Fan Affinity Laws
Affinity laws can be used to calculate volume capacity, head or power consumption - when speed or rpm, and wheel diameters are changed.
Volume Capacity
The volume capacity of a centrifugal fan can be expressed as:
q1/q2 = (n1/n2)x(d1/d2)3
where,
q = volume flow capacity (m3/s, gpm, cfm, etc.)
n = wheel velocity - revolution per minute - (rpm)
d = wheel diameter
Head or Pressure
The head or pressure of a centrifugal fan can be expressed like
dp1/dp2 = (n1/n2)2x(d1/d2)2
where,
dp = head or pressure (m, ft, Pa, psi, etc.)
n = wheel velocity - revolution per minute - (rpm)
d = wheel diameter
Power
The power consumption of a centrifugal fan can be expressed as
P1/P2 = (n1/n2)3x(d1/d2)5
where,
P = power (W, bhp, etc.)
n = wheel velocity - revolution per minute - (rpm)
d = wheel diameter
