1. The rear window of an car is defogged by attaching a thin warming component to its interior surface. By electrically heating the component. a unvarying heat flux may be established at the interior surface. For 4 millimeter midst window glass. find the electrical power required per unit window country to keep an interior surface temperature of 150C when the interior air temperature and convection coefficient are Ti = 25 0C and hi = 10 W/m2. K. while the outside ( ambient ) air temperature is ( – 10 0C and h0 = 65 W/m2. K ) 2. The walls of a icebox are typically constructed by sandwiching a bed of insularity between sheet metal panels. See a wall made from fiberglass insularity of thermic conduction qi = 0. 046 W/m. K and thickness Li = 50 millimeter and the steel panels. each of thermic conduction kp= 60 W/m. K and thickness Lp = 3 millimeter. If the wall separates refrigerated air at the Ti = 40C from ambient air at T0 = 250 C. what is the addition per unit surface country?

Coefficients associated with natural convection at the inner and outer surfaces may be approximated as hello = h0 =5 W/m2. K. 3. A spherical shell with interior radius r1 and the outer radius r2 has surface temperatures T1 and T2 severally where T1 & gt ; T2. Sketch the temperature distribution on T- R coordinates presuming steady province. one dimensional conductivity with changeless belongingss. Briefly justify the form of your curve. 4. A glass window of width W = 1 m and tallness H = 2 m is 5 millimeter midst and has a thermic conduction of kg= 1. 4 W/m. K. If the inner and the outer surface temperatures of the glass are 150 C and – 200 C severally. on a cold winter twenty-four hours. what is the rate of heat loss through Windowss. it is customary to utilize a dual window glass building in which bordering window glasss are separated by an air infinite. If the spacing is 10 millimeter and the glass surface in contact with the air have temperatures of 100 C and – 150 C. what is the rate of heat loss from a 1mX 2m window? The thermic conduction of air is ka = 0. 024 W/m. K 5. What is the thickness required of a masonry wall holding thermic conduction 0. 75 W/m. K if the heat rate is to be 80 % of the heat rate through a composite structural wall holding a thermic conduction of 0. 25 W/m. K and a thickness of 100 millimeter? Both walls are subjected to the same surface temperature difference.


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