Heat capacity: Heat capacity of furnace depend on
(1) Thermal conductivity (2) Specific heat and (3) Specific gravity of refractory.
The dense and heavy fire clay bricks have higher heat capacity and which are best suited for regenerators, checker-works as in coke-ovens, glass furnace and stoves for blast furnaces. On the other hand, intermittently operated furnaces require refractory material of low heat capacity (light weight refractory brick). Because the working temperature of such furnaces are achieved in less time with less fuel.