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Homework Help: Heat engine

  1. May 24, 2008 #1
    1. The problem statement, all variables and given/known data

    A machine with COP = 5.0 removes 25kJ of heat from a cold reservoar. If the machine is reversible and driven the other way as a heat engine, what is the efficiency?

    3. The attempt at a solution

    COP = QL/W --> W = 5kJ

    e = QH/W

    Is QH the same as QL som that e = 20%
     
  2. jcsd
  3. May 25, 2008 #2

    alphysicist

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    Homework Helper

    Hi kasse,

    No, I don't believe that [itex]Q_H[/itex] and [itex]Q_L[/itex] are the same. Using conservation of energy, you can find out how Qh, QL, and W are related. What do you get?

    Also, your efficiency formula needs to be:

    [tex]
    e=\frac{W}{Q_H}
    [/tex]
     
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