For an outdoor air temperature of 20°f, 45,000 btu/hr is required to maintain the temperature in a house at 72°f. a heat pump using r-22 as the refrigerant is used to supply this heat. the r-22 leaves the evaporator at p = 45 psi, t = 12°f and the condenser operates at a pressure of 250 psi. assuming an isentropic compressor efficiency of 82%, determine: a) the refrigerant flow rate, b) the compressor power input, and c) the coefficient of performance

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.