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Homework Help: Thermodynamics Problem

  1. Feb 8, 2010 #1
    1. The problem statement, all variables and given/known data
    Heat input of an engine is 1330 J/s at 375°C and heat output is 800 J/s.

    Each second, how much work is done in the process?


    2. Relevant equations
    QL/QH=1-e


    3. The attempt at a solution
    QL=(1-e)QH

    QH=W/e

    W=average of 1330 and 800 which is 1065J

    QH=1065J/.40 (e was calculated in part A, which I don't need help on).
    = 2.6625kJ

    QL=(1-.40)2.6625kJ
    QL=1.6kJ/s or 1.6kW

    I followed an example in my textbook, the part I am confused on is how to get W, I just took the average of the two that were given.
     
  2. jcsd
  3. Feb 8, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

    An engine converts heat to work.


    So heat is input to the engine, the engine does work and rejects some heat.

    If we apply conservation of energy we get.


    Heat input=Work done + heat rejected
     
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