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Homework Help: Heat engine

  1. May 11, 2006 #1
    I'm not sure if I'm interpreting this question correctly

    A heat engine operated between 40C and 380C. Being a real engine, it efficiency is only 60% of that theoretically possible for a Carnot engine at these temperatures. If it absorbs heat at a rate of 60kW at what rate does it exhaust heat?

    So should I be finding the ideal (Carnot engine) and then taking 60% of that?

    ideal = 1-Tl/Th = 1- (313K/653K) = 0.52

    so then I figured it runs at 60% of ideal so e should be 0.312

    Is this right or is e just 60% ??
     
  2. jcsd
  3. May 11, 2006 #2
    You are almost there. You did not answer what the question asked of you, it said what rate does it exhaust heat, not the efficiency.
     
  4. May 11, 2006 #3
    If e is 0.312

    then 0.312 = (Qh-Ql)/Qh
    0.312 = (60 kJ/s - Ql)/60 kj/s

    Ql = 41.3 kj/s So it exhausts at a rate of 41.3 kj/s

    Does this look right?
     
  5. May 11, 2006 #4
    seems reasonable.
     
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