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The shield of a nuclear reactor is idealized by a large 25-cm-thick flat plate having a thermal conductivity of
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Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
- 1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.arrow_forward1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.arrow_forward3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.arrow_forward
- Show that the rate of heat conduction per unit length through a long, hollow cylinder of inner radius ri and outer radius ro, made of a material whose thermal conductivity varies linearly with temperature, is given by qkL=TiTo(rori)/kmA where Ti = temperature at the inner surface To = temperature at the outer surface A=2(rori)/ln(ro/ri)km=ko[1+k(Ti+To)/2]L=lenthofcyclinderarrow_forward1.29 A spherical interplanetary probe with a 30-cm diameter contains electronic equipment that dissipates 100 W. If the probe surface has an emissivity of 0.8, what is its surface temperature in outer space? State your assumptions in the calculations.arrow_forward2.55 A long, 1-cm-diameter electric copper cable is embedded in the center of a 25-cm-square concrete block. If the outside temperature of the concrete is 25oC and the rate of electrical energy dissipation in the cable is 150 W per meter length, determine temperatures at the outer surface and at the center of the cable.arrow_forward
- A cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.arrow_forwardA flat surface is covered with insulation with a thermal conductivity of 0.08 W/m · K. The temperature at the interface between the surface and the insulation is 300 °C. The outside of the insulation is exposed to air at 30 °C, and the heat transfer coefficient for convection between the insulation and the air is 10 W/m2 • K. Ignoring radiation, determine the minimum thickness of insulation, in meter, such that the outside of the insulation is no hotter than 60 °C at steady state.arrow_forwardWhen the difference in temperature between the sides of a wooden board 80 cm long, 50 cm wide, and 10 mm thick is 400C, heat flows through the board at the rate of 240 W. The thermal conductivity of the wood isarrow_forward
- Ground turkey was made into me at balls and refrigerated at 2 ° C before being deep fried. The diameter of each meat ball is 9cm. To make sure that the meat balls are safe to be consumed, they must be cooked over 70 ° C. Assume that the cooking oil is at a constant temperature of 180 ° C and has a heat transfer coefficient of 50 W/(m 2 ∙ K). The conductivity and specific heat of the ground turkey are approximated at 2 W/( m∙K ) and 4 kJ/( kg ∙ K) respectively. The density of the ground turkey is 500kg/ m 3 . a) During the deep- frying process, do you anticipate that each meat ball has a uniform temperature distribution throughout its volume? Please show calculation to support your answer (5 pts) . b) Please calculate the minimum time required for cooking (1 5 p ts). c) When served, what are the surface and center temperatures of each meat ball ( 15 pts).arrow_forwardWhy does heat transfer increase initially with radius of insulation and then decrease beyond critical radius? Explain in details.arrow_forward10 hot rods (L = 5 m and d = 2 cm) are buried in the ground parallel to each other each rod is 10 cm apart and at a depth 3 m from the ground surface. The thermal conductivity of the soil is 0.6 W/m K. If the surface temperature of the rods and the ground are 600 K and 30 °C, respectively. Draw the figure and determine the rate of heat transfer from the fuel rods to the atmosphere through the soilarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning