# Prandtl number for liquids

The Prandtl number is a dimensionless number, defined as the ratio of kinematic viscosity (also called momentum diffusivity) to thermal diffusivity.

Symbol
$\mathrm{Pr}_w$
Formulae
$\frac{c_{p,w} \eta_w}{k_w}$
Related
$c_{p,w}$
$\eta_w$
Used in