In a 2.5 cm inner diameter (id) tube, water enters at 90 ° c and 6 m / s. the tube is copper and it has a thickness of 0.8 mm and a length of 3m. in the normal direction outside the tube, ambient air circulates at 1 atm and 20 ° c, with h = 7 w /m^2 ° c. calculate the air temperature at tube outlet. what would be the effect of reducing the hot air stream in half ? . kcobre =378.7 w / (mk)

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.