A centrifugal pump has an efficiency of 80 percent at its design-point specific speed of 2000 (units of rpm, gpm, and feet). The impeller diameter is 8 in. At design-point flow conditions, the volume flow rate is 300 gpm of water at 1170 rpm. To obtain a higher flow rate, the pump is to be fitted with a 1750 rpm motor. Use the pump “laws” to find the design-point performance characteristics of the pump at the higher speed. Show that the specific speed remains constant for the higher operating speed.

Determine the motor size required.