×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pressure drop vs. Valve opening in Critical flow

Pressure drop vs. Valve opening in Critical flow

Pressure drop vs. Valve opening in Critical flow

(OP)
Hi, I am struggling in modeling of multiphase flow valve in oil and gas production pipeline.

I am using Hydro long model, and trying to find C_T value (Throttling coefficient) to be matched with the measured pressure drop.

One interesting thing I found is for critical flow pressure drop decreases as decreasing valve opening (C_T value), while the pressure drop increases as decreasing valve opening for subcritical flow case.

I am looking for some theoretical background why pressure drop decreases as decreasing valve opening in critical flow. Is there anyone who knows why? Or my result is completely wrong?

Thanks.

Best regards,
Keunsoo

RE: Pressure drop vs. Valve opening in Critical flow

It sounds like the model drops into a phase-change subroutine in the critical flow case and stays out of that subroutine in the sub-critical case.

It may or may not be valid, but critical flow in a multiphase line is absolutely the most chaotic condition that we see in fluid mechanics--gas flow is choked, but liquid flow is not, at what point does the liquid see very low pressure, what is the JT component, and a thousand other unknowables. Any assumption will be wrong at least as often as it is right.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: Pressure drop vs. Valve opening in Critical flow

(OP)
Thank you very much for the answer.

Either subcritical or critical flow, my model includes phase change - mass fraction is from the pressure and temperature measurement in three positions of valve: 1) valve inlet, 2) valve outlet, 3) downstream of valve when flow reattach the wall.

Then can we find more clear answer why pressure drop decreases as closing valve more..?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources