# Radiation heat transfer, surface to air

Radiation heat transfer from outer surface to ambient air.

Symbol
$W_{rad,sa}$
Unit
W/m
Formulae
 $\sigma \pi D_o K_r \left(\left(\theta_e+\theta_{abs}\right)^4-\left(\theta_{film}+\theta_{abs}\right)^4\right)$ surface to air, by Stefan–Boltzmann law $\pi D_o h_{rad,sa} \left(\theta_e-\theta_{film}\right)$ surface to air, using heat transfer coefficient
Related
$D_o$
$\sigma$
$\theta_{abs}$
$\theta_e$
$\theta_{film}$
Used in
$T_{4iii}$
$T_{rad,sa}$