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-   -   Evaporation with population balance model (http://www.cfd-online.com/Forums/fluent/90726-evaporation-population-balance-model.html)

lihuang July 19, 2011 11:19

Evaporation with population balance model
 
Dear friends,

I have been modeling water droplets evaporation with Population Balance Model. My problem is that particle volume fraction does not converge very nicely, although overall mass is well balanced.

In my case, I use mixture model. Mass transfer from liquid drops to vapor phase (air+water vapor) is defined through DEFINE_MASS_TRANSFER. At the same time, changes in liquid drop's diameters is defined through DEFINE_PB_GROWTH_RATE. Residual plots are generally good for all other parameters than volume fraction of liquid particles (to only about 0.1 level).

Shall I also introduce source of energy and/or momentum to the mixture phase and source of particle volume fraction to particle phase to get nicely converged results?
Thanks for your suggestions.

vaibhavraikhare January 28, 2012 10:27

Sir,
i am working on same problem of yours. i also used mixture model and discrete model for population balance model.how can i give the nucleation rate and growth rate in this model for water vapor. and if you can tell what is the concept of Min and Max Bin size. How it can be defined.? help if you plzz...

lihuang January 28, 2012 21:50

Both rates were defined in Udfs. Or you can set constant rate. If you are using fluent 13.0, you need to click the phenomena option under PBM settings window to make changes on nuclear ion rate.

lihuang January 28, 2012 21:56

The min and max bin size are defined in the PBM settings window. You can check out the theory's guide for the calculation of each bin between min and max bins. You can also print out all bin size by one click there. Good luck

vaibhavraikhare February 5, 2012 00:19

Dear Lihuang,
i am still not getting my results, volume fraction does not converge..as there might be some problem in PBM or UDF. Can you tell me if i want to give the constant mass transfer value for it what it will be??? and i haven't found any UDF for PBM to specify the growth rate and nucleation rate.


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