CFD Online Discussion Forums - Evaporation due to Heat Transport using InterFoam (Correct Implementation?)

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Evaporation due to Heat Transport using InterFoam (Correct Implementation?)

Hi,

I have tried to implement phase change due to evaporation for an incompressible liquid flowing down a vertical heated wall using interFOAM with an energy transport equation. I have employed the methods suggested by Bitan Shu (Phase Change Model for Two-Phase Fluid Flow Based on VOF Method) and Wondra et al. (Evaporation Model for Interfacial Flows Based on a Continuum Field Representation of the Source Terms). However in both cases, I am unable to accurately reproduce the results presented in their papers. I am particularly interested in Bitan Shu's implementation because it allows for large grid sizes. Has anyone successfully done this?

If anyone has, please take a look at my code and tell me where I am wrong. Help is needed PLEASE!

STEP 1: Solve the energy transport equation for the entire domain i.e. (both liquid and gas):

STEP 2: Compute source terms using gradient of temperature:

Code:

               

volVectorField gradAlpha = fvc::grad(alpha1);

        

// to compute interface normal unit vector

volVectorField nHat = gradAlpha/(mag(gradAlpha) + interface.deltaN());

        

// compute interfacial area = magnitude of grad(alpha1)*volume of cell

volScalarField alpha1Prime = mag(gradAlpha);        

        

// set liquid and interfacial temperature to Tsat

forAll(mesh.cells(), celli)

{

        if (alpha1[celli] >= scalar(0.5)) 

        {

                T[celli] = Tsat.value();

        }                

                



// set this values to zero so that only liquid evaporation is accounted for

        if (alpha1[celli] < scalar(0.50))

        {

                alpha1Prime[celli] = scalar(0);

        } 

                

}

                

// Compute mass source field

mDot = -(kappa/evapEnthalpy)*(fvc::grad(T) & nHat)*alpha1Prime;



// Compute energy source field using enthalpy of evaporation

hDot = -evapEnthalpy*mDot;

kappa = thermal conductivity
evapEnthalpy = heat of vaporization
rho1 = liquid density

STEP 3: Solve alpha1 equation using MULES with source terms prescribed as

Code:

Su = -mDot/rho2;

Sp = 0.0;

STEP 4: Call Velocity and PISO loop

STEP 5: Repeat STEP 1

Please kindly review and tell me where this is wrong. Suggestions on more correct implementation of the source terms for evaporation would be well appreciated.

Thanks for the help.

Hi Ovie,
I am also struggling to implement temperature driven phase change. I tried the same as you did but my Su=mDot/rhoLiquid=HTC_liquid/rhoLiquid*(Tsat-T)/(latentHeat)*InterfacialAreaDensity. My Source term looks different because my phase change is due to condensation. My problems are that it crashes and I don’t get any reasonable results:).
What do you mean by ?

Quote:

Originally Posted by ovie (Post 277539)

However in both cases, I am unable to accurately reproduce the results presented in their papers.

Ciao,
Sabin

Hi Sabin,

Quote:

However in both cases, I am unable to accurately reproduce the results presented in their papers.

What I meant was that I successfully implemented the model proposed by Wondra et al. in the paper I referenced in the earlier post. I can send you the paper and my implementation if you want. I ran the code and it was well behaved and I had nice results. The only problem was that it under predicted the phase change compared to the results they reported in their paper. But the under-prediction was not by much though (really small but then the simulation was for micro scale and I fear this underprediction could be significant at macro scale). In any case, I SUSPECT the problem was with my boundary conditions because in their case they simulated 1-D stefan problems while I was unable to do that using interFoam so I used a 2-D mesh with zero gradient and no-slip conditions at planes normal to the transverse directions.

In the case of Bitan Shu's model, the simulation reports completely strange results. I really dont know where to start from at the moment. I am reading up another paper by P. Keller et al. (Numerical Simulation of Evaporating Droplets with Chemical Reactions using a Volume of FLuid Method) where they used interFoam and reported nice results. I think I might get some practical details on the implementation from there.

Thanks..

As far as I know Shu used OpenFOAM in his Ph.D. thesis.
I'm sure you can get more informations out of if that of the paper.
Try to get it!

Hi Sega

Quote:

As far as I know Shu used OpenFOAM in his Ph.D. thesis.
I'm sure you can get more informations out of if that of the paper.
Try to get it!

I already have the conference paper where Shu developed his model. I think my problem is with the implementation right now. If you have any additional materials please be kind to make it available.

Thanks

Quote:

Originally Posted by ovie (Post 277755)

Hi Sega

I already have the conference paper where Shu developed his model. I think my problem is with the implementation right now. If you have any additional materials please be kind to make it available.

Thanks

I have the Ph.D. thesis at hand, but I'm not sure Bitan Shu will be happy if I publish it here.
Please contact him directly: http://www.tecies.com/

Quote:

I have the Ph.D. thesis at hand, but I'm not sure Bitan Shu will be happy if I publish it here.

Actually, I have been in direct communication with Bitan Shu. But he/she told me his/her Thesis was in German and offered to send me a copy but I passed since I dont have a clue about German language. Maybe I got it wrong. I can send him a mail and ask again if he/she has an English version or something. But do you have an English version of the thesis?

Thanks...

Quote:

Originally Posted by ovie (Post 277765)

No, I just have the german version ...

Very well then.

Thanks for the help.

hi ovie
could you implement shu paper properly ?
i tried it, i have used interPhaseChangeFoam , but my results can't follow interface exactly,please inform me about ur last effort!!!!!
and i suggest you look at interPhaseChangeFoam and MULE code in it !!!!

Ovie, by the way, I found that my results depend on the timestep. The larger the timestep, the more liquid is evaporating.

Quote:

Originally Posted by LarsPT (Post 336074)

Ovie, by the way, I found that my results depend on the timestep. The larger the timestep, the more liquid is evaporating.

Well that comes down to your grid sizes and the size of your CFL number. In my case I used a well resolved grid (try the grid sizes specified in Wondra's paper) and specified variable time step in controlDict. The results were very comparable to those reported in Wondra's paper.

Quote:

Originally Posted by LarsPT (Post 336074)

Ovie, by the way, I found that my results depend on the timestep. The larger the timestep, the more liquid is evaporating.

look at here
http://www.cfd-online.com/Forums/blogs/nimasam/906-boiling-openfoam.html

and here
http://www.cfd-online.com/Forums/ope...hangefoam.html