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Thermodynamics - Steady State Nozzle, find area of inlet/exit

  1. Oct 25, 2015 #1
    1. The problem statement, all variables and given/known data
    In a jet engine, a flow of air at 1000 K, 200 kPa, and 40 m/s enters a nozzle, where the air exits at 500 m/s and 90 kPa. What is the exit temperature, inlet area, and exit area, assuming no heat loss?

    2. Relevant equations
    min = mout = m
    where m = mass air flow
    dE/dt cv = Qcv - Wcv + Σmin(h+ (Vin/2)2 + gz) - Σmout(h+ (Vout/2)2 + gz)

    exit area:
    m = ρAV
    where m = mass air flow, ρ = density, A = area, V = velocity

    3. The attempt at a solution
    I've already solved for the exit temperature to be 890 K. I just need to know how to find the exit/inlet areas.
     
  2. jcsd
  3. Oct 25, 2015 #2

    SteamKing

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    Staff Emeritus
    Science Advisor
    Homework Helper

    If there is no mass addition between the inlet and the exit, then doesn't continuity apply?

    I don't know if you will be able to find the individual areas, but you should be able to calculate an area ratio between the inlet and exit.
     
  4. Oct 25, 2015 #3
    In our problems with nozzles, I believe we are assuming the following:
    • closed system
    • steady state (de/dt = 0)
    • W = 0
    • Q = 0
    • PE = 0
    I have emailed my teacher regarding the problem with the areas. I figured she must have left m out on accident. I just wanted to come on here and make sure. Thanks for your help as always SteamKing
     
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