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-   -   modeling condensation in humid air... (http://www.cfd-online.com/Forums/fluent/91513-modeling-condensation-humid-air.html)

a.mashayekh August 13, 2011 07:12

modeling condensation in humid air...
 
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 September 22, 2011 11:26

condensation
 
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

Quote:

Originally Posted by a.mashayekh (Post 319979)
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 September 22, 2011 12:17

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 September 29, 2011 11:56

convergence issue
 
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

Quote:

Originally Posted by a.mashayekh (Post 325257)
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 September 29, 2011 14:11

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:
http://www.pic.iran-forum.ir/images/...jof9d9lmxa.jpg

2. this pic is my settings on Eulerian mode:
http://www.pic.iran-forum.ir/images/...vynzewc6vt.jpg

3. these are my materials:
http://www.pic.iran-forum.ir/images/...1jv5ds6915.jpg

4. my phases definition:
http://www.pic.iran-forum.ir/images/...pajrvpvkxd.jpg

5. "phase interaction" window:
http://www.pic.iran-forum.ir/images/...kp6ieznabc.jpg

6. settings on heat transfer method for this feature:
http://www.pic.iran-forum.ir/images/...v8f5l3yvku.jpg

7. and finally the mass transfer model settings:
http://www.pic.iran-forum.ir/images/...cxbmapxrja.jpg



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

manderson010 July 30, 2012 11:40

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 August 21, 2014 03:03

Similar Condensation problem
 
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 August 29, 2014 02:56

Quote:

Originally Posted by satty_00 (Post 506960)
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 August 29, 2014 17:04

Quote:

Originally Posted by kaganpe (Post 508275)
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 May 7, 2015 19:12

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


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