Is there any difference between coefficient of perfomance & efficiency

Asked by vrg.anayath | 17th Oct, 2010, 03:30: PM

Expert Answer:

Dear student
The coefficient of performance or COP (sometimes CP), of a heat pump is the ratio of the change in heat at the "output" (the heat reservoir of interest) to the supplied work.

The equation is:

where is the change in heat at the heat reservoir of interest, and

  • is the work consumed by the heat pump.

When one is interested in how well a machine cools, the COP is the ratio of the heat removed from the cold reservoir to input work.


  • is the heat moved from the cold reservoir (to the hot reservoir).

On the other hand, efficiency is defined as follows:

The efficiency of a heat engine relates how much useful work is output for a given amount of heat energy input.

A heat engine absorbs heat energy from the high temperature heat source, converting part of it to useful work and delivering the rest to the cold temperature heat sink.

In general, the efficiency of a given heat transfer process (whether it be a refrigerator, a heat pump or an engine) is defined informally by the ratio of "what you get out" to "what you put in."

In the case of an engine, one desires to extract work and puts in a heat transfer.

They are two different physical quantities defined as above.

We hope that clarifie syour doubt.


Answered by  | 19th Oct, 2010, 09:46: AM

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