# Radiation heat transfer coefficient surface-air

Radiation heat transfer coefficient from surface of GIL to the surrounding air.

Symbol
$h_{rad_{sa}}$
Unit
W/(K.m$^2$)
Formulae
$4 K_{r} \sigma \left(\frac{\theta_{a}}{2} + \frac{\theta_{e}}{2} + 273\right)^{3}$
$\sigma$
$\theta_{a}$
Ambient temperature [$^{\circ}$C]
$\theta_{e}$
Used in
$W_{rad_{sa}}$