# Nusselt number

Nusselt number is dimensionless number which is useful for convective heat transfer calculations. heat transfer can be expressed in terms of Nusselt number. It can be defined as follows:

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

Where

$Nu = \mbox{Nusselt number}$
$h = \mbox{Convection heat-transfer coefficient (constant of proportionality ) (W/m2 K)}$
$l = \mbox{Characteristic dimension of th esolid object (m)}$
$k = \mbox{Thermal conductivity of the solid (W/m k)}$