A 90-hp (shaft output) electric car is powered by an electric motor mounted in the engine compartment. If the motor has an average efficiency of 91 percent, determine the rate of heat supply by the motor to the engine compartment at full load.

A heat pump maintains a dwelling at 68°F. When operating steadily, the power input to the heat pump is 7 hp, and the heat pump receives energy by heat transfer from 55°F well water at a rate of 500 Btu/min.(a) Determine the coefficient of performance.(b) Evaluating electricity at $0.08 per kW · h, determine the cost of electricity in a month when the heat pump operates for 300 hours.

In a gas turbine, the temperature of the working fluid at inlet to the compressor is 289 K and outlet 438 K. At inlet to the turbine, the working fluid has a temperature of 1,064 K and exhausts from the turbine at a tempeature of 739 K. The specific heat capacity of the working fluid at constant pressure is 1.005 kJ/kg.K. Determine the efficiency of the plant

To maintain a dwelling steadily at 68°F on a day when the outside temperature is 40°F, heating must be provided at an average rate of 300 Btu/min. Determine the electrical power required, in kW, to deliver the heating using: (a) electrical-resistance heating. (b) a heat pump whose coefficient of performance is 2.5, (c) a reversible heat pump operating between hot and cold reservoirs at 68°F and 40°F, respectively.

When a man returns to his well-sealed house on a summer day, he finds that the house is at 35°C. He turns on the air conditioner, which cools the entire house to 20°C in 36 min. If the COP of the air-conditioning system is 2.8, determine the power drawn by the air conditioner. Assume the entire mass within the house is equivalent to 800 kg of air for which cy= 0.72 kJ/kg °C and cp = 1.0 kJ/kg-°C. 35°C 20°C W A/C The power drawn by the air conditioner is kW.