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Homework Help: Thermodynamics and Steam Engine

  1. Oct 21, 2009 #1
    1. The problem statement, all variables and given/known data
    If a steam engine operates at half of its theoretical maximum efficiency (emax) and does work at a rate of W J/s, calculate how much heat is discharged per second.

    2. Relevant equations
    WMax = [tex]\epsilon_{Max}*Q_{H}[/tex]
    W = QH-QC

    3. The attempt at a solution
    [tex]W = \frac{1}{2}*\epsilon_{Max}*Q_{H}[/tex]

    [tex]\frac{2W}{\epsilon_{Max}} = Q_{H}[/tex]

    [tex]W = Q_{H} - Q_{C}[/tex]

    [tex]W = \frac{2W}{\epsilon_{Max}} - Q_{C}[/tex]

    [tex]\epsilon_{Max} *W = 2W - \epsilon_{Max} * Q_{C}[/tex]

    [tex]\epsilon_{Max} *W - 2W= - \epsilon_{Max} * Q_{C}[/tex]

    [tex]W(\epsilon_{Max} - 2) = - \epsilon_{Max} * Q_{C}[/tex]

    [tex]\frac{W(\epsilon_{Max} - 2)}{- \epsilon_{Max}} = Q_{C}[/tex]

    [tex]Answer = \frac{2W (1-\frac{\epsilon_{Max}}{2})}{ \epsilon_{Max}}[/tex]

    Where did i go wrong?
  2. jcsd
  3. Oct 21, 2009 #2
    What is the given answer?
    Last edited: Oct 21, 2009
  4. Oct 22, 2009 #3

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Maybe they want you to express the maximum efficiency in terms of temperatures Tc and Th.

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