Substitution coefficient u

Substitution coefficient for the calculation of the thermal resistance of the equivalent radius of backfill to ambient.

Symbol
$u_{b}$
Formulae
$\frac{L_{b}}{r_{b}}$from $L_b$ and $r_b$
$\frac{\left(e^{G_{b}} + 1\right) e^{- G_{b}}}{2}$from $G_b$