# 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.  The calculation and equation for determining the Nusselt number is below.

 $$\large{ Nu=\frac{h l_c}{k} }$$          Where: $$\large{ Nu }$$ = Nusselt number $$\large{ l_c }$$ = characteristic length $$\large{ h }$$ = heat transfer coefficient $$\large{ k }$$ = thermal conductivity

Solve for:

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

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

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