# 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$^{\circ}$C.

Symbol
$\Delta \theta_{s}$
Unit
K
Formulae
 $\frac{\Delta \theta_{s}}{2} + \frac{\Delta \theta_{sun}}{2} + \frac{T_{4iii} W_{t} n_{cc}}{2}$ cables in air $\frac{\Delta \theta_{c} + \Delta \theta_{d}}{\Delta \theta_{s}^{0.25} K_{A} + 1}$ cables in trough $\frac{\Delta \theta_{s}}{2} + \frac{\Delta \theta_{sun}}{2} + \frac{T_{4iii} W_{tot}}{2}$ GIL in air (not used directly) $- T_{sa} W_{t} n_{cc} + \theta_{de}$ cables in channel $- \theta_{air} + \theta_{tube}$ cables in j-tube
Related
$\Delta \theta_{c}$
$\Delta \theta_{d}$
$\Delta \theta_{sun}$
$T_{4iii}$
$T_{sa}$
$\theta_{air}$
$\theta_{de}$
$\theta_{tube}$
Temperature of tube [$^{\circ}$C]
$W_{t}$
$W_{tot}$
Used in
$\alpha_{sa}$
$T_{4iii}$
$\theta_{c}$
$\theta_{e}$
$W_{tube}$