Chapter-1
Introduction o Introduction o Need
1
1.1 INTRODUCTION
Fig 1.1: Automobile Air-Conditioning System
The vapour absorption refrigeration system is one of the oldest methods of producing refrigerating effect. The principle of vapour absorption was first discovered by Michael Faraday in 1824 while performing a set of experiments to liquefy certain gases. The first machine was based on Vapour Absorption Refrigeration machine was developed by a French scientist, Ferdinand Carry, in 1860. This system may be used in both the domestic and large industrial refrigerating plants. The refrigerant commonly used in vapour absorption system is Ammonia. This system uses Heat energy instead of mechanical energy as in vapour compression system, in order to change the condition of refrigerant required for the operation of the refrigeration cycle.
2
This idea of refrigeration system is being utilized in our project for the purpose of air conditioning. Like other air conditioner systems, the automobile air conditioner must provide adequate comfort cooling to the passenger in the conditioned space under a wide variety of ambient conditions. In automobile air conditioning load factors are constantly and rapidly changing as the automobile moves over highways at different speeds and through different kind of surroundings. As the car moves faster there is greater amount of infiltration into the car and the heat transfer between the outdoor air and the car surface is increased. The sun baking down on a black top road will raise its temperature to 350C – 450C approximately and thus increases the amount of heat transmitted into car. When driving through a grassy terrain, much less radiant heat is experienced than when passing through sandy flats or rocky hills. Therefore, the car is subjected to varying amounts of heat load when its orientation changes during the journey. An automobile engine utilizes only about 35% of available energy and rests are lost in the form of heat and mechanical losses to cooling and exhaust system. If one is adding conventional air conditioning system to automobile, it further utilizes about 4-5% of the total energy. Therefore automobile becomes costlier, uneconomical and less efficient. The conventional air conditioning system in car decreases the life of engine and increases the fuel consumption, further for small cars compressor needs 3 to 4 bhp i.e. a significant ratio of the power output. Keeping these problems in mind, a car air conditioning system is proposed which is using exhaust heat. The advantages of this system over conventional air-conditioning system are that it does not affect designed efficiency life and fuel consumption of engine.
3
1.2 NEED An automobile engine utilizes only about 35% of available energy and rests are lost to cooling and exhaust system. If one is adding conventional air conditioning system to automobile, it further utilizes about 5% of the total energy. Therefore automobile becomes costlier, uneconomical and less efficient. Additional of conventional air conditioner in car also decreases the life of engine and increases the fuel consumption. For very small cars compressor needs 3 to 4 bhp, a significant ratio of the power output. Keeping these problems in mind, a car air conditioning system is proposed using exhaust gases. The advantages of this system over conventional air-conditioning system are that it does not affect designed efficiency life and fuel consumption of engine. And hence makes the running of the engine efficient and economical. Thus to have the more economical air conditioning and more efficient engine in the automobile the need of this system arises.
4
Chapter-2
Mechanism Details o Working Principle o Operational Stages
5
2.1 WORKING PRINCIPLE
Fig 2.1: Vapour Absorption Cycle
The underlying principle is the “Practical Vapour Absorption System” that uses a Generator, instead of compressor (i.e. used in vapour compression system). This Generator requires a Heat Source to generate Ammonia vapours from Aqueous Ammonia Solution received from Absorber. The above heat requirement is served by the exhaust heat of the engine.
Some power is also required to run the Pump, which is used to raise the pressure of Aqueous Ammonia Solution as well as to transmit it from Absorber to Generator. As the pump consumes very less amount of power in comparison to Compressor, it is quite comfortable to drive it from battery power or directly from crank-shaft.
Using the above setup, we can relieve the crank-shaft from excess load of compressor; this will help in decreasing the fuel requirement of engine. Thus, increases the fuel efficiency. 6
So, without using any other equipment or source of energy besides the vehicle itself, it is possible to introduce this air-conditioning system in existing automobiles/vehicles. Also it uses Ammonia as refrigerant, which do not affect the ozone layer as well as it does not contribute to the greenhouse effect, and it’s LCCP (Life-Cycle Climate Performance) is also highly favorable.
7
2.2 OPERATIONAL STAGES
Fig 2.2: Vapour Absorption Cycle
Stage 1-2: -The low pressure ammonia vapour leaving the evaporator enters the absorber where it is absorbed
by the cold water in the absorber.
-The water has the ability to absorb very large quantity of ammonia vapour and the solution thus formed, is known as aqua-ammonia.
Stage 2-3: -The strong solution thus formed in the absorber is pumped to the generator by the liquid pump to increase the pressure of the solution up to 10 bar.
8
Stage 3-4: -The strong solution of ammonia is heated by some external source, in our system by the exhaust heat of automobile.
-During the heating process the ammonia vapour is driven off the solution at high pressure leaving behind the hot weak ammonia solution in the generator.
Stage 4-5: -The weak ammonia solution flows back to the absorber at low pressure after passing through the pressure reducing valve.
Stage 6-7: -The high pressure vapour from the generator is condensed in the condenser to high pressure liquid ammonia.
Stage 7-8: -The condensed liquid ammonia from the condenser is stored in a vessel known as receiver valve, from where it is supplied to the evaporator through the expansion valve. Stage 8-9: -The liquid ammonia is passed to the expansion valve in which its high pressure and temperature is reduced at a controlled rate after passing through it.
Stage 9-1: -The liquid vapour ammonia at low pressure and temperature is evaporated and changed into vapour refrigerant. In evaporator, the liquid vapour ammonia absorbs its latent heat of vaporization from the medium to be cooled.
9
Chapter-3
Pros & Cons o Advantages o Disadvantages o Comparison
10
3.1 Advantages
Uses Engine heat as source of energy hence enhances the efficiency of engine.
Moving parts are only in the pump, which is a small element in the system hence operation becomes smooth and also wearing and tearing is reduced.
The system works at low evaporator pressures without affecting the COP of the system.
Environmental friendly, no release of CFC derivatives.
Helps in protecting OZONE layer from depletion.
Helps engine to cool, as it extracts heat from engine.
Low running cost.
Higher engine power efficiency.
11
3.2 Disadvantages 1) Initial capital cost Though the running cost of the absorption refrigeration system is much lesser than the vapor compression system, its initial capital cost is much higher. 2) Corrosive nature In case of the ammonia system, ammonia is corrosive to copper. In the vapor compression system copper is used with the halocarbon refrigerants and they are quite safe thus ensuring long life of the refrigeration system. As such the vapor compression system with reciprocating or centrifugal compressor has longer life than the absorption refrigeration system. 3) Low working pressures The working pressures of the absorption refrigeration cycle are very low. Due to this the refrigeration system should be sealed thoroughly so that no atmospheric gases would enter the refrigeration system. As such the system of the compression refrigeration should also be packed tightly, but this is to prevent the leakage of the refrigerant to the atmosphere. 4) Coefficient of Performance (COP) The coefficient of performance of the absorption refrigeration systems is very low compared to the vapor compression systems. Thus the absorption refrigeration system becomes competitive only if the ratio of the electricity to fuel (oil, gas or coal used to generate the steam in the boiler) becomes more than four. If this ratio is lesser there are chances that excess fuel would be required to generate the steam. However, if there is excess steam in the industry, this ratio may not be given importance.
12
3.3 Comparison of Vapor Absorption Air Conditioning over Vapor Compression Air Conditioning 1) Method of compression of the refrigerant: One of the most important parts of any air conditioning cycle is the compression of the refrigerant since all the further operations depend on it. In the vapor compression air conditioning system the compression of the refrigerant is done by compressor which can be of reciprocating, rotating or centrifugal type. In the vapor absorption air conditioning system, the compression of the refrigerant is done by absorption of the refrigerant by the absorbent. As the refrigerant is absorbed, it gets converted from the vapor state to liquid state so its volume reduces. 2) Power consumption devices: In the vapor compression cycle the compressor is the major power consuming device while in the vapor absorption cycle the pump used for pumping refrigerant-absorbent solution is the major power consuming device. 3) The amount of power required: The compressor of the vapor compression cycle requires large quantities of power for its operation and it increases as the size of the system increases. In case of the vapor absorption system, the pump requires very small amount of power and it remains almost the same (or may increase slightly) even for higher capacities of air conditioning. Thus the power consumed by the vapor absorption system is less than that required by the vapor compression system. 4) Type of energy required: The vapor absorption system runs mainly on the waste or the extra heat in the plant. Thus one can utilize the extra steam from the boiler, or generate extra steam for the purpose and also use the hot available water. Similarly the waste heat from the diesel engine, hot water from the solar water heater, etc. can also be utilized. In case of the vapor compression system, the compressor can be run by electric power supply only; no other types of energy can be utilized in these systems. 5) Running cost: The vapor compression air conditioning system can run only on electric power, and they require large amount of power. These days the electric power has become very expensive, hence the running cost of the vapor compression air conditioning 13
system is very high. In case of the absorption air conditioning system only small pump requires electric power and it is quite low. In most of the process industries, where the absorption refrigeration is used, there is some extra steam available from the boiler, which can be used for running the system. Thus in absorption air conditioning system no extra power in the pure electric form is required and the energy that would have otherwise gone wasted is utilized in the plant. Thus the running cost of the absorption air conditioning system is much lesser than the vapor compression system.
14
Chapter-4
Construction Details o List of Components o Component Details
15
4.1 LIST OF COMPONENTS
Evaporator
Condenser
Absorber
Receiver-Drier
Pump
Glass Cloth Tape
Insulation Foam Tube
Globe Valves
Heating Coil
Drier
Generator
Connection Tubes
16
4.2 COMPONENT DETAILS 4.2.1 EVAPORATOR
Fig 4.1: Evaporator
EVAPORATOR is a device used to turn (or allow to turn) the liquid form of a refrigerant into its gaseous form. An evaporator is used in an air conditioning system to allow the compressed cooling refrigerant (ammonia) to evaporate from liquid to gas while absorbing heat in the process. It is installed in the low pressure side of the cycle. How it works? Air conditioning evaporator works by absorb heat from the area (medium) that need to be cooled. It does that by maintaining the evaporator coil at low temperature and pressure than the surrounding air.
17
As the liquid refrigerant enters the evaporator at low pressure and flows through it continually and absorbs heat through the coil walls, from the medium being cooled during this the refrigerant continues to boil and evaporate. Why evaporators remain cold? The evaporator remains cold because of the following two major reasons:
The temperature of the evaporator coil is low due to the low temperature of the refrigerant inside the coil.
The low temperature of the refrigerant remains unchanged because any heat it absorbs is converted to latent heat as boiling proceeds.
18
4.2.2 CONDENSER
Fig 4.2: Condenser
The condenser is a device used to change the high-pressure refrigerant vapour to a liquid. It is mounted in front of the engine's radiator, and it looks very similar to a radiator. The vapour is condensed to a liquid because of the high pressure that is driving in it, and this generates a great deal of heat. The heat is then in turn removed from the condenser by air flowing through the condenser on the outside.
It is installed in the high pressure side of the cycle whose function is to remove the heat of the hot vapour refrigerant discharged, which consists of heat absorbed by the evaporator .The heat from the hot vapour refrigerant in a condenser is removed first by transferring it to the wall of condenser tubes and then from the tubes to the condensing or cooling medium which may water, air or combination of both. 19
4.2.3 ABSORBER
Fig 4.3: Absorber
Absorber is the part of the system where vapour ammonia at low pressure and weak solution from the generator comes through pressure reducing valve and get accumulated. 20
Here the vapour ammonia gets dissolved into the water as per the solubility ratio of water and ammonia. This water and ammonia vapour solution is known as aqua ammonia solution or strong solution which is pumped to the generator at high pressure where it is heated from some external source of heat. Thus, Ammonia vapour gets evaporated and the cycle continues.
21
4.2.4 RECEIVER-DRIER
Fig 4.4: Receiver-Drier
-
The receiver-drier is used on the high side of systems that use a thermal expansion valve.
-
This type of metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used.
-
The primary function of the receiver-drier is to separate gas and liquid.
-
The secondary purpose is to remove moisture and filter out dirt.
22
Fig 4.5: Schematic Diagram of Receiver-Drier
-
The receiver-drier usually has a sight glass in the top. This sight glass is often used to charge the system. Under normal operating conditions, vapor bubbles should not be visible in the sight glass.
-
This is a small reservoir vessel for the liquid refrigerant, and removes any moisture that may have leaked into the refrigerant.
-
Moisture in the system causes havoc, with ice crystals causing blockages and mechanical damage.
23
4.2.5 PUMP
Fig 4.6: Pump
-
A pump is a device used to move fluids, such as liquids, gases or slurries.
-
A pump displaces a volume by physical or mechanical action.
-
Pumps fall into three major groups: direct lift, displacement, and gravity pumps. Their names describe the method for moving a fluid.
Pump converts the mechanical energy from a motor to energy of a moving fluid; some of the energy goes into kinetic energy of fluid motion, and some into potential energy, represented by a fluid pressure or by lifting the fluid against gravity to a higher level
24
Fig 4.7: Schematic Diagram of Pump
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser or volute chamber, from where it exits into the downstream piping system. Centrifugal pumps are typically used for large discharge through smaller heads.
25
4.2.6 GLASS CLOTH TAPE Glass cloth tube is an electrical insulator and the heat conductor i.e. it enables the heat to be transmitted but insulate the system electrically. It is made from high grade heat resistant
glass
cloth
coated
with
special
silicone
backing.
Characteristics:
Highly conformable and easy to install
Very flexible accommodating angles and turns
Aggressive adhesive system
Removes easily without leaving residue
High tensile strength and abrasion resistant
Repositionable
Excellent performance in temperatures up to 500°F (260°C)
Can be single-sided or double-sided
Fig 4.8: Glass Cloth Tape
26
4.2.7 INSULATION FOAM TUBE Insulation is a product that blocks transfer of heat, thus helps in maintaining the desired temperature by obstructing the flow of heat. Characteristics:
Low thermal conductivity (K value) makes it highly efficient and effective in the insulation of cooling or heating systems.
The thermal blister close cell structure forms as impermeable layer which is in itself a good vapour barrier.
It is suitable for application within the temperature range of -40°C to 125°C.
The material has been specially compounded to self-extinguishing in nature.
It is CFC, asbestos, chlorine and fiber free and does not cause skin allergy.
It is inert to most chemical agent and neutral to pipe metals.
The extreme flexibility of the materials makes installation fast, easy and economical.
Fig 4.9: Insulation Foam Tube
27
4.2.8 GLOBE VALVE
Fig 4.10: Globe Valve
A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body. 28
Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat onto which a movable plug can be screwed in to close (or shut) the valve. The plug is also called a disc or disk. In globe valves, the plug is connected to a stem which is operated by screw action using a hand wheel in manual valves. Typically, automated globe valves use smooth stems rather than threaded and are opened and closed by an actuator assembly. Although globe valves in the past had the spherical bodies which gave them their name, many modern globe valves do not have much of a spherical shape. However, the term globe valve is still often used for valves that have such an internal mechanism. In plumbing, valves with such a mechanism are also often called stop valves since they don't have the global appearance, but the term stop valve may refer to valves which are used to stop flow even when they have other mechanisms or designs.
29
4.2.9 HEATING COIL (NICHROME) Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosionresistant, and has a high melting point of about 1400 °C. Due to its relatively high electrical resistivity and resistance to oxidation at high temperatures, it is widely used in electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters, and even electronic cigarettes. Typically, Nichrome is wound in coils to a certain electrical resistance, and current is passed through to produce heat.
Fig 4.11: Heating Coil (NICHROME)
30
The properties of Nichrome vary depending on its alloy. Figures given are representative of typical material and are accurate to expressed significant figures. Any variations are due to different percentages of nickel or chromium. Material property
Value
Units
Modulus of elasticity
2.2 × 1011
Pa
Specific gravity
8.4
Dimensionless
Density
8400
kg/m3
Melting point
1400
°C
Electrical resistivity at room temperature 1.0 × 10−6 to 1.5 × 10−6 Ωm Specific heat
450
Jkg−1°C−1
Thermal conductivity
11.3
Wm−1°C−1
Thermal expansion
14 × 10−6
°C−1
Table No 4.1: Properties of NICHROME
31
4.2.10 DRIER
Fig 4.12: Drier
Filter-driers play a pivotal role in the operation of air conditioning and refrigeration systems. At the heart of the unit is the desiccant held in its cylindrical metal container. As important as the filter-drier is, many actually do not understand how it works. Here are some details.
The word desiccate means to dry out completely and a desiccant is a material or substance that accomplishes the moisture removal. Moisture in the mechanical refrigeration cycle is detrimental to the operation and life of the system. The filter-drier is an accessory that performs the functions of filtering out particles and removing and holding moisture to prevent it from circulating through the system.
32
Moisture in a System Consider a chemist working with chemical elements to create new substances. The chemist combines atoms of selected elements to cause them to bond or link together to form new combinations of molecular structures. These new molecular structures are called compounds. Chemists perform such creations in the process of developing new synthetic oils, refrigerants, glues, rubbers, metal alloys, and a host of other products that are useful in many ways. Some combinations of atomic elements create molecular structures that can be either useful or harmful. Acids are formed when the right combination of elements are linked together chemically. If we have a use for the acid and use it for its intended purpose, all is well. However, in some cases unwanted chemical combinations occur where we least want them and where they cause serious harm. Under certain circumstances, hydrochloric and hydrofluoric acids chemically form in the mechanical refrigerant system. This, of course, is what we want to prevent. Again, let us consider how the chemist facilitates the chemical bonding process. The chemist wants certain chemical reactions to take place in an effort to create new substances that hopefully have special properties that are useful. Perhaps the chemist is attempting to create a new refrigerant to replace another that is being phased out. The chemist combines particular elements to form bonds or links that when complete meet all the qualities of a suitable refrigerant. A catalyst is anything that hastens, encourages, or helps bring about a result. Heat is one of chemistry’s most active catalysts. A chemist may purposely add heat to a beaker of chemicals to cause them to combine to form a new substance. Keep It Clean The case has been made as to how important it is to prevent chemical reactions from taking place in a system. It almost seems from what we have described up to this point that it could be difficult to prevent chemical breakdown from occurring. Fortunately, the installation crew and service technician can prevent system failure due to a chemical reaction. 33
It is imperative that installation and service technicians prevent foreign materials, air, moisture, brazing flux, carbon created during brazing, and insulation powder from entering or remaining in a system. Good piping practice includes bleeding a small amount of dry nitrogen through the system while brazing. Pipe ends need to be sealed prior to sliding pipe insulation over the piping. A good 500-micron evacuation should be reached to remove air and moisture before charging with refrigerant. And, the addition of a properly sized filter-drier is important on both new systems as well as anytime a system is opened for service. The filter-drier is designed to both remove any particulates that may circulate as well as collect and hold any moisture that may be present in the system. The use of a filter-drier containing a good desiccant has become even more important with the advent of R-410A systems, which utilize the highly hygroscopic synthetic polyolester oils. Capacity Capacity refers to the amount of moisture the desiccant in the filter-drier can hold. Capacity is measured in parts per million (ppm). One ppm is one part of water per million parts of refrigerant. In practical terms, this would be approximately equal to one drop of water in a 125-pound drum of refrigerant. Desiccant capacities are rated at 75 and 125 degrees F. The older desiccant, activated alumina, had a moisture holding capacity of 4 grams of moisture per 100 grams of desiccant. Silica gel had a moisture holding capacity of 3 grams of moisture per 100 grams of desiccant. Modern zeolite molecular sieve desiccants have a capacity of approximately 16 grams of moisture per 100 grams of desiccant. The capacity of a desiccant is temperature dependent. The colder the desiccant, the more moisture it can hold. Therefore, locating a filter-drier in a cooler location is an advantage. Removing a brazed filter-drier with a torch flame causes moisture to be driven out of the desiccant and into the system. Generally, it is better to cut the filter-drier out with a tubing cutter.
34
Location The desiccant works better at removing and holding moisture when it is placed in a refrigerant line where the refrigerant is in the liquid state. The filter-drier is often called a “liquid line filter-drier” for this reason. Suction Line Filter-Driers The desiccant is still able to absorb moisture when applied to the suction line but not quite as effectively. Special suction line filter-driers are made for cleaning up a system after a compressor burnout. A larger shell is used to minimize pressure drop on suction line driers. Suction line filter-driers marked as “HH” driers contain carbon filter material in addition to the zeolite desiccant. The carbon and zeolite are capable of capturing and holding acids as well as moisture. Suction line filter-driers used to clean up a system after a burnout should be replaced until the system is known to be clean and no longer tests positive for acids in the system. A suction line filter-drier with an excessive pressure drop across it should not be left in a system. An excessive pressure drop in the suction line reduces the volumetric efficiency of the compressor, thus reducing system operating capacity. Many suction line filterdriers have a pressure tap on the inlet end so the pressure on the inlet of the drier can be compared to the pressure at the suction service valve at the compressor. Still other suction line filter-driers have pressure taps on both the inlet and outlet.
35
4.2.11 GENERATOR
Fig 4.13: Generator
o It is a kind of heat exchanger. o Collects Heat from Exhaust and Coolant to vaporize Ammonia from strong solution of Aq. Ammonia. o Supplies Vaporized Ammonia to Condenser.
36
Chapter-5
Calculations o Engine Heat Data o Phase Diagrams Used o Calculations o Bill of Materials
37
5.0 ENGINE HEAT DATA 5.0.1 EXPERIMENTAL DATA OF FOUR CYLINDER FOUR STROKE PETROL ENGINE
S. No.
Voltage Current
Speed
Fuel to 10
Manometer
T1
T2
T3
T4
T5
T6
Rotameter Reading Engine
(V)
(A)
(RPM)
cc Time
Reading
(oC)
(oC)
(oC)
(oC)
(oC)
(oC)
1
230
7/7.3
1595
11.16
17-9
23
52
38
603
164
40
92
57
2
230
14
1550
10.13
17.6-8.4
21
52
38
607
168
40
92
57
3
208
21.2/21
1548
9.31
18.8-7.2
20
53
38
622
180
40
92
57
4
198
28
1523
8.31
18.8-6.2
19
52
39
630
189
40
92
57
5
195
31
1524
8.21
19.7-6.4
18
51
37
614
189
41
92
57
Jacket
Calorimeter
Table 5.1: Engine Heat Data Sheet
T1=
Temp of water inlet to engine & calorimeter
T2=
Temp of water outlet of engine jacket
T3=
Temp of water outlet of calorimeter
T4=
Temp of Exhaust Gas inlet to calorimeter
T5=
Temp of Exhaust gas outlet of calorimeter
T6=
Ambient Temp 38
Fig 5.1: Four Stroke Four Cylinder Engine Test Rig
39
5.0.2 Phase Diagram of Water
Fig 5.2: Phase Diagram of Water
40
5.0.3 p-h Chart of Ammonia (R-717)
Fig 5.3: p-h Chart of Ammonia (R-717)
41
5.1 CALCULATIONS For design considerations we have to take assumptions which are based on the basis of normal summer ambient weather/temperature conditions as well as the temperature to be maintained at Evaporator Coil is also assumed to be maintained for human comfort. Design Consideration of Automobile Air Conditioning Unit based on Vapour Absorption Refrigeration System (CAPACITY=1TR) Specific Enthalpy Temperature Temperature (oC)
(K)
(kJ/kg)
Pressure (bar)
Liquid (hf)
Specific Entropy (kJ/kg K)
Enthalpy (kJ/kg)
Latent (hfg)
Liquid (sf)
Vapour (sg)
(hg)
Absorber (T_A)
0
273
4.29586
181.20
1263.25
0.7151
5.3405
1444.45
Generator (T_G)#
100
373
11.66896
323.08
1145.79
1.2037
4.9842
1468.87
Condenser (T_C)
30
303
11.66896
323.08
1145.79
1.2037
4.9842
1468.87
Evaporator (T_E)
0
273
4.29586
181.20
1263.25
0.7151
5.3405
1444.45
Table 5.2: Data Table for Calculation
(For ease of calculation and compactness of the model we have made all of our calculations, taking Capacity = 1TR) (
)
[
]
[
]
42
(
(
)
(
)
)
43
( (
)
)
( (
)
)
44
Volume & Mass Database for Refrigerant (Excluding Water in Absorber & Generator) Pressure
Temperature
Temperature
Mass Flow Rate
Mass Flow Rate
Mass Flow Rate
(bar)
(oC)
(K)
(kg/min)
(kg/sec)
(gm/sec)
Absorber
4.29586
0
273
5.4561
0.0909
90.9357
Generator
11.66896
100
373
5.4561
0.0909
90.9357
Condenser
11.66896
30
303
5.4561
0.0909
90.9357
Evaporator
4.29586
0
273
5.4561
0.0909
90.9357
Temperature
Density
Density
Volume (m3/min)
Volume (m3/sec)
Volume (cm3/sec)
o
3
3
( C)
(kg/m )
(gm/cm )
Absorber
0
640.1000
0.6401
0.0085
0.1421
142.0649
Generator
100
594.5303
0.5945
0.0092
0.1530
152.9539
Condenser
30
594.5303
0.5945
0.0092
0.1530
152.9539
Evaporator
0
640.1000
0.6401
0.0085
0.1421
142.0649
Table 5.3: Volume & Mass Data Sheet
45
Solubility Matrix of Ammonia & Water Temperature
Mass (gm)
Solubility Factor (SF)
(oC)
(K)
Gas
Water
Gas/Water (SFgw)
Water/Gas (SFwg)
0
273
900
1000
0.9000
1.1111
10
283
700
1000
0.7000
1.4286
20
293
525
1000
0.5250
1.9048
30
303
410
1000
0.4100
2.4390
40
313
315
1000
0.3150
3.1746
50
323
215
1000
0.2150
4.6512
60
333
175
1000
0.1750
5.7143
Mass of Water Required in Absorber as a Solvent=
101.0397 gm/sec Water
Gross Mass of Refrigerant Flowing Between Absorber & Generator=
191.9754 gm/sec
Gross Mass of Refrigerant Flowing Between Absorber & Generator=
11.5185 kg/min
Gross Mass of Refrigerant Flowing Between Absorber & Generator=
0.1920 kg/sec
Table 5.4: Solubility Matrix of Ammonia & Water
46
Volume & Mass Database for Refrigerant (Including Water in Absorber & Generator) Pressure
Temperature
Temperature
Mass Flow Rate
Mass Flow Rate
Mass Flow Rate
(bar)
(oC)
(K)
(kg/min)
(kg/sec)
(gm/sec)
Absorber
4.29586
0
273
11.5185
0.1920
191.9754
Generator
11.66896
0
273
11.5185
0.1920
191.9754
Temperature
Density
Density
Volume
Volume (m3/sec)
Volume (cm3/sec)
o
3
3
3
( C)
(kg/m )
(gm/cm )
(m /min)
Absorber
0
640.1000
0.6401
0.0180
0.0003
299.9147
Generator
100
594.5303
0.5945
0.0194
0.0003
322.9026
Table 5.5: Volume & Mass Database for Refrigerant (including water)
Calculation of Diameter of Tubes Length of Tube (L)
Volume Flow Rate
Radius of Tube
Diameter of Tube
(m)
(cm)
(m3/sec)
(cm3/sec)
(m)
(cm)
(m)
(cm)
(mm)
Absorber
0.80
80.00
0.0003
299.9147
0.01
1.09
0.02
2.18
21.84
Generator
0.80
80.00
0.0003
322.9026
0.01
1.13
0.02
2.27
22.67
Condenser
8.00
800.00
0.1530
152.9539
0.08
0.25
0.16
0.49
4.93
Evaporator
10.00
1000.00
0.1421
142.0649
0.07
0.21
0.13
0.43
4.25
Table 5.6: Calculation of Diameter of Tubes
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5.2 BILL OF MATERIALS S. No.
Material
Particulars as per Cycle
1
GI Pipe (2")
Absorber
2
Sockets (2")
3
End Nuts (2")
4
Centrifugal Pump (1/2 HP) Pump
5
GI Pipe (2")
Generator
6
Stop Valve (1/2")
7
Quantity
Price (in INR)
80cm
100
Sealing Purpose
4
160
Sealing Purpose
4
40
1
1100
80cm
100
Flow Control Valve
1
150
PVC Pipe (1/2")
Connecting Hose
1
60
8
Nipple Pipes
Connecting Hose
2
20
9
Pipe Bends
Connecting Hose
2
40
10
Copper Pipe (1/4")
Connecting Hose + Evaporator
18 ft
450
11
Copper Pipe (1/2")
Connecting Hose
10 ft
70
12
Drier (1/2 by 1/2)
Drier
1
200
13
Condenser (Car A/c)
Condenser
1
1200
14
Receiver Valve
Receiver Valve
1
700
15
Expansion Valve
Expansion Valve
1
20
16
Insulation Foam
Insulation Purpose
1
30
17
1/4" to 1/4" Connector
Connections on Generator &
2
40
4
160
6
150
2
20
Absorber 18
1/4" to 1/2" Connector
Connections on Generator & Absorber
19
1/2" Nut
Connections on Generator & Absorber
20
1/4" Nut
Connections on Generator & Absorber
48
21
3/8" Pipe
Connecting Hose
1 ft
45
22
3/8" Nut
Connection Purpose
2
70
23
Threading/Drilling on
Connections on Generator &
-
150
Generator & Absorber
Absorber
24
Ply board (3'X3')
Base for Equipment
1
360
25
Glass Tape (40m)
Electrical Insulation Purpose
1
90
26
Heating Element (1000W)
Heating Coil
1
10
27
Heating Element (500W)
Heating Coil
1
10
Gross Total=
5545
Table 5.7: Bill of Materials
49
Chapter-6
Conclusion & References o Conclusion o Further Improvement Possible o References
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6.1 CONCLUSION As per our analysis and references, we have found that, it is possible to design an automobile air conditioning system using engine heat based on Vapour Absorption Refrigeration System. Also from the Environmental point of view this system is Eco-friendly as it involves the use of Ammonia as a refrigerant which is a natural gas and is not responsible for OZONE layer Depletion. Furthermore, it also saves the power of engine as it replaces the compressor by the four components i.e. Absorber, Pump, Generator & Pressure Reducing Valve out of which only the pump consumes some power that too is very feeble as compared to that of the Compressor, and thus helps in saving of fuel. Also this system can be employed to commercial heavy vehicles including those which are involved in the transportation of refrigerated products, as this system can easily provide the refrigeration/air-conditioning of cabin as per the requirements by using the exhaust heat of the vehicle’s engine (which is in abundance in such vehicles) thus will not add any additional engine to run the air-conditioning/refrigerating unit in vehicle and hence reduces the operational cost. All in all, it can be a very well and economical asset for the automobile and can completely change the scenario of Automobile Air-Conditioning System.
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6.2 FURTHER IMPROVEMENT POSSIBLE As the major limitation of the system is the use of ammonia which is a life causing gas if inhaled in large amounts, so to overcome this problem it can be suggested to couple this system electronically by the use of various ammonia detecting sensors, which when detect any leakage (which is hardly possible) will bring down the closed windows of the vehicle so the possibility of any damage will be eliminated, and will enable the driver to get aware of any problem and will release the leaked gas in to the atmosphere and thus the impeding danger will be eliminated.
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6.3 REFRENCES [1] Alam Shah (2006), A Proposed Model for Utilizing Exhaust Heat to run Automobile Air-conditioner, The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)” 21-23 Nov; 2006, Bangkok, Thailand. [2] G Vicatos, J Gryzagoridis, S Wang, Department of Mechanical Engineering, University of Cape Town, A car air-conditioning system based on an absorption refrigeration cycle using energy from exhaust gas of an internal combustion engine. “Journal of Energy in Southern Africa (Vol 19 No 4), November 2008” [3] M. Hosoz , M. Direk, Department of Mechanical Education, Kocaeli University, Umuttepe, 41100 Kocaeli, Turkey, Performance evaluation of an integrated automotive air conditioning and heat pump system “Received 5 November 2004; accepted 18 May 2005 Available online 14 July 2005.” Energy Conversion and Management 47 (2006) 545–559 [4] Khurmi R S, Gupta J K, Refrigeration and Air Conditioning- 2010, Vapour Absorption Refrigeration (Pg 238-249). [5] Ganeshan V, Internal Combustion Engine- 2010, Heat Rejection & Cooling (Pg 445467) [6] Domkundwar & Domkundwar, Refrigeration & Air-Conditioning Data book
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