Learning Forum

[satyam20]

Hello

I am simulating condensation inside a square channel of size 2mm X 2mm. I am using the built in VOF option with lee model but I am unable to see condensation properly. I have already varied the frequency coefficient but was unsuccessful to see condensation.

Do I need to use UDF for source terms?

Thank you

[Rob]

No, but as you need to track the free surface in VOF you may not be getting enough liquid to get started. In the current release I'd look at the Eulerian model for phase change. If you're expecting a "thin" film look at Eulerian Wall Film.

[satyam20]

Thank you for your reply. I am actually working on flow condensation in tube, basically I want to simulate the flow of vapor refrigerant in condenser tubes which will be converted to liquid as it moves through the tubes.

[satyam20]

I have gone through many research papers and in that they have used lee model and some of them have written udf for mass transfer. In my case I tried to use the model with inbuilt setting but I didn't saw any condensation happening.

[Rob]

Interphase mass transfer is still being researched, and therefore expanded on in Fluent: we can only code what's been discovered and quantified. Lee model works well, as do the UDFs: caveat that they're applied correctly. In your case it's potentially more complex, you'll start with a thin film and that may then develop to a "thick" film and/or liquid slugs. Depending on what you expect to happen you then choose the model(s) to suit.
Turn off multiphase (models) and try using the Eulerian Wall Film with phase interaction: you will want 2022R1 for all of the latest numerics. See whether you get condensation, but also check the near wall temperature & residence time. You won't be the first person to model something where the flow conditions mean it's too warm to condense!

[Ella]

hello! i am also running a simulation currently and cannot get the desired condensation in the cooling wall, I wanna try the approach you mentioned, which is using the Eulerian Wall Film model and i could not figure out how to set that, could you please kindly provide me with some detailed procedures. Thanks a lot!

Greetings,

Ella

[shitizsehgal]

Were you able to solve the problem? If not, please get in touch via email: shitizsehgal@tamu.edu. I can try to take a look.


Shitiz

[Rob]

If you have a look in the Help tutorials I think there's either a tutorial or video. Otherwise I'm slightly stuck as I can only offer general advice (that's explained when you register). Are you condensing from a gas mixture or is it a pure vapour?