Steam Condition after PSV of Boiler

[ropumar]

Considering a Boiler that produces dry saturated steam at 16barg.

I would like to known temperature of steam at psv of boiler outlet pipe.

Would be reasonable to consider adiabatic expansion and PSV would superheat the steam, and temperature would be around 150Celcius at ATM as shown on attached image?

 

[ropumar]

PSV discharge to atmosphere vent.

 

[Latexman]

Your methodology and answer is correct.

This is your second post. Both feel homework-ish to me. We don't do homework here. You can get help with homework here

http://www.engineering.com/AskForum/aff/28.aspx

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[EmmanuelTop]

... where all topics have zero replies - ultimately, you will have to do your homework.

Dejan IVANOVIC
Process Engineer, MSChE

 

[ropumar]

Is not homework, although no way I can convince you guys.

Will refrain posting then, until I have a more "professional" question.

Or post on the link suggested then.

 

[MortenA]

Be as it may, ropumar but please note that it was very early concluded that you methode was right (its just a rare thing that one would be concerned with the exit temperature and the degree of superheating for steam that is vented to the atmosphere expect maybe for curiosity).

 

[ione]

From a theoretical point of view your answer is correct, but since in the real world the “dry saturated” steam is hardly dry, depending on the starting quality of your steam the result could be that of having an increased steam quality.

 

[katmar]

The quality that is assumed for the steam can have an impact on the sizing of the downstream piping. The flow through the PSV (in mass terms) is probably a function of the steam quality. The lower the quality of the steam, the lower the temperature - and therefore the lower the velocity - of the exiting steam will be. This may or may not be important. This sort of question is best answered by the manufacturers of the valves. The top suppliers will have plenty of hands-on experience and engineering guide books to help you. In a case like this you are ususally more interested in a safe answer than a theoretically correct one.

Assuming adiabatic expansion and 100% quality will give you the highest temperature and velocity, and is therefore probably a safe assumption even if it is not entirely correct.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[ropumar]

I saw that Latexman first line was the answer I looked for and I am grateful to him, and to others that helped.
My comment is because I recognized that given that I am fresh out of college, this forum might be a sea for bigger fish than myself. Was out of humility, no sarcasm or rudeness intended.

The insight regarding quality of steam is interesting also and I appreciate.

I would believe that is safe to assume also that each Pressure reducing valve on the supply header would increase quality of steam immediately after, which is something I haven't thought before.

 

[ione]

Ropumar,

Just a final note. In your OP you have represented the process through the valve as an isenthalpic one on the P-H chart. Neglecting the heat loss due to friction (this confers irreversibility to the process) you can assume the starting and final enthalpies are the same, but it's not true to say that the enthalpy does remain constant during the overall process.