A steel pipe with 5-cm OD is covered with a 6.4-mm asbestos insulation [k = 0.096 Btu/h · ft · ◦F] followed by a 2.5-cm layer of fiberglass insulation [k = 0.028 Btu/h · ft · ◦F]. The pipe-wall temperature is 315◦C, and the outside insulation temperature is 38◦C. Calculate the interface temperature between the asbestos and fiberglass

The exhaust duct from a heater has an inside diameter of 114.3 mm with ceramic walls 6.4 mm thick. The average k=1.52 W/m· K. Outside this wall, an insulation or rock wool 102 mm thick is installed. The thermal conductivity of the rock wool is k= 0.046+ 1.56 x 104 T°C (W/m · K). The inside surface * = temperature of the ceramic is T1 = 588.7 K, and the outside surface temperature of the insulation is 311 K. Calculate the heat loss for 1.5 m of duct and the interface temperature T2 between the ceramic and the insulation. [Hint: The correct value of km for the insulation is that evaluated at the mean temperature of (T2 + T3)/2. Hence, for the first trial assume a mean temperature of, say, 448 K. Then calculate the heat loss and T2 Using this new T2, calculate a new mean temperature and proceed as before.]

Example • The cylinder is made from aluminum with diameter and thickness of 5 cm and 1 cm respectively. The wall temperature in the inside of cylinder is 50°C, while the temperature of the air is 30°C. the coefficient of convection in the air is 10 W/m2-C. Calculate the heat loss from the cylinder per unit length! • Calculate the thickness of the insulation so heat loss from cylinder will decrease 50% of initial condition. Thermal conductivity of the isolator (k) : 0.5 W/m°C state.pptx 7 MB VIEW Tampilkan semua

.240mm steam main pipe, 210m long is covered with 50mm of high temperature insulation (k-0.092 W/m °C) and 40mm of low temperature insulation (k-0.062 W/m °C). The inner and the outer surface temperature as measured are 390 °C and 40 °C respectively. Calculate: 1- The total heat loss per hour. 2- The temperature between two layers of insulation.