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A commercial grade cubical freezer, 3 m on a side,has a composite wall consisting of an exterior sheetof 6.35-mm-thick plain carbon steel, an intermediatelayer of 100-mm-thick cork insulation, and an innersheet of 6.35-mm-thick aluminum alloy (2024).Adhesive interfaces between the insulation and themetallic strips are each characterized by a thermal contactresistance of
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Chapter 3 Solutions
Introduction to Heat Transfer
- 1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.arrow_forwardAnswer correctly and quickly as possible please.arrow_forwardProblem 1 A hot water pipe is used for domestic applications is insulated with a layer of calcium silicate. If the insulation is 25 mm thick and its inner and outer surfaces are maintained at Ts,1 = 800 K and Ts,2 = 400 K, respectively. The outside diameter is 0.12 m. Given the thermal conductivity calcium silicate insulation equals to 0.09 W/m.K. A. Define the difference between lagged and unlagged pipes. B. Calculate the heat loss per unit length for this pipe.arrow_forward
- Two inches of urethane foam will reduce heat loss close to 1000% when applied to a 2-inch diameter uninsulated steel pipe. Assume the pipe wall thickness is 0.25-inches, the pipe interior convective heat loss (hi) is 500 BTU/hr-ft2-oF, and the pipe outside convective heat loss ho 20 BTU/hr-ft2-oF, k steel is 25 BTU/hr-ft-oF, and k insulaton is 0.023 BTU/hr-ft-oF. (hint - calculate heat loss with and without insulation.arrow_forwardTo maximize production and minimize pumping costs, crude oil is heated to reduce its viscosity during transportation from a production field. (1) Consider a pipe-in-pipe configuration consisting of concentric steel tubes with an intervening insulating material. The inner tube is used to transport warm crude oil through cold ocean water. The inner steel pipe (k, = 45 W/m-K) has an inside diameter of D₁, 1 = 150 mm and wall thickness t; = 20 mm while the outer steel pipe has an inside diameter of D₁,2 = 250 mm and wall thickness to = 1;. Determine the maximum allowable crude oil temperature to ensure the polyurethane foam insulation (k = 0.055 W/m-K) between the two pipes does not exceed its maximum service temperature of 7p,max = 70°C. The ocean water is at T, = -5°C and provides an external convection heat transfer coefficient of h, = 500 W/m²K. The convection coefficient associated with the flowing crude oil is h; = 450 W/m².K. (2) It is proposed to enhance the performance of the…arrow_forwardQ2/ A composite wall is formed of a 2.5 cm copper plate, a 3.2 mm layer of asbestos, and a 5 cm layer of fiberglass. The wall is subjected to an overall temperature difference of 560 C. Calculate the heat flow per unit area through the composite structure.arrow_forward
- 5. A 10-in nominal pipe (outside diameter = 10.75in) is covered with a composite pipe insulation consisting of 2.0 in of insulation I placed next to the pipe and 1.5 in of insulation II placed upon insulation I. Assume that the inner and outer surface temperatures of the composite insulation are 900F and 150F respectively, and that the thermal conductivity of material I is 0.05 BTU/hr-ft-F and for material II is 0.039 BTU/hr-ft-F. What is the individual thermal resistance of insulation I?arrow_forwardCalculate the overall heat loss and the temperature profile for each interface if the length of the cylinder is 50 m.Please write your answers legibly.arrow_forwardA boiler furnace wall must have a heat loss no greater than 700 Btu/hr~ft2 and is madeof a material with a thermal conductivity of 0.60 Btu/hr~ft~F. The inner wall surfacetemperature is '2000°F, and the outer surface temperature is 800°F. What wall thick~ness is required?arrow_forward
- If the length of the cylinder is 50 m, calculate the overall heat loss and the temperature profile at each interface. Please write the solution legibly.arrow_forward6. Make a diagram and show the step-by-step process. Do not use shortcut methods. Make it as detailed as it can be. Encode (not hand-written)! DO NOT COPY CHEGG'S ANSWERarrow_forwardjust aarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
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