Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls are maintained at a temperature of 145°c. circular aluminum alloy 2024-t6 fins (k = 186 w/m⋅k) of outer diameter 6 cm and constant thickness 1 mm are attached to the tube. the space between the fins is 3 mm, and thus there are 250 fins per meter length of the tube. heat is transferred to the surrounding air at t[infinity] = 25°c, with a heat transfer coefficient of 40 w/m2⋅k. determine the increase in heat transfer from the tube per meter of its length as a result of adding fins.

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.