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Question: Why does the efficiency of reciprocating pump increases as pressure gauge value increases?

(Posted by: Venkatesh R on 2008-12-25 20:05:47)

Posted by: wingstwo on 2008-12-25, 20:52:57

It doesn't necessarily. Look up some pump curves: google pump manufacturer to find some. Efficiency curves are basically concave down parabolas (arc's). The peak is in the middle at the design pressure, and the efficiency drops at either high or low pressure. For basically any pump, at no pressure, high flow, efficiency is low because power is consumed but little energy out, as energy out = Pressure * Flow. At high pressure, no flow, also about zero efficiency. Somewhere in the middle is the design point, with the max efficiency.

Posted by: frediwhite@verizon.net on 2008-12-25, 21:26:46

Say, '...does...increase' not 'does increases'.

Posted by: Маи beHiиd т�e мasК on 2008-12-25, 21:58:49

It depends on lot of factors like pressure ratio , cooling media , lubrication etc. The main reason of efficiency increase is that the additional work required for additional enhancement in pressure ratio reduces however the efficiency gain after a particular point is negligible and the size starts increasing tremendously so there is a limitation to volumetric efficiency! so, i would say that at full load the efficiency is highest and at part loads the power saved by motor is not as per the reduced pressure ratio and hence it is less efficient. However a statement like increase in pressure ratio will increase efficiency is restricted by the termendous increase in size of the cylinder with negligible efficiency gain , rather it is tried to improve the efficiency by cooling etc. The rated point is the total best efficiency point including pump and motor !