A 5-m-wide, 4-m-high, and 40-m-long kiln used to cure concrete pipes is made of 20-cm-thick concrete walls and ceiling (k = 0.9 W/m·K). The kiln is maintained at 40°C by injecting hot steam into it. The two ends of the kiln, 4 m × 5 m in size, are made of a 3-mm-thick sheet metal covered with 2-cm-thick Styrofoam (k = 0.033 W/m·K). The convection heat transfer coefficients on the inner and the outer surfaces of the kiln are 3000 W/m²·K and 25 W/m²·K, respectively. Disregarding any heat loss through the floor, determine the rate of heat loss from the kiln when the ambient air is at 24°C.

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4 m 40 m Tin = 40°C 5 m Tout = -4°C 20 cm