# Thermal resistance of steel pipe filling

The thermal resistance of the gas or oil between the surface of the cores and the pipe is calculated in the same way as that part of $T_{4i}$ which is between a cable and the internal surface of a duct.

Symbol
$T_{spf}$
Unit
K.m/W
Formulae
$\frac{U_{spf}}{1+0.1\left(V_{spf}+Y_{spf} \theta_{spf}\right) D_{eq}}$
Related
$D_{eq}$
$\theta_{spf}$
$U_{spf}$
$V_{spf}$
$Y_{spf}$
Used in
$T_2$