Calculate the overall heat transfer coefficient and the duty (rating) of heat flow from the hot gases to the cold air in the cross-flow tube bank of the heat exchanger sketched in Pig. P3-16. The following operating conditions are given:
air flow rate = 3,000 lbm/hr
hot-gas flow rate = 5,000 lbm/hr
hot-gas inlet temperature = 1,0000P
air inlet temperature = 1OOOP
Both the hot gas and the air are at near atmospheric pressure. Approximate the physical properties of the hot gas as those of air.