Radiation heat transfer from outer tube wall to ambient air.

Symbol
$W_{rad_{ext}}$
Unit
W/m
Formulae
 $D_{o} K_{r} \pi \sigma \left(- \left(\theta_{air} + 273\right)^{4} + \left(\theta_{do} + 273\right)^{4}\right)$ surface to air, by Stefan–Boltzmann law $D_{o} h_{rad ext} \pi \left(- \theta_{air} + \theta_{do}\right)$ surface to air, using heat transfer coefficient
Related
$D_{o}$
$\sigma$
$\theta_{air}$
Used in
$T_{rad_{ext}}$