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I Rankine and Otto cycles

  1. May 28, 2018 #1
    Hello!

    In ideal Rankine cycle, we say that during the isobaric expansion, the heat provided to the system is Qin = h3 - h2
    However, in my opinion, it is Qin - W = Δh -> Qin - PΔV = Δh. Which is correct?

    Secondly,
    In Otto cycle, let's say you have calculated Wnet in kJ/kg. In order to be able to calculate Power, isn't it necessary to know mass flow rate?

    Thanks!
     
  2. jcsd
  3. May 28, 2018 #2
    The answer to the question about the Rankine cycle is that the first equation is correct (and yours is wrong).

    The answer to the question about the Otto cycle is yes and no. It is acceptable to express the power as Wnet in kJ/kg if you also know that all you need to do to get the actual power is multiply by the mass flow rate.
     
  4. May 31, 2018 #3
    Why my equation is wrong?
    Isn't 2->3 a constant pressure process where the volume expands?
    Isn't there work generated? Why we don't count it?
     
  5. May 31, 2018 #4
    It is counted. It’s lumped in with the enthalpy.
     
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