Learning Forum

[Gloria]

I am trying to build a model that predicts the adsorption of a species present in a liquid phase onto the surface of a solid particle. Is it possible to model this scenario using Ansys Fluent? If so, what would be a suitable approach?

Any reply would be much appreciated. Thank you in advance.

[Rob]

It'll depend on particle volume fraction and, then what the rate limiting step for the mass transfer is. 

[Gloria]

Thank you for your reply, Rob. The particles are present in a low volume fraction (below 10%) and the process is limited by the mass transfer of the target species from the liquid bulk to the solid particle surface; once the species of interest contacts the solid surface, it becomes instantaneously attached to it.

[Rob]

OK, so with that volume fraction DPM is OK. There's then whether you need to model the mass transfer, or just show a good particle distribution. The trick with CFD is to know how little you can do to answer the question that's been posed. Also whether the mass transfer is condensation or absorption as there's a difference in what else you need to think about. Do particle saturate? Lots to consider before getting to the solver. 

[Gloria]

The main objective of the model at this point is to predict the selective and continuous capture of a certain species present in a liquid solution onto the surface of functionalized solid particles. Once the species of interest reaches the surface of the particle, instantaneously an ion exchange reaction takes place; the species of interest is captured by the solid, while another species is released into the liquid medium. The reaction is reversible, although the capture is favoured. No gas phases are involved in my system. 

If DPM is a suitable approach, what type of particles should I consider? How can I include the reversible reaction that takes place between the species present in the liquid solution and the species attached to the solid particle, taking into account that this reaction only takes place once the targeted species get into contact with the solid?  One of the ultimate goals of the model is to obtain the concentration variation of the targeted species from the inlet of the system to the outlet. 

[Rob]

Best guess is to use DEFINE_DPM_HEAT_MASS or DEFINE_DPM_SOURCE along with multicomponent droplets and a species mixture for the fluid phase. Most of the default examples are for evaporation, if you set a negative rate it ought to condense too (I don't know for sure).  The rate of transfer is going to be fun too: it's possibly concentration rather than temperature based. I suspect the latter may be easier to control. 

We're not permitted to get too specific on here, so I can't give too much more advice on the macros. I do advise breaking the model down, start with looking at whether you have good fluid mixing and particle distribution.