1. The rear window of an automobile is defogged by attaching a thin, transparent film type heating element to its inner surface. By electrically heating this element, a uniform flux may be established at the inner surface.For a 4mm thick window glass, determine the electrical power required per unit window area to maintain the inner surface temperature of 15 when the interior air temperature and convection coefficient, while the exterior (ambient ) temperature and convection coefficient are

2. A house has a composite wall of wood , fibreglass insulation , and plaster board. On a cold winter day the convection heat transfer coefficient are .the total wall surface area is 350.Plywood siding

Plaster

Outside

Glass fiber blanket , 28kg/m^3

Inside

a. Determine the symbolic expression for the thermal resistance of the wall , including the inside and outside convection effects for the prescribed conditions.b. Determine the total heat loss through the wall c. If the wind were blowing violently , raising to , determine the percentage increase in the heat lossd. What is the controlling resistance that determines the amount of heat flow through the wall?CONTACT RESISTANCE3. Approximately 10^6 discrete electrical components can be placed on a single integrated circuit (chip) with electrical heat dissipation as high as 30000.the chip , which is very thin , is exposed to a dielectric liquid at its outer surface , with and , and is joined to circuit board at its inner surface . The thermal contact resistance between the chip and the board isand the board thickness and thermal conductivity are and , respectively . the other surface of the board is exposed to ambient air for which and Coolant

Thermal contact resistance Chip ,

Board Air

a. Sketch the equivalent thermal circuit corresponding to steady state conditions .In variable form, label appropriate resistances, temperatures and heat fluxes.b. Under steady state conditions for which the chip heat dissipation is , what is the chip temperature?4. Consider a composite wall that is composed of 2 materials of thermal conductivity and thickness and thicknesses and The contact resistance at the interface between the two materials is known to be Material A adjoins a fluid at 200 for which and material B adjoins a fluid at for which a. What is the rate pf heat transfer through a wall that is 2m high and 2.5m wide?b. Sketch the temperature distribution.CYLINDRICAL WALL5. A thin electrical heater is wrapped around the outer surface of a long cylindrical tube whose inner surface is maintained at 5. The tube has inner and outer radii of 25mm and 75mm respectively , and a thermal conductivity of . The thermal contact resistance between the heater and the outer surface of the tube (per unit length of the tube ) is . Determine the heater power per unit length of tube required to maintain the heater at .CONDUCTION WITH HEAT GENERATION PLANE WALL AND CYLINDER6. A plane wall of thickness 0.1m and thermal conductivity having a uniform volumetric heat generation of 0.3is insulated on one side, while the other side is exposed to a fluid at 92.The convection coefficient between the wall and the fluid is 500. Determine the maximum temperature of the wall.7. A high temperature gas cooled nuclear reactor consists of a composite cylindrical wall for which a thorium fuel element ( is encased in graphite (and gaseaous helium flows through an annular coolant channel. Consider the conditions for which the helium temperature is and the convection coefficient at the outer surface of the graphite is if the thermal energy is uniformly generated in the fuel element at a rate , what are the temperatures and at the inner and outer surfaces respectively, of the fuel element?

r18mm

r211mm

r314mm

T2T3T1ThoriumGraphite Coolant channel with helium flow