Radiation coefficient mutual

Radiation view factor coefficient for radiation thermal resistance calculation within a cable system.

Symbol
$F_{m}$
Formulae
$0$1 cable
$\frac{\sqrt{-1 + \frac{s_{air}^{2}}{D_{o}^{2}}} + \arcsin{\left(\frac{D_{o}}{s_{air}} \right)} - \frac{s_{air}}{D_{o}}}{\pi}$2 cables
$\frac{2 \left(\sqrt{-1 + \frac{s_{air}^{2}}{D_{o}^{2}}} + \arcsin{\left(\frac{D_{o}}{s_{air}} \right)} - \frac{s_{air}}{D_{o}}\right)}{\pi}$3 cables (middle)
$\frac{\sqrt{-1 + \frac{s_{air}^{2}}{D_{o}^{2}}} + \arcsin{\left(\frac{D_{o}}{s_{air}} \right)} - \frac{s_{air}}{D_{o}}}{\pi}$3 cables (outer)
$0.166666666666667 + \frac{\frac{\pi}{2} - 1}{\pi}$3 cables touching trefoil
Related
$D_{o}$
Choices
Example installationValue
1 cable0
2 cables touching0.182
2 cables spaced 2*D0.081
2 cables spaced 3*D0.054
3 cables touching0.363 (middle cable)
0.182 (outer cables)
3 cables spaced 2*D0.163 (middle cable)
0.081 (outer cables)
3 cables spaced 3*D0.107 (middle cable)
0.054 (outer cables)
3 cables touching trefoil0.348