A 5-m-wide, 4-m-high, and 40-m·long kiln used to eure concrete pipes is made of 20-cm-thic...

A 5-m-wide, 4-m-high, and 40-m·long kiln used to eure concrete pipes is made of 20-cm-thick concrete walls and ceil- ing (k = 0.9 W/m·K). The kiln is maintained at 40°C by in- jecting 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/nr·K and 25 W/m·K, respectively. Disre- garding any heat loss through the floor, determine the rate of heat loss from the kiln when the ambient air is at −4°C.