My watch list
my.chemeurope.com

Lewis number

Lewis number is a dimensionless number defined as the ratio of thermal diffusivity to mass diffusivity. It is used to characterize fluid flows where there is simultaneous heat and mass transfer by convection.

It is defined as:

$\mathit{Le} = \frac{\alpha}{\mathit{D}}$

where α is the thermal diffusivity and D is the mass diffusivity.

The Lewis number can also be expressed in terms of the Schmidt number and the Prandtl number :

$\mathit{Le} = \frac{\mathit{Sc}}{\mathit{Pr}}$.