Power Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Power number is a dimensionless number proportional to drag force and inertial force and is used in momentum transfer and power consumption by fans, mixers and pump impellers at a specified rotational speed.


\(N_p = \frac {k_dP}  {N^3\rho l^5} \)


\(N_p\) = Power number

\(k_d\) =  dimensional constant

\(P\) = power

\(N\) = rate of rotation

\(\rho\) (Greek symbol rho) = density

\(l\) = characteristic length


Tags: Equations for Power