a duct is being designed to transport waste gas from a processing unit to a pollution control device. the duct will be 5 ft high 6 ft wide and 100 ft long. in order to determine whether the duct will need to be insulated, the rate of heat loss to the environment must be estimated. based on the following design conditions, compute the rate of heart loss from the duct. average duct surface temperature=250F ambient air temperature=10F wind speed=20 miles/h

Steel pipe 3 cm thick, 1.0 m long and 10 cm deep, covered with 6 cm thick insulation. The wall temperature in the steel pipe is 100 ° C. The ambient temperature around the insulated pipe is 24 ° C. The convection heat transfer coefficient outside the insulation surface is 50 W / (m² K). The thermal conductivity of steel is 54 W / (m K), and the thermal conductivity of the insulation is 0.04 W / (m K). Count; a. Heat loss per meter of pipe = Answer watt. b. Temperature between steel pipe and insulation. = Answer ° C.

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.]

Calculate the mean flame height of a liquid pool with a circular diameter of 1.0m. Assume the liquid is ethyl acetate and has a heat release rate of 2.48 MW