Pitot Static Tube

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. 2. 3. 4. 5. 6.

Pitot tube made of copper. Centrifugal pump, valves, Fixed below pointer gauge. Transparent test section. A CCl4 pressure measuring unit. Stop watch

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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 Where, D=0.028 m μ =.00098 at 210C Vmax=2 x Average velocity average theoretical velocity = ʃvdA/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.

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 

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 Q = 0.00066667 m3/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

Δh (mm)

Height

Time

100

10

138

FOR FLOW RATE 2: Time = 37 sec Height = 10 cm Q = 0.0002703 m3/sec

Sr No

Distance from centre r (mm)

1

10

2

5

3

0

4

-5

5

-10

ME-313 IIT-Gandhinagar

Δh (mm)

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

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FOR FLOW RATES: 15 10

Velocity

5 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.

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Theoratical