Estimation of heat losses in furnaces

In furnaces operating at high temperatures, heat losses from the outer wall of the shell are important to estimate, when the furnace operates at steady state. These losses correspond to loss in energy. In order to estimate the heat losses, wall temperature should be known. Shell temperature can either be calculated or measured. In the following lecture a method is discussed to calculate the shell temperature of the furnace.
Consider wall of the furnace at temperature which is lined with refractory material of thickness , thermal conductivity  as shown in the figure.