olrayt.ppt

Unit Operation Lab

Arnuco, Arjay

Baligod, Jeffrey

Cruz, Nichole

Martin, Jeanell

Penalba, Benjie

PERFORMANCE AND BENEFITS OF PUMPS IN SERIES/PARALLEL OPERATIONS

Engr. Albert Evangelista

Adviser

Copyright © 2006 Pearson Education Canada Inc.

Abstract

In this experiment, the students were asked to examine the performance and benefits of single pump and pumps connected in series and in parallel operations. The materials used were series and parallel pump test rig, water and adjustable counterweight. The experiment was done thrice using 2000, 2200 and 2400 revolutions per minute. At the end of the experiment, the discharge, total head, output power, input power, efficiency and the specific speed of the pumps were calculated. The performance and efficiency versus discharge curve was also plotted.

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Introduction: Centrifugal pumps Are often used together to enhance either the flow rate or the delivery pressure beyond that available from the single pump. For some piping system designs, it may be desirable to consider a multiple pump system to meet the design requirements.

The experimental unit provides the determination of the characteristic behavior for single operation and interaction of two pumps. The apparatus consists of a tank and pipework which delivers water to and from two identical centrifugal pumps

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Materials and Equipment

1. Series/Parallel Pump Test Rig

2. Water

3. Adjustable Counterweight

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Copyright © 2006 Pearson Education Canada Inc.3-5

Ooooppps!Safety first…


Safety Rules:

1. Before running the experiment or turning power on, check all electric cords and hoses and make sure that there are no cracks or exposed areas.

2. This experiment is equipped with a mercury manometer. Extreme care should be taken not to break it.

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Set Up

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Procedure

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1. For the start- up of the system, the valves except the flow- regulating valve was opened and the pump system

was filled with water through the filling plug.

1. For the start- up of the system, the valves except the flow- regulating valve was opened and the pump system

was filled with water through the filling plug.

2. The motor stator was balanced using the adjustable counter weight.2. The motor stator was balanced using the adjustable counter weight.

3. The water level was adjusted to in the approach channel to the “V” notch so that it is exactly level with the apex, taking

account of the surface tension effect.

3. The water level was adjusted to in the approach channel to the “V” notch so that it is exactly level with the apex, taking

account of the surface tension effect.

4. The point gauge in the stilling well was set to zero.4. The point gauge in the stilling well was set to zero.


5. The speed controller was set to zero5. The speed controller was set to zero

6. With the regulating valve closed, the suction and delivery valves appropriate to the test were selected.

6. With the regulating valve closed, the suction and delivery valves appropriate to the test were selected.

7. The initial readings on the two relevant pressure gauges were recorded7. The initial readings on the two relevant pressure gauges were recorded

8. The motor was run up to the chosen speed (2100 rev/min).

8. The motor was run up to the chosen speed (2100 rev/min).

9. With the regulating valve closed again, the pressure gauge readings were also recorded. The valves were opened in intervals such that

regulator increments of discharge were attained

9. With the regulating valve closed again, the pressure gauge readings were also recorded. The valves were opened in intervals such that

regulator increments of discharge were attained


10. At each interval, after adjusting the speed controller as necessary to maintain the chosen speed, the pressure gauge readings and the head

over the crest of the “V” notch in the stilling well were recorded.

10. At each interval, after adjusting the speed controller as necessary to maintain the chosen speed, the pressure gauge readings and the head

over the crest of the “V” notch in the stilling well were recorded.

11. Weights were applied to the torque arm until it was balanced and the total weight applied was noted.

11. Weights were applied to the torque arm until it was balanced and the total weight applied was noted.

12. These set of procedures were repeated for 1800 and 1600 rev/min and for each of the other pump arrangements (series and parallel).

12. These set of procedures were repeated for 1800 and 1600 rev/min and for each of the other pump arrangements (series and parallel).


Result and Discussion

FORMULAS:For total suction head

TSH= HS+ (Q/AS)2/(2g)

Where

AS= πds^/2

For total delivery head

TDH=HD+(Q/AS)2/(2g)+ z

Where

AS= πdd^/2

For total head

THM= TDH-TSH

For total Q

TOTAL Q= (8/15)*(2g)0.5*Ce(THM+kh)

Where

Ce= 0.5765

Kh= 0.00085 m3-12


For input power to the pump

Wi=(MgL)*(2ΠN/60) – 0.1 Kw

For output power to

the pump

Wa=(TOTAL Q)*(THM)*(s.g)/3960

Where

Sg= spec grav of water

For efficiency

EFFICIENCY= 100*(Wi/Wa)

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Results and Discussion:For Pumps 1 and 2

For trial 1 @ 2000 rev/min

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For trial 2 @ 2200 rev/min

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For trial 3@ 2400 rev/min

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Table I. PERFORMANCE OF PUMPS AT DIFFERENT SPEEDS FOR 3 TRIALS

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Table II. VARIATION OF TOTAL HEAD AND EFFICIENCY OF PUMPS 1 AND 2 FOR 3 TRIALS

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Table III. VARIATION OF DISCHARGE AND EFFICIENCY OF PUMPS 1 AND 2 FOR 3 TRIALS

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For series and parallel pumps

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Table IV. PERFORMANCE OF SERIES AND PARALLEL PUMPS AT DIFFERENT SPEED FOR

2400 rev/min

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Table V. PERFORMANCE OF SERIES AND PARALLEL PUMPS AT DIFFERENT SPEED FOR

2200 rev/min

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Table VI. PERFORMANCE OF SERIES AND PARALLEL PUMPS AT DIFFERENT SPEED FOR

2000 rev/min

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Conclusion:

From the experimental data and tabulated results, it can be shown that with pumps in parallel, the flow rate can be increased almost twice for the same head delivered whereas the head delivered can be increased twice by arranging the pumps in series. Hence, where a single pump is inappropriate for large flow rate or high head, pumps can be arranged in series or parallel or combination of the both depending on the requirement.

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Also, it can be concluded that pumps in series and parallel are more efficient than a single pump and pumps in series have higher efficiency than pumps in parallel. Efficiency of pumps in series is better in lower flow rate or at higher head delivered and pumps in parallel is more suitable for higher flow rates or lower head.

Lastly, increased power input can be obtained in pumps connected in series and parallel than that of a single pump.

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