# Nusselt Number

Written by Jerry Ratzlaff. Posted in Dimensionless Numbers

Nusselt Number is a dimensionless number ratio of convective heat transfer to conductive heat across a boundary.

## FORMULA

$$Nu=\frac{h l}{k}$$

Where:

$$Nu$$ = Nusselt Number

$$h$$ = heat transfer coefficient

$$l$$ = characteristic length

$$k$$ = thermal conductivity

Solve for:

$$h=\frac{ Nu k }{ l }$$

$$l=\frac{ Nu k }{ h }$$

$$k=\frac{ h l }{ Nu }$$