3 A concrete wall, which has a surface area of 20 m² and is 0.30 m thick, separates conditioned room air from ambient air. The temperature of the inner surface of the wall is maintained at 25°C, and the thermal conductiv- ity of the concrete is 1 W/m K. (a) Determine the heat loss through the wall for outer surface temperatures ranging from -15°C to 38°C, which correspond to winter and summer extremes, respectively. Display your results graphically. Keb) (b) On your graph, also plot the heat loss as a function of the outer surface temperature for wall materials hav- ing thermal conductivities of 0.75 and 1.25 W/m.K. Explain the family of curves you have obtained.
