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Homework Help: Carnot engine problem

  1. Aug 1, 2012 #1
    1. The problem statement, all variables and given/known data

    A Carnot engine uses hot and cold reservoirs that have temperatures of 1684 and 842 K, respectively. The input heat for this engine is |QH|. The work delivered by the engine is used to operate a Carnot heat pump. The pump removes heat from the 842-K reservoir and puts it into a hot reservoir at a temperature T`. The amount of heat removed from the 842-K reservoir is also |QH|. Find the temperature T`.

    2. Relevant equations

    Qc/Qh = Tc/Th
    Qh = W + Qc

    3. The attempt at a solution
    This problem was posted before with no solution and now I'm running into the same problem. I've attempted the problem by first getting Qh=2Qc for the carnot engine. Then this input heat + W is used to operate a heat pump. So I got Qh + w = 2Qc. I'm stuck starting here. I'm not sure how this input heat would fit into the heat pump cycle.

    The answer is suppose to be 1263
  2. jcsd
  3. Aug 4, 2012 #2


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    Homework Helper

    For the Carnot Engine section, how do you find the efficiency of the engine? (express W in terms of Qh).

    For the heat pump section, we are inputting W to move Qh to some other reservoir Q (at temp T'). How do you find the effectiveness of a heat pump?
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