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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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
There is a 1.20-cm-thick stagnant air pocket. A) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of cork is 0.0460 W/m·K.in cm B) What thickness of tin would be required for the same R-factor as a 1.20-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of tin is 66.8 W/m·K . in m i asked how to do this but got the wrong soloution
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.)
A cast iron pipe (k = 80 W/m - oC) whose inner and outer diameters are 5 cm and 5.5 cm respectively is coverd with a 3 cm thick glass wool insulation (k = 0.05 W/m - oC) The temperature at the inner surface of the pipe is 320 oC and the interface temperature between the pipe and insulation is 300 oC. Determine the surface temperature of the insulation.
Consider a power transistor encapsulated in an aluminum case that is attached at its base to a square aluminum plate of thermal conductivity k= 240W/m.K, thickness L= 6mm, and width W= 20mm. The case is joined to the plate by screws that maintain a contact pressure of 1 bar, and the back surface of the plate transfers heat by natural convection and radiation to ambient air and large surroundings at T∞ =Tsur -25°C. The surface has an emissivity of ε=0.9, and the convection coefficient is h=4 W/m².K. The case is completely enclosed such that heat transfer may be assumed to occur exclusively through the base plate. a) If the air-filled aluminum-to-aluminum interface is characterized by an area of A₁=2×10-4 m² and contact resistance of R+c= 1.375 K/W, what is the maximum allowable power dissipation if the surface temperature of the case, Ts,c, is not to exceed 85°C? S,C' Transistor case Ts. Pelec S,C' Enclosure W Isur Base plate, (k,ε) Interface, Ac Air Th 801 b) How much should the h be…

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