CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

Mass Transfer without Phase Change in InterPhaseChangeFoam

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 15, 2014, 11:18
Default Mass Transfer without Phase Change in InterPhaseChangeFoam
  #1
Member
 
Parisa
Join Date: Feb 2013
Posts: 51
Rep Power: 4
Parisa_Khiabani is on a distinguished road
Hello everyone,
I am working with interPhaseChangeFoam and diagnosing the solver. I modified the solver based on the tutorial of Andxersen, such that I implemented TEqn.H and also pSat as a function of temperature.
I created a simple case, flow in a duct. The inlet and the whole domain is vapor, with alpha=0. The temperatures for the walls, inlet flow and inside the domain is the same. So, no phase change happens, such that the minimum and maximum values of alpha are zero.
However, in alphaEqn.H, when I print "vDotvmcAlphal" I see strange values for that, that is -330.
Here is my question: If alpha doesn't change (that means no phase change occurs), why "vDotvmcAlphal" has a value. Since "vDotvmcAlphal" is calculated based on the evaporated/condensed mass rate, it seems that mass is transferred whitout a phase change.
I really appreciate if you guide me.

Best,
Parisa
Parisa_Khiabani is offline   Reply With Quote

Old   October 15, 2014, 15:57
Default
  #2
New Member
 
Alex
Join Date: Jun 2011
Posts: 14
Rep Power: 6
liquidspoon is on a distinguished road
Hi Parisa,

In your setup, the fluid is initially vapor everywhere (alpha1 = 0). In the solver, the vDotvmcAlphal parameter is applied as an implicit proportional source term. This is the equivalent of applying vDotvmcAlphal*alpha1 (= 0 for alpha1 = 0). So there won't be any condensation for this particular case.

Code:
fvScalarMatrix alpha1Eqn  (
     fv::EulerDdtScheme<scalar>(mesh).fvmDdt(alpha1)
     + fv::gaussConvectionScheme<scalar>
     (
       mesh,
       phi,
       upwind<scalar>(mesh, phi)
     ).fvmDiv(phi, alpha1)
   - fvm::Sp(divU, alpha1)    ==
     fvm::Sp(vDotvmcAlphal, alpha1)
    + vDotcAlphal
 );
I think you will want to modify your code so that your phase fraction source shows up the explicit term: vDotcAlphal.

You may want to look at the MS thesis by Thiele (2010). He made a similar modification to the interPhaseChangeFoam solver to handle thermally driven condensation. I have some concerns about the approach in that thesis, but it should give you some helpful pointers for your project.
liquidspoon is offline   Reply With Quote

Old   October 15, 2014, 16:01
Default
  #3
Member
 
Parisa
Join Date: Feb 2013
Posts: 51
Rep Power: 4
Parisa_Khiabani is on a distinguished road
Thanks Alex for your help,
So, if you think it can handle correctly (by the modification that you pointed), so there is no any worries about the lack of accuracy in mass transfer. Am I right?


Quote:
Originally Posted by liquidspoon View Post
Hi Parisa,

In your setup, the fluid is initially vapor everywhere (alpha1 = 0). In the solver, the vDotvmcAlphal parameter is applied as an implicit proportional source term. This is the equivalent of applying vDotvmcAlphal*alpha1 (= 0 for alpha1 = 0). So there won't be any condensation for this particular case.

Code:
fvScalarMatrix alpha1Eqn  (
     fv::EulerDdtScheme<scalar>(mesh).fvmDdt(alpha1)
     + fv::gaussConvectionScheme<scalar>
     (
       mesh,
       phi,
       upwind<scalar>(mesh, phi)
     ).fvmDiv(phi, alpha1)
   - fvm::Sp(divU, alpha1)    ==
     fvm::Sp(vDotvmcAlphal, alpha1)
    + vDotcAlphal
 );
I think you will want to modify your code so that your phase fraction source shows up the explicit term: vDotcAlphal.

You may want to look at the MS thesis by Thiele (2010). He made a similar modification to the interPhaseChangeFoam solver to handle thermally driven condensation. I have some concerns about the approach in that thesis, but it should give you some helpful pointers for your project.
Parisa_Khiabani is offline   Reply With Quote

Old   October 15, 2014, 16:29
Default
  #4
New Member
 
Alex
Join Date: Jun 2011
Posts: 14
Rep Power: 6
liquidspoon is on a distinguished road
There are some major questions to consider in your code development with respect to modeling phase change. In particular:
  • Do you apply phase change only on the interface? If so, how do you identify the interface? If not, is this appropriate for your problem?
  • How do you handle the internal thermal resistance and thermal time constant in each cell?
  • How do you maintain interface sharpness when there is a volumetric source term in the vicinity of the interface
My point is that I can't give you a guarantee about the accuracy of your code, especially without reviewing it and your algorithms thoroughly. The best advice I can give is to perform careful verification and validation as you develop your code.
liquidspoon is offline   Reply With Quote

Old   October 15, 2014, 16:33
Default
  #5
Member
 
Parisa
Join Date: Feb 2013
Posts: 51
Rep Power: 4
Parisa_Khiabani is on a distinguished road
No, I don't apply to interface since in interPhaseChangeFoam phase change can occur anywhere that there are gradients of pressure.
I just simply add net rate of evaporation and condensation multiply to latent heat, into energy equation.
But, for sure I need to validate my code. What do you recommend for the validation? Except Stephan Problem that is a benchmark.

Thanks,
Parisa_Khiabani is offline   Reply With Quote

Old   May 26, 2015, 09:40
Default validation
  #6
Senior Member
 
rkhr
Join Date: May 2011
Posts: 211
Rep Power: 7
Kanarya is on a distinguished road
Hi Parisa,

Did you manage to validate your code?
Do you get reasonable results?
thanks in advance!

Kanarya

Quote:
Originally Posted by Parisa_Khiabani View Post
No, I don't apply to interface since in interPhaseChangeFoam phase change can occur anywhere that there are gradients of pressure.
I just simply add net rate of evaporation and condensation multiply to latent heat, into energy equation.
But, for sure I need to validate my code. What do you recommend for the validation? Except Stephan Problem that is a benchmark.

Thanks,
Kanarya 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
Water subcooled boiling Attesz CFX 7 January 5, 2013 04:32
Phase change heat transfer Lexa FLUENT 0 October 10, 2011 02:53
Multiphase Mass transfer UDF issue therandomestname FLUENT 0 April 21, 2011 14:51
mass transfer coefficient for boundary condition niek Main CFD Forum 0 March 29, 2011 05:33
help needed about phase change Yanhu Guo Main CFD Forum 4 January 24, 2001 00:16


All times are GMT -4. The time now is 10:07.