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Homework Help: Calculating work output of an engine, using ideal gas

  1. May 12, 2009 #1
    1. The problem statement, all variables and given/known data

    A model Stirling engine uses n = 8.04 × 10–3 mol of gas (assumed to be ideal) as a working substance. It operates between a high temperature reservoir at TH = 98.0 °C and a low temperature reservoir at Tc = 25.0 °C. The volume of its working substance doubles during each expansion stroke. It runs at a rate of 0.7 cycles per second. Assume the engine is ideal.

    How much work does the engine do per cycle?

    2. Relevant equations

    W(eng) = Qh - Qc

    3. The attempt at a solution

    I assume that you have to find the energy input and output by using the temperatures, and the mol of gas, taking into account it's an ideal gas. However, taking the first step is the problem. I have no clue how to work out Qh and Qc, from the given data. Or perhaps there's some other way you have to solve it?
    Last edited: May 12, 2009
  2. jcsd
  3. May 12, 2009 #2


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    Homework Helper

    What does the problem actually ask you to calculate? You don't seem to have included that in the problem statement... does it actually say you need to find the energy input and output, or are you just guessing at that?
  4. May 12, 2009 #3
    I can't believe I forgot to put that question in. I edited the original - sorry about that.
  5. May 12, 2009 #4


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    Have you drawn the PV diagram for an idealized Stirling cycle? If not, that would help with figuring out what's going on.
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