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xnou December 2, 2019 03:14

LNG BOG Ejector
Hello everyone,

Could anyone please help me to simulate the LNG BOG Ejector.


Gert-Jan December 2, 2019 03:53

I think no one on this forum knows what a LNG BOG Ejector is..........

xnou December 2, 2019 23:58

1 Attachment(s)
Hello Jan,

Thanks for reply!!

Ejector is a device in which pumping effect is achieved using motive fluid.

In a jet ejector the static pressure energy of the
motive flow which cannot be directly transferred
is thus converted into kinetic energy. This kinetic
energy can be released to the suction flow
by impulse transfer while both flows mingle.
the diffuser converts the kinetic energy of the
mixture consisting of motive flow and suction
flow back into static pressure energy.

so basically it acts as CD nozzle but having two inlets for different fluids. In my case LNG is entering from one inlet and BOG is entering form the second inlet, and then both the fluid gets mixed and passes through the diffuser section. During the mixing of both fluid phase transferred happens and because of this phase transfer and geometric diffuser section there is pressure rise happened at the diffuser outlet.

i am facing the difficulty in defining the phenomenon for phase transfer.
I have attached "ejector.jpg".


Ravi Karan

Gert-Jan December 3, 2019 02:32

Still don't know what BOG is.

Nevertheless, accurate phase transfer in such a system is very difficult. You need to include nucleation, (over)saturation, mass transfer, bubble growth, etc. And all that in a case where total energy is required. This is very difficult.
Since I don't know your background and your starting point, I don't know how to start helping.

Without a decent background, your options are 1) a very simplified case, 2) read a few PhD-thesis and come back in a year or 2, or 3) quit.

xnou December 3, 2019 04:28

Hello Jan,

I really appreciate your effort to help me.

Lets move step by step as suggested by you. could you help me how to simulate evaporation of LNG (Liquefied Natural Gas).


ghorrocks December 3, 2019 06:19

Have a look at the CFX tutorials, available on the ANSYS Customer website. There are no LNG evaporation examples, but there are some phase change examples. If you want an example closer to your exact case contact ANSYS support as they have a wide range of examples so if you talk to them they might be able to give you a starting point.

xnou December 4, 2019 00:57

@ghorrocks, I am discussing with them, even Ansys guys are also figuring out. i got some paper in internet who has done in fluent. will it be possible for you to look into that and guide me.

xnou December 4, 2019 01:04

Hi Jan,

I am working in CFD domain from last 6-7 years. i have performed many external and internal CFD simulation for HP and LP bypass control valve. recently i have simulated erosion (sand erosion using tabak-off and finnie model in choke valve) and also in wet steam erosion.

but so far i have not work for any phase change simulation.

ghorrocks December 4, 2019 05:15

You are doing a very complex simulation which is going to take a lot of development to get working. So no, I cannot guide you through it as I am a busy person. If you ask a specific question we will try to answer it. But no guarantees as your topic is very specialised.

Gert-Jan December 4, 2019 08:14

And the same applies for me. I am very busy and do not have time to start with you from scratch. Please come with specific questions. Then we can see what we can do.

xnou December 5, 2019 02:59

@ghorrocks&Jan, i can understand. will come back with some specific question.

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