# Nusselt Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Nusselt number, abbreviated as Nu, is a dimensionless number that describes the ratio of convective heat transfer to conductive heat across a boundary.

### Nusselt number Formula

$$\large{ Nu=\frac{h \; l_c}{k} }$$

Where:

$$\large{ Nu }$$ = Nusselt number

$$\large{ l_c }$$ = characteristic length

$$\large{ h }$$ = heat transfer coefficient

$$\large{ k }$$ = thermal conductivity