# 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)
Related
$\Delta \theta_c$
$\Delta \theta_d$
$\Delta \theta_{sun}$
$T_{4iii}$
$T_{sa}$
$\theta_{air}$
$\theta_{at}$
$\theta_{de}$
$W_t$
$W_{tot}$
Used in
$\alpha_{sa}$
$\alpha_{st}$
$T_{4iii}$
$\theta_e$
$W_{de}$