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

Simulation of Humid Air

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

Like Tree5Likes
  • 1 Post By Suryan
  • 1 Post By vvvms
  • 1 Post By coglione
  • 1 Post By savate moh
  • 1 Post By A CFD free user

Reply
 
LinkBack Thread Tools Display Modes
Old   March 18, 2010, 19:56
Default Simulation of Humid Air
  #1
New Member
 
Suryan
Join Date: Mar 2010
Location: Dalseo, Daegu
Posts: 3
Rep Power: 8
Suryan is on a distinguished road
Hi All,

How can I simulate the flow of air with a relative humidity of, say, 60% in FLUENT? And how to check the RH once the solution is converged?

Thank you
savate moh likes this.
Suryan is offline   Reply With Quote

Old   March 23, 2010, 05:35
Default
  #2
New Member
 
purple
Join Date: Mar 2010
Posts: 3
Rep Power: 8
vvvms is on a distinguished road
you can use airpak to simulate the RH
savate moh likes this.
vvvms is offline   Reply With Quote

Old   March 23, 2010, 07:52
Default
  #3
Senior Member
 
Max
Join Date: Mar 2009
Posts: 133
Rep Power: 9
coglione is on a distinguished road
If you define your fluid as a gas mixture of chemical species with one component being h20vap relative humidity is automatically available as variable in Fluent.

cheers
savate moh likes this.
coglione is offline   Reply With Quote

Old   May 29, 2013, 16:16
Default
  #4
New Member
 
Join Date: Mar 2013
Posts: 6
Rep Power: 5
savate moh is on a distinguished road
Quote:
Originally Posted by coglione View Post
If you define your fluid as a gas mixture of chemical species with one component being h20vap relative humidity is automatically available as variable in Fluent.

cheers
hi suryan, i'd like to know what have you done with your work? did you find how to simulate it?? i'm simulating thins kind ,i was wondering if you could show me please thx
aiouss likes this.
savate moh is offline   Reply With Quote

Old   April 15, 2015, 11:03
Default humid air simulation
  #5
New Member
 
abidi saad aissa
Join Date: Apr 2012
Posts: 8
Rep Power: 6
aiouss is on a distinguished road
Quote:
Originally Posted by savate moh View Post
hi suryan, i'd like to know what have you done with your work? did you find how to simulate it?? i'm simulating thins kind ,i was wondering if you could show me please thx
hello savate
did youfind how to simulate it in flueunt
I am doing the same thing but I did not know how to simulate it in fleunt

waiting for your answer
best regards
aiouss is offline   Reply With Quote

Old   April 15, 2015, 18:12
Default
  #6
Senior Member
 
A CFD free user's Avatar
 
A-A Azarafza
Join Date: Jan 2013
Posts: 189
Rep Power: 5
A CFD free user is on a distinguished road
Quote:
Originally Posted by aiouss View Post
hello savate
did youfind how to simulate it in flueunt
I am doing the same thing but I did not know how to simulate it in fleunt

waiting for your answer
best regards
My friends,
There is a relationship between relative humidity and water vapor pressure as follows:

RH = P_H2O/ P_sat;

in which, P_H2O is defined as P_tot *y_H2O and P_sat is saturate pressure which is dependent on operating temperature. y_H2O is also water vapor mass fraction. So, having the RH, let's say 0.6, you have, P_H2O = 0.6*P_sat. From which, the y_H2O is obtained as :

y_H2O = P_H2O /P_tot;

and hence if you have air as a gas mixture, then the values for Oxygen and Nitrogen are calculated as:

y_O2 = 0.21*(1-y_H2O);
y_N2 = 0.79*(1-y_H2O);

Finally, you need to input these values as species mass fraction values. You can do that manually or using UDF, if you want to change the RH values. That's all.

I hope it helps
Sylwia likes this.
__________________
Regard yours
A CFD free user is offline   Reply With Quote

Old   April 15, 2015, 21:11
Default
  #7
New Member
 
The Nguyen
Join Date: Jan 2015
Posts: 2
Rep Power: 0
the901 is on a distinguished road
I am doing a simulation of humid air over a flat plate. I am waiting for my paper published then I can send you my work and the paper. General speaking, You need to transfer Relative Humidity to mass fraction of H20 by using the Psychrometrics chart. In material you'd better specify dry air mixing with water vapor in Fluent data. For boundary conditions you prescribe mass fraction for each Boundary in "species tab". Then run the calculation in Transient mode. For relative humidity contour, choose "species"/ relative humidity in "contours graphic". I hope it would help you!
the901 is offline   Reply With Quote

Old   April 16, 2015, 09:49
Default simulation of humid air in fluent
  #8
New Member
 
abidi saad aissa
Join Date: Apr 2012
Posts: 8
Rep Power: 6
aiouss is on a distinguished road
hallo my friends thanks for ur usefull replly

I am simulating heat and mass transfer of humid air in porous media using Fluent
please, I have some questions
1- when I use 0.45 as mass fraction for water vapor and I start my simulation for 10 sec and I want to see the variation of relative humidity, I found RH min(%)= 2133.051 and max(%)=2143.051 that is abnormal values. is it correct or no? or I must divide the mass fraction value by 100 (=0.45/100) firstly.?
2- What is the appropriate model to consider the evaporation and condensation phenomenen because there is condensation of vapor and evaporation with time and temperature variations
3- how can I plot the variation of thermal conductivity as a function of moisture content or as a function of relative humidity?

waiting for your reply
best regards
aiouss is offline   Reply With Quote

Old   April 16, 2015, 09:52
Default
  #9
New Member
 
abidi saad aissa
Join Date: Apr 2012
Posts: 8
Rep Power: 6
aiouss is on a distinguished road
Quote:
Originally Posted by the901 View Post
I am doing a simulation of humid air over a flat plate. I am waiting for my paper published then I can send you my work and the paper. General speaking, You need to transfer Relative Humidity to mass fraction of H20 by using the Psychrometrics chart. In material you'd better specify dry air mixing with water vapor in Fluent data. For boundary conditions you prescribe mass fraction for each Boundary in "species tab". Then run the calculation in Transient mode. For relative humidity contour, choose "species"/ relative humidity in "contours graphic". I hope it would help you!
thank you the901 for your help
I hope you recieve the acceptation quickly
this is my email: asais83@yahoo.fr

thank you again best regards
aiouss is offline   Reply With Quote

Old   April 16, 2015, 09:54
Default
  #10
New Member
 
abidi saad aissa
Join Date: Apr 2012
Posts: 8
Rep Power: 6
aiouss is on a distinguished road
Quote:
Originally Posted by A CFD free user View Post
My friends,
There is a relationship between relative humidity and water vapor pressure as follows:

RH = P_H2O/ P_sat;

in which, P_H2O is defined as P_tot *y_H2O and P_sat is saturate pressure which is dependent on operating temperature. y_H2O is also water vapor mass fraction. So, having the RH, let's say 0.6, you have, P_H2O = 0.6*P_sat. From which, the y_H2O is obtained as :

y_H2O = P_H2O /P_tot;

and hence if you have air as a gas mixture, then the values for Oxygen and Nitrogen are calculated as:

y_O2 = 0.21*(1-y_H2O);
y_N2 = 0.79*(1-y_H2O);

Finally, you need to input these values as species mass fraction values. You can do that manually or using UDF, if you want to change the RH values. That's all.

I hope it helps
hallo azarafza
thank you for your important help
cheers
aiouss is offline   Reply With Quote

Old   November 29, 2015, 00:46
Default
  #11
New Member
 
Join Date: Nov 2015
Posts: 5
Rep Power: 2
amasugi14 is on a distinguished road
Quote:
Originally Posted by the901 View Post
I am doing a simulation of humid air over a flat plate. I am waiting for my paper published then I can send you my work and the paper. General speaking, You need to transfer Relative Humidity to mass fraction of H20 by using the Psychrometrics chart. In material you'd better specify dry air mixing with water vapor in Fluent data. For boundary conditions you prescribe mass fraction for each Boundary in "species tab". Then run the calculation in Transient mode. For relative humidity contour, choose "species"/ relative humidity in "contours graphic". I hope it would help you!
Hi, actually im having the same problem, could you help me too? this is my email amasugi14@yahoo.com. thank you so much
amasugi14 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
Chemical Equilibrium Composition of Air and other Species enigma Main CFD Forum 0 November 11, 2009 20:08
Simplifaction of a CHT transient simulation MichaelPage CFX 2 November 2, 2009 09:55
Improve accuracy on air foil blade simulation? Bian CFX 4 December 12, 2006 12:29
3-D Contaminant Dispersal Simulation Apple L S Chan Main CFD Forum 1 December 23, 1998 11:06
air jet simulation Yue zou Main CFD Forum 0 September 28, 1998 08:30


All times are GMT -4. The time now is 22:22.