Consider a 25-m·long thick-walled concrete duct (k = 0.75 W/m·K) of Square cross section....

Consider a 25-m·long thick-walled concrete duct (k = 0.75 W/m·K) of Square cross section. The outer dimensions of the duct are 20 cm × 20 cm, and the thickness of the duct wall is 2 cm. If the inner and outer surfaces of the duct are at 100°C and 30°C, respectively, determine the rate of heat transfer through the walls of the duct. Answer. 47.1 kW

FIGURE P3-143