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October 15, 2014, 11:18 
Mass Transfer without Phase Change in InterPhaseChangeFoam

#1 
Member
Parisa
Join Date: Feb 2013
Posts: 51
Rep Power: 4 
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 

October 15, 2014, 15:57 

#2 
New Member
Alex
Join Date: Jun 2011
Posts: 14
Rep Power: 6 
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 ); 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. 

October 15, 2014, 16:01 

#3  
Member
Parisa
Join Date: Feb 2013
Posts: 51
Rep Power: 4 
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:


October 15, 2014, 16:29 

#4 
New Member
Alex
Join Date: Jun 2011
Posts: 14
Rep Power: 6 
There are some major questions to consider in your code development with respect to modeling phase change. In particular:


October 15, 2014, 16:33 

#5 
Member
Parisa
Join Date: Feb 2013
Posts: 51
Rep Power: 4 
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, 

May 26, 2015, 09:40 
validation

#6  
Senior Member
rkhr
Join Date: May 2011
Posts: 211
Rep Power: 7 
Hi Parisa,
Did you manage to validate your code? Do you get reasonable results? thanks in advance! Kanarya Quote:


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