[a.mashayekh]

Hi everybody;

I am working on a project in which I have to consider condensation in humid air.
it is a cross-flow condenser, which it's use is in air conditioning; in it's hot air inlet, the air is mixed with some water vapor, and the other side is cold air. in this process I have to capture the phase change from water-vapor, to water-liquid.

can anyone plz help me in this?! which multiphase model is proper for this simulation?! may I use the mixture model, or it won't include phase changes?! if I should use species to model this project, does anyone know the coefficients that I have to use for condensation (latent heat modelling) and properties that I should set?!

tnx in advance for your helps...

[CFDtoy]

Hi,

use either a two-fluid or even a mixture model - doesnt matter. You need to write appropriate mass transfer function. Not only volumetric condensation - you probably have to model wall condensation as well.

which code are you using to perform these calculations?

Good luck,

CFDtoy

Originally Posted by a.mashayekh

Hi everybody;

I am working on a project in which I have to consider condensation in humid air.
it is a cross-flow condenser, which it's use is in air conditioning; in it's hot air inlet, the air is mixed with some water vapor, and the other side is cold air. in this process I have to capture the phase change from water-vapor, to water-liquid.

can anyone plz help me in this?! which multiphase model is proper for this simulation?! may I use the mixture model, or it won't include phase changes?! if I should use species to model this project, does anyone know the coefficients that I have to use for condensation (latent heat modelling) and properties that I should set?!

tnx in advance for your helps...

[a.mashayekh]

Hi CFDtoy; tnx for ur answer...

I'm using ANSYS 13.0 which seems that have the mass transfer functions embedded in its own models! but the problem is that when I use it, even for the most simple geometries, it won't converge!!! (the equation which this mass transfer function uses is "ranz-marshall")
I've tried it with several different models like, Eulerian and mixture and I've tried each one with different inlet types, different magnitudes for inlets and etc. I just don't know which option I'm using wrong that makes it diverge!!!

so I would be more thankful if you could help me out here...

[CFDtoy]

Hi,

I dont have the recent ANSYS 13 manual - so dont know what input is being specified from your end. Is it possible for you to upload / send ANSYS manual for this feature alone?

I think the settings in the model can clearly help you out here.

I have experience in boiling models both coding and usage (commercial) - convergence can purely be manipulated by the implemented model.

Thanks,

CFDtoy

Originally Posted by a.mashayekh

Hi CFDtoy; tnx for ur answer...

I'm using ANSYS 13.0 which seems that have the mass transfer functions embedded in its own models! but the problem is that when I use it, even for the most simple geometries, it won't converge!!! (the equation which this mass transfer function uses is "ranz-marshall")
I've tried it with several different models like, Eulerian and mixture and I've tried each one with different inlet types, different magnitudes for inlets and etc. I just don't know which option I'm using wrong that makes it diverge!!!

so I would be more thankful if you could help me out here...

[a.mashayekh]

Hi again, and thank for your patience;

as this new version of ansys has a help in java format, I couldn't get a print out of it to send to you; but I got some screen pictures of the settings I set:

1. this picture shows my "Models" tab:


2. this pic is my settings on Eulerian mode:


3. these are my materials:


4. my phases definition:


5. "phase interaction" window:


6. settings on heat transfer method for this feature:


7. and finally the mass transfer model settings:




I hope that these pictures can help both of us!
thanks again; I'm waiting to hear from you...

[manderson010]

I know this thread is a bit old, but did you try changing the "from" and "to" phases in your evaporation-condensation model settings? I am trying to model condensation in my own simulation, and the evaporation-condensation only works for me when it's going from liquid to gas (condensation would then be a negative mass transfer).

-Mike

[satty_00]

Hi ,

I've been trying to solve a similar condensation case. Can I do it without a UDF in Fluent 14 ? I activated the mass transfer model to " Evaporation-Condensation". But when i plot the Volume fraction i do not find proper phase change.

[kaganpe]

Originally Posted by satty_00

Hi ,

I've been trying to solve a similar condensation case. Can I do it without a UDF in Fluent 14 ? I activated the mass transfer model to " Evaporation-Condensation". But when i plot the Volume fraction i do not find proper phase change.

This is the what i have meet before and i cant fixed it. What should i do ? Does anyone has any idea ?

[syavash]

Originally Posted by kaganpe

This is the what i have meet before and i cant fixed it. What should i do ? Does anyone has any idea ?

That built-in model acts based on semi-empirical coefficients which should be specified in the corresponding panel. Actually there is no clear reasoning what it should be considered. You'd better write a UDF and define appropriate source terms for condensation/evaporation phase change.
Bests

[farr24]

hii
and finally did you find a solution for your problem ?