For the variable density model, I did not find a specific explanation in the mfix help literature. Please let me know if there is specific help documentation. I’d also like to ask, do I have to set up an inert particle for the variable density model? If I don’t want to set an inert particle, can I use two of the same reactive particles？Is this reasonable?
Have you worked through the variable density Biomass gasification tutorial?
If you are using variable density, then there must be a non-reacting species within each particle phase. This is not the same as having an inert particle. It just means that not all of the chemical species within a particle can be reactive.
Hope this helps,
– Charles
Thank you very much for your answer, I see what you mean. But I would like to ask if you have a more detailed explanation of the variable density model, because in practice, particles do not have non-reactive components.
The variable density model as implemented in MFiX requires a non-reacting (inert) species. If this is not usable, you may attempt to change the code, but I have no idea how difficult this would be…
You could also try making the mass fraction of the non-reacting species very low.
Thanks for your reply. I’m still wondering if there are any specific instructions or formulas for the variable density model? Is it a uniform transformation model or a shrinking core model?
Please see
section 2.7.4.2 of Madhava Syamlal, M. Musser, J., and Dietiker, J.-F., “The two-fluid model in the open-source code MFiX”, book chapter in CRC Multiphase Flow Handbook Computational Methods, CRC Press, October 2016.
or
section 3.5.1 of Theoretical Review of the MFIX Fluid and Two-Fluid Models (Technical Report) | OSTI.GOV
Thank you very much for your answer! I’d like to make sure, can I set the inert particle to the reactive particle as one component? And the ratio of the two is 0.01:0.99. Does that have any other effect?
Sorry I don’t understand your question. The solids phase chemical composition is defined with chemical species. If you want to use the variable density model, one of these species must be inert.
If you are talking about CaCo3 and CaCO3_s, these are treated as different species (they have different names), although they can have the same properties (Cp, density, MW).