Pump efficiency

Pump Efficiency = (Power Input to pump shaft from driver)/ (Power output by pump to water)

BigInch-born in the trenches.

Isentropic efficency, This the how we generally calculate centrifugal pump work. You'll see the effiency curves from pump manufacturers and the major componet is this. They will sometimes have slip, mechanical and others thrown in somewhere. Values are 60% to 80%.

The volumetric effiency is used to describe the efficency of postive displacement pumps. PD pumps are almost 100% efficent, but because they have gaps between the piston and the cylinder walls (on the end and where the suction discharge valves are), they are rated in volumetric effenciency. This really means you put work into the liquid to raise the pressure, but the liquid cannot get out of the cylinder and the work is lost. Yes, you can get some temperature increase on the fluid as it is pumped, just like a gas because that lost work has to go somewhere. Volumetric effiency will be different for different fluids. Water will be 100% volumetric efficent times the pump rated volumetric efficency, whereas propane will be 95% times the pump rated VE, its a compressibility thing, its not a perfect fluid.

ok, thanks for the answers, but neither one answered my question. I'm not talking about centrifugal pumps, I'm talking about positive displacement pumps. Volumetric efficiency is one kind of efficiency, now simply, what is the other type of efficiency?

And, in my experience, PD pumps have higher efficiencies than centifugal, but I wouldn't say they are almost 100%, they usually run about 85%

get out the mollier diagram. pumps pump along the entropy line. If they don't follow that line, the energy required to raise the pressure goes into heat. with PD pumps the s lines in the liquid phase are verticle and and the amount of entropy change is next to nothing, you can not lose very much energy to heat. So, PD pumps have a very high thermodynamic effiency, over 95%. The losses in energy are mechanical, the VE is the govenering efficency.

thank you, that's more along the lines of what i was looking for

In addition to what pipehead said go


may be it helps…


luis marques