As the outlet pressure to be lower than the inlet, the stream won't flow backwards to Expander. Is it right?

long ago, i inquired to the head engr at Mafi-Trench regarding liquid formation at/downstream of the expander and the response was that liquid does not form until long downstream from the expander. in this case, the pipe from expander went to the demethanizer.

You need to characterize the two phase flow downstream of the expander, which is vertical upflow, to understand what is going on.

Good Luck,
Latexman

Dear All,
Thanks to All,
I think the difference of pressure is not a good explanation, since from the outlet of Expander up to Vessel inlet the differential pressure is so low.
However, Can you Mr Latexman be clearer by characterization of the Flow, to understand this matter.

Regards,

It's not an exact science, but it can give you insight into the flow patterns. I just snipped random examples below to show the basic idea.



You'll need to research and find a correlation and phase map for your situation.

Good Luck,
Latexman

Thanks Mr Latexman for your technical reply that I do actually appreciate them very well. for our case, Which of the Flow patterns can be our case in order achieve this flow without problem.
Regards,

This was an interesting 2 phase flow observation which I believe is assisted by the formation of very fine drops from the expander, and easily carried along with the gas flow. The coalescing to a liquid phase requires low velocity and a little time. The actual settling time is from Stokes Law considering the droplet size and density.

Condensation of a liquid phase from gas (or second liquid phase from liquid) by dropping bulk fluid temperature is very fine droplets. Ground fog and clouds in the sky are common examples of mists with drop size way smaller than any liquid condensed on heat transfer surfaces.

best wishes always,
sshep

Thanks sshep, your explanation seems to be covering our case. However, is there any software can give answer to our phenomenon.
Regards,