Reconsider Prob. 8–29. Using the EES (or other) software, evaluate the effect of the tube length on the average convection heat transfer coefficient of air. By varying the tube length from 3 to 18 m, plot the average convection heat transfer coefficient as a function of the tube length.

Data from problem 29

In a gas-fired boiler, water is being boiled at 120°C by hot air flowing through a 5-m-long, 5-cm-diameter tube submerged in water. Hot air enters the tube at 1 atm and 300°C at a mean velocity of 7 m/s, and leaves at 150°C. If the surface temperature of the tube is 120°C, determine the average convection heat transfer coefficient of the air and the rate of water evaporation, in kg/h.