Reconsider Prob. 3–64. Using EES (or other) software, investigate the effects of the thickness of the wall and the convection heat transfer coefficient on the outer surface of the rate of heat loss from the kiln. Let the thickness vary from 10 cm to 30 cm and the convection heat transfer coefficient from 5 W/m2·K to 50 W/m²·K. Plot the rate of heat transfer as functions of wall thickness and the convection heat transfer coefficient, and discuss the results.

Data From problem 64

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.

Transcribed Image Text:

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