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Homework Help: Question regarding non flow steam process

  1. Apr 27, 2013 #1
    Hi There, quite an informative forum.

    Im struggling with a question which reads as follows:
    At a certain point during the expansion cycle in a steam engine cylinder, the steam pressure was 1.1 MPa and the dryness 0.85, At the end of the expansion process the pressure was 0.28Mpa and the dryness 0.80, assume that the expansion obeys the law PV^n=C.

    The value of the the n, index is asked. Im struggling to find it.

    I used the steam table to get the values of vf and vg for a pressure of P1 1100kPa and used the formula v= xvg +(1-x)vf and get v= 0.15m^3/kg,

    I cant find the value 0.28Mpa=280kPa on the steam table and i cant get v2 which will allow me to calculate the index n by using P1V1^n=P2V2^n as the steam will be behaving like a ideal gas as i understand it?

    Thanks in advance for the help.

    Any tutorials with worked out examples on non flow steam processes that anybody can make available to me?

    Last edited: Apr 27, 2013
  2. jcsd
  3. Apr 27, 2013 #2


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    Staff Emeritus
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    Homework Helper

    Atmospheric pressure is 101.325 kPa. Your exhaust steam is 280 kPa. Get a better set of steam tables. Hint: Google is your friend.
  4. Apr 29, 2013 #3
    Thanks for the hint, helped me alot :)
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