TABLE OF CONTENT

TABLE OF CONTENT.....................................................................................................................

TITLE...............................................................................................................................................

OBJECTIVE.................................................................................................................................................

APPARATUS...............................................................................................................................................

THEORETICAL BACKGROUND..............................................................................................................

PROCEDURE.............................................................................................................................................

RESULT.......................................................................................................................................................

SAMPLE OF CALCULATION..........................................................................................................

DISCUSSION & CONCLUSION...............................................................................................................

REFERENCES ………………………………………………………………………………………….…

APPENDIX ………………………………………………………………………………………………....

TITLE : Centrifugal Pump Performance Characteristics.

OBJECTIVES

To obtain performance characteristics for a variable speed centrifugal pump operating at 3

different impeller speeds. Performance characteristics of pump:

a) Pressure (head) pump

b) Power requirement

c) Flow rate influence

d) Pump speed influence

EXPERIMENTAL APPARATUS

The experimental set-up consists of:

a) Water-flow bench and centrifugal pump

b) Instrumentation for data acquisition consists of:

a. The instrument panel

i. Speed control to change pump speed. Pump speed can be varied over range of 0

to 3000 rpm.

ii. Pump suction and delivery pressures.

iii. Torque measurement.

b. Flow measurement – using ‘V’ notch weir

i. Flow rate in the system can be measured relating the height of water seen in the

sight glass to graph TI and reading off the flow rate in litres per minute.

c. Speed measurement

i. Pump motor speed measurements are made using hand held digital tachometer.

THEORY

The centrifugal pump was developed in Europe in the late 1600s and was seen in the United

States of America in the early 1800s. However, its usage has only gathered momentum in the

early 1940s, as the positive displacement pumps were more popular prior to that time. Its

increasing popularity was due to the development of high speed electric motors, steam turbines,

and internal combustion engines. Research and development in the area of centrifugal pump

has also improved its performance up to the efficiencies of 93%, while the availability of new

material for the constructions of centrifugal pumps has lead to the expansion of its applicability.

All centrifugal pumps use an impeller and volute to create the partial vacuum and discharge

pressure necessary to move water through the casing. The impeller and volute form the heart of

the pump and help determine its flow, pressure and solid handling capability. An impeller is a

rotating disk with a set of vanes coupled to the engine/motor shaft that produces centrifugal

force within the pump casing. A volute is the stationary housing (in which the impeller rotates)

that collects, discharges and recirculates water entering the pump. A diffuser is used on high

pressure pumps and is similar to a volute but more compact in design.

A centrifugal pump is a kinetic device. Liquid entering the pump receives kinetic energy from the

rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity,

transferring mechanical (rotational) energy to the liquid. That kinetic energy is available to the

fluid to accomplish work. In most cases, the work consists of the liquid moving at some velocity

through a system by overcoming resistance to flow due to friction from pipes, and physical

restrictions from valves, heat exchangers and other in-line devices, as well as elevation

changes between the liquid's starting location and final destination. When velocity is reduced

due to resistance encountered in the system, pressure (P) increases. As resistance is

encountered, the liquid expends some its energy in the form of heat, noise, and vibration in

overcoming that resistance. The result is that the available energy in the liquid decreases as the

distance from the pump increases. The actual energy available for work at any point in a system

is a combination of the available velocity and pressure energy at that point.

Both of the graphs below showed the typical performance curve for centrifugal pump.

The head of a pump in metric units can be expressed in metric units as:

h = (p2 - p1)/(ρ  g) + v22/(2 g)

where:

h = total head developed (m) 

p2 = pressure at outlet (N/m2)

p1 = pressure at inlet (N/m2)

ρ = density (kg/m3)

g = acceleration of gravity (9.81 m/s2)

v2 = velocity at the outlet (m/s)

On the other hand, the pump efficiency, η (%) is a measure of the efficiency with which the

pump transfers useful work to the fluid, given by the equation:

η = Pin/Pout

where:

η = efficiency (%)

Pin  = power input

Pout = power output

PROCEDURES

a) The pump speed of the centrifugal pump test set was settled at 50% of the motor’s

capability.

b) Step (a) above is repeated using the 75% and 100% motor speed usage.

c) Suction valve is opened and the maximum values are noted.

d) Suction valve is then closed to indicate the minimum values.

e) An average of 9 units between the maximum and minimum values of the discharge

pressure was taken into consideration.

f) The values of torque, height of water, and inlet pressure are recorded.

g) All the data are recorded as accurately as possible.

RESULT

SAMPLE OF CALCULATION

Shaft power =

Converting kW to hp

kW hp

745.7 W = 1 hp

Converting Volume flow rate, L/min to m 3 /s

Converting mH2O to N/m 2

101325 Pa = 10.3323 mH2O

1 mH2O = 101325/10.3323 N/m2

= 9806.626 N/m2

Head

P1 = 980.266 N/m2

1 psi = 6894.757Pa (N/m2)

Therefore, P2 = 8 psi x 6894.757

= 55158.08 N/m2

h= (P2 - P1)

ρg

h1=55158.08- (980.6626)

1000 x 9.81

=5.5227 m

Break Horsepower

Break horsepower, bhp1 = T x N1

5252

= 0.4 x 1436

5252

= 0.109

Efficiency

η = Pf / Wshaft

= ρgQh / TN

η1

= 5.99 %

DISCUSSION

&

CONCLUSION

FATHASYA NURUL AISHAH BINTI IZANY

2009420372

DISCUSSION

Test 1 of the experiment was made using 50% of the total of the motor’s capability. On this

particular speed usage, the pump speed (N) is recorded at 1439 rpm while the angular velocity

(ω) is recorded at 150.71 rad/s. In Test 1, there were 8 different readings being taken, ranging

from the lowest water height, which is 6 mm, to the highest water height, which is 75 mm. At the

minimum water height of 6 mm, the data shows that on this level, the shaft power is recorded at

the lowest, which registered at 0.06 kW or 0.0808 Hp. The volume flow rate is also recorded at

its lowest, which is 4 l/min or 6.67E-05 m3/s. However, the water head (h) is recorded at its

highest among any other level, which is at 5.5227 m, while the output power is recorded at the

lowest, which is 3.61 Watt. At the maximum water weight of the pump, which is established at

75 mm, most of data recorded shows the highest value compared to any other point. The shaft

power is recorded at 0.18 kW or 0.2425 Hp, and the volume flow rate is recorded at 132 l/min or

2.20E-03 m3/s. The output power recorded at this water height was not at its highest, which

recorded at 25.96 Watt, while the water head (h) is recorded at its lowest, which is 1.2027 m.

The highest recorded data for the output power is recorded at the height of 65 mm, in which the

output power is recorded at 53.77 Watt. The highest efficiency for the pump is recorded at the

height of 55 mm which is at 40.03% efficiency, while the lowest efficiency is recorded at the

height of 6 mm, which reads at 5.99% efficiency.

In contrast, Test 2 of the experiment was completed by setting the motor’s capability at only

75% from the total speed. The pump speed (N) is recorded at 2178 rpm while the angular

velocity (ω) is recorded at 228.11 rad/s. For Test 2, 11 different readings were taken, ranging

from the lowest water height, which is 20 mm, to the highest water height, which is 91 mm. At

the water height of 20 mm, the shaft power is recorded at its lowest which is 0.23 kW or 0.3059

Hp. The same characteristic is shown for the volume flow rate, which is recorded at its lowest at

11 l/min or 0.0002 m3/s. The water head (h), on the contrary, is registered at its highest which is

at 12.6509 m. The output power for this particular water height is also recorded at its lowest,

which is at 22.75 Watt. For the water height of 91 mm, which is the maximum, the shaft power is

recorded at its highest, which is at 0.64 kW or 0.8565 Hp, while the volume flow rate is also

recorded at its highest of 210 l/min or 0.0035 m3/s. The water head (h) is recorded at its lowest,

which is 3.8079 m, while the output power is recorded at 130.74 Watt. The highest value for the

output power for Test 2 is recorded at the water height of 80 mm, which read at 235.99 Watt.

The highest efficiency is at the water of 80 mm with 43.11% while the lowest efficiency is

recorded at the water height or 20 mm with 9.97%.

For Test 3, the centrifugal pump is left to run at its highest capability, which is at 100%. The

pump speed (N) is recorded at 2945 rpm while the angular velocity (ω) is recorded at 308.44

rad/s. For this test, there were 8 different readings being taken, ranging from the lowest water

height, which is 10 mm, to the highest water height, which is 101 mm. The water height of 10

mm, which is the lowest water height, has shown the lowest value for three data, which are the

shaft power at 0.49 kW or 0.6618 Hp, the volume flow rate at 5 l/min or 8.33E-05 m3/s, and the

output power at 19.37 Watt. However, the highest water head (h) for this particular water height

is recorded at its highest, which is at 23.6963 m. For the maximum water height of 101 mm,

most of the data has shown the highest value compared to any other water height level. The

shaft power at this level is recorded at 1.45 kW or 1.9440 Hp which is the highest, while the

volume flow rate is also recorded at its height, registered at 275 l/min or 4.58E-03 m 3/s. The

water head (h) is recorded at its lowest, which is 6.6131 m, while the output power is recorded

at 297.34 Watt. The highest output power is recorded at the height of 91 mm, which is recorded

at 585.81 Watt. The pump shows the highest efficiency at the height of 82 mm with 48.06%

efficiency, while illustrated the lowest efficiency at the height of 10 mm with 3.93% efficiency.

CONCLUSION

We can securely concluded that we have achieved this experiment’s objectives in obtaining the

performance characteristics for a variable speed centrifugal pump operating at 3 different

impeller speeds, which is at 50%, 75%, and 100%, with the performance characteristics of the

pump is being defined by the pressure (head) pump, power requirement, flow rate influence,

and the pump speed influence. All the tests have shown that the level of water height of the

pump has influences with the shaft power, volume flow rate, water head, output power, and the

pump’s efficiencies. When the water height is recorded at its lowest, the same attribute is shown

by the shaft power and volume flow rate. The same, however, cannot be linked with the water

head, as it will shows the highest water head (h) for the lowest water height, and vice versa. The

value for the output power and efficiency, on the hand, does not have a direct trait with the

water height level in the pump.

NUR FARIS BIN AHMAD

2008400918

DISCUSSION

From this experiment, we have to obtain a performance characteristic for a variable

speed centrifugal pump operating at 3 different impeller speeds. This characteristic including

pressure, power required, flow rate and pump speed. All the required data had been collected

and calculated in order to produce a performance curve. A y-axis had represented efficiency,

shaft power and water head versus the flow rate at the x-axis. The pump speed operated at

1436, 2178 and 2945 (rpm).

For the first performance curve with pump speed at 1436 rpm, a shaft power curve was

increase due to the decreasing of shaft power. The efficiency was increase linearly after 5 value

of flow rate before its decrease to the end. At 2178 rpm of speed, water head curve is slightly

different because at first 5 reading, it just increasing before its decreasing again. Refer to the

efficiency curve, it shows same as the water head curve. Furthermore, at the 2945 rpm of

speed, the shaft power curve is slightly different than other because at the last 2 reading, it just

same. However we can say that all curves showed same characteristic between them.

This showed that the pump head is inversely proportional to the shaft power. By

comparing maximum efficiency for each performance curve, the highest maximum efficiency

occurs at the highest speed of pump. Not only that both head pump and shaft power also

showed same characteristic at the different speed.

There are some errors occur during experiment. The reading taken was by analog meter

so it’s less accurate. The water height reading taken at a short time without wait till it’s static. As

a precaution, the reading taken must at 2 or 3 decimal place although it was take from analog

meter. Other the water height must wait till it’s static before took the reading.

CONCLUSION

As a conclusion, we had obtained a performance curve at 3 different speed of pump by a

variable characteristic. The efficiency of pump have related to the losses mean energy during

the process. This efficiency will be increase if less loss occurs.

MUHAMMAD NAZREEN BIN ZULKARNAIN

2008400848

DISCUSSION

In this experiment, there are three tests were conducted on the centrifugal pump. For the

first test, the pump speed was set at 1439 rpm. As for the second and third test, the pump

speed was set to be at 2178 rpm and 2945 rpm respectively.

From the graph, it was found that the curve for shaft power for all three tests increase

slightly with the increase of the volume flow rate. For the three tests, the water head curve

decrease slightly for the first 50% of the volume flow rate. However, the curve decreases rapidly

for the next 50% of the volume flow rate. The efficiency curve shows a significant increase.

However, at a certain point, the curve starts to decrease.

Based on the graph, we can see that the highest efficiency for Test 1, 2 and 3 are

40.03%, 43.11% and 48.06% respectively.

From our data and calculation, the efficiency of the centrifugal pump is barely exceeds

50%. This pump is inefficient may due to the losses at the blades and also in the pipe. The

losses in the pipe are caused by friction between the walls of the pipe. As a result, the output

power obtain is less than the input power.

In order to increase the efficiency of the pump, we may decrease the friction in the pipe

by selecting the right material to use for the pipe which has less friction between the fluids and

the surface of the pipe. Besides that, the blade of the pump should also be check to make sure

that the blade is in good condition so that there will not be any losses due to the blade of the

pump.

CONCLUSION

From the experiment, we can conclude that the best performance of this centrifugal pump to

operate is at speed N3 = 2945 rpm and flow rate, Q between the range of 0 to 163

(liter/minutes). The characteristics of the pump can be obtained by using a different speed of

pump, and thus the objective of this experiment is achieved. Therefore it can be acceptable in

order to define any centrifugal pump characteristics.

WAN ZULHAZRI BIN WAN

ZULKIFLI

2008400614

DISCUSSION

CONCLUSION

REFERENCES

a) Joe Evans, A Brief Introduction to Centrifugal Pumps, Pacific Liquid & Air Systems,

Hawaii, available on: www.pacificliquid.com/pumpintro.pdf (visited on 1st August 2010)

b) Anon, Pump Training, Sykes Innovative Solutions, Australia, available on:

www.rainforrent.com/Training/PumpTraining.pdf (visited on 1st August 2010).

c) Mukesh Sahdev, Centrifugal Pumps: Basics Concepts of Operation, Maintenance, and

Troubleshooting, Part I, available on www.idcon.com/pdf-doc/centrifugalpumps.pdf

(visited on 1st August 2010).

d) An introduction to Centrifugal Pumps, available on:

http://www.engineeringtoolbox.com/centrifugal-pumps-d_54.html (visited on 1st August

2010)

e) Selection criteria for centrifugal pumps and installation layouts, available on:

http://www.savinobarbera.com/english/scelta-pompe.html (visited on 1st August 2010).

f) Centrifugal pump designs, available on:

http://www.pumps-in-stock.com/centrifugal_pump_designs.html (visited on 1st August

2010).

APPENDIX