Thermal resistivity steel pipe filling medium

The values for the possible filling material of the steel pipe are listed.

Sources:

Symbol
$\rho_{spf}$
Unit
J/(K.m$^3$)
Choices
CodeValueMaterialReference
Air35.0AirDaniel L. Carrol at al 1968
N236.2NitrogenJ. Vermeer 1983
Oil10.0Dielectric oilWikipedia