×
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

DIERS applicability for two phase flow

DIERS applicability for two phase flow

DIERS applicability for two phase flow

(OP)
I am into process engineering and part of my job involves specifying
thermophysical data and flows for various safety valves.Currently I am working on a process which contains C1-C4 hydrocarbons.I have this process fluid which is vapor at normal condition but when I flash it adiabatically to a higher pressure i.e. at its relieving pressure under a blocked outlet condition I get a two phase fluid.Now when I am reporting data for the the relief valve should I take into account DIERS criteria or simply report data for two phase flow

RE: DIERS applicability for two phase flow

ab84 - I suggest you re-state your inquiry. It's not clear.

I'm guessing that you're trying to describe a supercritical fluid in the protected vessel, which transitions to a 2-phase stream on the outlet side of the PSV. But, that's not what you wrote, so I'm not sure I'm interpreting it correctly.

RE: DIERS applicability for two phase flow

(OP)
I wanted to know whether DIERS analysis should be carried out for any scenario involving two phase flow in sub-critical region

RE: DIERS applicability for two phase flow

(OP)
I intend to say two phase flow at PSV inlet at relieving pressure

RE: DIERS applicability for two phase flow

Yes, Diers methodology should be used whenever there is 2-phase flow entering the PSV.  

RE: DIERS applicability for two phase flow

What pressures and fluids are you talking about? It looks like you have a supercritical relief (reported as two phase by simulators?)

RE: DIERS applicability for two phase flow

(OP)
Well I was of the view that DIERS analysis only applies when we are concerned about fire scenario....but does it applies to all other relief scenario's as well

RE: DIERS applicability for two phase flow

It also applies to exothermal reactions, decompositions, anything that may makes your liquid foam and have a biphasic relief stream at the relief device inlet.

RE: DIERS applicability for two phase flow

DIERS is simply a methodology to evaluate relief valve capacity for two phase relief.

The PSV doesn't care how/why it has to handle two phase flow.

RE: DIERS applicability for two phase flow

(OP)
I was of the view that DIERS is applicable when you are not certain about the mass fraction of the phases at the PSV inlet.For a blocked outlet case when you know the mass fraction of the phases at PSV inlet,I am certain that DIERS does not apply

RE: DIERS applicability for two phase flow

@ab84 - DIERS methodology provides a way to calculate the orifice size for a relief device that has a 2-phase stream entering the device. That calculation methodology doesn't depend on the cause of the 2-phase relief. There's a wide range of possible causes, and fire exposure is just one of them. In almost every 2-phase case the phase composition is a transient - the phase split varies from the time the relief begins until the time that it ends. In many cases, the 2-phase stream will transition into an all-vapor relief. In others, such as those in which the fluid is foamy, the 2-phase release may continue until the vessel is empty.

So, be cautious about says you know the phase fraction, and regardless of that split, the DIERS method is the best available technology for safely sizing the relief device.

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