Flow measurement lab report discussion

EGME-306B-06

Spring 2015

Engineering Report

EXPERIMENT #1

Flow Through A Venturi Meter

Using Water As The Working Fluid

(Ref. Experimental Data Group 02- Taken on Feb 6, 2015)

By

02/20/2015

TABLE OF CONTENTS

List of Symbols………...…………………………………………………………………………………………2

Abstract…………………………………………………………………………………………................3

Procedure………………………………………………………………………………………………….4

Theory……………………………………………………………………………………………………..5

Results……………………………………………………………………………………………………10

Sample Calculations………………………………………………………………………………………………18

Error Analysis…………………………………………………………………………………………………..22

Discussion………………………………………………………………………………………………..26

References………………………………………………………………………………………………..28

LIST OF SYMBOLS

………………………………………………………………………………………..Mass flow rate ()

……………………………………………………………………………………………..flow rate ()

………………………………………………………………………………………...Mass density ()

……………………………………………………………………………………………...…gravity ()

……………………………………………………………………………………..…inlet pressure ()

………………………………………………………………………………………….inlet velocity ()

…………………………………………………………………………………………...inlet area ()

………………………………………………………………...inlet throat height from datum point ()

………………………………………………………………………………………outlet pressure ()

………………………………………………………………………………………...outlet velocity ()

………………………………………………………………………………………….outlet area ()

……………………………………………………………….outlet throat height from datum point ()

C…………………………………………………….………………discharge coefficient (dimensionless)

c………………………………………………………………………………………...speed of sound ()

Re……………………………………………………………………...Reynold’s number (dimensionless)

M…………………………………………………………………………...Mach number (dimensionless)

ABSTRACT

The motivation of this laboratory experiment is to analyze the flow of a fluid passing through a Venturi meter. The scheme is to compare the experimental volumetric flow rate to the theoretical volumetric flow rate. Deriving the Venturi velocity formula from the Bernoulli and continuity equations attains the theoretical volumetric flow rate.

It was found that the assumption of a frictionless surface through the Venturi meter was incorrect. When the water flows there is a head loss, which causes dissipation of energy throughout the system. Other factors such as human error, air bubbles in the fluid, and calculation round-offs led to discrepancies in the data.

RESULTS SUMMARY

Table 1: Pressure in piezometer tube and distance the fluid elevated to in Venturi meter

Venturi data and Piezometer Station

Piezo tube H2O height at station X , hX in.± .1in.

Distance from end, X in.

Venturi diameter D in. at X

Piezo. Station

Run 1

Run 2

Run 3

Run 4

Run 5

Run 6

hA-hD≈10 inH20

hA-hD≈8 inH20

hA-hD≈6 inH20

hA-hD≈4 inH20

hA-hD≈2 inH20

hA-hD≈.6 inH20

0

1

A-

9.3

8.8

8.0

7.0

6.1

5.5

1.125

1

A

9.3

8.8

8.0

7.0

6.1

5.5

1.625

1

A+

9.3

8.8

8.0

7.0

6.1

5.5

1.875

0.906

B

8.9

8.3

7.7

6.9

6.0

5.4

2.375

0.719

C

5.4

5.3

5.4

5.3

5.3

5.2

2.625

0.6445

D-

0.2

0.8

1.9

3.0

4.1

4.9

2.9375

0.6445

D

0.2

0.8

1.9

3.0

4.1

4.9

3.25

0.6445

D+

0.2

0.8

1.9

3.0

4.1

4.9

3.5

0.652

E

0.7

1.2

2.2

3.1

4.2

4.9

3.875

0.705

F

3.4

3.6

3.9

4.3

4.7

5.0

4.5

0.759

G

4.9

4.9

5.0

5.1

5.1

5.1

5

0.813

H

5.9

5.9

5.6

5.5

5.3

5.2

5.5

0.866

K

6.7

6.4

6.1

5.8

5.5

5.5

6

0.92

L

7.1

6.9

6.5

6.0

5.6

5.3

6.75

1

M-

7.8

7.4

6.9

6.3

5.7

5.3

6.875

1

M

7.8

7.4

6.9

6.3

5.7

5.3

7.875

1

M+

7.8

7.4

6.9

6.3

5.7

5.3

Graph 1: Piezometer tube versus distance of fluid in Venturi meter

Graph 2: Volume flow rate versus the square root of the height difference

Graph 3: Ideal Volume Flow Rate versus Discharge Coefficient

Graph 4: Free Stream and Throat velocity versus actual volume flow rate

Graph 5: Free stream and throat Mach number versus actual volume flow rate

Graph 6: Free stream and throat Mach number versus actual volume flow rate

DISCUSSION AND CONCLUSION

The Venturi meter is one of the most efficient systems with minimal error for use in experimentation surfaces. In comparison to the sharp-edged orifice of flow nozzle, the Venturi meter shows the most minimal head loss caused by friction and heat.

Analyzing the data acquired, the values attained for velocity and volumetric flow rate are in correlation with the Venturi meter experiment. There were slight deviations that occurred in conducting the experiment due to realistic conditions; thus, compared to the calculated values where ideal conditions were taken into account. The factors such as heat loss and friction affected the system and prevented the ideal-condition results. Another factor affecting the measurements is the readings taken from the manometer are the students’ readings, they may not have been as accurate as possible which have resulted in a percentage error.

Contained in the “Results” section the dimensionless measurements of Reynolds number and the discharge coefficient show the Reynolds number increases and so does the discharge coefficient. This concludes that the larger the cross-sectional area the more efficient the system becomes, this is true for a certain ratio.

Errors cannot be completely avoided therefore a margin of error is expected given the high possibility of factors affecting error. In our attempt to eliminate all air bubbles, it appeared as if they were all gone but our visual judgment only goes so far, causing small errors in data collected. Other errors arise in the contents of the water such as impurities; even though the water was distilled, the distillations might not have been 100% effective. Due to the minimal amount of theoretical background, an error in precision is inevitable. Calculation round-offs are another contributing factor in our error margin.