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Homework Help: Power Output & Thermodynamics

  1. Apr 23, 2010 #1
    1. The problem statement, all variables and given/known data

    At a coal-burning power plant a steam turbine is operated with a power output of 491 MW. The thermal efficiency of the power plant is 39.0%.
    (a) At what rate is heat discarded to the environment by this power plant?
    ______ GW

    (b) At what rate must heat be supplied to the power plant by burning coal?
    ______ GW

    2. Relevant equations
    e = W/Qh = Qh-Qc / Qh

    3. The attempt at a solution
    I don't know how to approach this problem. Is there some equation for power to use for thermodynamics?

  2. jcsd
  3. Apr 23, 2010 #2


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    Homework Helper

    Start with the definition of efficiency η.

    Remember power is nothing but the rate of change of energy. (1 W = 1 J/s)
  4. Apr 23, 2010 #3
    I think this problem should be really straightforward, but I am still having trouble understanding how to solve it.
  5. Apr 23, 2010 #4


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    Homework Helper

    In your relevant equations you posted


    So what is Qh ?
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