Radiation shape factor from object surface to ambient tunnel or free air considering the view factor for one system and for concentric cylindrical annuli (cable to duct) such as in a riser/J-tube.
$\frac{1-F_m}{1-F_m \left(1-K_t\right)}$ | in tunnel or free air |
$\frac{1}{1+\frac{1-\epsilon_e}{\epsilon_e}+\frac{A_{er} \left(1-\epsilon_{di}\right)}{A_{di} \epsilon_{di}}}$ | riser/J-tube single cable |
$\frac{1}{1+\frac{\eta_e}{\epsilon_e}+\frac{\zeta_{er} A_{er} \eta_{di}}{A_{di} \epsilon_{di}}}$ | riser/J-tube touching cables |