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Centrifugal pump minimum required flow

What is the minimum flow of a pump ?

Why a recirculation is important and why to ensure a minimal flow ?

How to calculate the required minimum flow of a pump ?

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Section summary
1. What is a minimum flow for a pump
2. How to calculate a centrifugal pump minimal flow

1. What is the minimum flow for a pump ?

Due to the rotation of the impeller, energy is transferred to the fluid in a centrifugal pump. Part of this energy is actually dissipated in heat. If the flow through the pump is too low, the fluid temperature may increase and reach the saturation temperature at the pressure within the pump, leading to cavitation and damages of the pump. It is therefore necessary to ensure a minimal flow through a centrifugal pump. This minimum flow can be done thanks to a recirculation.

2. How to calculate a centrifugal pump minimal flow ?

The minimum flow to ensure with a centrifugal pump can be calculated the following way :

q = Cp.P.sg / 2.95

With :
q = Minimum flow rate through the pump in m3/s
P = Pump power in W
Cp = Liquid specific heat capacity in J/kg/K
sg = Liquid specific gravity

Note : this gives an estimation of the minimal flow to avoid cavitation, however even with this flow, other kind of damages can happen to a pump if run long time in these conditions (bearing, impeller...), it is therefore recommended to check the value calculated with the pump manufacturer.