"A mass-loaded piston-cylinder system containing air is at 40 lbf/in^2" , 500 °R with a volume of 11 ft3 , while at the stops V = 38 ft3 . An air supply line at 1040 °R is connected to the system by a valve. The valve is then opened until a final pressure of 55 lbf/in.2 at T = 620 °R is reached inside the piston-cylinder assembly. Determine (a) the air mass that enters, (b) the work done in Btu, and (c) the heat transfer in Btu. (Hint: The air is modeled as an ideal gas and the pressure is constant until it reaches to the final pressure).

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.