A heat engine running backward is called a refrigerator if its purpose is to ext

Question

A heat engine running backward is called a refrigerator if its purpose is to extract heat from a cold reservoir. The same engine running backward is called a heat pump if its purpose is to exhaust warm air into the hot reservoir. Heat pumps are widely used for home heating. You can think of a heat pump as a refrigerator that is cooling the already cold outdoors and, with its exhaust heat , warming the indoors. Perhaps this seems a little silly, but consider the following. Electricity can be directly used to heat a home by passing an electric current through a heating coil. This is a direct, 100conversion of work to heat. That is, 17.0 of electric power (generated by doing work at the rate 17.0 at the power plant) produces heat energy inside the home at a rate of 17.0 . Suppose that the neighbor's home has a heat pump with a coefficient of performance of 5.00, a realistic value. Part A How much electric power (in ) does the heat pump use to deliver 17.0 of heat energy to the house? Part B An average price for electricity is about 40 per dollar. A furnace or heat pump will run typically 100 per month during the winter. What does one month's heating cost in the home with a 17.0 electric heater? Part C What does one month's heating cost in the home of the neighbor who uses an equivalent heat pump? Help please!

Explanation / Answer

the answer is far more complex than that the electric heater is said to be 100% efficient the heat pump if the outside temperature is about +10º and the inside temperature is about +20ºC for 10ºC rise the heat pump will consume about hale the power of the resistive heater now if the outside T is -40ºC for 10ºC rise the low cost heat pump will consume at least twice as much as the resistive element a more expensive dual stage unit will extract heat at a lower temperature the same goes with cooling to cool from 90ºF to 70ºF is one thing to cool from 160º to 40ºF is another thing

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