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I Proof of fundamental thermodynamics equation for open systems

  1. May 27, 2017 #1
    Hi !

    I'm having a bit of trouble understanding something.
    Let 'u' be internal energy, 'h' enthalpy, 'e' work and 'q' heat. ('r' are dissipations and 'S' entropy)

    From a book , i read that de+dr=PdV= -du + TdS
    This seems to stand for closed cycle.
    Yet, my teacher uses the formula

    de+dr=vdP= -dH + TdS

    I guess this is different because it is an open cycle.

    But the thing is, how to go from one to another ? I can't find any proof of the second one.. So if someone could explain it to me ! Thank you
  2. jcsd
  3. May 27, 2017 #2
    The second equation doesn't look correct. dH=TdS+vdP
  4. May 27, 2017 #3
    Maybe I miswrote it, lets consider that dH=TdS+vdP then
  5. May 27, 2017 #4
    The ball is in your court.
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