The composite walls of a building are made up of threematerials. The inside layer of the walls is 1-cm thick wall board(kwb = 0.2 W/mK). The middle layer is 10 cm thick insulation (kI =0.06 W/mK) and the outside layer is 3 cm of wood (kw = 0.15 W/mK).The total wall area is 350 m2. The outside air temperature is -10oC and the inside air temperature is maintained at 20 oC. Theinside and outside average convective heat transfer coefficientsare 7 and 35 W/m2K, respectively. You are asked to: a. Sketch andlabel the thermal circuit diagram for the rate of heat transfer, q,from the inside of the room, through the composite walls and to theoutside. Evaluate all individual thermal resistances, the totalthermal resistance and the overall heat transfer coefficient. [10]b. Evaluate q. [2] c. Determine the unknown temperatures on bothsides of the insulation layer. [3] Hint: Neglect radiation, contactresistance and conduction in air. The walls are large enough sothat 1-dimensional conditions exist.
