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

Symbol
$F_m$
Formulae
 $0$ 1 cable $\frac{1}{\pi} \left(\\arcsin\left(\frac{D_o}{s_{air}}\right)+\sqrt{\left(\frac{s_{air}}{D_o}\right)^2-1}-\frac{s_{air}}{D_o}\right)$ 2 cables $\frac{2}{\pi} \left(\\arcsin\left(\frac{D_o}{s_{air}}\right)+\sqrt{\left(\frac{s_{air}}{D_o}\right)^2-1}-\frac{s_{air}}{D_o}\right)$ 3 cables (middle) $\frac{1}{\pi} \left(\\arcsin\left(\frac{D_o}{s_{air}}\right)+\sqrt{\left(\frac{s_{air}}{D_o}\right)^2-1}-\frac{s_{air}}{D_o}\right)$ 3 cables (outer) $\frac{1}{6}+\frac{1}{\pi} \left(\frac{\pi}{2}-1\right)$ 3 cables touching trefoil
Related
$D_o$
$s_{air}$
Used in
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