6 replies to this topic

[tkeung]

Hello all,

It has been a pleasure reading through threads and getting professional advice from experienced professionals here!

We are designing a gas plant, where 2-phase flow (gas-liquid) is present in several lines.
In general, how is slug flow analysis done? Is there any reference or books that talk about predicting slug flow behavior?
We are particularly concerned about problems presented by slugging in vertical lines going into fractionation columns.

Thank you,

tkeung

[aransari85]

Hi,

Vertical line with a mixed flow should have annular flow or bubble flow for entire range of flow of operations. Slug flow shall be avoided beacuse it gives sudden fluctuations in pressure in the line or downstream equipment if its column, if downsteam equipment is vessle it may be considered to have sufficient residance time to withstand the fluctuation.
Froath motion to be avoided in all cases.

Aziz's plot is used to determine the regim of flow of operation.

Attached is its formula version which tells about region of operation of flow..

Regards,
ARA

[aransari85]

Hi,
this is the attached file..
Regards,
ARA

[kkala]

I once tried to assure annular flow in a ~300 mm dia tube to be self cleaned (Fertilizers,1980). Flow patterns in vertical parts of pipes looked uncertain and flow could be unstable, due to holdups. Reduced flow at turn over made situation more complex. See http://www.engineeri...ples_slug2.html.
Gas and liquid are separated in critical applications, e.g. upstream gas burners, but not upstream distillation columns. N.P. Lieberman (A working guide to Process equipment, 2008, para 39.3 mixed phase velocity) recommends 5 m/s (*) as sum of gas+liquid flow, in order to have homogeneous flow, thus no slug flow. This may not be easily realized, but it could be helpful in combination ⁽¹⁾ with modern software to predict flow paterns. Modern software can be more precise, I am not aware of its possibilities, neither I am expert. Other members can probably help. Of course turn down situation (not only normal) should be considered.

Note (*) : Please verify N P Lieberman (my book is in the country for summer vacations), I do not remember whether 5 m/s concerns vertical flow too.

(1) editing note: sum of velocities>5m/s for critical lines, prediction by software in other lines.

Edited by kkala, 14 January 2012 - 02:59 AM.

[eman3001]

The most complete book on this topic is : " The flow of Complex Mixtures in Pipes", Van Nostrand Reinhold, New York (1972). For flow patterns with supporting data there is a classic reference by Lochart R.W. and Martinelli, R. C. , Chem. Eng. Progr, 45,39 (1949).
Another classic reference is " One -dimensional Two-phase Flow" By G. B. Wallis. McgrawHill (1969).
I hope this helps.

[aransari85]

Hi Kkala,

Here is the file..

Regards,
ARA

Attached Files

•  Document1.pdf   30.39KB   184 downloads

[tkeung]

Thank you for everyone's reply.

Coincidentally I came across a literature that contains guidelines for using equations outlined in attachment by aransari85. I have learned that HYSYS does not do a good job on slug flow analysis, so this is a good tool for determining the fluid flow regime.