Consider a plate whose top surface is being cooled by air where as the bottom surface is exposed to a hot stream at 200 C with a convection heat transfer coefficient of 35 W/m2 .K. The air thermal conductivity is 0.243 W/m. K whereas the thermal conductivity of the plate is about 237 W/m. K. If the bottom surface of the plate 150 C, determine the temperature gradient in the air and the temperature gradient in the plate at the top surface of the plate.

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.