Temperature difference surface to ambient

Difference between the surface temperature of a cable or duct in air and the ambient temperature.

This equation is solved by iteration with an initial value for $\Delta\theta_s$ of 16°C.

Symbol
$\Delta \theta_s$
Unit
K
Formulae
$\frac{\Delta \theta_s+T_{4iii} n_{cc} W_t+\Delta \theta_{sun}}{2}$cables in air
$\frac{\Delta \theta_c+\Delta \theta_d}{1+K_A {\Delta \theta_s}^{0.25}}$cables in air-filled trough
$\theta_{de}-T_{sa} n_{cc} W_t$cables in channel (Heinhold)
$\theta_{de}-\theta_{air}$cables in riser/J-tube
$\theta_{de}-\theta_{at}$heat source in air-filled trough
$\frac{\Delta \theta_s+T_{4iii} W_{tot}+\Delta \theta_{sun}}{2}$PAC/GIL in air
$\frac{\Delta \theta_c}{1+K_A {\Delta \theta_s}^{0.25}}$PAC/GIL in air-filled trough
$\theta_{de}-T_{sa} n_{cc} W_{tot}$PAC/GIL in channel (Heinhold)