What is the exit steam velocity?

In summary, the problem involves steam at 15 bar and 280°C entering a nozzle with an initial velocity of 125 m/s. The steam exits with a specific enthalpy of 2800 kJ/kg and experiences a heat loss of 25 kJ/kg. The task is to find the exit steam velocity, using equations for heat transfer and specific enthalpy. By referencing steam tables, the specific volume and specific enthalpy of the steam can be determined. The problem can then be solved per unit mass, without needing to find the mass or area.
  • #1
Nemo's
69
0

Homework Statement


Steam, at 15 bar and 280oC, enters a nozzle with an initial velocity of 125 m/s. The steam enthalpy at the exit section is 2800 kJ/kg and the heat loss is 25 kJ/kg. What is the exit steam velocity?.

Homework Equations


1)Qin - Qout = m [h2-h1+((c22-c12))/2]
2)h = Pv + u
3)A1c1/ρ1 = A2c2/ρ2

The Attempt at a Solution


0-25k = m((2800-h1)+-125^2/2)

Steam is not an ideal gas so I can't use Pv=mRT. I have two unknowns and I don't know where to start. I hope you can help.
 
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  • #2
For steam at 15 bar and 280 C, from your steam tables, what is the specific volume and the specific enthalpy?
 
  • #3
Nemo's said:

Homework Statement


Steam, at 15 bar and 280oC, enters a nozzle with an initial velocity of 125 m/s. The steam enthalpy at the exit section is 2800 kJ/kg and the heat loss is 25 kJ/kg. What is the exit steam velocity?.

Homework Equations


1)Qin - Qout = m [h2-h1+((c22-c12))/2]
2)h = Pv + u
3)A1c1/ρ1 = A2c2/ρ2

The Attempt at a Solution


0-25k = m((2800-h1)+-125^2/2)

Steam is not an ideal gas so I can't use Pv=mRT. I have two unknowns and I don't know where to start. I hope you can help.
1. What's the enthalpy of the steam in the nozzle inlet?
2. What have you done with the heat loss of 25 kJ/kg which occurs while the steam passes thru the nozzle?
 
  • #4
Chestermiller said:
For steam at 15 bar and 280 C, from your steam tables, what is the specific volume and the specific enthalpy?
Thanks for letting me pay attention to the tables.
h1=2789.88
v=0.132
Now if I can only get the area I can use m= A*c1/ρ1 to get m and then substitute in 1 to get c2.
 
  • #5
Nemo's said:
Thanks for letting me pay attention to the tables.
h1=2789.88
v=0.132
Now if I can only get the area I can use m= A*c1/ρ1 to get m and then substitute in 1 to get c2.
You don't need to determine m or A, because you are going to solving the problem per unit mass. The 25 kJ/kg is already per unit mass. So the m should not be in your equation.
 
  • #6
Chestermiller said:
You don't need to determine m or A, because you are going to solving the problem per unit mass. The 25 kJ/kg is already per unit mass. So the m should not be in your equation.
O.k thanks a lot
 
  • #7
I solved it . Thank you anyway
 

Related to What is the exit steam velocity?

1. What is the definition of exit steam velocity?

The exit steam velocity is the speed at which steam exits a system or process, typically measured in meters per second.

2. Why is exit steam velocity important in scientific experiments?

Exit steam velocity is important because it affects the efficiency and effectiveness of a system. It can impact heat transfer, pressure, and flow rate, which can in turn affect the results of an experiment.

3. How is exit steam velocity calculated?

Exit steam velocity can be calculated using the formula v = (2gΔh)^1/2, where v is velocity, g is the acceleration due to gravity, and Δh is the change in height of the steam.

4. How does exit steam velocity vary in different systems?

The exit steam velocity can vary depending on the design and specifications of a system. Factors such as temperature, pressure, and the size and shape of the exit opening can all affect the velocity of the steam.

5. What are the potential hazards of high exit steam velocity?

High exit steam velocity can pose safety hazards in certain situations. It can cause burns or injuries if it comes into contact with skin, and it can also damage equipment or structures if not properly controlled.

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