The roof of a refrigerated truck compartment is of composite construction, consisting of a layer of foamed urethane insulation ( t, = 50 mm, k = 0.026W/m - K) sandwiched between aluminum alloy panels ( t, = 5 mm, k p = 180 W/m - K). The length and width of the roof are L = 10 m and W = 3-5 m,respectively, and the temperature of the inner surface is T5, i- -10°c. Consider conditions for which the truck is moving at a speed of V – 105 km/h, the airtemperature is T = 32°C, and the solar irradiation is G, = 750 W/m². Turbulent flow may be assumed over the entire length of the roof.%3DTE, a,Frank & Dave'sFraen Desserts for These WheDon't Count Caleries(a) For equivalent values of the solar absorptivity and the emissivity of the outer surface ( a s = ɛ = 0,5), estimate the average temperature Ts, o of the outersurface. What is the corresponding heat load imposed on the refrigeration system?(b) A special finish ( as = 0.15, € = 0.8) may be applied to the outer surface. What effect would such an application have on the surface temperature and theheat load?(c) If, with a s = e = 0.5, the roof is not insulated ( t, = 0), what are the corresponding values of the surface temperature and the heat load?

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Answered: The roof of a refrigerated truck…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Oil whose temperature is 30°C is flowed through a pipe with a diameter of 50 cm. The pipe is in an environment where the temperature is 20°C. So that not a lot of heat comes out of the pipe, the pipe is wrapped with an insulating material (k = 0.007 W/mK) as thick as 5 cm. If the convection coefficient of the outer surface of the pipe is 12 W/m²K, calculate the heat flow from the pipe per meter of length.
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A cylindrical cold storage facility with an inner diameter of 4m and height of 2m is constructed. For the wall, the first layer is 6 cm of glass wool (0.1 W/m-C), followed by 30 cm of concrete. The temperature inside is maintained at -10C (hin = 55 W/m^2-C) while the outside temperature is 10°C (hout = 22 w/m^2-C). If the steady rate of heat transfer is at 60W, (a) what is the thermal conductivity of concrete? (b) At what radius is the temperature at 0°C? To prevent water condensation inside the concrete wall (which damages the structure), A 5 cm layer of insulation (k = 0.15 W/m-C) is added to the exterior of the facility. (c) What is the new rate of heat transfer? (d) What is the temperature at the interface of the concrete wall and new insulation? (e) is condensation within the core of the wall prevented?
A dormitory at a large university, built 50 years ago, has exterior walls constructed of Ls = 32-mm-thick sheathing with a thermal conductivity of ks = 0.2 W/m · K. To reduce heat losses in the winter, the university decides to encapsulate the entire dormitory by applying an Li = 35-mm-thick layer of extruded insulation characterized by ki = 0.021 W/m · K to the exterior of the original sheathing. The extruded insulation is, in turn, covered with an Lg = 5-mm-thick architectural glass with kg = 1.1 W/m · K. Determine the heat flux through the original and retrofitted walls when the interior and exterior air temperatures are T∞,i = 20°C and T∞,o = -5°C, respectively. The inner and outer convection heat transfer coefficients are hi = 6 W/m2 · K and ho = 27 W/m2 · K, respectively
A wall with a brick and concrete layer is shown in the figure. The wall has a length of 15 m and 6 m high. The brick (k = 1.3 W/m-K) has a thickness of 75 mm and the concrete (k = 2 W/m-K) is 150 mm thick. Determine the total heat resistance, the heat transfer rate through the wall, and the temperature of its inner surface for a day during which the room is maintained at 20°C while the temperature of the outdoors is 32°C. Take the convection heat transfer coefficients on the inner and outer surfaces of the wall to be 12 W/m²-K and 18 W/m²-K, respectively, which includes the effects of radiation. Round off your final answer to three (3) decimal places. (20 pts.) Tooout Outdoor Brick Concrete Wall Heat Transfer, Q (W) = Total Heat Resistance, RT (K/W) = input: 2.01234x10^-3) T₂ Inner Surface Temp, T2 (°C) = Toin Indoor (5 decimal places - example
Finned heat sinks are used to keep computer chips in an acceptable temperature range. The heat sink base is 53 mm x 57 mm, and the maximum allowable chip temperature is 75 C. An array of 54 aluminum fins (k = 237 W/m*K) which have a square cross-section (3 mm x 3 mm) are attached to the heat sink. The length of each fin is 30 mm. The cooling air supplied to the heat sink is 25 C. If the convection heat transfer coefficient is 125 W/m2*K, what is the heat transfer rate (in W) from the heat sink, assuming adiabatic fin tips? (Hint: heat transfer does not solely occur from the fins.)
Approximately 106 discrete electrical components are placed on a single integrated circuit (chip) with electrical heat dissipation of q = 30,000 W/m². The chip, which is very thin, is exposed to a dielectric liquid at its outer surface, with ho = 450 W/m²/K and To= 20°C, and is joined to a circuit board at its inner surface. The thermal contact resistance between the chip and the board is R = 104 m² K/W, and the board thickness and thermal conductivity are L = 4 mm and 00,0 kb = 0.95 W/m/K, respectively. The other surface of the board is exposed to ambient air for which hi = 30 W/m²/K and T = 20°C. a) Provide a resistance diagram labeling appropriate variables associated with this problem. b) Determine a symbolic expression for the temperature of the chip T. c) Calculate the chip temperature for the given parameters. Coolant ho 00,01 Air Too,i hi 三三 -Chip q Te -Thermal contact resistance, Re -Board, kp
Consider the composite wall below. The inner side of the wall is subjected to air flow at 430°C with a heat transfer coefficient of 25 W/m² C and the outter side is subjected to air flow at 55°C with heat transfer coefficient of 10 W/m²-C. If KA 150 W/m-C, Kg = 30 W/m-C, Kc = 65 W/m-C, and Kp = 50 W/m-C, and assuming one dimensional heat flow. Find the rate of heat transfer across the wall. Q Inner 10 cm 3 cm B C 8 cm Outer side D 5 cm 3 cm 7 cm
A wall with a brick and concrete layer is shown in the figure. The wall has a length of 15 m and 6 m high. The brick (k = 1.3 W/m-K) has a thickness of 75 mm and the concrete (k = 2 W/m-K) is 150 mm thick. Determine the total heat resistance, the heat transfer rate through the wall, and the temperature of its inner surface for a day during which the room is maintained at 20°C while the temperature of the outdoors is 32°C. Take the convection heat transfer coefficients on the inner and outer surfaces of the wall to be 12 W/m2-K and 18 W/m2-K, respectively, which includes the effects of radiation. Round off your final answer to three (3) decimal places.
A steel tube, with a thermal conductivity of 50 W /m K, has an inner diameter of 20-mm and outer diameter of 26-mm. Hot gases flow over the tube with a convection heat transfer coefficient of 200 W/m2 K; while, cold water flows through the tube with a convection heat transfer coefficient of 8000 W/m2 K. What is the hot-side overall heat transfer coefficient in W/m2 K?
An industrial freezer is designed to operate with an internal air temperature of -20°C when the external air temperature is 27°C, and the internal and external heattransfer coefficients are 8 W/m2 -K and 12 W/m2 -K, respectively. The walls of thefreezer are composite construction, comprising an inner layer of plastic (k = 0.33 W/m-K, and thickness of 10 mm), and an outer layer of stainless steel (k = 15 W/m-K, and thickness of 3 mm). Sandwiched between these two layers is a layer of insulation material with k = 0.07 W/m-K. Find the width (mm) of the insulation thatis required to reduce the convective heat loss to 60 W/m2.
A thick-walled tube of stainless steel (L = 0.50 m; k = 21.63 W/m-K) with an inside diameter of 0.0254 m and outside diameter of 0.0508 m, is covered with an insulation (∆x =0.0254 m) with k = 0.2423 W/m-K. If the inside wall temperature of the pipe is at 400 oC, calculate the temperature at the interface between the metal and the insulation (in oC) if the outside surface of the insulation is at 29.8 oC. 99 K in Pa.

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