. A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use...

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Physics

. A leading manufacturer of household appliances is proposing aself-cleaning oven design that involves use of a composite windowseparating the oven cavity from the room air. The composite is toconsist of two high-temperature plastics (A and B) of thickness LA= 2LB and thermal conductivities kA = 0.15 W/mK and kB = 0.08 W/mK.During the self-cleaning process, the oven wall and inside airtemperatures, Tw and Ta are 400 ÂºC, while the room air temperatureis 25 ÂºC. The inside convection and radiation heat transfercoefficients hi and hr as well as the outside convectioncoefficient ho, are each 25 W/m2K.
(a) Define and sketch the system and identify heat entering andleaving the system on the sketch.
(b) Write the conservation of energy equation (or energybalance) for this system.
(c) Construct a thermal resistance circuit for the systemdefined in part (a).
(d) Write an expression for the total resistances entering thesystem.
(e) What is the minimum window thickness, L = LA + LB, needed toensure a temperature that is 50 ÂºC or less at the outer surface ofthe window? This temperature must not be exceeded for safetyreasons

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4.2 Ratings (652 Votes)

The thermal circuit can be constructed by recognizing thatresistance to heat flow is associated with convection at the outersurface conduction in the plastics See Answer

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