Consider a wall made of fiberglass insulation (with thermal conductivity k; = 0.046 W /m · K and thicknessL; = 40 mm) which is sandwiched as a layer ofinsulation, between metal panels made of steel panels (each of thermal conductivity k, = 60 W /m · K andL, = 3 mm), in a typically constructed walls of arefrigerator. If the wall separates refrigerated air at T = 5°C from ambient air at To = 26°C, what is the heat gain per unit surface area? Coefficientsassociated with natural convection at the inner and outer surfaces may be approximated as h; = h, = 5 W/m² · K%3D

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Answered: Consider a wall made of fiberglass…

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 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.
A w=40 mm square computer CPU is air cooled with fans shown in the figure below. The surrounding air in the case has convection coefficient h = 100 W/m2⋅K and temperature T∞ = 30oC. If the aluminum heat sink (k = 230 W/m⋅K) on your computer has N = 20 exposed equally-spaced rectangular fins of thickness t =1 mm and length Lf = 15 mm: a) Calculate the overall efficiency ηo of the fins b) Given that the CPU is generating QCPU = 90 W, determine the temperature of the CPU, assuming the CPU is a uniform temperature and well-insulated on its sides. Ignore thermal contact resistance and fin array base resistance
A square pin fin (w=0.6 mm, L=33 mm) is attached to hot surface [87 mm * 69 mm] Ts= 172°C with convection heat transfer coefficient of (1383 W/m K) and surrounding air at 24°C, if the fin efficiency is 0.81 and the center to center distance between any two successive fins =1.5 mm. What is the heat transfer rate (W) from the base surface ONLY when the fins are attached to it?
Example: Steam in a heating system flows through tubes whose outer diameter isD1=3 cm and whose walls are maintained at: = 1.5 cm 2= 3 cm temperature of 120°C. Circular aluminun fins ( k=180 W/m °C) of outer diamete D2 6 cm and constant thickness t =2 mn T r32 mm are attached to the tube, as shown in Fig The space between the fins is 3 mm, an thus there are 200 fins per meter lengtl of the tube. Heat is transferred to th surrounding air at T= 25°C, with a combined heat transfer coefficient of h= 60 W/m2 °C. Determine the increase in heat transfer from the tube per meter of its length as a result of adding fins. S 3 mm
Heat Transfer - Fins See image attached.
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…
solve a to c

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