Transient thermal resistance for weekly load

Effective transient thermal resistance in the earth for weekly load (transient period $\tau$ of 7 days):

In the majourity of practical cases, the load variations will exhibit a more complex pattern than the one described by a daily load cycle, such as for example, loading of cables is usually much lighter during the weekend than during the weekdays.

Symbol
$T_{4w}$
Unit
K.m/W
Formulae
$\frac{\rho_4}{2\pi} \ln\left(\frac{D_{x,w}}{Do_d}\right)$buried
$\frac{\rho_4}{2\pi} \ln\left(\frac{D_{x,w}}{Do_d}\right)+\frac{\rho_d}{2\pi} \ln\left(\frac{Do_d}{Di_d}\right)+\frac{\rho_{d,fill}}{2\pi} \ln\left(\frac{Do_d}{D_{eq}}\right)$buried in bentonite-filled ducts
Used in