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Homework Help: Thermodynamics Steam Turbine Internal Efficiency Question

  1. Dec 10, 2012 #1
    1. Steam into a steam turbine at 7 MPa and 500 deg C. The turbine has an internal efficiency of 90 %. The steam exhausts at 20 kPa.

    1) What is the exhaust enthalpy?
    2) What is turbine work?
    3) What is the quality of the exhaust steam?

    This is a question I got on a 2nd class boilers branch thermodynamics exam, can anyone tell me what is the equation for internal efficiency of a steam turbine?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Dec 10, 2012 #2


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    Check out the following article:

    [/PLAIN] [Broken]

    Scroll down until you reach the section titled "Isentropic Turbine Efficiency"
    Last edited by a moderator: May 6, 2017
  4. Dec 10, 2012 #3
    I don't see any link steamking.......????
  5. Dec 10, 2012 #4
    Hi Frock,
    The equation I suspect you are looking for is as follows:

    efficiency (turbine) = Actual turbine work / isentropic turbine work
  6. Dec 10, 2012 #5


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  7. Dec 11, 2012 #6
    Thanks for all the replies guys. It was so simple, I am embarrassed. I have never heard Isentropic Efficiency referred to as Turbine Internal Efficiency and that threw me. If I didn't go into panic mode in the exam and had thought about it as Isentropic then I would have seen that the info they had given pointed to Isentropic. Once again thanks for the help.
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