Orifice and Jet Flow Meter Sarmiento, Yvone M. CHE131L – Chemical Engineering Laboratory 1 / A03 1st term of A.Y. 2017-2018
Mapúa Institute of Technology at Laguna Malayan Colleges Laguna
ABSTRACT The
where,
experiment
performed
was
about
the
g = gravitational acceleration
measurement of the flow of fluid using an orifice and H = water elevation above the orifice
jet flow meter. The trajectory of the jet was measured by getting the horizontal and vertical distance from the orifice. The coefficient of velocity and discharge was calculated by the derived formula. Bernoulli equation was the basis of the calculation of the coefficient of velocity while the flowrate equation was the basis of the coefficient of discharge. The results of the experiment concluded that the distance of the fluid from the orifice and water level in the vessel affects the coefficient of velocity and discharge.
Figure 1. Illustration of fluid leaving the orifice. Accounting for the energy losses present, the
INTRODUCTION Measuring and controlling the flow of fluid entering
discharge velocity is modified by a coefficient of velocity, Cv .
and leaving is very important in fluid dynamics. There
= 2 2 .2
are many measuring devices for fluid flows. One of the measuring devices is the orifice. Orifice plates
After the fluid exits the orif ice, the jet flow dro ps in
restricts the flow of the fluid and causes pressure
free fall due to the forces of gravity. Figure 2 shows
drop. These plates also help to determine the validity
the trajectory of jet with a constant head tank. The
of the Bernoulli’s equation.
vertical dropping distance Y from the starting point
The Bernoulli equation predicts the horizontal jet velocity of the fluid leaving the orifice at the vena contracta as illustrated in Figure 1. It is defined as,
is:
= 12 .3
= 2 2 .1 Experiment 1. Orifice and Jet Flow Meter CHE131L – A03
By: Sarmiento, Yvone M. BS in Chemical Engineering
EXPERIMENT OBJECTIVES
1.
Operate an Orifice and Jet Flow instrument using a hydraulic bench.
2.
Determine
the
coefficient
of
velocity
and
coefficient of discharge under various constant heads for a given orifice diameter. 3.
Properly compare jet trajectories with that by theory of mechanics.
4.
Determine the effect of modifying the mass flow rate of water to the coefficient of discharge of the orifice.
Figure 2. Trajectory of the jet from constant head tank METHODOLOGY Coefficient of velocity, Cv , can also be defined as the ratio of actual velocity to the theoretical velocity.
= ℎ / .4 = 2 Deriving t, from Eq.3, and substituting it to Eq.4 will give a definition of coefficient of velocity as,
= 12 √ .5 The coefficient of discharge, Cd, is measured by getting the time it will take to fill up a certain volume.
Materials 1.
Hydraulics Bench
2.
Stopwatch
3.
500mL Beaker
4.
12-inch Ruler
Procedures
1.
behind the probes. 2.
= = ℎ = Further derivation will give the expression of Cd as,
= .6 4 2
Place the apparatus on the Bench and adjust for leveling.
3.
Connect the Bench outlet to the apparatus inlet.
4.
It can also be defined as the ratio of the actual flowrate to the theoretical flowrate.
Clip on a graph paper on the probe board
Adjust the overflow pipe to obtain a required level in the tank.
5.
Open the water supply valve to obtain a steady flow with minimum overflow.
6.
Wait until the water level in the tank and jet profile is stable before adjusting the tips of the probes to be in line with the center of the jet.
7.
Record the tip of the probe profile (upper tips) as well as Y = 0 mark.
2
8.
Record the volume of flow using a stop watch and the bench measuring tank or
Distance from the graph, mm X1 = 50, Y1 = ? X2 = 100, Y2 = ? X3 = 150, Y3 = ? X4 = 200, Y4 = ? X5 = 250, Y5 = ? X6 = 300, Y6 = ? X7 = 350, Y7 = ? X8 = 400, Y8 = ?
Table 1.1. Tabulated results and calculation of flow
rate (1x10-5m3 /s)
Trial
Trial 1
2
3
4
5 Water Level H, mm Volume, L
1
2
3
4
5
410
390
370
350
250
0.5
0.5
0.5
0.5
0.5
0
0
0
0
0
5
4.5
4.5
5.5
8
13
12.5
14.5
14.5
21
Time, s
33.38
35.81
36.90
38.54
46.22
24
25.5
26.5
27.5
45
1.498
1.396
1.355
1.297
1.082
39
41.5
44.5
46.5
67
Flow rate, (x10-5) m3 /s
58
59.5
63.5
67.5
99
79
83.5
89.5
92.5
138
104
108.5
117.5
122.5
182
measuring cup.
DATA AND RESULTS
Technical Data of the Equipment
Orifice Diameter
: 3mm
Trajectory probe
: 8, stainless steel
Maximum constant head: 420 mm Cylinder diameter
: 200 mm
The following table below shows the gathered and calculated data:
Table 1.2. Tabulated Results of Distance from the graph, mm
Distance from the graph, mm X1 = 50, Y1 = ? X2 = 100, Y2 = ? X3 = 150, Y3 = ? X4 = 200, Y4 = ? X5 = 250, Y5 = ? X6 = 300, Y6 = ? X7 = 350, Y7 = ? X8 = 400, Y8 = ?
Trial 1
2
3
4
5
0
0
0
0
0
5
4.5
4.5
5.5
8
13
12.5
14.5
14.5
21
24
25.5
26.5
27.5
45
39
41.5
44.5
46.5
67
58
59.5
63.5
67.5
99
79
83.5
89.5
92.5
138
104
108.5
117.5
122.5
182
3
Table 1.3. Tabulated Results of Coefficient of velocity,
ANALYSIS, INTERPRETATION, & CONCLUSION
Cv The results in Tables 1.1-4 shows how varying water
Coefficient of velocity, Cv
Trial
level affects the coefficient of velocity and coefficient of discharge of the fluid. By looking at Eq.5, the
1
2
3
4
5
Cv,1
-
-
-
-
-
Cv,2
1.104
1.194
1.225
1.140
1.118
Cv,3
1.027
1.074
1.024
1.024
1.035
in the vessel. As the fluid gets farther away from the
Cv,4
1.008
1.003
1.010
0.991
0.943
orifice, both vertically and horizontally, the coefficient
Cv,5
0.989
0.983
0.974
0.953
0.966
of velocity decreases. The coefficient of discharge
Cv,6
0.973
0.985
0.979
0.947
0.953
Cv,7
0.972
0.970
0.962
0.946
0.942
Cv,8
0.969
0.972
0.958
0.939
0.938
coefficient of velocity varies with change in the horizontal distance of fluid from the orifice, the vertical distance of the jet from the orifice, and the water level
decreases as the water level decreases.
The
coefficient of discharge is affected by the volume of the water in the vessel. The volume of the water determines the flowrate which is used to calculate the coefficient of discharge. Some errors that can be Table 1.4. Tabulated Results of Coefficient of
observed is the measurement of the distance of the
discharge, Cd
trajectory of jet and the inconsistent inlet flow of the fluid in the vessel. Trial
Coefficient of discharge, Cd Cd
1
2
3
4
5
0.75
0.71
0.71
0.70
0.69
REFERENCES Geankoplis, C.J., (1993). Transport Processes and Unit Operations, 3rd ed. Englewood Cliffs, New Jersey 07632: Prentice-Hall, Inc.
Trajectory of Jet Chemical Engineering Laboratory 1 Manual
0
M M , E -50 C I F I R O-100 M O R F-150 Y E C N-200 A T S I D
50 100 150 200 250 300 350 400 500
APPENDICES
For F low Rate (as i n Table 1.1): (a) Flow rate DISTANCE X FROM ORIFICE, MM
〖 〖 〖 〖 〖
〗 〗 〗 〗 〗
EXP1: Qact = 1.498x10 ^(-5) EXP2: Qact = 1.396x10 ^(-5) EXP3: Qact = 1.355x10 ^(-5) EXP4: Qact = 1.297x10 ^(-5) EXP5: Qact = 1.082x10 ^(-5)
Actual flow rate
= Equation 2 Actual Volumetric Flow Rate
3 0. 5 L 1m Qact = 33.38s x 1000L Qact =.− ⁄ 4
For C oefficient of Velocity (as in Table 1.3):
Coefficient of velocity
= √ 0.100m =. Cv,2 = 12 √ XYH = 12 √ 0.005mx0. 410m For C oefficient of Dis charg e (as in Table 1.4):
Coefficient of discharge
= = √ −5 m3⁄s 1. 4 98x10 Cd = π(0.003m)2 m 4 2x9.81 s2 x0.41m =.
5
