Power number

For Newton number, see also Kissing number in the sphere packing problem.

For use in arithmetic and algebra, see Exponentiation.

The power number N_p (also known as Newton number) is a commonly used dimensionless number relating the resistance force to the inertia force.

The power-number has different specifications according to the field of application. E.g., for stirrers the power number is defined as:^[1]

${\displaystyle N_{\mathrm {p} }={\frac {P}{\rho n^{3}D^{5}}}}$

with

• P: power
• ρ: fluid density
• n: rotational speed in revolutions per second
• D: diameter of stirrer

References

1. Seinfeld, John H (1991). Wei, J; Anderson, J L; Bischoff, K B (eds.). Advances in Chemical Engineering. Academic Press. p. 44. ISBN 978-0-08-056564-4.