Define coefficient of discharge, volumetric efficiency and slip in reciprocating pump. Describe negative slip with proper reason.
1 Answer

1. Coefficient of Discharge ($C_d$):It is defined as the ratio between the theoretical discharge $(Q_{th})$ and the actual rate of discharge $(Q_{act})$.

$\hspace{5cm}C_d = \frac{Q_{th}}{Q_{act}}$

2.Volumetric efficiency: Volumetric efficiency is defined as the percentage of theoretical pump flow available to do useful work. It is the measure of a pump’s volumetric losses through internal leakages.

3.Slip: It is defined as the difference between the theoretical discharge and the actual discharge of the pump.

$\hspace{5cm}S = Q_{th} - Q_{act}$

Negative slip: When $Q_{act} \gt Q_{th}$, the slip of the pump becomes negative.

This phenomenon occurs when the length of the suction pipe is long and the discharge pipe is short and the pump is running at at a very high speed.

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