Fan Efficiency

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Fan efficiency, abbreviated as $$\eta_f$$ (Greek symbol eta), a dimensionless number, is the ratio of input and output power.

Fan Efficiency formula

 $$\large{ \eta_f = \frac{ P_{out} }{ P_{in} } }$$

Where:

$$\large{ \eta_f }$$  (Greek symbol eta) = fan efficiency

$$\large{ P_{in} }$$ = input power (watt)

$$\large{ P_{out} }$$ = output power output (watt)

$$\large{ I }$$ = current

$$\large{ V }$$ = volt

$$\large{ p }$$ = air pressure ($$inch\; H_2 O$$)

$$\large{ Q }$$ = air flow (cfm)

Solve for:

$$\large{ P_{in} = V \; I }$$

$$\large{ P_{out} = \frac{ p \; Q }{ 8.5 } }$$