An insulating wall is constructed of three homogeneous layers with conductivities k 1 , k 2 , and k.

An insulating mole is concocted of three homogeneous layers delay conductivities k 1 , k2 , and k3 in exact continuity (see Fig. P3.17). Under steady-state provisions, the temperatures at the boundaries of the layers are characterized by the external manner temperatures T 1; and T4 and the interface temperatures T2; and T3. Formulate the gist to determine the temperatures T1; (i = 1, ... , 4) when the ambient temperatures To and T3 and the (surface) film coefficients βo and β3 are known. Assume that there is no inner ebullition epoch and that the ebullition glide is one-dimensional (ƏT/ Əy = 0).