# Pump efficiency is defined as the ratio of

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Pump efficiency is defined as the ratio of
1. Pressure to temperature
2. Temperature to pressure
3. Water horsepower to pump horsepower
4. Pump horsepower to water horsepower

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Correct Answer - Option 3 : Water horsepower to pump horsepower

Pump efficiency: Pump efficiency is defined as the ratio of water horsepower output from the pump to the shaft horsepower input for the pump.

Water horsepower is determined by the flow rate and pressure delivered from the pump.

The shaft horsepower is delivered to the pump from the power unit, which usually is an electric motor or internal combustion engine.

Determining Pump Efficiency:

Water horsepower can be calculated by using this formula:

WHP = HQ/3960

Where H is the total head of the water in feet and Q is the flow rate in gallons per minute.

Pump input horsepower is determined by measuring the speed and torque of the motor shaft input to the pump.

Important Points:

The following are the important efficiencies of a centrifugal pump:

1. Manometric Efficiency (ηman): It is the ratio of the manometric head to head imparted by the impeller to the water.

${\eta _{man}} = \frac{{{H_m}}}{{\frac{{{V_{w2}}{u_2}}}{g}}} = \frac{{g{H_m}}}{{{V_{w2}}{u_2}}}$

1. Mechanical Efficiency (ηm): It is the ratio of the power available at the impeller to the power at the shaft of the centrifugal pump.

${\eta _m} = \frac{{{\rm{Power\;at\;the\;impeller}}}}{{{\rm{Power\;at\;the\;shaft}}}} = \frac{{\frac{W}{g}\left( {\frac{{{V_{w2}}{u_2}}}{{1000}}} \right)}}{{{\rm{SP}}}}$

1. Overall Efficiency (ηo): It is defined as a ratio of the power output of the pump to the power input to the pump.

η= ηman × ηm