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Homework Help: SFEE + Air Question (REPLY SOON PLEASE)

  1. May 9, 2009 #1
    1. The problem statement, all variables and given/known data

    See attachment please (Note: a lot of extra information is given, all of the information given for the compressor is possibly redundant).

    2. Relevant equations

    1) SFEE (steady flow energy equation): q + W = (h2 - h1) + c2^2 - c1^1/2000 + g(z2 - z1)/1000

    2) Isentropic relationship: T2/T1 = (p2/p1)^(y-1/y).. (where y = gamma = 1.4)

    3. The attempt at a solution

    Apply the SFEE to find T2, but how?

    I have tried the following:

    q + W = (h2 - h1) + c2^2 - c1^1/2000 + g(z2 - z1)/1000.. where W = 0 (no shaft used), c2^2 - c1^1/2000 = 0 (no velocity information provided) and g(z2 - z1)/1000 = 0 (no change in height).

    Therefore: q = (h2 - h1)
    q = cp (T2 - T1).. where cp = 1.01kg/K, and cp (T2 - T1) is (h2 - h1) for an isobaric process.

    Multiplying both sides of the equation by mass flow rate (so that the power given (i.e. heat) can be used in the equation).
    q x m = heat energy [kW].

    I get an answer of 5229.3 degrees C. (convert units to Kelvins during calculations).

    Thanks in advance.

    Attached Files:

    Last edited: May 9, 2009
  2. jcsd
  3. May 10, 2009 #2
    Never mind. I got my answer.
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