IIT Hyderabad, ME 08,experimental report, Determination of velocity profile of air using pitot tube
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Anil Chejara Roll No. 9003022 Group No. 4
PITOT STATIC TUBE BACKGROUND: The Pitot tube measures a fluid velocity by converting the kinetic energy of the flow into potential energy. The conversion takes place at the stagnation point, located at the Pitot tube entrance. A pressure higher than the free-stream (i.e. dynamic) pressure results from the kinematic to potential conversion. This static pressure is measured by comparing it to the flow's dynamic pressure with a manometer.
AIM: To determine velocity of fluid at various points across the cross section of pipe. APPRATUS: 1. Pitot tube made of copper. 2. Centrifugal pump, valves, 3. Fixed below pointer gauge. 4. Transparent test section. 5. A CCl4 pressure measuring unit. 6. Stop watch
ME-313 IIT-Gandhinagar
Page 1
FORMULE USED: Relationship between the velocity and pressure along a streamline can be give by Bernoulli’s equation.
Evaluated at two different points along a streamline, the Bernoulli equation yields,
If z1 = z2 and point 2 is a stagnation point, i.e.,
v2
= 0, the above equation reduces to,
The velocity of the flow can hence be obtained,
Reynolds No=Re=ρvD/μ No=Re=ρvD/μ Where, D=0.028 m μ =.00098 at 210C 210C Vmax=2 x Average velocity average theoretical velocity = ʃ vdA/Atotal vdA/Atotal Coefficient of pitot can be calculated as average vactual/average vtheoritical
PROCEDURE:
Make sure that the apparatus are free from Dust. Now close the drain valve. Open Flow Control Valve given on the discharge line and Control valve given on suction line. Check the level of CCl4 in all the manometer tube. It should be up to half. Set power output of the motor. Regulate Flow of water through pipe with the help of given Flow Control Valve. Make sure that there is no water bubbles in the tube for measuring pressure heads. Measure Flow Rate using Measuring Tank and Stop Watch.
ME-313 IIT-Gandhinagar
Page 2
Take readings at sufficient number of points to plot the velocity profile across the cross section Repeat the experiment with different flow rates
OBSERVATION TABLE:
FOR FLOW RATE 1: Time = 15 sec Height = 10cm 3
Q = 0.00066667 m /sec
Sr No
Distance from centre r (mm)
1
10
2
5
3
0
4
-5
5
-10
V (m/s) (Theoretical)
V calculated (m/s)
Coeff of pitot tube
15
1.766
1.061
0.6005
10
15
2.075
1.889
0.9106
155
10
15
2.199
2.166
0.9848
135
10
15
2.052
1.889
0.9207
103
10
15
1.793
1.061
0.5917
V (m/s) (Theoretical)
V calculated (m/s)
Coeff of pitot tube
Height
Time
100
10
138
Δh
(mm)
FOR FLOW RATE 2: Time = 37 sec Height = 10 cm 3
Q = 0.0002703 m /sec
Sr No
Distance from centre r (mm)
1
10
2
5
3
0
4
-5
5
-10
ME-313 IIT-Gandhinagar
Height
Time
15
10
37
0.684
0.430
0.6286
21
10
37
0.809
0.766
0.9463
27
10
37
0.918
0.878
0.9566
23
10
37
0.847
0.766
0.9042
16
10
37
0.706
0.430
0.6086
Δh
(mm)
Page 3
FOR FLOW RATES: 15 10 5 y t i c o l e V
0 0.000
Calculated 0.500
1.000
1.500
2.000
2.500
-5 -10 -15
Velocity
CONCLUSION
The average coefficient of Pitot tube was found to be 0.8076.
SOURCES OF ERROR AND PRECAUTIONS:
Human error possible while taking reading
Make sure there is no bubble present in manometer.
Make sure that there is not high flow of fluid.
Make sure that CCl4 is present in sufficient quantity.