Flow Meter Measurement 173w5b

TABLE OF CONTENTS CONTENT 1

Abstract / Summary

2

Introduction

3

Aims / Objectives

4

Theory

5

Apparatus and Material

6

Experimental procedure

7

Result

8

Sample calculation

9

Discussion

PAGE

10 Conclusion 11 Recommendation 12 References / Appendix

ABSTRACT This experiment used Flow Meter Measurement Apparatus which used concept of basic hydraulic bench by using flow of water. Any incompressible fluid can be measured with different

types of method. This apparatus have three parts of measurements which is orifice, venturimeter and rotameter. Fluids that enter this apparatus will flow in different types of flow path which is different in pressure, velocity and types of flow (laminar or turbulent). By using this apparatus, the data of properties of fluid flow in motion is accurate eventhough there is pressure drop in each types of path.

INTRODUCTION There are a lot of applications of measurement of fluid flow in daily life such as measurement of blood flow rates in human artery, measurement of liquid oxygen in a rocket, measurement of fluid flow in industrial machines and so on. Output of the instrument can be calculated by having accurate pressure and temperature. Flow meter principles that widely used in daily life is by placing a fixed area flow restriction at the certain part of pipe or duct that carrying the fluid. At the point that has flow restriction, there is pressure drop that relate with the flow rate. Each type of the flow measurement devices has its own advantages and disadvantage. Devices that used in the flow measurement devices are venture meter and orifice.

Venture Meter

Venturi meter is a device that can decrease pressure and increase velocity by using its tube which is constricted. It can measure compressible and incompressible fluid. When any fluids flow through the constricted part, the velocity measured after ing the constricted part is higher

than velocity measured before entering the constricted part. The diameter constricted part is smaller than the diameter of the pipeline. That’s why there is difference velocity reading. Discharge of the fluid can be calculated by measuring the pressure drop. This venturi meter used Bernoulli principles which state that an inviscid flow of a nonconducting fluid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. Venturi tube is suitable for viscous, clean and dirty liquid. Pressure loss is low and its viscocity is high.

Orifice Meter

Figure (2) shown above is an orifice meter which made of thin and flat orifice plate which has a circular hole at the centre of the plate. There is two pressure tap which is tap upstream and tap downstream. The taps can be place at three places which each of the place have different value of coefficient. The first one known as flange location which is the position of the tap is 1 inch for both upstream and downstream from the face of orifice. Next, vena contracta which is located 1 inch pipe diameter (actual inside) upstream and 0.3-0.8 inch pipe diameter from face of the orifice. The last one tap location is 2.5 times nominal pipe diameter upstream and 8 times nominal pipe diameter from face of orifice. This tap location is known as pipe location. Discharge coefficient is denoted with symbol , Co which varies with changes in area ratio and Reynolds’ number. Usually, the standard value of discharge coefficient is 0.6 but when the value of Reynolds number is low, it varies. The pressure loss is medium and the viscocity effect is high.

OBJECTIVES   

To investigate and contrast the operation and characteristics of three different basics types of flow meter which venture, variable, and orifice including accuracy and energy losses. To measure a pressure drop at different segment of device To determine a flow rate through a pipe.

THEORY Venturi meter and orifice meter use principle of Bernoulli equation to yield the result: P1 v 12 P2 v 22 + +z = + +z ρg 2 g 1 ρg 2 g 2 z 1=z 2 2

2

P 1 v 1 P2 v 2 + = + ρg 2 g ρg 2 g P1 −P 2 v 22−v 12 = ρg 2g Q1=Q2 A 1 v 1= A2 v 2

v 1=

A2 v 2 A1 2

A 2 v2 / A 1 ¿ ¿ v 22−¿ P1−P2 =¿ ρg So,

2

A2/ A1 ¿ ¿ 1−¿ v 22 ¿ ¿ 1−¿ ¿ ¿ √¿ 1 v 2= ¿

Q=Cd A 2 V 2 (3) in (4) 1−¿ ¿ ¿ √¿ Cd A Q= ¿ 2

Flow rate,

√ 2 ΔP=

√

2 gΔh P

Where; �h : head difference in meter (m) from the manometer readings for the appropriate meter g : acceleration due to gravity (m/s2) Cd : discharge coefficient for meter A1 : area of the test pipe upstream of the meter (m2) A2 : throat area of the meter (m2) Use of discharge coefficient, Cd is necessary because of the simplifying assumptions made when applying the Bernoulli equations. Values of this coefficient are determined by experiment; the assumed values used in the software are: Venturi meter Cd= 0.98 Orifice plate Cd =0.63

APPARATUS

Staddle Valve

Manomete r Tubes Rotamet er Discharg e Valve Water Outlet

900 Elbow

Water Supply Orifice Venturi

PROCEDURE General start-up 1. The flow control valve of hydraulic bench were fully closed while the discharge discharged valve were fully opened.

2. The pump supply from hydraulic bench were started up and the bench valve were opened slowly. 3. When the flow in the pipe was steady and there were no trapped bubble, the bench valve was closed to reduce the flow to the maximum measurable flow rate. 4. If the water level of manometer was too high, the water level can be adjusted by using staddle valve. 5. The discharge valve were fully closed and the flow were slowly reduced by controlled the flow discharge valve. 6. The water in the manometer was level into a straight level.

A. Operation and characteristic of three different basic type of flowmeter. 1. The rotameter were set at 5 m/min by adjusted the bench valve. 2. The reading of the manometer from A to J were recorded. 3. The time taken in minutes for every 3 L volume were recorded to calculated the flowrate. 4. Step 1 was repeated by different level such as 10 m/min,15m/min and 20m/min. 5. The flowrate for the venturi and orifice were calculated by using Bernoulli’s equation.

B. Loss coefficient of fluid through a 90 degree elbow. 1. The rotameter were set at 5 m/min by adjusted the bench valve. 2. The reading of the manometer from I and J were recorded. 3. The time taken in minutes for every 3 L volume was recorded to calculated the flowrate. 4. Step 1 was repeated by different level such as 10 m/min,15 m/min and 20m/min. 5. The graph �H against losses.

v2 2 g for 90 degree elbow were plotted to determine the coefficient of

General shut-down procedures 1. The water supply valve and the venturi discharge valve were closed. 2. The water supply pump was turned off. 3. The water was drained off from the unit when not in use.

RESULTS Operation and Characteristics of Three Different Basic Types of Flowmeter Manometer reading (mm)

Rotameter ( l/min)

Volume ( l)

Time (min)

A

B

C

D

E

F

G

H

I

J

259

25 8

24 8

25 5

25 6

25 8

25 8

23 2

24 3

24 2

5

3

0.5138

285

28 0

24 0

26 6

27 1

27 6

27 7

19 3

22 5

22 3

10

3

330

31 8

24 2

29 0

30 3

31 3

31 3

12 2

19 9

19 5

15

365

34 5

22 5

30 3

32 1

33 8

33 8

29

14 9

14 2

20

Flowrat e ( l/min)

Bernoulli’s Equation (l/min) Venturi

Orifice

5.8388

5.45

5.87

0.2622

11.4416

12.01

10.54

3

0.1875

16.0000

16.79

15.90

3

0.1625

18.4615

21.18

20.22

Determination of The Loss Coefficient When Fluid Flows Through a 90 Degree Elbow Volume (L)

Time (s)

Flowrate (l/min)

3 3 3 3

30.83 15.73 11.25 9.75

5.8388 11.4416 16.0000 18.4615

Piezometer Height Elbow(hi-hj) 1 2 4 7

V (m/s)

V2/2g (mm)

0.1833 0.3592 0.5023 0.5795

1.7124 6.5762 12.8600 17.1200

p i e z o m e t r i c h e a d ( m m ) ( � � H )

�H against V2/2g 18 16 14 12 10 8 6 4 2 0 0

1

2

3

4

5

6

7

8

Velocity Head (mm)(V2/2g)

CALCULATION Demonstration of the operation and characteristic of three different basic types of flowmeter For rotameter flowrate = 20 l/min

Venturi Meter 2 −1/ 2

[ ( )]

At Qv =Cd × At × 1− A

[ 2 g ( h A −hC ) ]

[ (

1/2

2.011 ×10−4 m2 Qv =0.98 × 2.011 ×10 m × 1− 5.309× 10−4 m2 −4

Qv =21.18 l/min

Orifice Meter

2

2 −1/ 2

)]

[ 2 ×9.81 m/s ( 0.365 m−0.225m ) ]

1 /2

×

1000 l 1 min/60 s

[

2 −1/ 2

( )]

At Q o=Cd × At × 1− A

[ 2 g ( h g−h h) ]

1/ 2

[ (

−4

−1/ 2 2 2

2.011 ×10 m Qo=0.98× 2.011 ×10 m × 1− −4 2 5.309× 10 m −4

2

)]

[ 2 ×9.81 m/s ( 0.365 m−0.225m ) ]

Qo=20.22 l/min

( Qv −Q r )

Venturi meter Flow Rate Error=

Qr

× 100

( 21.18−20 ) ×100 20

Venturi meter Flow Rate Error=

Venturi meter Flow Rate Error=5.9 % Orifice Meter Flow Rate Error=

Orifice meter Flow Rate Error=

( Qo−Qr ) Qr

×100

( 20.22−20 ) ×100 20

Orifice meter Flow Rate Error=1.1

Determination of the loss coefficient when fluid flows through a 90 degree elbow For Flow Rate, Q = 5.388 l/min = 9.7313 x 10-5 m3/s

V=

Q A 3

−5

V=

9.7313 ×10 m / s 2 π ( 26× 10−3 ) 4

()

V =0.1833 m/s 2

V 2 ( 0.1833 m/s ) = =1.7124 × 10−3 m=1.7124 mm 2 g 2 ×9.81 m/ s

1 /2

×

1000 l 1 min/60 s

K=

K=

hi−h j V 2 /2 g 1 1.7124

K=0.5840

DISCUSSION From these experiments, we can see the three operations and characteristic of three different types of flow meter which is venturi meter, orifice meter and variable area meter. We also record all the readings during these experiments and we can see which one of the flow meter give the accurate value. Besides that, we also determine the energy losses that occur in the three different flow meters. After conduct these experiments, we are able to determine the value of flow rate of three flow meters, the value of flow rate error and the value of head loss. Besides that, we also determine the value of flow rate error for the three flow meters. From the results, percentage flow rate error for venturi meter is 5.9% while for the orifice meter is 1.1%. From the theory, the more efficiency of flow meter has a less flow rate % error. So, from these results, the orifice has a less flow rate % error. The accuracy of flow meter is depends on the flow rate % error. From the experiment, we also obtain the value of head loss for the three flow meters. From the theory, the venturi meter has a low head loss, continued by variable are a meter and then orifice meter. So, from the results, the value of head loss for venturi meter is 0.0227m, orifice meter is 0.0315m and variable area meter is 0.0556m. We can say that this result is agreed with the theory. After calculate the flow rate % error, we noticed that there must be some errors. It is because from the theory, venturi meter is a more accurate than orifice and variable area meter. From the calculation, we determine that orifice meter is more accurate than others. Actually, it should be the venturi meter. We found that one of the major factors that affect the readings is the bubble in pipeline. Besides that, the position of eyes also gives effect to the manometer reading.

CONCLUSION As a conclusion, we can say that the most accurate flow meter is a venturi meter. From this experiment, we determine that the flow rate % error for venturi meter is higher than the orifice meter. From the theory, the more efficiency of flow meter has a less flow rate % error.

RECOMMENDATION After conduct this experiment, we can say that value of flow rate and the flow rate %error are not follow the theoritical results. From the theory, the most accurate flow meter is a venturi meter. So, it means that the most efficiency flow meter has a less value of flow rate %error. In this experiment, the value of flow rate % error for venturi meter is higher than the orifice meter. For the first recommendation for this experiment is make sure that there is no bubble in the pipeline. The existence of bubble may cause the less accuracy of flow meter. The second is make sure there is no small particles in the fluid because some of the devices are very sensitive to these particles. Besides that, during record the manometer reading, make sure the position of eyes is parallel to the level of reading

REFERENCES 1. 2. 3. 4. 5.

https://en.wikipedia.org/wiki/Bernoulli%27s_principle https://en.wikipedia.org/wiki/Venturi_effect http://www.slideshare.net/NofalUmair/fluid-mechanics-applications http://fluidmechanics-megan.blogspot.my/ http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-3-Physics-Vol1/Fluid-Mechanics-Real-life-applications.html 6. https://www.idoub.com/doc/39317662/Flow-Measurement 7. https://www.idoub.com/doc/47666485/Experiment-No-4-Flow-Measurements 8. https://www.idoub.com/doc/47475587/Lab-1-Fluid-flowmeters-me-final

APPENDICES