The following design and operating data were taken for a largeindustrial centrifugal water pump:
| Parameter | Design | Operating |
| Flow Q (m^3/h) | 800 | 550 |
| Head H (m) | 55 | 24 (after delivery valve) |
| Power P (kW) | 160 | 124 |
| RPM | 1485 | 1485 |
Required water flow rate varies from 500 m3/h to 700 m3/h. Forthe pump to deliver 550 m3/h, the flowrate has been reduced bypartially closing the delivery valve. Motor efficiency is 93%.
a. Calculate the pump operating efficiency (the ratio of pumpingpower to operating pump input power delivered TO THE MOTOR.
b. Pump operating efficiency is low because of the partial valveclosing to control the flowrate. What would be the best way toimprove pump operating efficiency?
c. The ratio of two pump volumetric flowrates would be equal tothe ratio of two pump shaft speeds to what power? The ratio of twopump operating heads would be equal to the ratio of two pump shaftspeeds to what power? The ratio of two pump operating powers wouldbe equal to the ratio of two pump shaft speeds to what power?
d. Suppose the pump energy improvement idea suggested in part b.was used for the pump. From the relations in part c., calculate thepump speed required to give a volumetric flowrate 550 m3/h. Thatis, (550 m3/h / design flowrate) = (RPM to deliver 550 m3/h /design RPM). From this, calculate the pumping power needed todeliver 550 m3/h using the design pumping power ratio. Thedifference in the operating values of the pumping power (124 kW andthe pumping power with the new energy efficiency feature) is theenergy savings.
