2.The vertical flat wall of the combustion chamber of a furnace isconstructed with a layer of firebrick 200 mm thick, a layer of insulation100 mm thick and a mild steel plate 10 mm thick on the outside. Theinner surface of the firebrick is at a temperature of 815°C and the airtemperature outside the furnace is 21 °C. To estimate the heat lossfrom the furnace, a hole is drilled through the plate and insulation sothat the temperature at the junction of the firebrick and insulation canbe determined. This is found to be 730°C.Estimate:(i) the rate of heat loss per m² of wall surface.(ii)the heat transfer coefficient from the outer surface of the steel tothe surrounding air.The thermal conductivities of the materials used are:Firebrick 1.0, insulating material 0.07, and steel 45W/mK.Answer: 425 W/m² 4.2 W/m²K

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Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

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Author:Kreith, Frank; Manglik, Raj M.

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Chapter7: Forced Convection Inside Tubes And Ducts

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3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the atmosphere from outer space. If its original temperature is 38°C, the effective average temperature of the atmosphere is 1093°C, and the effective heat transfer coefficient is , estimate the temperature of the shell after reentry, assuming the time of reentry is 10 min and the interior of the shell is evacuated.
The air-conditioning system in a Chevrolet van for use in desert climates is to be sized. The system is to maintain an interior temperature of 20C when the van travels at 100 km/h through dry air at 30C at night. If the top of the van is idealized as a flat plate 6 m long and 2 m wide and the sides as flat plates 3 m tall and 6 m long, estimate the rate at which heat must be removed from the interior to maintain the specified
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J 5 A cylindrical steel tank with a diameter of 1.8m and a height of 2m, is insulated with polyurethane on its lateral faces and its lid. The insulation is 40 mm thick and covered with a thin layer of metal. The tank contains water that is kept warm by an electric heater in such a way as to maintain the inner surface of the tank at a temperature of 55C. The ambient air temperature is 10C and the external skin coefficient is 10 w/m2K. If the energy cost is $0.15/kwh. What is the monthly energy cost for water storage?
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Please fats. The answer in the box is incorrect
A double window called thermopane is one in which two layers of glass are used separated by a layer o dry stagnant air: In a given window, each of the glass layers is 6.35 mm thick separated by a 6.35 mm space of stagnant air. The thermal conductivity of the glass is 0.869 W/m K and that of air is 0.026 over the temperature range used. For temperature drop of 27.8 K over the system, calculate the heat loss for a window 0.914 m 1.83 m.
Air at 4 °C is being carried within a metal cylindrical pipe to astorage room at a bioprocessing facility, where a heat-sensitive protein product must be stored until it is transferred to another facility. The outer diameter of the pipe is 400 mm, and the thickness of the pipe is 2 mm. The pipe is installed within a larger room where the room temperature is kept at 20°C. There is a layer of insulating material around the metal pipe. Thermal conductivity of the metal pipe is 60 W/m*K, whereas the thermal conductivity of the insulating material is 0.04 W/m*K. Heat gain by the air being transported occurs at a steady rate of 40 W. A while later, it becomes necessary to reduce the temperature of the flowing air down to 0 °C for another protein product. By how much (in percentages) should the insulation material thickness should increase in order to maintain this air temperature within the pipe? Assume the inner surface temperature of the metal pipe is equal to the air temperature in the…
Thermal jackets are typically put on cryogenicstorage tanks to minimize the heat transfer gainsfrom the surroundings. Consider a cylindercontainer that is 1.5 m long made from steel (k = 750W/m.K) with an inner diameter of 0.5 m and outerdiameter of 0.7 m. If the liquefied natural gas (LNG)inside the cylinder is maintained at 90 K, ambientconditions are Tamb = 20 °C, h = 7 W/m2.K. What is the required insulationmaterial to maintain the outer temperature of that jacket of 15 °C? Usethe end of the book and write your assumption with the right value.(Take a maximum allowed jacket thickness of Lins = 7 cm)
Thermal jackets are typically put on cryogenicstorage tanks to minimize the heat transfer gainsfrom the surroundings. Consider a cylindercontainer that is 1.5 m long made from steel (k = 750W/m.K) with an inner diameter of 0.5 m and outerdiameter of 0.7 m. If the liquefied natural gas (LNG)inside the cylinder is maintained at 90 K, ambientconditions are Tamb = 20 °C, h = 7 W/m2.K. What isthe required thermal jacket thickness to maintainthe outer temperature of that jacket of 15 °C? (Takea thermal conductivity of the insulation to be kins =0.015 W/m.K). Image credit: Okorder. Image forillustrative purposes only.

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