It refers to the ratio of the pump effective power to the shaft power, η=Pe/P.
The power usually refers to the input power, that is, the power transmitted from the prime mover to the pump shaft, so it is also called shaft power, expressed by P.
The effective power is: the multiply of the pump's head, mass flow, and gravitational acceleration.
Pe=ρg QH (W) or Pe=γQH/1000 (KW)
ρ:The density of the liquid delivered by the pump (kg/m3)
γ:The weight of the liquid delivered by the pump, γ=ρg (N/m3)
g:acceleration of gravity (m/s)
Mass flow Qm=ρQ (t/h or kg/s)
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