centrifugal pump

At 100% efficiency, the power required for any fluid mover is the rise in pressure multiplied by the volumetric flowrate.

....multiplied by the density!

You may calculate using following equation :

Power in Watt = (9810 x flow in m³/sec x Total head in MWC) / (% efficiency)

Look at the pump curve for your particular pump.

Check out the details from a manufacturer. Here's a link to Grundfos On-line product catalogue

http://net.grundfos.com/Appl/WebCAPS/custom?userid=GPU

Every pump will have specific characteristics depending on the motor size, impellor design and the speed that the motor is running at, as well as the overall effeciency of the total product.

Follow the link above and click on 'Sizing/selection' , chose the application (heating, pressure boosting, etc) and then just type in the required pressure and flow (don't worry about all the other options, just click 'Start Sizing' in the bottom right corner). Then you can look at the differnt pump curves and see what power the pumps will use.

Its the only way to be sure, as each pump will require different power even to do the same thing.

Rejiraj

Power=flow*specific gravity*differential head*g/Efficiency. (kW)

Flow in m^3/s

g=9,81

head in m.

The only thing you do not know is the efficiency unless you have the manufacturer's test curve. If this is not available then a rough estimate can be made from the diagram below. (Note that it is in USA gallons, feet etc) This is care of Lobanoff and Ross, but similar can be found in any good pump book.