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Homework Help: Thermodynamics Steam Question

  1. Jul 11, 2017 #1
    1. The problem statement, all variables and given/known data
    Steam at a pressure of 4 MPa and 400 C and flow rate of 10 kg/s is expanded in a turbine to a pressure of 10 kPa. If the isentropic efficiency of the turbine is 0.85 then the actual power produced by the turbine is?
    2. Relevant equations:
    ηt= (m(h1-h2))/(m(h1-h2s)) = (W act) / (W max)
    s2s=sf +x(sfg) <~~ To get quality
    h2=hf +x(hfg)
    3. The attempt at a solution
    I started by looking up enthalpies and entropies at state one and two. Since s2s = s1, i used sf and sfg of P2 to find the quality and used that quality to find h2. I substituted all known values into the isentropic efficiency equation and i found h2s. After that, i plugged in all known values back into the Isentropic Eff eqn to solve for Wact and its incorrect. Did i miss a step or did them incorrectly?
  2. jcsd
  3. Jul 15, 2017 #2
    Please show the details of your calculations so I can check your numbers.
  4. Jul 15, 2017 #3
    I figured out what I did wrong, I used: h2=h1-nt(h1-h2s) to solve for h2 and my number was correct.
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