The exhaust pipe of a heater has an internal diameter of 114.3 mm with ceramic walls 6.4 mm thick. The average value of k is 1.52 w / m-k. 102 mm mineral wool insulator is installed outside this wall....

The exhaust pipe of a heater has an internal diameter of 114.3 mm with ceramic walls 6.4 mm thick. The average value of k is 1.52 w / m-k. 102 mm mineral wool insulator is installed outside this wall. The thermal conductivity of mineral wool is k = 0.046 + 1.56 x 10-4 t (° c) (w / m-k). the internal temperature of the ceramic surface is t1 = 588.7 k and the temperature of the external surface of the insulator is t3 = 311 k. Calculate the heat loss for 1.5 m of duct and the interfacial temperature t2 between the ceramic and the insulator. [suggestion: the appropriate value of k of the insulator is that obtained at the average temperature (t2 + t3) / 2. therefore, for the first approximation an average temperature of approximately 488 k is assumed. With this the heat loss and t2 are calculated.