| In consideration that total porosity in an insulating material together
with bulk density provides the usual guidance for selecting appropriate
quality of heat-combating devices in industrial furnaces, a comprehensive
study has been attempted on the significance of the different
aspects of pore as the controlling criteria. The interrelationship of heat
flows and thermal conductivity in the context of geometrical and
dimensional features of pores has been dwelt upon. Of the different
equations, the one derived by Loeb appears to be reasonably depend·
able, specially since it took into account the part played by tbe shape,
size, distribution and orientation of pores. The observation bas been
corroborated by illustrations and tabular statements. The criticality
of phonon and photon conductivities of solid as well as its emissivity
as factors to determine the insulating characteristics bas been emphasized. |
