7 replies to this topic

[moein_omg]

Dear friends,

 

Does anybody have any experience regarding PRVs which relieve two phase flow. As far as know there are two separate categories of such scenarios: 1) subcooled or saturated liquids which flashes upstream or downstream of the throat making a two-phase flow and 2) when the fluid is initially 2 phase

actually the first scenario is quite plausible; however, the latter scenario (when the fluid is initially 2 phase) seems impractical as PSV/PRVs are usually installed in high point therefore they have to relieve only gas which is accumulated at the top to depressurize the system.

 

Actually this is a question that has occupied my mind for a long time and I doubt about necessity of existence of the second scenario. I want to know when we Have to size the PRV for multiphase flow.

 

please kindly provide me with industrial example if you have reverent experience.

 

Best Regards

[ahmadikh]

 Moein,

 

Interesting question! I used to think about chemical reactions only, but it seems that there would be other scenarios though remote. Take a look at the following link that I found on Google:

 

http://www.equityeng...tion-and-sizing

 

Hope this helps...

 

Best,

Milad

[shan]

When a separator loose its separation function (such as a blowby scenario from upstream HP vessel due of level control valve failure), the PSV has to release 2 phase flow.

[moein_omg]

Dear ahmadikh,
Such an excellent link.
Thanks

[moein_omg]

Dearshan,
The case you mentioned is quite plaussible but are there any real industrial case in which the PRV is sized considering a 2 phase relief senario?

[latexman]

Moein,

 

In the synthetic latex industry, there can be a significant amount of surfactant in an aqueous mix of monomer and polymer in various tanks and vessels, the reactor included.  As such, it is difficult to imagine there will not be 2-phase flow in the fire exposure and runaway reaction scenarios; i.e. 2-phase flow is a certainty when boiling.

[shan]

Please refer to Section 3.15.3.3 Mixed Phase of API-521.

[serra]

many processes can require two phase

depending from operating conditions,

many authors as Leung have published papers on the subject,

Leung has introduced the (simplified HEM) omega method and discussed applications for valves, piping etc.

Rigorous models for

HEM (Homogeneous Equilibrium),

HNE (Homogeneous Non Equilibrium),

NHNE (Non Homogeneous Non Equilibrium) are available,

the different models have specific areas of application, see for example

 

"http://www.cheresour...design-rating/"

 

the topic has been discussed at cheresources,

you may find several threads discussing different aspects.

Edited by serra, 10 December 2014 - 02:49 AM.