- #1
Xyius
- 508
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I am doing a problem about steam flowing through a nozzle. Here are the initial and final conditions..
P1=30 bar = 3000kPa
T1=320 C
v= 100 m/s
(v= velocity!)
P2=10 bar = 1000kPa
T2= 200 C
Mass flow rate = 2 kg/s (Steady flow process)
To me it seems like a cut and dry energy balance problem. There is a problem however.
Attempt at a Solution
The mass balance yeilds..
[tex]\dot{m_1}=\dot{m_2}[/tex]
So putting this result in the energy balance.. (PE=0, W=0, Q=0)
[tex]\dot{E_{in}}=\dot{E_{out}}[/tex]
[tex]h_1+\frac{1}{2}v_{1}^2=h_2+\frac{1}{2}v_{2}^2[/tex]
This is where the problem comes in. The enthalpies for these two states (from the tables) are..
h1=3043.5 kJ/kg
h2=2828.3 kJ/kg
I am getting a velocity LESS than the initial. This doesn't make sense considering it is a nozzle and should be speeding up. And yes I converted the KE into KJ.
P1=30 bar = 3000kPa
T1=320 C
v= 100 m/s
(v= velocity!)
P2=10 bar = 1000kPa
T2= 200 C
Mass flow rate = 2 kg/s (Steady flow process)
To me it seems like a cut and dry energy balance problem. There is a problem however.
Attempt at a Solution
The mass balance yeilds..
[tex]\dot{m_1}=\dot{m_2}[/tex]
So putting this result in the energy balance.. (PE=0, W=0, Q=0)
[tex]\dot{E_{in}}=\dot{E_{out}}[/tex]
[tex]h_1+\frac{1}{2}v_{1}^2=h_2+\frac{1}{2}v_{2}^2[/tex]
This is where the problem comes in. The enthalpies for these two states (from the tables) are..
h1=3043.5 kJ/kg
h2=2828.3 kJ/kg
I am getting a velocity LESS than the initial. This doesn't make sense considering it is a nozzle and should be speeding up. And yes I converted the KE into KJ.
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