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Homework Help: Thermodynamics; Pressure and Temperature at the Nozzle inlet

  1. May 7, 2012 #1
    1. The problem statement, all variables and given/known data
    CO2 gas enters a nozzle with an isentropic efficiency of 83% with a low velocity. It exits the nozzle at 110 kpa and 59K and 246m/s. Determine the pressure at the nozzle inlet assuming:

    2. Relevant equations
    -Constant specific heats at room temperature
    -Variable specific heats

    3. The attempt at a solution
    I first started by using the energy balance equation of a single stream steady flow device, and simplified it to:
    Q=m(h2-h1) + 1/2(V2^2)

    The isentropic equation is ╬ĚNozzle= (T2a-T1)/(T2s-T1)

    I am at a loss in finding the inlet temperature and pressure. I am not sure how i should start of solving this question and what method to use.
  2. jcsd
  3. May 7, 2012 #2

    rude man

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    Gold Member

    Anyone know what "83% isentropic efficiency" means? That 17% of the heat escapes?
  4. May 7, 2012 #3
    Isentropic Efficiency= Measures the deviation of actual processes from the corresponding isentropic ones.

    Thus, for a nozzle:

    0.83= Actual Kinetic Energy at Nozzle Exit/ Isentropic KE at Nozzle Exit
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