Thermal resistance 11 of multi-layer backfill

Thermal resistance of 1st segment along flow path $\Phi_1$ of the multi-layer backfill method.

Symbol
$R_{q11}$
Unit
K.m/W
Formulae
$\frac{\rho_b \ln\left(\frac{s_{b3}+C_{b1} \left(d_{b3}-s_{b3}\right)}{r_o}\right)}{\arctan\left(\frac{w_{b4}}{s_{b3}}\right)}$