# Radiation heat transfer surface-tube

Radiation heat transfer from surface to tube inner wall.

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