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Homework Help: Converging and diverging nozzles

  1. Apr 29, 2015 #1
    1. The problem statement, all variables and given/known data
    air flows through a device such that the stagnation pressure is 0.6 MPa, the stagnation temperature is 400° C, and the velocy is 570 m/s.
    Determine the static pressure and temperature of the air at this state.

    2. Relevant equations
    Tt=T + V2 / 2 Cp where Cp is 1.005 Kj/ Kg* ° K

    3. The attempt at a solution
    what I did was Isolate for T since that is what I am looking for.

    2 Cp x Tt - v2 = T
    somewhere in here I know I have to throw in 1000m2/s2/ Kj/kg °k
    when I do that I get -323.5 ° K

    the answer is 518.6 ° K

    Someone please let me know where I have gone wrong. Thank you
  2. jcsd
  3. Apr 29, 2015 #2


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    Your algebra is a little dodgy in solving for T.

    The correct equation is:
    Tt = T + [V2 / (2 Cp)]

    which means your equation for T is incorrect. :frown:
  4. Apr 29, 2015 #3
    brackets or no brakets, wouldn't T stay the same when isolating it?
  5. Apr 29, 2015 #4


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    Tt = T + [V2 / (2 Cp)]

    T = Tt - [V2 / (2 Cp)]

    But you had

    2 Cp x Tt - V2 = T

    which is not the same. Apparently, you multiplied only one side of the equation by (2 Cp).
  6. Apr 29, 2015 #5
    hmm, not sure how you get that equation but I'm still not getting the right answer. I will have to ask the professor tomorrow
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