FLOW MEASUREMENT

1. Introduction: We’ll go in this experiment to study some of the famous instruments used in flow measurements. And we’ll use the instruments which shown in fig (1)

Fig (1): Flow measurement instruments

In this experiment the flow of a fluid was calculated using three method listed below:

a. Sudden Enlargement:

Fig (2): Sudden Enlargement

ℎ

The head loss through the Sudden Enlargement 

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   ℎ =  

,

 =  ()

ℎ ℎ − ℎ  =     =    =   Where

=

,

Where,

is the coefficient of discharge.

 b. Venturi Meter: The flow through venture meter can calculated from the following equations:

Fig (3): Venturi Meter 

 =  ()  ℎ − ℎ  =     =    =  Where

=

,

, Where Cd is the co efficient efficient of o f discharge.

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c. Orifices plate: The flow through venturi meter can calculated from the following equation

 =  ()  ℎ − ℎ  =     =    =  Where

=

Fig (4): Orifices plate

,

, Where Cd is the co efficient of discharge.

d. Elbows: The head loss through the elbow h b.

Where kb is the coefficient of the elbow (let Kb= 0.5)

 =     =    =  . = . ,

,

Where Cd is the coefficient of discharge.

e. Rotameter:

The Rotameter reads the flow directl y.

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2. Objective: 

To study some of t he famous instruments used in flow measurements.



To become familiar with Venturi & Orifice Ori fice plate &Variable area meter.

3. Apparatus: Water Flow Measuring Apparatus is designed as a free-standing apparatus for use on the Hydraulics Bench, although it could be used in conjunction with a low pressure water supply controlled by a valve and a discharge to drain. Water enters the apparatus through the lower  left- hand end and flows horizontally through a sudden enlargement into a transparent venturi meter, and into an orifice plate, a 90º elbow changes the flow direction to vertical and connects to a variable are a flow meter, a second  bend passes the the flow into a discharge discharge pipe which which incorporates an atmospheric break.

Fig (5): Apparatus

4. Procedure: Prepare the instruments such that the water passes Sudden Enlargement, then Venturi meter, Orifice plate, Elbow, and finally Rotameter. 2. Switch the pump on, allow the water to enter the flow measurement instruments, Which are connected to Manometers tubes. 3. Control the flow valve to obtain ob tain different readings readings of the heads in manometers and The corresponding flow from the volume tank. 4. Record the results. 5. Calculate the head losses from the manometer readings and the flow and C d for  Venturi and orifice plate.

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5. Results: a. Sudden Enlargement: A1= 0.0000785 m2

,

Table (1): Sudden Enlargement Readings Volume (m3)

0.01

0.01

0.008

0.006

Time (sec)

135

152.4

142.2

141

h1 (m)

0.427

0.372

0.324

0.2485

h2 (m)

0.43

0.373

0.338

0.249

he= h2 – h1

0.003

0.001

0.003

0.0005

V1 (m/s)

0.4852

0.2801

0.4852

0.1981

Qth. (m3/s)

3.809E-05

2.199E-05

3.809E-05

1.56E-05

Qact.(m3/s)

7.40741E-05

6.56168E-05

7.40741E-05

4.25532E-05

We have a plot with Qact. in Y-Axis and Qthe. In X-Axis See Fig (6)

Fig (6):Sudden Enlargement 0.00008 0.00007 y = 1.949x

0.00006 0.00005  .      t     c 0.00004     a      Q 0.00003 0.00002 0.00001 0 0

0.0000050.000010.00001 0.00 00050.000010.000015 5 0.00 0.000020.0000250.0000 0020.0000250.00003 3 0.0 0.00003 00035 5 0.00 0.00004 004

Qthe.

When we graph the best line passes through all points and Zero point and find the slope of this line (Cd) is 1 .949.

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 b. Venturi Meter: A1=0.0000785 m2 ,

Table (2): Venturi Meter Readings Volume (m3)

0.01

0.01

0.008

0.006

Time (sec)

135

152.4

142.2

141

h3(m)

0.449

0.388

0.338

0.256

h4 (m)

0.393

0.345

0.305

0.237

H = h3 - h4

0.056

0.043

0.033

0.019

1.21

1.061

0.9291

0.705

Qth. (m3/s)

9.5E-05

8.33E-05

7.29E-05

5.53E-05

Qact.(m3/s)

7.407 E-05

6.56 E-05

5.63 E-05

4.26 E-05

V1 (m/s)

We have a plot with Qact. in Y-Axis and Qthe. In X-Axis See Fig (7)

Fig (7): Venturi Meter  0.00008 0.000075 y = 0.7789x 0.00007 0.000065  .      t     c 0.00006     a       Q 0.000055 0.00005 0.000045 0.00004 0.0 .000 0004 04

0.00 0. 000 005

0.0 .00 000 006 6

0.0 .00 000 007 7

0.0 0. 0000 008 8

0.00 0. 000 009

0.00 0. 000 01

Qthe.

When we graph the best line passes through all points and Zero point and find the slope of this line (Cd) is 0. 7789.

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c. Orifices plate: A= 0.000113 m2

, Table (3): Orifices plate Readings

Volume (m3)

0.01

0.01

0.008

0.006

Time (sec)

135

152.4

142.2

141

h6(m)

0.434

0.377

0.329

0.25

h7 (m)

0.163

0.162

0.163

0.162

H = h6 – h7

0.271

0.215

0.166

0.088

V1 (m/s)

2.882

2.567

2.256

1.642

Qth. (m3/s)

0.000326

0.00029

0.000256

0.000186

Qact.(m3/s)

7.4074E-05

6.56 E-05

5.63 E-05

4.26 E-05

We have a plot with Qact. in Y-Axis and Qthe. In X-Axis See Fig (8)

Fig (8): Orifices plate 0.00008 y = 0.2258x

0.00007 0.00006 0.00005  .      t     c0.00004     a       Q 0.00003 0.00002 0.00001 0 0

0.00 0. 000 005

0.00 0. 0001 01

0.0 0. 000 001 15

0.00 0. 000 02

0.00 0. 0002 025 5

0.00 0. 0003 03

0.0 0. 00035

Qtheo. When we graph the best line passes through all points and Zero point and find the slope of this line (Cd) is 0. 2633.

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d. Rotameter: Table (4): Rotameter Readings Qthe. (Qrot.) (Qrot. ) (L/s) Qact. (L/s)

4.15

3.63

3.15

2.2

0.0741

0.06562

0.05626

0.04255

We have a plot with Qact. In Y-Axis and Qthe. In X-Axis See Fig (9)

Fig (9): Rotameter  0.08 0.07 y = 0.0181x

0.06 0.05  .      t     c0.04     a       Q 0.03 0.02 0.01 0 0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Qthe.

When we graph the best line passes through all points and Zero point and find the slope of this line (Cd) is 0.02.

6. Conclusion & Recommendations: We see that the flow of a fluid can be measured in many ways. And t he expected error  is the human error, if the experimenter red the outputs and calculate incorrectly. And we note that the magnitude of cd decrease after doing any experiment. In other word the cd in first is 1.989 and in the second experiment is 0.02, there is a loss in energy  between two experiments. experiments.

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