Thermal resistance of armour bedding

Thermal resistance of the bedding between sheath and armour consists of the bedding between the sheath and the first armour layer plus the separation material between the first and second armour layer if any. In case of three-core cables with jacket around each core, this is the thermal resistance of the filler between sheath and armour for three-core cables type SS with sheath. This includes the thermal resistance of the jacket around each core and of the armour bedding.

The thermal resistance of the gas or oil between the surface of the cores and the pipe is calculated in the same way as that part of $T_{4i}$ which is between a cable and the internal surface of a duct.

$\frac{\rho_{ab}}{2\pi} \ln\left(1+\frac{2t_2}{D_{sh}-\Delta d_{sh}}\right)$Single-core cables or multi-core cables with common sheath
$\frac{\rho_f}{6\pi} G_2$Three-core cables type SS with sheath
$\frac{U_{spf}}{1+0.1\left(V_{spf}+Y_{spf} \theta_{spf}\right) D_{eq}}$Pipe-type cables