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

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