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Carnot engine rejected heat problem

  1. Feb 10, 2009 #1
    1. The problem statement, all variables and given/known data
    From the hot reservoir at a temperature of T1, Carnot Engine A takes an input heat of 5550J, delivers 1750J of work and rejects heat to a cold reservoir that has a temperature of 503K. This cold reservoir also serves as the hot reservoir for a second Carnot Engine, B, which uses the rejected heat from the first engine as input heat. Engine B also delivers 1750J of work, while rejecting heat to an even colder reservoir that has a temperature T2. Find T1 and T2.

    2. Relevant equations

    3. The attempt at a solution

    I plugged in my values into the e=1-Tc/Th and e=W/Qh equations to solve for the Th, or T1. As an answer, I got 734.3K. However, I'm missing a variable for my second Carnot engine. What is the input heat for engine B? I tried doing 734.3-503K, but that gives me answers in K and makes the equation not work. I don't know what I'm supposed to use for the input heat.
  2. jcsd
  3. Feb 11, 2009 #2


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    Welcome to PF :smile:

    It's the same as the output heat from engine A:
    Engine A has 5550 J of input heat. Of that 5550 J energy, 1750 J is used to do work. The remaining energy has to go somewhere (conservation of energy) ...
  4. Sep 23, 2010 #3
    so what does this mean? what do i do with the conservation of energy?
  5. Sep 26, 2010 #4


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    Equate the input energy with the total output energy.
    Qin = W + Qout
    If you need more help with the problem, you will have to show how far you have gotten and the work you have done.
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