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How is coefficient of performance different from efficiency?

  1. Feb 23, 2009 #1
    Efficiency is essentially the ratio of what you get to what you put in. COP also seems to represents the same thing (i.e. COP of a refrigerator is Ql / W, which is the amount of heat removed / the amount of work done to remove it). I know efficiency cannot exceed 1, but how come COP can have values greater than 1?
  2. jcsd
  3. Feb 23, 2009 #2
    Suggested Googling:

    Heat pumps/engines
    2nd Law of Thermodynamics
    Carnot cycles.

    The fridge isn't trying to create energy out of nothing,
    just transfer it from one temperature to another.
  4. Feb 23, 2009 #3
    COP is exactly the same thing as efficiency. (what you want/ what you pay for)

    The only reason it isnt called efficiency is because it the coefficient can be higher than 1. You have to remember that the cycle isnt creating anything but shifting heat about.

    That is basically the answer, however do read up on refrigerant/heat pump cycles. If you have a library available to you this stuff is in

    Cengel and Boles - Thermodynamics. (University undergraduate level textbook)
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