In a gasfired boiler, water is being boiled at 120°C by hot air flowing through a 5.6mlong, 5.3cm 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.