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Radiation heat transfer surface—air

Radiation heat transfer from outer surface to ambient air.

Symbol
$W_{rad,sa}$
Unit
W/m
Formulas
$\sigma \pi D_{o} K_{r} \left(\left(\theta_{e}+\theta_{abs}\right)^4-\left(\theta_{film}+\theta_{abs}\right)^4\right)$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
$D_{o}$
Outer diameter [m]
$h_{rad,sa}$
Heat transfer coefficient radiation surface—air [W/(K.m$^2$)]
$K_{r}$
Radiation shape factor
$\pi$
Archimedes' constant $\pi$
$\sigma$
Stefan Boltzmann constant [W/m$^2$K$^4$]
$\theta_{abs}$
Absolute temperature [K]
$\theta_{e}$
External temperature object [°C]
$\theta_{film}$
Film temperature [°C]
Used in
$T_{4iii}$
Thermal resistance ambient [K.m/W]
$T_{rad,sa}$
Thermal resistance radiation surface—air [K.m/W]