Consider heat transfer through a wall comprised of two solid layers, each 4m x 4m. When perfect contact is maintained between the layers, the steady state temperature profile across the wall might look like that shown below, in Figure 1. If the layers are not in perfect contact, the steady state temperature profile might look like that shown below in Figure 2. For the case of Figure 2, assuming that the bulk temperature in the air gap equals the average of the temperatures at each solid surface in contact with it, what is the temperature drop from surface 1 to surface 2? The product of the Grashof and Prandtl numbers evaluated in the air gap is 106, and the thermal conductivity of air can be taken as 0.028 W/m °C
