Apiston-cylinder device contains 1.329 kg of nitrogen gas at 120 kpa and 27 degree c. the gas is now compressed slowly in a polytropic process during which pv^1.49 = constant. the process ends when the volume is reduced by one-half. determine the entropy change of nitrogen during this process.

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.