Thermal resistance 31 of multi-layer backfill method

Thermal resistance offered by the material in layer 1 along the flow path q3.

Symbol
$R_{q31}$
Unit
K.m/W
Formulae
$\frac{\ln{\left(\frac{2 \left(C_{2} \left(d_{T} - s_{4}\right) + s_{4}\right)}{D_{o}} \right)}}{k_{3} \operatorname{atan}{\left(\frac{s_{T}}{s_{4}} \right)}}$
Related
$D_{o}$