# Radiation heat transfer surface-air

Radiation heat transfer from outer surface to ambient air.

Symbol
$W_{rad_{sa}}$
Unit
W/m
Formulae
 $D_{o} K_{r} \pi \sigma \left(- \left(\theta_{a} + 273\right)^{4} + \left(\theta_{e} + 273\right)^{4}\right)$ surface to air, by Stefan–Boltzmann law $D_{o} h_{rad_{sa}} \pi \left(- \theta_{a} + \theta_{e}\right)$ surface to air, using heat transfer coefficient
Related
$D_{o}$
$\sigma$
$\theta_{a}$
Ambient temperature [$^{\circ}$C]
$\theta_{e}$
Used in
$T_{4iii}$
$T_{rad_{sa}}$