Hmmm? We see slip in real world operation, but I have never found any equations for calculating theoretical slip. The only equations that I have ever seen for slip where empirical equations based on pump testing for a specific pump model.
Slip is the loss of capacity, expressed as a fraction or percentage of displacement, due to back-flow caused by delayed closing and leaks through the drive side of the pump (it does not however include fluid compressibility or leaks through the discharge of the pump)
IT is primarily due to the space created by the pump clearances. Some factors that increase slip are the presence of suspended solids in the pumping fluid and the discharge pressure of the application. One factors that can decrease slip is fluid viscosity.
Good luck. If you find a good way to model theoretical slip I will be interested in learning how this is done too.
The following is available on-line at Available on-line,
Slip & Efficiency
A major effect on positive displacement pump performance is the loss in flow due to slip. The expanding cavity on the inlet side of a positive displacement pump creates a low pressure area that asks to be filled with fluid. This cavity can be filled with fluid from the inlet line in normal performance. However, if slip occurs, the cavity will also be partly filled with fluid flowing back through the pump clearances from the outlet side.
Pump performance is dependent on the slip which occurs in a pump.
a) Slip Increases Directly with Pressure
b) Slip Increases Directly with Clearance
c) Slip Increases Inversely with Viscosity
