Fan Law used to express the relationship between variables involved in pump or fan performance (such as head, volumetric flow rate, shaft speed) and power. They apply to pumps, fans, and hydraulic turbines. In these rotary implements, the affinity laws apply both to centrifugal and axial flows.

Symbols

Q = Volumetric flow rate
SP = Static pressure
P = Shaft power
N = Rotational speed

Q1/Q2 = N1/N2
SP1/SP2 = (N1/N2)2
P1/P2 = (N1/N2)3


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