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Quick Question- carnot efficiency

  1. Nov 3, 2009 #1
    Suppose an engine uses multiple heat reservoirs:

    When calculating the carnot (maximum possible efficiency) is it valid to simply take the average of the temperatures of the hot reservoirs from which the heat is extracted as T(hot) and the average of the temperatures of the heat sinks to which heat is rejected as T(cold)??
    (regardless of the amounts of energy Q rejected/extracted from each of the reservoirs)
  2. jcsd
  3. Nov 3, 2009 #2
    I think you'd have to do a weighted average, based on flow rates and heat capacities or how they mix.

    Put it this way if you have 99% flow from 400K reservoir and 1% from 1000K
    using a average temp of 700K would give an unrealistically high efficieny.

    This is all assuming i've undersood your original question correctly.
  4. Nov 3, 2009 #3


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    I agree with xxChrisxx; it all depends on how much heat is being removed from each reservoir per cycle.
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