Aheat pump with a cop of 3.2 is used to heat a perfectly sealed house (no air leaks). the entire mass within the house (air, furniture, etc.) is equivalent to 1200 kg of air. when running, the heat pump consumes electric power at a rate of 5 kw. the temperature of the house was 7∘c when the heat pump was turned on. if heat transfer through the envelope of the house (walls, roof, etc.) is negligible, the length of time the heat pump must run to raise the temperature of the entire contents of the house to 22∘c is a. 13.5 min b. 43.1 min c. 138 min d. 18.8 min e. 808 min

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.