Film temperature

 ( Fluid Dynamics ) 

In Thermal fluids, the film temperature () is an approximation of the temperature of a fluid inside a convection boundary layer. It is calculated as the arithmetic mean of the temperature at the surface of the solid boundary wall () and the free-stream temperature ():Incropera & DeWitt Fundamentals of Heat and Mass Transfer, 4th Ed

$T\_f=\backslash frac\{T\_w\; +\; T\_\backslash infty\}\{2\}$

The film temperature is often used as the temperature at which fluid properties are calculated when using the Prandtl number, Nusselt number, Reynolds number or Grashof number to calculate a heat transfer coefficient, because it is a reasonable first approximation to the temperature within the convection boundary layer.

Somewhat confusing terminology may be encountered in relation to and , where the same term is used to refer to the limit (hot) temperature of a fluid in contact with a hot surface. Film Temperature Bulk and Film Temperatures