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

adsorption of moisture

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 1, 2005, 21:36
Default adsorption of moisture
  #1
prasanth
Guest
 
Posts: n/a
hi,

what model would you suggest to simulate adsorption of moisture from air flowing through the silica-gel bed by the particles of the silica gel?

In multiphase model, we can specify these phases, but adsorption is a kind of reaction, hence i am thinking mass-tranfer in multiphase model wont do this.

will species transport model can do this?

awaiting an early response
  Reply With Quote

Old   June 1, 2005, 22:33
Default Re: adsorption of moisture
  #2
us
Guest
 
Posts: n/a
How about flow through porous media?
  Reply With Quote

Old   June 1, 2005, 22:43
Default Re: adsorption of moisture
  #3
prasanth
Guest
 
Posts: n/a
yeah, I too had thought about it. Actually, silica gel bed consists of small particles of silica gel. Also, how can we specify moisture being observed by silica gel.
  Reply With Quote

Old   June 2, 2005, 09:31
Default Re: adsorption of moisture
  #4
Amir
Guest
 
Posts: n/a
I have the same problem to solve but I haven't been able to get it converged yet First I tried to just solve for energy and species transport then I specified a porous media and solved for momentum and continuity too. It's been hard to get a realistic answer out of that. Still working on that though. I would be glad to hear what you guys come up with in this regards

Amir
  Reply With Quote

Old   June 2, 2005, 15:31
Default Re: adsorption of moisture
  #5
Allan Walsh
Guest
 
Posts: n/a
  Reply With Quote

Old   June 2, 2005, 19:13
Default Re: 2nd try adsorption of moisture
  #6
Allan Walsh
Guest
 
Posts: n/a
Hit the post message a bit too quickly last time.

Your options depend on how much time you want to spend and what sort of information you need.

If you just want mass loss, you could specify the absorbent region as porous cells and then go in and specify the region as a global sink for gas-phase H2O. Porous cells have the added benefit that you can set the parameters to give a representative pressure loss, if that is your intent.

Otherwise, you could add include some internal walls and have the absorption set to be a surface reaction (i.e water vapor to a hydrated form of the silica gel).

Or, you could set the gel region of your domain as porous cells and then write a UDF that does a better job of representing the physics of absorbtion (effects of surface area, velocity, temperature, etc.) For me, I would allocate at least a few weeks to write this kind of UDF. The previous approaches should require somewhat less time.
  Reply With Quote

Old   June 6, 2005, 00:27
Default Re: 2nd try adsorption of moisture
  #7
prasanth
Guest
 
Posts: n/a
hello Allan

thanks for your prompt reply and sorry for not replying immediately.

in your message: "If you just want mass loss, you could specify the absorbent region as porous cells and then go in and specify the region as a global sink for gas-phase H2O. Porous cells have the added benefit that you can set the parameters to give a representative pressure loss, if that is your intent."

our aim is to get that mass loss of h2o and air with reduced moisture comes out the unit. As u said, HOW TO SPECIFY THE POROUS CELL AS GLOBAL SINK FOR GAS-PHASE H20. looking for your reply

thanks prasanth
  Reply With Quote

Old   June 6, 2005, 13:30
Default Re: 2nd try adsorption of moisture
  #8
Allan Walsh
Guest
 
Posts: n/a
For global source/sink term, just click off the source box for the fluid region of interest and then go to the source tab and specify it. But, perhaps that really wasn't your question?
  Reply With Quote

Old   June 7, 2005, 06:23
Default Re: 2nd try adsorption of moisture
  #9
prasanth
Guest
 
Posts: n/a
hi alan

i know the optin of source term, infact i used for my earlier analysis. As you said, if we specify mass source, the mass transfer will be between air and water vapour. but we want the porous medium (silica gel) to absorb moisture from moist air.

Hope you understood my point and thanks for your kind response

prasanth
  Reply With Quote

Old   July 9, 2009, 10:41
Default
  #10
New Member
 
Join Date: Jul 2009
Posts: 7
Rep Power: 8
_Greg_ is on a distinguished road
Hi,

If you want the porous media to adsorb moisture then i see 2 possibilites :

if you use a local equilibrium model for adsorption kinetic then the surface reaction capabilites of FLUENT could be enough.

if you use another kinetic model like Linear Driving Force to represent the mass transfer between column scale and macropores then you can use an UDF to modelize it. Then you will need to implement adsorption isotherms and add source terms on species transport, continuity and energy equations.
_Greg_ is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
moisture flow in wall assembly Saba FLUENT 0 January 20, 2009 11:42
no input for moisture content rayy FLUENT 2 March 14, 2007 08:09
Need help on PDEs for Adsorption process Miles Main CFD Forum 0 March 23, 2006 11:59
moisture transfer through membrane m. Nasif FLUENT 0 October 23, 2003 03:41
moisture in coal combustion Sheng FLUENT 3 June 15, 2003 19:43


All times are GMT -4. The time now is 01:19.