A steel pipe (k=25 Wim K) having a 005 mouter diameter is covered with a 0042m thick layer of magnesia ik 0.07 Wim K) which in turn covered with a 24 m layer of fiberglass insulation ( = 0048 Wim K) The pipe wall outside temperature is 360 K and the outer surface temperature of the fiberglass is 300 K The number of active thermal stances are KAN) The resistance for fiberglas only Total resistances ww The seady heat transformat per un length of pipe W ka The interfacial temperature between the magnosis and be