Power Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Power Number

Power number ( \(N_p\) ) (dimensionless number) is 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.

Power Number FORMULA

\(N_p = \frac {k_dP}  {N^3\rho l^5} \)          \( Power \; number  \;=\; \frac { dimensional \; constant   \;\;x\;\;  power }  { rate \; of \; rotation^3\  \;\;x\;\;  density   \;\;x\;\;  characteristic \; length^5} \)


\(N_p\) = Power number

\(k_d\) =  dimensional constant

\(P\) = power

\(N\) = rate of rotation

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

\(l\) = characteristic length


Tags: Equations for Power