A refrigerator is built to operate with a low-temperature reservoir of 275 K. If the refrigerator is to have a coefficient of performance of 15 or greater, what can be said about its high-temperature reservoir?
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15000 J must be dumped into the high-temperature reservoir per cycle |
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The high-temperature reservoir must be (roughly) 294 K or higher |
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The high-temperature reservoir must be (roughly) above 273 and below 293 K |
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None of the above can realistically achieve this |
Given that :
A refrigerator is built to operate with a low-temperature reservoir of 275 K.
Reason :
Coefficient of Performance of a Refrigerator :"The coefficient of performance (briefly written as C.O.P.) is the ratio of heat extracted in the refrigerator to the work done on the refrigerant.
It is known as theoretical coefficient of performance.
Mathematically, Theoretical C.O.P. = Q W,
where Q = Amount of heat extracted in the refrigerator (or the amount of refrigeration produced, or the capacity of a refrigerator), and W = Amount of work done.
Notes: 1. For per unit mass, C.O.P. = q w
2. The coefficient of performance is the reciprocal of the efficiency (i.e. 1/) of a heat engine. It is thus obvious, that the value of C.O.P. is always greater than unity.
3. The ratio of the actual C.O.P. to the theoretical C.O.P. is known as relative coefficient of performance, Mathematically. Relative C.O.P = Actual C.O.P. Theoretical C.O.P.
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