Thermal resistance between sheath and 1st armour layer

Thermal resistance of the bedding between sheath and armour.

Symbol
$T_{2_{1}}$
Unit
K.m/W
Formulae
$\frac{\rho_{ab} \ln{\left(1 + \frac{2 t_{2}}{D_{s}} \right)}}{2 \pi}$general case
$\frac{G_{2} \rho_{f}}{6 \pi} + \frac{\rho_{ab} \ln{\left(\frac{2 t_{ab_{1}}}{d_{a_{1}} - d_{f_{1}} - 2 t_{ab_{1}}} + 1 \right)}}{2 \pi}$multi-core cables type SS with sheath
Related
$d_{a_{1}}$
$d_{f_{1}}$
$\theta_{ar_{1}}$