CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

modeling condensation in humid air...

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By farr24

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 13, 2011, 08:12
Default modeling condensation in humid air...
  #1
New Member
 
Alireza Mashayekh
Join Date: Aug 2011
Posts: 3
Rep Power: 15
a.mashayekh is on a distinguished road
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 is offline   Reply With Quote

Old   September 22, 2011, 12:26
Default condensation
  #2
Senior Member
 
CFDtoy
Join Date: Mar 2009
Location: United States
Posts: 145
Blog Entries: 2
Rep Power: 17
CFDtoy is on a distinguished road
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 View Post
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
CFDtoy is offline   Reply With Quote

Old   September 22, 2011, 13:17
Default
  #3
New Member
 
Alireza Mashayekh
Join Date: Aug 2011
Posts: 3
Rep Power: 15
a.mashayekh is on a distinguished road
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 is offline   Reply With Quote

Old   September 29, 2011, 12:56
Default convergence issue
  #4
Senior Member
 
CFDtoy
Join Date: Mar 2009
Location: United States
Posts: 145
Blog Entries: 2
Rep Power: 17
CFDtoy is on a distinguished road
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 View Post
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
CFDtoy is offline   Reply With Quote

Old   September 29, 2011, 15:11
Default
  #5
New Member
 
Alireza Mashayekh
Join Date: Aug 2011
Posts: 3
Rep Power: 15
a.mashayekh is on a distinguished road
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...
a.mashayekh is offline   Reply With Quote

Old   July 30, 2012, 12:40
Default
  #6
New Member
 
Mike
Join Date: Jun 2012
Location: Wooster, OH
Posts: 5
Rep Power: 14
manderson010 is on a distinguished road
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
manderson010 is offline   Reply With Quote

Old   August 21, 2014, 04:03
Post Similar Condensation problem
  #7
New Member
 
Sathya Narayanan
Join Date: Apr 2014
Posts: 18
Rep Power: 12
satty_00 is on a distinguished road
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.
satty_00 is offline   Reply With Quote

Old   August 29, 2014, 03:56
Default
  #8
New Member
 
Kağan Peneklioğlu
Join Date: Oct 2013
Posts: 2
Rep Power: 0
kaganpe is on a distinguished road
Quote:
Originally Posted by satty_00 View Post
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 ?
kaganpe is offline   Reply With Quote

Old   August 29, 2014, 18:04
Default
  #9
Senior Member
 
Ehsan Asgari
Join Date: Apr 2010
Posts: 473
Rep Power: 18
syavash is on a distinguished road
Quote:
Originally Posted by kaganpe View Post
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
syavash is offline   Reply With Quote

Old   May 7, 2015, 20:12
Default
  #10
New Member
 
anonymous
Join Date: Jan 2015
Posts: 3
Rep Power: 11
farr24 is on a distinguished road
hii
and finally did you find a solution for your problem ?
haidernuceng likes this.
farr24 is offline   Reply With Quote

Reply

Tags
condensation, multiphase, phase change

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Humid Air Wim Uyttenhove FLUENT 3 April 9, 2018 10:10
air bubble is disappear increasing time using vof xujjun CFX 9 June 9, 2009 08:59
Modeling air phase diffusion w radioactive decay John Tauxe Main CFD Forum 0 July 3, 2007 16:55
modeling open air conditions Balaji FLUENT 2 November 14, 2004 12:10
Charge air system modeling Lars Ola Liavåg Siemens 0 September 10, 2001 09:23


All times are GMT -4. The time now is 23:59.