Compact Conduction Models of BGA Under An Expanded Boundary Condition Set", Proceedings of the ITHERM 2002, May 2002, San Diego, Ca, USA.

304


Step 3: Generate a Mesh C.

Input the estimated Θjc (1.4 C/W) and Θjb (6.75 C/W) values in the Rjc and Rjb fields respectively.

D.

Input a Junction power of 2.0 W.

E.

Click Done to finish.

ii.

Edit the Cabinet. In the Properties tab, you have the option to define the boundary condition (Wall type) for each side of the cabinet. Set the Wall type for Min x and Max x as Opening.

iii.

Press Edit for the Min x side to open the Openings panel.

iv.

In the Properties tab of the Openings panel, assign an X velocity of 1 m/s.

v.

Click Done to close the Openings panel.

vi.

The Max x side opening should have the default settings (free opening).

vii. All other cabinet boundaries should be Default.

viii. Click Done in the Cabinet panel to confirm changes. ix.

You should see the openings on the min and max X sides of the cabinet.


Click the mesh icon

.


305

Chapter 19: Microelectronics Packages - Compact models a.

Make sure Hexa unstructured is selected as the Mesh type and Normal is selected for Mesh parameters.

b.


Figure 19.7 Mesh control panel

c. 2.

Evaluate your mesh from the Display and Quality tabs.

(optional) Create non-conformal assemblies around each package set to reduce the mesh count. As a start, use 3 mm slack values for all sides of each assembly. Resize the assemblies if required. With nonconformal assemblies, it is possible to reduce the number of elements in the mesh significantly. Display and compare the conformal and non-conformal meshes.

19.7. Step 4: Physical and Numerical Settings Let us solve the board model with a 1 m/s inlet velocity. 1.

Go to Problem setup → General setup tab.

Basic parameters and set the Flow regime to Turbulent in the


306


Step 6: Calculate a Solution 2.

Go to Solution settings → Basic settings panel and click Reset. It is advisable to always click the reset button in the Basic settings panel before starting the solver. Set the number of iterations Adto 200 in the Basic settings panel and close the panel. Then go to Solution settings → vanced settings to open the Advanced solver setup panel. Note that in the Advanced solver setup panel, under the Linear solver, the solver inputs for temperature have changed.

19.8. Step 5: Save the Model Save the model after the model building and meshing is complete. File → Save project


Define point monitors of temperature for 232-Lead_PQFP package and DIP objects. A point monitor will be created to monitor the temperature change with iterations (Figure 19.8 (p. 308)).


307


Figure 19.8 Monitor Point Definition

2.

Go to Solve → Run solution and enable Sequential solution of flow and energy equations.

308



Figure 19.9 Solve panel

3.

Click Start solution.

19.10. Step 7: Examine the Results First we would like to get an idea of the general temperature distribution pattern on the board. 1.

Create temperature contours of the PCB by clicking the Object face icon ( ), selecting Show contours, clicking Parameters and selecting This object for the Calculated drop-down list. •

Probe temperatures values at desired location after clicking on probe icon (

•

Note the higher temperatures in the parts of the PCB under the PQFP packages.

).

2.

Go to Report → Network block values. The Message window lists all network block temperatures. Network junction temperatures can also be obtained from the overview report.

3.

The closeness of the PBGAs to each other is a cause for their overheating. How much is the problem due to the temperature of the air approaching these components? •

4.

A picture of the thermal boundary layer over the PBGAs can be seen by taking XY cut plane of temperature contours over the PBGA blocks.

What is the cause for the somewhat high temperatures of the TO-220 devices?


309

Chapter 19: Microelectronics Packages - Compact models •

5.

Are the heat spreaders too close? If so, the air flowing between the spreaders will overheat preventing further heat dissipation to the air. You can find out if this is the case by creating XZ cut planes of vectors and contours that cut across the spreader blocks.

The highest temperatures are in the 400-PBGA blocks. Effective cooling solutions can be designed by understanding heat flow pathways. •

Generate a summary report of heat flow for the 400-PBGA blocks. By deactivating the button under Comb in the summary report panel, you can generate an itemization of heat flow through each of the sides of the object.

19.11. Step 8: Summary In this tutorial, you performed a board level simulation and determined cooling solutions in the event there is overheating.

19.12. Step 9: Additional Exercise Post-processing showed that the components of 400-PBGA are the most critical object since they are the hottest. Here are some cooling ideas to set up and perform ANSYS Icepak simulations: What if... 1.

The flow is in the negative X direction?

2.

The flow is in the negative X direction, and by judicious use of flow resistances, more flow is diverted toward the PBGAs (for the same overall flow rate)?

3.

The bottom side of the PCB is not dissipating any heat as a result of lying on domain boundary. On the other hand, there seem to be plenty of space above the board. The main reason for the headroom above the PCB is the height of the spreader blocks. While there is room to move up the spreader by a little bit, more room can be gained if the spreader is longer in the X direction but shorter in Y height. What if both sides of the PCB are exposed to airflow by moving it up?

4.

A heatsink is mounted on the PBGA blocks? Will it be possible to use a heatsink in contact with all PBGAs? Are there any practical issues?

310


Chapter 20: Multi-Level Meshing 20.1. Objective The objective of this exercise is to provide a means to improving the mesh resolution and optimizing the mesh count of a model consisting of CAD objects using the multi-level meshing technique. The procedure from this exercise should help you make appropriate modeling and meshing choices during your thermal modeling project.

20.2. Prerequisites The trainee should be familiar with: •

ANSYS Icepak modeling objects

•

Basics of meshing

•


20.3. Skills Covered •

Basic meshing techniques

•


•

Multi-level meshing

•

Uniform mesh parameters option

20.4. Training Method Used A model with potential for improvement is provided. Then, an approach for improving the model is presented. Feel free to explore the software interface, collaborate with another trainee, or ask a Technical Services Engineer.

20.5. Loading the Model •

Unpack and load the model named “HangingNode.tzr"

•

Rename it to any other name of your choice.

20.6. Step-by-Step Approach Without making any changes, the model results in about 650000 finite volume cells. Please note that this mesh count has been obtained making use of the non-conformal meshing technique that allows for localized fine meshing, thus eliminating mesh bleeding. However, this mesh does not fully resolve the fine-level geometric features of the CAD objects. It is possible to further reduce the mesh count and improve mesh resolution on and around the CAD objects using the multi-level meshing technique. This procedure starts with a coarse background mesh and resolves fine level features through a series of successive mesh refinements. It is possible to reduce the mesh count to approximately 500000 and Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

311

Chapter 20: Multi-Level Meshing improve mesh resolution at the same time using this technique along with the uniform mesh parameters option. •

Generate mesh without modifying the model. You will see a mesh count of about 650,000 cells.

Note The mesh count may differ slightly on different machines.

312


Step-by-Step Approach

Figure 20.1 Mesh of Flow Guide Without Multi-Level Meshing


313

Chapter 20: Multi-Level Meshing

Figure 20.2 Mesh of Sheetmetal_HS Without Multi-Level Meshing

20.7. Modification 1: Multi-Level Meshing of the Fan_Guide •

In the Meshing tab of the fan_guide.1 assembly, retain the slack and minimum gap values. However, change the Max element size values to 4.0 mm.

•

Toggle on Set uniform mesh params.

•

In the Multi-level tab, toggle on Allow multi-level meshing and set Max Levels to 2.

•

Keep the default selection of Proximity and Curvature.

314


Modification 2: Multi-Level Mesh of the Sheetmetal_hs_assy.1

20.8. Modification 2: Multi-Level Mesh of the Sheetmetal_hs_assy.1 •

In the Meshing tab of the Sheetmetal_hs_assy.1, retain the slack and minimum gap values. However, change the Max element size values to 3.5 mm.

•

Toggle on Set uniform mesh params.

•

In the Multi-level tab, toggle on Allow multi-level meshing and keep Max Levels as 2.

•

Keep the default selection of Proximity and Curvature.

•

Enter a value of 1 for Mesh buffer layers.


315


20.9. Generate a Mesh •

316

Generate a mesh with the modifications using the same settings as before.


Generate a Mesh

•

Observe the decrease in element count.

•

Display the mesh of the FLOW_GUIDE and the sheetmetal_hs_assy.1. Figure 20.3 (p. 318) shows the surface mesh on the flow_guide. Fine mesh resolution in some regions is necessary for a body fitted mesh. This can be clearly seen in the figure. In addition, it can be observed that the mesh resolution is coarser in regions where a fine resolution is not necessary to describe the geometry accurately. Figure 20.4 (p. 318) shows the mesh on and around the sheetmetal heatsink. It can be seen that the mesh resolution is fine in the fin region and coarser as we move away from the heatsink.


317


Figure 20.3 Flow_Guide Mesh

Figure 20.4 Sheetmetal Heatsink Mesh

318


Conclusion

20.10. Conclusion Using multi-level meshing, we were able to improve the mesh resolution and instantly transition to coarser meshes thus reducing the overall mesh count. Hence, this approach significantly reduces run time while enhancing the accuracy of the simulation.


319

320


Chapter 21: Characterizing a BGA-package by Utilizing ECAD Files 21.1. Introduction In Tutorials "Trace Layer Import for Printed Circuit Boards" and "Joule/Trace Heating" you learned how to import trace layouts for a PCB. In this tutorial, you will learn how to import trace layouts on a BGA package substrate by using TCB files. In this tutorial, you will learn how to: •

Import trace layout of a BGA package substrate in TCB format.

•

Display traces using the Color by trace option.

•

Plot temperature contours on the wirebonds.

•

Determine junction-to-case resistance for the package.

21.2. Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS Icepak and that you have solved or read the tutorial "Finned Heat Sink" of this guide.

21.3. Problem Description In this tutorial, you will see how to determine temperature profiles on the wirebonds of a BGA package and junction-to-case resistance.



2.


3.

Specify a name for your project (i.e., BGA-package) and click Create.

21.5. Step 2: Build the Model To build the model, you will change the units, create the PCB, import the traces and resize the cabinet to its proper size. Then you will create a wall object. 1.

Change the unit of length to mm. Edit → Preferences

2.

a.

In the Preferences panel, click on Units, under the Defaults node. In the Category box, scroll down and select Length, and under Units, select mm.

b.

Click Set as default, Set all to defaults and then This project.

Create the package object.


321

Chapter 21: Characterizing a BGA-package by Utilizing ECAD Files a.

Click on the packages object button (

) in the objects toolbar.

b.

In the Packages panel, click the Dimensions tab and select ASCII TCB from the Import ECAD file drop-down list.

Figure 21.1 The Packages Panel (Dimensions Tab)

c.

Select block_1.tcb in the Trace file panel and click Open.

Note block_1.tcb can be found in the installation directory at ICEPAK_ROOT/tutorials/BGA-package/block_1.tcb.

322

d.

Keep the numbers for the layers and vias and click Accept in the Board layer and via information panel.

e.

Click on the Die/Mold tab and assign a die Power of 0.5 W.

f.

Click Done.

g.

Click on the Cabinet in the object tree and click the Autoscale button located in the edit window in the lower right corner of the main menu. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.


Note Click the Scale to fit icon ( h.

) to refocus your model.

Right click on the package object in the object tree, choose Traces → Color by trace to display the traces.

Figure 21.2 Display of Traces

As can be seen in Figure 21.2 (p. 323), the wirebonds are lumped into polygonal plates by ANSYS Icepak. i.

Change the cabinet zS to -1.2 mm.

j.

Create a PCB object and input the following in the Geometry tab:

k.

Plane

X-Y

Specify by

Start / end

xS

-7.03 mm

xE

7.03 mm

yS

-7.03 mm

yE

7.03 mm

zS

-1.2 mm

zE

—

In the Properties tab, set the substrate thickness as 0.8 mm, then enter the following Cu percentages for the layers: Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

323

Chapter 21: Characterizing a BGA-package by Utilizing ECAD Files

Figure 21.3 Properties Tab of the Printed Circuit Boards Panel

l.

Click on Update. Note that the thermal conductivity information (plane and normal) for the PCB is updated.

m. Press Done to close the panel. n.

Create a wall object and align it with the min-z side of the cabinet and Rename it as Bottom.

o.

Edit the wall object and insulate it by keeping the heat flux as zero in the Properties tab.

p.

Make a copy of the wall and translate it in the z direction by 2.95 mm and rename the new wall to Top. We would like to determine the heat transfer coefficient on the top surface with the wellknown correlation in the literature, (Incropera et. al 1). In order to do that, you can follow the procedure in Figure 21.4 (p. 325).

1

Frank Incropera and David DeWitt, Fundamentals of Heat and Mass Transfer, John Wiley & Sons, Inc., New York, 1981.

324



Figure 21.4 Determining Heat Transfer Coefficient on the Top Wall


Click the Generate mesh button (

).

2.

In the Mesh control panel, enter 0.5 mm, 0.5 mm, and 0.14 mm for the Max element size for x, y, and z, respectively. Change the Minimum gap values to 0.05 mm, 0.05 mm, and 0.01 mm for x, y and z, respectively. In the Misc tab, unselect Allow minimum gap changes and click Change value and mesh in the Minimum separation panels.

Note Ensure that Mesh type is Mesher-HD.


325

Chapter 21: Characterizing a BGA-package by Utilizing ECAD Files 3.

Click Generate.

Figure 21.5 Mesh control Panel

4.

Click Close to close the panel once you have created the mesh.


2.

3.

Go to

Basic parameters.

a.

Uncheck Flow in the General setup tab.

b.

Turn off the radiation and click Accept to close the panel.

Go to


Basic settings.

a.

Change the Number of iterations to 25 and the Convergence criteria for Energy to 1e-15.

b.


Go to a.

326

Problem setup →


Advanced settings.


Choose W from the Type drop-down list.

ii.


b.

In the Precision drop-down list, select Double.

c.

Click Accept to save your settings and close the panel.




21.9. Step 6: Calculate a Solution Go to Solve → Run solution. Click Start solution.


When the model converges, plot the temperatures contours on the wirebond and view the variation/symmetry of the temperature profiles. a.

Go to Post → Object face and choose the wirebonds under the package object.

Figure 21.6 Object face Panel

b.

Select Show contours and click Parameters.

c.

Select This object from the Calculated drop-down list.

d.

Press Done in the Object face contours and Object face panels to close the panels and view the temperature contours.


327

Chapter 21: Characterizing a BGA-package by Utilizing ECAD Files

Figure 21.7 Temperature Contours on the Wirebonds (Top View)

2.

Go to the Report → Summary report and click on New twice. a.

Choose Source_DIE1 under the package object for the first object and the Top wall for the second object.

b.

Keep the default selection of Temperature under Value for both.

c.

Press Write to create the Summary report.

Max die and max top wall temperatures are determined as 142.0 and 129.9°C, respectively. Note that the top wall represents the case for the package. Therefore, junction-to-case resistance for this package is determined as: 328


Step 8: Summary

= Where

−

(21–1)

is the die power (0.5 W in this case). Therefore,

− = =

°

(21–2)

21.11. Step 8: Summary In this tutorial, you learned how to import trace layouts for a PCB on a BGA package substrate by using a TCB file.


329

330


Chapter 22: Zero Slack with Non-Conformal Meshing 22.1. Introduction This tutorial compares the mesh of a non-conformal assembly with and without slack values around a heat sink, package and board. The zero slack scenario will be solved and the number of iterations, and temperature distribution on objects in the model will be performed. In this tutorial you will learn how to use the zero slack capability in ANSYS Icepak.

22.2. Prerequisites This tutorial assumes that you have reviewed Sample Session in the Icepak User's Guide and the tutorials "Finned Heat Sink" and "RF Amplifier" of this guide.

22.3. Problem Description The model consists of a detailed heat sink, a BGA package, a block with traces and fluid blocks. The model setup is shown in Figure 22.1 (p. 332).


331

Chapter 22: Zero Slack with Non-Conformal Meshing

Figure 22.1 Problem Schematic

The objective of this exercise is to illustrate the advantage of using the zero slack capability. The model will be constructed using the default metric unit system.

332


Step 4: Import Traces


Copy the file ICEPAK_ROOT/tutorials/ZeroSlack/ZeroSlack_Tut.tzr to your working directory. You must replace ICEPAK_ROOT by the full path name of the directory where ANSYS Icepak is installed on your computer system.

2.


3.


4.

In the File selection panel, select the packed project file ZeroSlack_Tut.tzr and click Open. The Location for the unpacked project file selection dialog appears.

5.

In the Location for the unpacked project file selection dialog, select a directory where you would like to place the unpacked project file, enter a project name (e.g.0–slack) in the New project text field then click Unpack.

22.5. Step 2: Default Units Make sure the default unit of length is mm. Edit → Preferences 1.

2.

In the Preferences panel, click on Units under the Defaults node. In the Category box, scroll down and select Length, and under Units, make sure mm has an asterisk next to it. If there is no asterisk next to mm: a.

Select mm from the Units box.

b.

Click Set as default.

Click Set all to defaults and click This project.

22.6. Step 3: Build the Model This tutorial uses an existing model. The model contains existing package, board and heatsink assemblies.

22.7. Step 4: Import Traces 1.

In the model tree, expand the Board assembly to display the pcb object if it is not already visible. Right click pcb in the Model manager window and click Edit to display the Blocks panel.

2.

In the Geometry tab, select ASCII TCB from the Import ECAD file drop-down list.

Note You need to unzip the tcb file before you can import it. 3.

In the Trace file panel, select BOARD_OUTLINE.tcb. Turn off the Resize Block option because the pcb was imported using an idf file, so the dimensions are already correct. This process may take a few minutes depending on the speed of your computer.


333


Note The Resize Block option is necessary when the board size is not known or an idf file is not available. 4.

5.

Once the import is completed, you can edit the layer information in the Board layer and via information panel. Enter the layer thickness as shown in the table below. Layer

Thickness (mm)

Layer 1

0.04

Layer 2

0.45364

Layer 3

0.062

Layer 4

0.467

Layer 5

0.055

Layer 6

0.442

Layer 7

0.045

By default, layers are lumped for each sub-grid, therefore, the Model layers separately option is off and will need to be enabled. a.

Click Accept to close the Board layer and via information panel.

b.

Then click Edit next to Trace layers and vias in the Blocks panel to reopen the Board layer and via information panel.

c.

The Model layers separately option can now be enabled.

6.

The via information is imported automatically, so keep the default settings.

7.

Click Accept to save your settings.

Note

8.

•

You can view the traces in three different ways, i.e. Single color, Color by trace, or Color by layer.

•

The meshing plates are placed at the location of the different layers; they are used to ensure the mesh resolution is high enough at the different layers.


22.8. Step 5: Add Slack Values You will add slack values to the heat sink assembly.

Note Non-conformal assemblies are used to reduce mesh count in models and to improve mesh quality. 1. 334

Set the slack values for the heat sink assembly as shown in the figure below. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 6: Generate Mesh (with Slack Values)

22.9. Step 6: Generate Mesh (with Slack Values) You will generate a mesh for the heatsink assembly with slack values. 1.

Go to Model → Generate mesh to open the Mesh control panel.

2.

Make sure that the Min elements in gap is 2, the Min elements on edge is 1, and the Max size ratio is 3.

3.

Go to the Local tab and click Edit next to Object params. You will see the following requested values in the Per-object meshing parameters panel (scroll down to see the inside ratios):

Table 22.1 Object Parameters Object type

Object name

Parameter

Requested

block

pcb

X count

25

Z count

5

assembly

heatsink.1

all inside ratios

2

assembly

board

all inside ratios

2

assembly

package

all inside ratios

2

4.

Press Done to close the Per-object meshing parameters panel.

5.

Keep all other settings as default and click Generate. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

335

Chapter 22: Zero Slack with Non-Conformal Meshing 6.

Take note of the mesh count and view a cut plane of the mesh from the Display tab.

Note The package is not well resolved and it is divided between the heatsink and board assemblies. Moreover, mesh bleeding from the meshing plates extends beyond the board because of the slack values.

22.10. Step 7: Zero Slack Next, we will consider a board with non-conformal meshing with zero slack values. Non-conformal assemblies with zero slack help in resolving specific objects without extending the mesh to the rest of the cabinet. Also, zero slack non-conformal assemblies remove certain limitations that are present with regular non-conformal assemblies like intersections with other non-conformal assemblies. In this tutorial, the use of zero slack non-conformal assemblies allows us to have a separate non-conformal assembly for the package and to accurately resolve the mesh.

Note Currently, zero slack assemblies are unable to participate in radiation when a surface coincides with the assembly interface. 1.

336

Change the slack values for the heat sink assembly as shown in the figure below.



2.

In addition, enable Mesh separately in the package and board assemblies (do not change any other values in these assemblies).

22.11. Step 8: Generate Mesh (with Zero Slack) Generate a mesh with the same global mesh settings as in Step 6: Generate Mesh (with Slack Values) (p. 335) so that you can compare the mesh count. Observe that the mesh count is significantly less than that of the mesh with slack values.


In the model tree, go to Solution settings → Basic settings and Advanced settings, and verify that the following values are set:


2.

Go to Problem setup → Basic parameters and make sure the Flow regime is Turbulent and the turbulence model is Zero equation in the General setup tab. Also, give a small initial (global) X velocity of –1.5 m/s in Transient setup tab. Accept the changes made and exit this window. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

337


22.13. Step 10: Save the Model ANSYS Icepak saves the model for you automatically before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. File → Save project

22.14. Step 11: Calculate a Solution Go to Solve → Run solution. Click Start solution.

22.15. Step 12: Examine the Results After the solution has converged, create the following post processing objects: Object

Specifications

Description

cut.1

Set position: Y plane through center

Plane cut (x-z) view of the velocity vectors in the y plane.

Show vectors face.1

Object: pcb

Object-face view of temperature on pcb

Show contours / Parameters

Note the min & max temperatures and the temperature distribution.

Calculated: This object face.2

Object: pcb Show contours / Parameters

Object-face showing the conductivity, K_X.

Contours of : K_X

22.16. Step 13: Summary Zero slack is a feature in ANSYS Icepak that alleviates most restrictions encountered while using the original non-conformal assemblies. Zero slack non-conformal assemblies not only reduces mesh count further than original non-conformal assemblies but also allow the user to mesh specific objects separately. For example in this model, the zero slack capability allowed meshing of the package object separately.

338


Chapter 23: ANSYS Icepak - ANSYS Workbench IntegrationTutorial 23.1. Introduction This tutorial demonstrates how to create and solve an ANSYS Icepak analysis in ANSYS Workbench. You will model a geometry using the direct CAD modeling feature in ANSYS Icepak and create a non-conformal mesh for the complex shapes. The project will also include postprocessing the results in ANSYS CFD-Post and performing a static structural analysis. In this tutorial, you will learn how to: •

Create an ANSYS Icepak analysis in ANSYS Workbench.

•

Postprocess results in ANSYS CFD-Post.

•

Solve a project and transfer to ANSYS Mechanical for further analysis.

23.2. Prerequisites This tutorial assumes that you have little experience with ANSYS Workbench and so each step will be explicitly described.

23.3. Problem Description The graphics board contains a heat sink with extruded fins having aerofoil cross section, a PCB, capacitors, memory cards and ports. These objects are placed in a setup as shown in the figure below.


339

Chapter 23: ANSYS Icepak - ANSYS Workbench IntegrationTutorial

Figure 23.1 Problem Schematic


Start ANSYS Workbench.

Note When ANSYS Workbench starts, the Toolbox and Project Schematic are displayed.

340




Add a Geometry template by dragging the template from the Toolbar under the Component Systems node into the Project Schematic. Perform a right mouse click on the Geometry cell (A2) and go to Import Geometry. Click Browse and select graphics_card_simple.stp to load the geometry. The file graphics_card_simple.stp can be found at ICEPAK_ROOT/tutorials/Workbench.

Note A green check mark in the Geometry cell indicates the geometry has been imported successfully. 2.

Double-click the Geometry (A2) cell to open DesignModeler as you need to edit the geometry first before exporting into ANSYS Icepak. a.

Keep the selection of Meter as the desired length unit and press OK.

b.

Click Generate to display the model.

c.

Edit the geometry in DesignModeler using the Electronics option in the Tools menu. Select Simplify and choose the appropriate simplification level and select bodies. i.

Select All objects for Selection Filter.

ii.

Keep the Simplification Type as Level 2 and click Generate.

Refer to the Design Modeler documentation for more detailed information on using the Electronics options.

Note The Electronics menu is shown only if the DesignModeler option Enable Electronics Options is turned on. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

341

Chapter 23: ANSYS Icepak - ANSYS Workbench IntegrationTutorial d.

Close DesignModeler and return to ANSYS Workbench.

3.

Drag and drop an Icepak template into the Project Schematic on top of the Geometry cell (A2) to transfer the geometry into ANSYS Icepak.

4.

Right click on the Setup cell (B2) and select Edit to launch ANSYS Icepak. a.

The CAD model appears in the graphics display window and has been converted into ANSYS Icepak objects. Click the isometric toolbar icon (

b.

) to display the isometric view of the model.

In the object edit panel of each of the objects, rename the object (if necessary) in the Info tab and enter the specifications in Properties tab as shown in Table 23.1: Object Properties (p. 342).

Caution It is recommended to use unique names for Icepak objects when importing from DesignModeler as objects may be erroneously skipped when re-importing the model or duplicated when refreshing the geometry.

Note To open the object edit panel, perform a right mouse click on the object and select Edit. After editing the object, you can press Update to save the changes and click a different object in the Model tree to go to that object without closing the panel.

Table 23.1 Object Properties Object

New name

Solid Material

Total Power

SERIAL_PORT

SERIAL_PORT

default

0.0 Watts

MEMORY1

MEMORY_1

Ceramic_material

5 Watts

MEMORY1.1

MEMORY_2

Ceramic_material

5 Watts

CAPACITOR

CAPACITOR_1

default

0.0 Watts

CAPACITOR.1

CAPACITOR_2

default

0.0 Watts

KB

KB

default

0.0 Watts

HEAT_SINK

HEAT_SINK

default

0.0 Watts

CPU

CPU

Ceramic_material

20 Watts

ALHPA_MAIN_PCB

PCB

Custom- PCB solid_material

0.0 Watts

Conductivity type- Orthotropic X = 20, Y = 0.4, Z = 20

Note Edit the Solid material by selecting a material in the drop down list. To create a (Custom) material, select Create material in the drop down list and click the Properties tab in the Materials panel and enter the specifications.

342


Step 2: Build the Model c.

Resize edit the properties of the default cabinet in the Cabinet panel. Model → i.

Cabinet

In the Cabinet panel, click the Geometry tab. Under Location, enter the following coordinates:

Table 23.2 Coordinates for the Cabinet

ii.

d.

xS = -0.19 m

xE = 0.03 m

yS = 0 m

yE = 0.02848 m

zS = -0.11 m

zE = 0 m

Edit the cabinet properties to specify Min x and Max x sides as openings. A.

In the Properties tab of the Cabinet object panel, select Opening from the drop-down menu under Wall type for Min x and Max x.

B.

Select Edit to display the opening for the Max x object panel.

C.

In the Properties tab, specify the x velocity to be –2 m/s. Click Done in the Openings and Cabinet panels to apply the changes and close the panels.

The final model should correspond to the one shown below.


343


Figure 23.2 The Final Model Display

23.6. Step 3: Generate a Mesh Note For more information on how to refine a mesh locally, refer to Refining the Mesh Locally in the Icepak User's Guide. 1.

Click the assembly toolbar icon ( ) to create an assembly. Add the HEAT_SINK and CPU objects to the assembly and rename it CPU_assembly.

Note To add objects to an assembly, select one or more objects in the Model manager window and drag them into the desired assembly node.

344


Step 3: Generate a Mesh 2.

Go to the CPU_assembly object panel and click the Meshing tab. Enable the Mesh separately option and enter the following slack values. Click Done to close the panel.

Table 23.3 Slack Values

3.

Min X = 0.005 m

Max X = 0.005 m

Min Y = 0.0016 m

Max Y = 0 m

Min Z = 0.001 m

Max Z = 0.005 m

Specify the overall mesh controls as shown in the Mesh control panel below. Model → Generate mesh

Note The Mesh units and Minimum gap values are in mm, and Set uniform mesh params is checked in the Global tab. Press Generate to create the mesh. You can check the mesh using the Display and Quality tabs in the Mesh control panel. Press Close when you are done. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

345



2.

Go to

Problem setup →

Basic parameters in the Model manager window.

a.

In the General setup tab, make sure that both flow and the temperature fields are switched on.

b.

Select Turbulent and Zero equation for the Flow regime and turn Off the Radiation.

c.


Go to Solution settings → Basic settings and Solution settings → Advanced settings in the Model manager window and verify that the following values are set for each variable: Basic settings No. of iterations = 100 Flow = 0.001 Energy = 1e-7 Advanced settings Pressure = 0.3 Momentum = 0.7

23.8. Step 5: Save the Model 1.

Go to File → Save project.

Note You can click the save icon (


The Save As panel appears. 2.

Specify the name ice_wb for your project and click Save.

3.

ANSYS Workbench will close ANSYS Icepak to save the model, you will need to launch ANSYS Icepak again to continue.


Go to Solve → Run solution to display the Solve panel.

2.

Keep the default settings in the Solve panel.

3.

Click Start solution to start the solver. ANSYS Icepak begins to calculate a solution for the model and a separate window opens where the solver prints the numerical values of the residuals. ANSYS Icepak also opens the Solution residuals graphics display and control window, where it displays the convergence history for the calculation. Note that the actual values of the residuals may differ slightly on different machines, so your plot may not look exactly the same as the figure below.

346


Step 7: Examine the Results with CFD-Post

4.

Once the solution converges, click Done in the Solution residuals window to close it.

23.10. Step 7: Examine the Results with CFD-Post Note The postprocessing of results can be done within ANSYS Icepak; however, you can also examine results in ANSYS CFD-Post. This section will describe how to transfer information to ANSYS CFD-Post and use its postprocessing options, so you may close ANSYS Icepak.


347

Chapter 23: ANSYS Icepak - ANSYS Workbench IntegrationTutorial 1.

After calculating a solution in ANSYS Icepak, a green check mark will be displayed in the Icepak Solution cell in the Project Schematic. The green check mark indicates that all data is up to date. Select Results under the Component Systems node in the Toolbox. Drag the Results cell on top of the Icepak Solution cell (B3) to transfer the data.

2.

Double click the C2 Results cell to launch ANSYS CFD-Post. The model should appear in the display window.

3.

To generate contours, please do the following: a.

Go to Insert → Contour or click on the Contour button “Contour 1” and click OK.

b.

In the Geometry tab under Details of Contour 1:

to create a contour. Retain the name

i.

Keep the default selection of All Domains in the Domains drop-down list.

ii.

Click on the ... button next to Locations to display the Locations Selector dialog box. Highlight all CPU, PCB and HEAT_SINK objects and click OK to close the panel.

Note You can select multiple objects by holding down either Shift or Ctrl and selecting the objects.

4.

iii.

Select Temperature in the Variable drop-down list.

iv.

Select Apply to display the contours.

To generate a 3D streamline, please do the following: a.

Go to Insert → Streamline or click on the Streamline button the name “Streamline 1” and click OK.

b.

In the Geometry tab under Details of Streamline 1:

c.

i.

Keep the default selection of 3D Streamline in the Type drop-down list.

ii.

Keep the default selection of All Domains in the Domains drop-down list.

iii.

Select cabinet_default_side_maxx minx from the Start From drop-down list.

iv.

Keep the default selection of Velocity in the Variable drop-down list.

v.

Keep all other defaults and click Apply to display the streamline.

You can also animate the streamline. To animate the streamline, go to Tools → Animation or click on the animation button

5.

348

to create the streamline. Retain

.

When you are done examining the results, close ANSYS CFD-Post and return to ANSYS Workbench.


Step 9: Summary

23.11. Step 8: Thermo-Mechanical Structural Analysis In addition to solving this problem in ANSYS Icepak, you can also perform a static structural analysis. 1.

Select Static Structural from the Toolbox and drag and drop this cell on top of the Icepak Solution cell (B3).

2.

Click on the Geometry cell (A2) and drag and drop it on top of the Static Structural Geometry cell (D3). The geometry is now shared.

3.

Right click on the Setup cell (D5) and click Update.

4.

Double click on the Model cell ( D4) to launch ANSYS Mechanical.

5.

Click on the Imported Body Temperature object. This object is found under the Imported Load (Solution) node.

6.

Under Details, ensure that the Scoping Method is Geometry Selection. Click the Box Select button

, hold down the Ctrl key and drag a box around the entire model to select it. Click on the cell to the right of Geometry and then click Apply. Nine bodies should be selected. 7.

Select All from the Icepak Body drop-down list.

8.

Click Solve.

23.12. Step 9: Summary In this tutorial, you imported CAD objects and set up a problem. You then created a non-conformal mesh using the hex-dominant mesher. This forced convection problem was solved for flow and heat transfer and the results were examined on contours and 3D streamlines in the model.


349

350


Chapter 24: Postprocessing Using ANSYS CFD-Post 24.1. Introduction This tutorial demonstrates the use of ANSYS CFD-Post for post-processing results from ANSYS Icepak analyses. In this tutorial, you will learn how to: •

Create a workflow in ANSYS Workbench.

•

Postprocess ANSYS Icepak results in ANSYS CFD-Post.

24.2. Prerequisites •

Familiarity with the ANSYS Workbench interface

•

Familiarity with the ANSYS Icepak interface

Figure 24.1 Quick Reference - CFD Post Interface


351

Chapter 24: Postprocessing Using ANSYS CFD-Post

Figure 24.2 Quick Reference - Mouse Button Mapping (default) in CFD Post:

To adjust or view the mouse mapping options, go to Edit → Options, then Viewer Setup → Mouse Mapping in ANSYS CFD-Post.

24.3. Problem Description Figure 24.3 (p. 352) shows the ANSYS Icepak model of a graphics card that contains a printed circuit board. The board components include memory cards, capacitors, CPU, and serial connectors for peripheral devices. The CPU is cooled by a heat sink. A fan and grille have been used to enhance the convective heat transfer within the system. Two configurations, varying the positioning of the fan and grille, will be considered for CFD analysis.

Figure 24.3 Problem Schematic - Graphics Card Model (two configurations)


Create a workflow by linking ANSYS Icepak and ANSYS CFD-Post in ANSYS Workbench. a.

352

Start a new ANSYS Workbench session.


Step 1: Create a New Project b.

Drag an ANSYS Icepak component module from the Toolbox and drop it on the Project Schematic window as shown in Figure 24.4 (p. 353).

Figure 24.4 Creating an ANSYS Icepak Component

c.

Rename the ANSYS Icepak component module as Parametric Setup as shown in Figure 24.5 (p. 353). To rename the title, double click on the title Icepak or click the left mouse button on the down arrow (

) and select the Rename option from the drop down list.

Figure 24.5 Renaming the ANSYS Icepak Component Module

d.

As shown in Figure 24.6 (p. 354) and Figure 24.7 (p. 354), drag and drop a Results (ANSYS CFDPost) component module onto the Solution cell of the Parametric Setup to link the ANSYS Icepak analysis to ANSYS CFD-Post. Rename the Results component module to CFD Post.


353


Figure 24.6 Linking the Results (ANSYS CFD-Post) Component to the ANSYS Icepak Component

Figure 24.7 Final Project Schematic

e. 2.

Save the project using File/Save (name the project as ice-cfdpost) from the ANSYS Workbench interface.

Import project into ANSYS Icepak a.

Right click the ANSYS Icepak Setup cell and import the packed ANSYS Icepak project file icecfdpost.tzr located in the project directory.

b.

The ANSYS Icepak interface will launch with the selected project loaded for modeling/analysis.

24.5. Step 2: Parametric Trials and Solver Settings 1.

Go to Edit → Preferences → Postprocessing and confirm that Merge zones when possible for CFD-post data option is selected.

2.

Go to Solve → Run solution → Results and verify that Create Heat Flux Vector in CFD Post is enabled and click Dismiss.

354


Step 4: Postprocessing Using ANSYS CFD-Post 3.

Go to Solve → Run optimization. a.

In the Design variables tab, review the parametric setup.

b.

In the Trials tab, note that two of the four trials will be considered for CFD analysis.

Figure 24.8 Solution Trials


Click Run in the Parameters and optimization panel.

2.

ANSYS Icepak will run two trials and automatically write out the results for post-processing in ANSYS CFD-Post at the end of each trial.

3.

Save the project by going to File → Save project.

4.

Close ANSYS Icepak by going to File → Close Icepak.

24.7. Step 4: Postprocessing Using ANSYS CFD-Post 1.

2.

Open the results in ANSYS CFD-Post. a.

On the project schematic, double click the Results cell to launch the ANSYS CFD-Post interface.

b.

ANSYS CFD-Post automatically reads in the most recent solution set (trial 004).

Create a Surface Group for the board and all the components. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

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Chapter 24: Postprocessing Using ANSYS CFD-Post a.

Go to Insert → Location → Surface Group.

b.

Name the group as BoardANDComponents.

c.

Go to the Details view located on the lower left hand side of the screen (see Figure 24.1 (p. 351)).

Figure 24.9 Details View for BoardANDComponents Surface Group

d.

In the Geometry tab, click i.

next to Locations to open the Location Selector panel.

As shown in Figure 24.10 (p. 356), hold down Shift and the left mouse button to select all but the last eight (cabinet*, fan and grille) surfaces from the list.

Figure 24.10 Selection for the BoardANDComponents Surface Group

ii. e. 3.

Click Apply in the Geometry tab to apply the settings.

Create another Surface Group for the cabinet. a.

356

Click OK to close the Location Selector panel and add the surfaces.

Go to Insert → Location → Surface Group and name the group CabinetSurfaces.


Step 4: Postprocessing Using ANSYS CFD-Post

Figure 24.11 Listing of Surface Groups under User Locations and Plots

b.

As before, open the Location Selector panel, but this time select only the cabinet surfaces, and press OK.

Figure 24.12 Selection for the CabinetSurfaces Surface Group

c.

In the Render tab, apply the settings as shown in Figure 24.13 (p. 358) and click Apply.


357


Figure 24.13 Rendering Details for the CabinetSurfaces Surface Group

d.

358

Uncheck the BoardANDComponents object from User Locations and Plots.



Figure 24.14 Updated Model

e. 4.

Note that these newly create Surface Groups are listed under User Locations and Plots in the Outline tab.

Plot Contours of Temperature on the Surface Group BoardANDComponents. a.

Change the Units for this postprocessing session. i.

Go to Edit → Options → Units.

ii.

Set the System to Custom.

iii.

Set the unit for Temperature to C.


359


Figure 24.15 Setting Units in CFD Post

iv.

360

Click Apply and then OK to set the units and close the panel.

b.

Go to Insert → Contour and create a new contour object named TemperatureContours.

c.

For the contour TemperatureContours, update the settings for the Geometry tab of the Details view as shown in Figure 24.16 (p. 361) and click Apply.



Figure 24.16 Geometry Settings for TemperatureContours

d.

Go to the Render tab and deselect Show contour lines.

e.

Click Apply to create the contour.

Note TemperatureContours is listed under User Locations and Plots. 5.

Modify the display of the default legend view. a.

Double click Default Legend View 1 listed under User Locations and Plots to access the corresponding Details view.

b.

Modify the settings in the Definitions and the Appearance tabs as shown in Figure 24.17 (p. 362) and click Apply.


361


Figure 24.17 Settings for Default Legend View 1

Figure 24.18 Modified Legend View

6.

362

Plot Vectors, displaying heat flux on the Surface Group BoardANDComponents.


Step 4: Postprocessing Using ANSYS CFD-Post a.

Deselect TemperatureContours in the User Locations and Plots node.

b.

Go to Insert → Vector and create a new Vector object named HeatFluxVectors and click OK.

c.

Modify the Geometry tab of the Details view as shown in Figure 24.19 (p. 363) and click Apply.

Figure 24.19 Geometry Settings for HeatFluxVectors

Figure 24.20 Display of HeatFluxVectors

7.

Plot Thermal Chokepoint, displaying regions of high heat flux on the Surface Group BoardANDComponents. a.

Deselect HeatFluxVectors in the User Locations and Plots node. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

363

Chapter 24: Postprocessing Using ANSYS CFD-Post b.

Go to Insert → Contour and create a new Contour object named Chokepoint and click OK.

c.

Open the Location Selector panel and select only the ALPHA_MAIN_PCB surfaces. Press OK to close the Location Selector panel and add the surfaces.

Figure 24.21 Selection for Thermal Chokepoint

d.

364

Modify the Geometry tab of the Details view as shown in Figure 24.22 (p. 365) and click Apply.



Figure 24.22 Geometry Settings for Chokepoint


365


Figure 24.23 Display of Chokepoint

8.

366

Plot Streamlines originating from the fan and colored by temperature. a.

Deselect Chokepoint and select TemperatureContours in the User Locations and Plots node.

b.

Go to Insert → Streamline and create a new Streamline object named StreamlinesFan and click OK to access the Details view panel.

c.

Modify the Geometry tab as shown in Figure 24.24 (p. 367) and click Apply.



Figure 24.24 Geometry Settings for StreamlinesFan

d.

Modify the Color tab as shown in Figure 24.25 (p. 367) and click Apply.

Figure 24.25 Color Settings for StreamlinesFans

e.

Modify the Symbol tab as shown in Figure 24.26 (p. 368) and click Apply.


367


Figure 24.26 Symbol Settings for StreamlinesFan

Figure 24.27 Display of StreamlinesFan

9.

368

Create a Keyframe Animation of StreamlinesFan. a.

Go to Tools → Animation and select Keyframe Animation.

b.

Click the

button to insert a new frame called KeyframeNo1 as shown in Figure 24.28 (p. 369).



Figure 24.28 Keyframe Animation Panel

c.

Right click the background next to the model in the 3D viewer and select the View from +Y option under Predefined Camera.

Figure 24.29 View From +Y

d.

Add another keyframe called KeyframeNo2 to the Animation panel.

e.

Check the Animate Camera option on the Keyframe Animation panel (you may need to activate the display of the lower half of the Animation panel using the drop down arrow ).

f.

Similarly, update the display and add new frames as follows: i.

View from -Z and add KeyframeNo3.


369

Chapter 24: Postprocessing Using ANSYS CFD-Post ii.

View from +X and add KeyframeNo4.

iii.

Isometric view (Y up) and add KeyframeNo5.

g.

Click

h.

Click the Options button on the Animation panel to access the Animation Options panel.

i.

Set the Animation Speed to Slower from the drop-down menu by a factor of 20 and click OK.

to view the animation.

Figure 24.30 Animation Options Panel

j.

Replay the animation and note that the animation is less choppy compared to the original one.

k.

Close the Keyframe Animation panel.

l.

Deselect the TemperatureContours and StreamlinesFan objects under User Locations and Plots.

10. Create a Plane object displaying temperature contours and velocity vectors.

370

a.

Go to Insert → Location → Plane and create a plane named PlaneCut.

b.

Modify the Details for PlaneCut as shown in Figure 24.31 (p. 371) and click Apply.



Figure 24.31 Details for PlaneCut

c.

Deactivate the display of the plane by deselecting PlaneCut and activate the contour display by selecting TemperatureContours under User Locations and Plots.

d.

Double click on TemperatureContours or right click Edit to access the Details view. Update the details as shown in Figure 24.32 (p. 371) and click Apply.

Figure 24.32 Details for TemperatureContours


371


Figure 24.33 Display of PlaneCut

e.

f.

Go to the Details view for the PlaneCut (do not activate the display of the PlaneCut) and make the following modifications: i.

Switch Method to XY Plane and click Apply.

ii.

Use the scroll bar to change the Z location for PlaneCut.

The plane cut can also be traversed across the domain using the animation tools in CFD Post. i.

Go to Tools → Animation and select Quick Animation (default) and highlight the PlaneCut object.

ii.

Using the scroll bar, adjust the number of frames for the animation as shown in Figure 24.34 (p. 373) and click the

372

button.



Figure 24.34 Quick Animation Settings

iii.

The animation can be viewed on the screen or can be written out to an animation file by checking the Save Movie option.

iv.

Stop the animation by clicking the

v.

Close the Animation panel.

button.

g.

Deactivate the display of the contours by deselecting the TemperatureContours object under User Locations and Plots.

h.

Go to Insert → Vector and create a vector object named VelVectors.

i.

Modify the Details for VelVectors to set the Location to PlaneCut and click Apply.

j.

As before, use the Details view for the PlaneCut to manually traverse the plane displaying the vectors across the domain.

k.

Deactivate the display of the vectors by deselecting Velvectors under User Locations and Plots.

11. Create an Isosurface of 27°C and 3 m/s. a.

Go to Insert → Location → Isosurface and create an Isosurface name HotSpots.

b.

Modify the Details for HotSpots to create an isosurface for 27°C (Variable: Temperature, Value: 27°C).

c.

Similarly, modify the Details to create an isosurface for 3 m/s (Variable: Velocity, Value: 3 m/s).

d.

Deactivate the display of the isosurface by deselecting HotSpots under User Locations and Plots.

12. Create a Volume for values above 25°C. a.

Go to Insert → Location → Volume and create a Volume named IsoVolume.

b.

Modify the Details for IsoVolume as shown in Figure 24.35 (p. 374) and click Apply.


373


Figure 24.35 Details of IsoVolume

Figure 24.36 Display of IsoVolume

c.

374

Deactivate the display of the volume by deselecting IsoVolume under User Locations and Plots.


Step 4: Postprocessing Using ANSYS CFD-Post 13. Create a Chart of Temperature variation across a Line. a.

Go to Insert → Location → Line and create a Line named ForChart.

b.

Modify the Details for ForChart as shown in Figure 24.37 (p. 375). and click Apply.

Figure 24.37 Details for Line ForChart

c.

Deactivate the display of the line by deselecting ForChart under User Locations and Plots.

d.

Go to Insert → Chart to create a Chart named TemperatureVariation.

e.

Modify the Details for TemperatureVariation as follows:

f.

i.

General tab: Set the Type to XY.

ii.

General tab: Set the Title to Temperature Variation along Z axis.

iii.

Data Series tab: Set Location to ForChart.

iv.

X Axis tab: Set Variable to Z.

v.

Y Axis tab: Set Variable to Temperature.

Leave all other settings as their defaults and click Apply.


375


Figure 24.38 Plot of TemperatureVariation Along ForChart

Note The chart TemperatureVariation is added under the Report node of the Outline tree.

14. Create an Expression and Variable that can be used for postprocessing. a.

376

Switch to the Expressions tab (located next to the Outline tab) and review the list of available expressions.


Step 4: Postprocessing Using ANSYS CFD-Post i.

Right click in the white space and click New to create a new expression named VelocityRatio.

ii.

Click Ok to access the Details view for VelocityRatio.

iii.

Right click the white space in the Definition tab to access the Functions, Expressions, Variables, Locations and Constants which will be used to create the expression VelocityRatio.

iv.

Create the expression as shown in Figure 24.39 (p. 377) and click Apply.

Figure 24.39 Expression for VelocityRatio

Note Velocity is found under Variables, volumeAve()@ is found under Functions → CFDPost, and default_fluid is found under Locations → Other.


377

Chapter 24: Postprocessing Using ANSYS CFD-Post b.

Switch to the Variables tab and review the list of Derived, Geometric, Solution, and User Defined variables. i.

Right click the white space and click New to create a new variable named VelRatio.

ii.

Click Ok to access the details view for VelRatio.

iii.

Select Expression for the Method and set VelRatio to correspond to the Expression VelocityRatio.

iv.

Click Apply to create VelRatio.

Note VelRatio is listed under the User-Defined type of Variables. c.

Contours, Isosurfaces, Vectors, Charts, etc. can now be plotted using this new variable.

24.8. Step 5: Comparison Study 1.

378

Open a new ANSYS CFD-Post session a.

Go to File → Close CFD Post to close the existing ANSYS CFD-Post session.

b.

In the ANSYS Workbench project schematic, right click the Solution cell of the parametric setup component to transfer the solution data to a new Results component, as shown in Figure 24.40 (p. 379).

c.

Rename the Results component to Comparison Study.


Step 5: Comparison Study

Figure 24.40 Creation of New Results Component and Updated Project Schematic

d.

Double click the Results cell of Comparison Study to launch a new ANSYS CFD-Post session.

Note As before, ANSYS CFD-Post automatically reads in the most recent solution set (trial 004). 2.

As shown in Figure 24.41 (p. 380), go to File → Load Results to load an additional solution set. Navigate to the ~ice-cfdpost_files/dp0/IPK/Icepak/IcepakProj folder to pick trial001.cfd.dat as the second solution set for the comparison study.


379


Figure 24.41 The Load Results Panel

3.

4.

Set up the display of the two solution sets. a.

Synchronize the camera and the visibility in the displayed views by turning on the corresponding features from the Shortcuts Toolbar (located above the models in 3D viewer displays).

b.

Rotate, Zoom, or Pan one of the displays and confirm that the other display follows suit.

c.

Using the Shortcuts Toolbar, modify the display to a landscape view (switch from

to

As before, go to Insert → Location → Surface Group and create a Surface Group named BoardAndComponents.

Important The Surface Group in this ANSYS CFD-Post session should include the board and component surfaces from BOTH solution sets. Use the Location Selector to select all but the last eight surfaces from each list. The easiest way to do this is to select all the objects from both groups using Shift and the left mouse button, then deselecting the cabinet objects from both groups using Ctrl and the left mouse button.

380

)


Step 5: Comparison Study

Figure 24.42 Display of BoardANDComponents

5.

Deselect BoardAndComponents from User Locations and Plots.

6.

As before, go to Insert → Contour and create a new contour object named TemperatureContours and set its Locations to the BoardAndComponents Surface Group. Set Variable to Temperature and click Apply.

7.

Update the display of the Default Legend View (each display will need to be updated individually) as before.


381


Figure 24.43 Display of Legend View

8.

382

Go to Insert → Streamline and create a Streamline object named StreamlinesFans and edit the Details as below: a.

Geometry tab: Select fan1_minx from both solution sets for Start From and set # of Points to 50.

b.

Color tab: Set Mode to Variable and select Temperature for Variable.

c.

Symbol tab: Select Show Symbols and Show Streams. Set the Interval to 0.005 s.

d.

Click Apply.


Step 6: Summary

Figure 24.44 Display of Streamlines Comparison

e.

Perform a detailed comparison study using the various features (Isosurface, Plane, Animation etc.) discussed earlier in this tutorial.

24.9. Step 6: Summary In this tutorial, you learned how to import an ANSYS Icepak project from a .tzr file in ANSYS Workbench. You then learned how to use a solution that was solved in ANSYS Icepak and postprocess it in ANSYS CFD-Post. You also learned how to compare parametric solutions side-by-side in ANSYS CFD-Post.


383

384


Chapter 25: High Density Datacenter Cooling 25.1. Introduction This tutorial demonstrates how to model a datacenter using ANSYS Icepak. In this tutorial, you will learn how to: •

Use macros to create computer room air conditioning units (CRACs), server cabinets, power distribution units (PDUs), and perforated floor tiles in the datacenter.

•

Organize the model using groups.

•

Include effects of gravity and turbulence in the simulation.

•

Define object-specific meshing parameters.

•

Create contours, particle traces, iso-surfaces to better understand the airflow patterns and temperature stratification within the datacenter space.

25.2. Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS Icepak and that you have solved or read the tutorial "Finned Heat Sink" of this guide. Some steps will not be shown explicitly.

25.3. Problem Description This tutorial considers a 1200 sq. ft. datacenter with a slab to slab height of 12 ft as shown in Figure 25.1 (p. 386). The datacenter consists of a 1.5 ft underfloor plenum and a 2 ft ceiling plenum. The CRACs discharge cold air into the underfloor plenum. The cold air enters the main datacenter space mainly through the perforated floor tiles and returns back to the air conditioning units as shown in Figure 25.2 (p. 386). The cooling load, as summarized in Table 25.1: Size and Capacity of Heat Sources in Datacenter (p. 385) corresponds to the heat output from the server cabinets and the PDUs.

Table 25.1 Size and Capacity of Heat Sources in Datacenter Heat Source

Size

Power

Server Cabinet

2 ft x 3 ft x 7 ft

3000 W

High Density

2 ft x 3 ft x 7 ft

7000 W

PDU

4 ft x 2 ft x 5 ft

3600 W


385

Chapter 25: High Density Datacenter Cooling

Figure 25.1 Geometry of the Datacenter Model

Figure 25.2 Expected Airflow Path



2.


3.

Specify a name for your project such as datacenter and click Create. ANSYS Icepak creates a default cabinet with the dimensions 1 m × 1 m × 1 m, and displays the cabinet in the graphics window.

386


Step 2: Set Preferences


25.5. Step 2: Set Preferences 1.

Go to Edit → Preferences. The Preferences panel opens.

2.

Go to Display in the Options node. a.

3.

Go to Editing in the Options node. a.

4.

Select Float for the Color legend data format and enter 2 under Numerical display precision. Set the Default dimensions to Start/length.

Go to Object types in the Options node. a.

Turn off Decoration for all object types and update line Width to 2 for blocks, fans, openings, plates, resistances and grilles.

Figure 25.3 The Preferences Panel - Object types


387

Chapter 25: High Density Datacenter Cooling 5.

Go to Units in the Defaults node. a.

Click Set all to Imperial.

b.

Click This project to apply the preferences to this project.

25.6. Step 3: Build the Model To build the model, you will first resize the cabinet to its proper size. Then you will create the features of the datacenter, including CRACs (2), server cabinets (44), perforated floor tiles (44), raised floor (1), dropped ceiling (1), return grilles (8), PDUs (2), cable trays (4), columns (2) and miscellaneous blockage (1). 1.

Resize the default cabinet. a.

Select the Cabinet in the Model tree and specify the following in the object geometry window:

b.

Press Apply to resize the cabinet.

c.

Click the Isometric view button (

) to show a scaled-to-fit isometric view of the cabinet.

Note The walls of the cabinet are adiabatic and do not participate in radiation by default. Radiation will not be considered for this analysis. 2.

Create the raised floor. a.


).

ANSYS Icepak creates a free rectangular plate in the x-y plane in the center of the cabinet. You need to change the orientation and size of the plate and its location within the cabinet. b.

3.

i.

Set the Name to raisedfloor.

ii.

Change the Plane to xz.

iii.

Enter the following dimensions:

iv.

Press Apply to resize and rename the object.

Create the first CRAC unit. a.

388

In the object geometry window:

Go to Macros → Datacenter components → CRAC to open the CRAC panel. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 3: Build the Model b.

Enter the dimensions as shown below in Figure 25.4 (p. 389).

c.

Make sure the Flow direction is -Y.

d.

Select Mass flow rate and input a value of 15.9 lbm/s.

e.

Specify a Supply temperature of 55 F.

Figure 25.4 The CRAC Panel

Note Mass flow rate has units of lbm/s. f.

Press Accept to create the CRAC unit.


389


Figure 25.5 The CRAC Unit in the Graphics Window

4.

390

Set the per-object meshing parameters for the fans crac_intake and crac_exhaust. a.

Open the Mesh control panel by clicking the Generate mesh button (

b.

In the Local tab, check Object params and press Edit.

).

i.

In the Per-object meshing parameters panel, Ctrl+left click crac_exhaust and crac_intake to select both objects.

ii.

Check the Use per object parameters option.

iii.

Check the X count and Z count options and specify a Requested value of 4 for both options.



Figure 25.6 Per-object Meshing Parameters for the Fans

5.

6.

c.

Click Done to close the Per-object meshing parameters panel.

d.


Create a new group for the CRAC unit. a.

Select all the CRAC objects by Shift+left clicking cracunit and then crac_exhaust in the Model manager window.

b.

Right click one of the selected objects and go to Create and then Group.

c.

In the Create group panel, enter CRACs in the Name for new group text field.

d.

Press Done to create the new group.

Create the second CRAC unit. a.

Expand the Groups node in the Model manager window.

b.

Right click CRACs and select Copy.

c.

In the Copy group panel, check Group name and enter CRACs.

d.

Check Translate and set the Z offset to 10 ft.


391


Figure 25.7 The Copy Group CRACs Panel

e.

392

Press Apply and Done to copy the CRAC unit and close the panel.



Figure 25.8 Two CRAC Units in the Graphics Window

f. 7.

Now may be a good time to Save the project (

).

Create a row of server racks. a.

Go to Macros → Datacenter components → Rack (Front to Rear).

b.

Input the dimensions as show below in Figure 25.9 (p. 394).

c.

Set the Flow direction to -X.

d.

Specify a Heat load of 3000 W.

e.

Specify a Volume flow of 450 cfm.

f.

Set the Number of racks to 11.

g.

Under Create additional racks along select +Z.


393


Figure 25.9 The Rack (Front to Rear) Panel

h.

394

Press Accept to create the server racks.



Figure 25.10 Row of Server Racks in the Graphics Window


395


Note The volumetric flow rate input for the recirculation opening is converted by ANSYS Icepak to a mass flow rate input to the computational stage of the analysis. For this conversion, ANSYS Icepak uses the density specified for Air in the materials panel as shown below.

8.

9.

396

Create a new group for the server racks. a.

Select all the server rack objects by Shift + left clicking rack and then rack-opns.10 in the Model manager window.

b.


c.

In the Create group panel, enter RACKs in the Name for new group text field.

d.


Create a second row of server racks a.

Right click RACKs in the Groups node and select Copy.

b.

In the Copy group panel, check Group name and enter RACKs.

c.

Check Rotate and Translate in the Operations group box.

d.

Set the Axis to Y and the Angle to 180. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 3: Build the Model e.

Set the X offset to 7 ft.

Figure 25.11 The Copy Group RACKs Panel

f.

Press Apply and Done to copy the row of server racks and close the panel.


397


Figure 25.12 Two Rows of Server Racks in the Graphics Window

10. Create a row of high density server racks.

398

a.

Go to Macros → Datacenter components → Rack (Front to Rear).

b.

Enter hdrack in the Name text field.

c.

Input the dimensions as show below in Figure 25.13 (p. 399).

d.

Set the Flow direction to -X.

e.

Specify a Heat load of 7000 W.

f.

Specify a Volume flow of 1000 cfm.

g.

Set the Number of racks to 11.

h.

Under Create additional racks along select +Z.



Figure 25.13 The Rack (Front to Rear) Panel

i.

Press Accept to create the high density server racks.

11. Create a new group for the high density server racks. a.

Select all the high density server rack objects by Shift+left clicking hdrack and then hdrackopns.10 in the Model manager window.

b.


c.

In the Create group panel, enter HDRACKs in the Name for new group text field.

d.


12. Create a second row of high density server racks. a.

Right click HDRACKs in the Groups node and select Copy.

b.

In the Copy group panel, check Group name and enter HDRACKs.

c.

Check Rotate and Translate in the Operations group box.

d.

Set the Axis to Y and the Angle to 180.

e.

Set the X offset to 7 ft.

f.

Press Apply and Done to copy the row of high density server racks and close the panel.


399


Figure 25.14 Two Rows of High Density Server Racks in the Graphics Window

13. Create a row of perforated tiles.

400

a.

Go to Macros → Datacenter components → Tile.

b.

Set the Number of tiles to 11.

c.

Enter the dimensions as show below in Figure 25.15 (p. 401).

d.

Choose +Z.

e.

Enter 0.35 for Uniform under % Open area.



Figure 25.15 Tile Panel

f.

Press Accept to create the tiles.


401


Figure 25.16 Row of Tiles in the Graphics Window

14. Set the per-object meshing parameters for all the resistance objects.

402

a.


b.

In the Local tab, press Edit next to the Object params option.

).

i.

In the Per-object meshing parameters panel, Shift+left click tile and then tile.10 to select all the resistance objects.

ii.


iii.


iv.

Check the Y count option and specify a Requested value of 3.



Figure 25.17 Per-object Meshing Parameters for the Tiles

c.


d.


15. Create a new group for the perforated tiles. a.

Select all the tile objects by Shift+left clicking tile and then tile_open_bottom.10 in the Model manager window.

b.


c.

In the Create group panel, enter TILEs in the Name for new group text field.

d.


16. Create three more rows of perforated tiles. a.

Right click TILEs in the Groups node and select Copy.

b.

In the Copy group panel, check Group name and enter TILEs.

c.

Check Translate and set the X offset to 2 ft.

d.

Press Apply and Done to copy the row of perforated tiles and close the panel.

e.

Right click TILEs in the Groups node again and select Copy.

f.

In the Copy group panel, check Group name and enter TILEs.

g.


h.

Press Apply and Done to copy both rows of perforated tiles and close the panel.


403


Figure 25.18 Four Rows of Tiles in the Graphics Window

17. Create the ceiling plenum. a.


b.


).

i.

Set the Name to ceilingplenum.

ii.

Change the Plane to xz.

iii.


iv.


18. Create a return grille.

404

a.

Click the Create grille button (

b.

Double click the grille.1 object in the Model manager window to open the Grille panel.

c.

In the Info tab, enter ceiling-return under Name and enter CEILING-RETURN under Groups.

d.

In the Geometry tab, set the Plane to X-Z and enter the following dimensions:

).



e.

In the Properties tab, set the Free area ratio to 0.5.

f.

Press Done to apply the settings and close the panel.

19. Create two rows of return grilles. a.

Right click CEILING-RETURN in the Groups node and select Copy.

b.

Set the Number of copies to 2.

c.

In the Copy group panel, check Group name and enter CEILING-RETURN.

d.


e.

Press Apply and Done to copy the return grille and close the panel.

f.

Right click CEILING-RETURN in the Groups node again and select Copy.

g.


h.

Check Translate and set the X offset to -14 ft.

i.

Press Apply and Done to copy the row of return grilles and close the panel.

Figure 25.19 Two Rows of Return Grilles in the Graphics Window


405

Chapter 25: High Density Datacenter Cooling 20. Create two more return grilles.

406

a.

Click the Create grille button (

b.

Double click the newly created object to open the Grille panel.

c.

In the Info tab, enter ceiling-return-crac1 under Name and select CEILING-RETURN from the Groups drop-down list.

d.

In the Geometry tab, set the Plane to X-Z and enter the following dimensions:

e.

In the Properties tab, set the Free area ratio to 0.5.

f.

Press Done to apply the settings and close the panel.

g.

Right click the vent ceiling-return-crac1 from the Model tree and select Copy.

h.


i.


j.

Press Apply and Done to copy the return grille and close the panel.

k.

Right click ceiling-return-crac1.1 and Rename the object to ceiling-return-crac2.

).



Figure 25.20 Two CRAC Return Grilles in the Graphics Window

21. Set the per-object meshing parameters for the return grilles. a.


b.

In the Local tab, press Edit next to the Object params option.

).

i.

In the Per-object meshing parameters panel, Shift+left click ceiling-return and then ceiling-return.3 to select all the return grilles.

ii.


iii.



407


Figure 25.21 Per-object Meshing Parameters for the Return Grilles

c.


d.


22. Create a PDU.

408

a.

Go to Macros → Datacenter components → PDU to open the PDU panel.

b.

Enter the dimensions as shown below in Figure 25.22 (p. 409).

c.

Set the PDU flow direction to +Y.

d.

Set the Heat output to 3600 W.

e.

Set the Percent open area on top and the Percent open area on bottom to 0.25.



Figure 25.22 The PDU Panel

f.

Press Accept to create the PDU.

23. Set the per-object meshing parameters for the grilles pdu_vent_in and pdu_vent_out. a.


b.

In the Local tab, check Object params and press Edit.

).

i.

In the Per-object meshing parameters panel, Ctrl+left click pdu_vent_in and pdu_vent_out to select both objects.

ii.


iii.


c.


d.


24. Create a new group for the PDU. a.

Select all the PDU objects by Shift+left clicking pdu_unit and then pdu_part4 in the Model manager window.

b.


c.

In the Create group panel, enter PDUs in the Name for new group text field.

d.


25. Create the second PDU. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

409

Chapter 25: High Density Datacenter Cooling a.

Right click PDUs in the Groups node and select Copy.

b.

In the Copy group panel, check Group name and enter PDUs.

c.

Check Translate and set the X offset to 14 ft and the Z offset to 28 ft.

d.

Press Apply and Done to copy the PDU and close the panel.

Figure 25.23 Two PDUs in the Graphics Window

e.

Now may be another good time to Save the project (

).

26. Create blockages.

410

a.


b.


).

i.

Set the Name to piping and the Group to BLOCKAGE.

ii.

Set the Type to Hollow.

iii.


iv.

Press Apply to resize and rename the object. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Step 3: Build the Model c.


d.


).

i.

Set the Name to blockage and the Group to BLOCKAGE.

ii.


iii.


iv.


27. Create columns. a.


b.


).

i.

Set the Name to column1 and the Group to COLUMNS.

ii.


iii.


iv.


c.


d.


).

i.

Set the Name to column2 and the Group to COLUMNS.

ii.


iii.


iv.


28. Create cabletrays. a.


b.


).

i.

Set the Name to cabletray1 and the Group to CABLETRAYS.

ii.

Set the Type to Hollow. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

411


c.

iii.


iv.


Create three more cabletrays. i.

Right click CABLETRAYS in the Groups node and select Copy.

ii.

In the Copy group panel, check Group name and enter CABLETRAYS.

iii.


iv.

Press Apply and Done to copy the cabletray and close the panel.

v.

Right click CABLETRAYS in the Groups node again and select Copy.

vi.

In the Copy group panel, check Group name and enter CABLETRAYS.

vii. Check Translate and set the X offset to 14 ft. viii. Press Apply and Done to copy the cabletrays and close the panel.

Figure 25.24 The Completed Model

412


Step 5: Create Monitor Points


Click the Generate mesh button (

).

2.

In the Mesh control panel, enter 2 ft, 0.5 ft, and 1 ft for the Max element size for x, y, and z, respectively. Change the Minimum gap values to 1 in, 0.36 in, and 1 in for x, y and z, respectively.

Figure 25.25 Mesh Control Panel

Note The units for the Minimum gap values are in inches. 3.

Click Generate.

4.

Use the Display and Quality tabs to view the mesh and check the mesh quality.

5.

Click Close to close the panel once you have finished viewing the mesh.

25.8. Step 5: Create Monitor Points Create two temperature monitor points for the CRAC fans exhaust fans by dragging crac_exhaust and crac_exhaust.1 from the Model node to the Points node. ANSYS Icepak will automatically monitor values at the centers of these objects. The default setting is to monitor Temperature. You can also monitor Pressure and/or Velocity by double clicking the monitor point in the Points folder and choosing which variables to monitor at that location.


413


Figure 25.26 Creating Monitor Points


Go to a.

b.

c.

e. 2.

3.

414

Basic parameters.

In the General setup tab: i.

Turn Off the Radiation.

ii.

Select Turbulent and Zero equation for the Flow regime.

iii.

Enable the Gravity vector.

In the Defaults tab: i.

Select Mica-Typical from the Insulators section of the Default solid drop-down list.

ii.

Select Paint-non-metallic from the Paint section of the Default surface drop-down list.

In the Transient setup tab: i.

d.

Problem setup →

Set the initial Y velocity to be 0.5 ft/s (a non-zero initial velocity is recommended for problems involving natural convection).

In the Advanced tab: i.

Select the Ideal gas law (recommended for problems involving significant temperature differences).

ii.

Check Operating density and keep the default value.

Press Accept to apply the settings and close the panel.

Go to


Basic settings.

a.

Change the Number of iterations to 1000 and the Convergence criteria for Energy to 1e-6.

b.

Click Accept to apply the settings and close the panel.

Go to


Advanced settings.

a.

Set the Discretization scheme for Pressure as Body Force Weighted.

b.

Set the Under-relaxation to 0.2 for Momentum and to 0.1 for Body forces.

c.

Click Accept to apply the settings and close the panel.





Go to Solve → Run solution.

2.

In the Results tab, check Write CFD Post data.

3.

Click Start solution. ANSYS Icepak begins to calculate a solution for the model, and a separate window opens where the solver prints the numerical values of the residuals. ANSYS Icepak also opens the Solution residuals graphics display and control window, where it displays the convergence history for the calculation. Upon completion of the calculation, your residual and monitor plots will look something like Figure 25.27 (p. 416) and Figure 25.28 (p. 417). You can zoom in the residual plot by using the left mouse.

Note The actual values of the residuals may differ slightly on different machines, so your plots may not look exactly the same as Figure 25.27 (p. 416) and Figure 25.28 (p. 417).


415


Figure 25.27 Solution Residuals

416



Figure 25.28 Temperature Point Monitors

4.

Click Done in the Solution residuals and Temperature Point monitors windows to close them.

25.12. Step 9: Examine the Results The objective of this exercise is to consider the airflow patterns and identify problem areas such as hot spots, stagnant zones, and recirculation zones through out the datacenter. You will accomplish this by examining the solution using ANSYS Icepak's graphical postprocessing tools. 1.

Display contours of temperature on the CRACs, Racks, and PDUs. ).

a.


b.

Enter surface-temp-contours in the Name field.

c.

In the Object drop-down list, expand the Groups node and Ctrl+left click CRACs, HDRACKs, PDUs, and RACKs, and click Accept.


417


d.

Check Show contours and click Create.

e.


Figure 25.29 Object Face Temperature Contours

2.

418

Display animated contours of temperature on plane cuts in all 3 coordinate planes. a.

Right click surface-temp-contours under the Post-processing node in the Model manager window, and make the object face inactive by unchecking Active in the context menu.

b.

Click the Plane cut button (

c.

Enter plane-temp-contours in the Name field.

).


Step 9: Examine the Results d.

Check Show contours and click Create to view a plane cut of the temperature contours.

Figure 25.30 Plane Cut Temperature Contours

3.

e.

Check the Loop mode option and click Animate to display a loop of the plane cut traversing from the min z to the max z side of the datacenter.

f.

Click Interrupt on the progress bar to return to the Plane cut panel.

g.

Repeat the above procedure for plane cuts in the Y-Z and X-Z planes by changing the Set position to X plane through center and Y plane through center respectively.

h.


Display animated contours of temperature on an isosurface. a.

Right click plane-temp-contours in the Model manager window and make the plane cut inactive by unchecking Active in the context menu.

b.

Click the Isosurface button (

c.

Enter iso-temp in the Name field.

d.

Enter 90 in the Value field.

e.

Check Show contours and click Create to view the isosurface of 90°F.

).


419


Figure 25.31 Isosurface of 90°F

f.

g. 4.

420

To view an a loop of isosurfaces from 90°F to 80°F: i.

In the Animation group box, enter 90 for Start, 80 for End, and 10 for Steps.

ii.

Check the Loop mode option and click Animate.

iii.

Click Interrupt on the progress bar to return to the Isosurface panel.


Display airflow patterns in the datacenter. a.

Right click iso-temp in the Model manager window and make the isosurface inactive by unchecking Active in the context menu.

b.


c.

Enter airflow in the Name field.

d.

In the Object drop-down list, expand the Groups node and Ctrl+left click CEILING-RETURN, HDRACKs, PDUs, RACKs, and TILEs, and click Accept.

).



e.

Check Show particle traces and click Parameters.

f.

Set the Display options to Mesh points.

g.

Set the End time under Particle options to 5.

h.

Check Loop mode under Animation and set the Steps to 50.

i.

Click Apply to display the airflow patterns.

Note ANSYS Icepak will take a few moments to generate the airflow patterns.


421


Figure 25.32 Particle Traces

j.

Click Animate to visualize the airflow patterns in a transient manner.

k.

View the animated airflow patterns from various angles from the Orient menu.

l.

Press Interrupt to stop the animation.

m. Click Done in the Object face particles and Object face panels to close them. n. 5.

422

Right click airflow in the Model manager window and make the particle traces inactive by unchecking Active in the context menu.

Report the volumetric flow rate distribution at the perforated floor tiles. a.

Go to Report → Summary report to open the Define summary report panel.

b.

Click New to get a new field to define the Summary report.

c.

In the Objects drop-down list, expand the Groups node and select TILEs, and click Accept.

d.

Select Volume flow from the Value drop-down list and deselect Comb.



6.

e.

Click Write to display the summary report.

f.


g.


Save (

) the project and Close ANSYS Icepak.


423


25.13. Step 10: Additional Exercise: Visualize and analyze the results in ANSYS CFD-Post In addition to using the postprocessing tools contained within ANSYS Icepak, you can also postprocess using the advanced tools in ANSYS CFD-Post through ANSYS Workbench. See "Postprocessing Using ANSYS CFD-Post" for details on how to use the features in ANSYS CFD-Post.

25.14. Step 11: Summary In this tutorial, you learned how to model a datacenter using macros, and how to organize a model using groups. You also learned how to use animated postprocessing objects to examine the results.

424


Chapter 26: Design Modeler - Electronics 26.1. Introduction This tutorial demonstrates how to use ANSYS DesignModeler to convert a model for analysis in ANSYS Icepak. In this tutorial, you will learn how to: •

Use the Slice, Opening, Fan, and Simplify options in ANSYS DesignModeler.

•

Organize the model using Parts.

26.2. Prerequisites •

Familiarity with the ANSYS Workbench interface

•

Familiarity with the ANSYS Icepak interface

26.3. Problem Description You will convert an imported STEP file for use in ANSYS Icepak. Figure 26.1 (p. 425) shows the geometry in ANSYS DesignModeler before the conversion and in ANSYS Icepak after conversion.

Figure 26.1 Comparison of the Geometry in ANSYS DesignModeler and ANSYS Icepak


Open ANSYS DesignModeler through ANSYS Workbench. a.

Start a new ANSYS Workbench session. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

425

Chapter 26: Design Modeler - Electronics b.

Drag a Geometry (ANSYS DesignModeler) component module from the Toolbox and drop it on the Project Schematic window as shown in Figure 26.2 (p. 426).

c.

Rename the Geometry component module to STEP Import and DME to Icepak Translation. To rename the title, double click on the title Geometry or click the left mouse button on the down arrow (

) and select the Rename option from the drop down list.

Figure 26.2 Creating a Geometry Component Module

d.

Save the project (name the project as DME).

e.

Double click cell A2 to open ANSYS DesignModeler.


426

Once ANSYS DesignModeler opens, select Millimeter as the desired unit, and press OK.


Step 3: Add Shortcuts to the Toolbar

2.

Go to File → Import External Geometry File and select DME.stp and press Open.

3.

Click

to create the model.

Figure 26.3 Imported Model

26.6. Step 3: Add Shortcuts to the Toolbar 1.

Go to Tools → Options

2.

In the Options panel, go to DesignModeler → Toolbar.

3.

Set Slice, Freeze, and Electronics to Yes.


427

Chapter 26: Design Modeler - Electronics

Figure 26.4 Options Panel

4.

Press OK to add the options to the toolbar.

Note •

The Electronics drop down menu in the toolbar contains several options:

•

You can also access the

•

You can also access the

option from the Create menu. and Electronics options from the Tools menu.

26.7. Step 4: Edit the Model for ANSYS Icepak 1.

Click

2.

Check which bodies are already recognized as ANSYS Icepak objects. a.

428

to make the model transparent and to allow for the Slice operation. Go to Electronics → Show Ice Bodies. Only bodies with simple geometries recognized as ANSYS Icepak objects will be visible.


Step 4: Edit the Model for ANSYS Icepak

Figure 26.5 Bodies Recognized as ANSYS Icepak Objects

Note We will not have to make modifications to export these bodies into ANSYS Icepak. b.

Go to Electronics → Show CAD Bodies. Only bodies with complex geometries not recognized as ANSYS Icepak will be visible.


429


Figure 26.6 Bodies not Recognized as ANSYS Icepak Objects

Note These are the bodies we will have to modify in order to export these bodies into ANSYS Icepak. c. 3.

430

Go to Electronics → Revert View to return to the previous display.

Create a Slice for one set of fins. a.

In the Tree Outline, right click Housing and select Hide All Other Bodies.

b.

Select

c.

In the Details view, set the Slice name to FinsSlice1.

d.

Select Slice by Surface for Slice Type.

e.

Click on the field to the right of Target Face and select the one of faces at the base of the fins, as shown in Figure 26.7 (p. 431) and click Apply.

from the Shortcuts toolbar.



Figure 26.7 FinsSlice1 Face Selection

Note If you cannot select the face, try pressing the Model Faces selection filter ( ).

4.

f.

Make sure Slice Targets is set to Selected Bodies.

g.

Click the field to the right of Bodies and select the Housing body.

h.

Click Apply and then

.

Likewise, create a Slice for the other set of fins. a.

Use the procedure described above on the other set of fins and name the second Slice FinsSlice2.


431


Note Make sure that the Bodies selection is the larger section of the housing containing the fins.

Figure 26.8 FinsSlice2 Bodies Selection

5.

Create Parts for the sliced fins.

Note The Parts will become Assemblies in ANSYS Icepak.

432

a.

Press +Y on the Triad (the axes) to get a clear view of the fins.

b.

Select Box Select from the Shortcuts toolbar.

c.

Select the Bodies selection filter ( ).

d.

Drag the bounding box around one set of fins, and rotate the model to make sure that all the fins are selected as shown in Figure 26.9 (p. 433) (you should have 13 bodies selected).



Figure 26.9 Selecting a Row of Fins

6.

e.

Right click anywhere in the Model View and select Form New Part.

f.

In the Details view, set the Part name to Fins1 and press enter on the keyboard.

g.

Repeat steps a to f for the other set of fins, except name the part Fins2.

Create a Housing slice. from the Shortcuts toolbar.

a.

Select

b.

In the Details view, set the Slice name to HousingSlice1.

c.

Select Single Select from the Shortcuts toolbar.


433

Chapter 26: Design Modeler - Electronics d.

Click the field to the right of Target Face and select the inner face of bottom of the Housing as shown in Figure 26.10 (p. 434) and press Apply.

Figure 26.10 HousingSlice1 Selection

434

e.

Make sure Slice Targets is set to Selected Bodies.

f.

Click the field to the right of Bodies and select the Housing object in between the fins.



Figure 26.11 HousingSlice1 Bodies Selection

g. 7.


.

Create another Housing slice. a.

Select

b.

In the Details view, set the Slice name to HousingSlice2.

c.

Select the inner face of the top of the Housing as shown in Figure 26.12 (p. 436) and press Apply.

from the Shortcuts toolbar.


435


Figure 26.12 HousingSlice2 Face Selection

8.

436

d.

Click the field to the right of Bodies and select the top part of the Housing object in between the fins.

e.


f.

You should have ten Housing objects outside of the Fins parts in the Tree Outline.

.

Create Openings for the fan. a.

Show all bodies again by right clicking one of the objects in the Tree Outline and clicking Show All Bodies

b.

Go to the +Y view.

c.

Go to Electronics → Opening.

d.

In the Details view, set the Opening name to FanOpenings.

e.

Click the field to the right of Faces and select the face as shown in Figure 26.13 (p. 437) and press Apply and .



Figure 26.13 FanOpenings Face Selection

9.

Create Openings for the back panel. a.

Go to the -Y view.

b.

Go to Electronics → Opening.

c.

In the Details view, set the Opening name to BackOpenings.

d.

Click the field to the right of Faces and select the face as shown in Figure 26.14 (p. 437) and press Apply and .

Figure 26.14 BackOpenings Face Selection

10. Create a Fan. a.

Right click the Fan body in the Tree Outline and select Hide All Other Bodies.


437


Note If you cannot view the object correctly, press Zoom to Fit ( ). b.

Go to Electronics → Fan.

c.

In the Details view, set the Fan name to FanGeom.

d.

Click the field to the right of Body To Extract Fan Data, select the entire fan body and press Apply.

e.

Click the field to the right of Hub/Casing Faces and select the faces as shown in Figure 26.15 (p. 438).

Figure 26.15 Hub/Casing Faces Selection

Note You can select multiple faces by holding down Ctrl and left clicking the objects. f.

Click Apply and

.

Note Although it may seem like there was no change, this step creates a fan object in ANSYS Icepak. To confirm this, you can go to Electronics → Show Ice Bodies and check if the fan is present.

438


Step 4: Edit the Model for ANSYS Icepak g.

Add the fan to the Front-Panel part. i.

In the Tree Outline, select the Front-Panel part and then Ctrl and left click the Fan object.

ii.

Right click the Fan object and select Form New Part.

iii.

In the Details view, rename the Front-Panel Part to Front-Panel-Fan.

11. Perform a Simplify operation on the Housing. a.

Show all bodies again by right clicking one of the objects in the Tree Outline and clicking Show All Bodies

b.

Go to Electronics → Simplify.

c.

In the Details view, set the Simplify name to HousingFrontBack.

d.

In the field to the right of Simplification Type, select Level 1.

e.

Click the field to the right of Select Bodies and select the front and the rear panels of the Housing as shown in Figure 26.16 (p. 439).

Figure 26.16 HousingFrontBack Bodies Selection

f.

Click Apply and

.

12. Perform a Simplify operation on the PWB and the T0220 objects. a.

Select all the Housing, Fin, Panel, Opening, and Fan objects from the bottom of the Tree Outline by holding down Shift and using the left mouse button.

b.

Right click one of the selected objects and select Hide Body to view just the internal components.

c.


d.

In the Details view, set the Simplify name to PWB_T0220.

e.



439

Chapter 26: Design Modeler - Electronics f.

Click the field to the right of Select Bodies and select the PWB and all the HS_AF0 and T0220_Case objects.

Note Because they are simple bodies that are already recognized as ANSYS Icepak objects, do not select the LEAD_1_AF0 or the HS_AF0 objects. i.

Go to the +Z view.

ii.

Make sure the Select Mode is Single Select.

iii.

Hold down Ctrl and select the objects as shown in Figure 26.17 (p. 440).

Figure 26.17 PWB_T0220 Bodies Selection

iv. g.

Using this method, only the 13 correct bodies will be selected.

Click Apply and

.

13. Add all the package objects to the Parts. a.

440

Change the Selection Mode to Box Select and make sure the selection filter is set to Bodies.


Step 4: Edit the Model for ANSYS Icepak b.

Select a package object as shown in Figure 26.18 (p. 441). There should be 6 bodies selected.

Figure 26.18 Package Object Selection

c.

Right click the model and select Form New Part. All the bodies will be added to the part.

d.

Name the part T0220_Case1.

e.

Repeat steps a to e for the rest of the packages, except naming the parts T0220_Case2, T0220_Case3, etc.

14. Perform a Simplify on the Coil. a.


b.

In the Details view, set the Simplify name to CoilAssembly.

c.


d.

Click the field to the right of Select Bodies and select the bodies as shown in Figure 26.19 (p. 442). There should be 4 bodies selected.


441


Figure 26.19 Coil Bodies Selection

e.

Click Apply and

.

15. Add the rest of the Coil bodies to the part. a.

Make sure the selection filter is set to Bodies.

b.

Make the same selection as in the simplify operation. Notice that there are now 8 bodies instead of 4.

c.

Right click the model and select Form New Part.

d.

In the Details view, set the Part name to CoilAssembly2.

16. Perform a Simplify on the Capacitors.

442

a.


b.

In the Details view, set the Simplify name to Capacitors.

c.


d.

Click the field to the right of Select Bodies and select the bodies as shown in Figure 26.20 (p. 443). There should be 3 bodies. Release 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.


Figure 26.20 Capacitors Bodies Selection

e.

Click Apply.

f.

Set the Face Quality to Medium

g.

Click

.

17. Form a part for the Capacitors. a.


b.

Make the same selection as the simplify operation. There should still be 3 selected bodies.

c.

Right click the model and select Form New Part.

d.

In the Details view, set the Part name to Capacitors.

18. Form parts for the Heat Sink and Components. a.


b.

Follow the same steps as before to create a part called BGAHS for the Heat Sink and Components for the Components:


443


Figure 26.21 BGAHS and Components Parts Selections

19. Right click a body in the Tree Outline and select Show All Bodies. Your model should look like Figure 26.22 (p. 444) and your Tree Outline should look like Figure 26.23 (p. 445).

Figure 26.22 Final Model in ANSYS DesignModeler

444


Step 5: Opening the Model in ANSYS Icepak

Figure 26.23 Final Tree Outline

Note Some of your parts and bodies may be in a different order than what is shown in Figure 26.23 (p. 445). 20. Check if all the bodies have been converted to ANSYS Icepak objects. a.

Go to Electronics → Show CAD Bodies.

b.

Confirm that the view contains no bodies. This means all the bodies have been recognized by ANSYS Icepak.

21. The model is now ready to use in ANSYS Icepak.

26.8. Step 5: Opening the Model in ANSYS Icepak 1.

Go to File → Save Project and then File → Close DesignModeler.

2.

In ANSYS Workbench, drag an ANSYS Icepak component to cell A2 to create an ANSYS Icepak component module.


445


Figure 26.24 Creating an ANSYS Icepak Component Module

3.

Double click the Setup cell (B2) to open the model in ANSYS Icepak.

4.

In the model manager window, right click the Model node and select Expand all to view the geometry inside the assemblies.

5.

Notice that the bodies have been successfully transferred into ANSYS Icepak.

446


Step 6: Summary

Figure 26.25 Final Model

26.9. Step 6: Summary In this tutorial, you learned how to get a CAD model ready for ANSYS Icepak using ANSYS DesignModeler. You used the slice, simplify, openings, and fan operations to convert the model.


447

448


individual side specification, 79

Index

J B

joule heating, 283

BGA-package, 157, 321

L

C CAD geometry, 245 import, 247 CFD Post, 351 CFD Post in Workbench, 351 cold-plate, 97, 101

D Datacenter cooling high density, 385 Design Modeler electronics, 425 Dimensions tab, 322

loss coefficient, 143 loss coefficient vs Re, 155

M mesh exercise, 133 microelectronics, 295 modeling model layers separately, 281 radiation, 196 monitor point, 308 mouse conventions, 2 multi-level meshing, 311, 314

N

E Edit object panel, 7 Electronics Design Modeler, 425

F

non-conformal assembly, 101 mesh, 121, 127, 129 nested, 113

O object parameters, 221 obtaining support, 2 optimization run, 181 orthotropic material properties, 110

finned heat sink, 3, 17 Functions compound, 178 objective, 178 primary, 178

P

H heat pipe, 107, 113 heat sink, 49 finned, 3, 17 inline or staggered, 157 heat transfer coefficient, 325 help obtaining support, 2 hex-dominant, 257

param value, 175 parameterization, 71 parametric runs, 162 parametric trials, 147 multiple trials, 84

R radiation model discrete ordinates, 185, 197 ray tracing, 197 rf amplifier, 37, 53

I Icepak in Workbench, 339 import CAD file, 247 IDF, 235, 268 tcb file, 322 trace layer, 271, 333

S search fan library, 50 summary report, 126 support obtaining help, 2


449

Index

T Thermal Resistance, 173 trace heating, 283 trace layer, 267 import, 271, 333 transient simulation, 201 typographical conventions, 1

W Workbench Icepak, 339

Z zero slack, 136, 331, 336 zoom-in modeling, 217, 224

450


Ansys Icepak Tutorials

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