# 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:

 Units English Metric $$\large{ \eta_f }$$  (Greek symbol eta) = fan efficiency $$\large{ dimensionless }$$ $$\large{ P_{in} }$$ = input power (watt) $$\large{ W }$$ $$\large{ W }$$ $$\large{ P_{out} }$$ = output power output (watt) $$\large{ W }$$ $$\large{ W }$$ $$\large{ I }$$ = current $$\large{ I }$$ $$\large{ I }$$ $$\large{ V }$$ = volt $$\large{ V }$$ $$\large{ V }$$ $$\large{ p }$$ = air pressure ($$inch\; H_2 O$$) $$\large{ \frac{lbf}{in^2} }$$ $$\large{ Pa }$$ $$\large{ Q }$$ = air flow (cfm) $$\large{ \frac{ft^3}{min} }$$ $$\large{ \frac{m^3}{min} }$$

### Solve for:

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

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

Tags: Efficiency Equations