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Equivalent radius backfill

Equivalent radius of the backfill area.

Symbol
$r_b$
Unit
mm
Formulas
$e^{\frac{\operatorname{Min}\left(w_b, h_b\right)}{2\operatorname{Max}\left(w_b, h_b\right)} \left(\frac{4}{\pi}-\frac{\operatorname{Min}\left(w_b, h_b\right)}{\operatorname{Max}\left(w_b, h_b\right)}\right) \ln\left(1+\left(\frac{\operatorname{Max}\left(w_b, h_b\right)}{\operatorname{Min}\left(w_b, h_b\right)}\right)^2\right)+\ln\left(\frac{\operatorname{Min}\left(w_b, h_b\right)}{2}\right)}$rectangular backfill
$\frac{d_b}{2}$circular backfill
Related
$d_b$
Diameter backfill [mm]
$h_b$
Height backfill [mm]
$\pi$
Archimedes' constant $\pi$
$w_b$
Width backfill [mm]
Used in
$T_{4pii}$
Thermal resistance pipe wall [K.m/W]
$u_b$
Substitution coefficient u