I have problem to making the Pt / Alumina catalyst and alumina inert particles in fixed bed reactor in design modeler or space claim of ansys fluent. I should make the each particle one by one and with a real model in glass tube or is there better method to making the particle regions?
which method is applied in industries for making fixed bed reactors and catalytic regions?
Wow! Generally, the bed is modeled such as porous media. Because the scale of the particle is small compared to the whole domain, that is, on AVERAGE, each volume fo control has some number of particle that is statically fixed or near of this. If it is a packed bed, the particles have a fixed position, and on a higher scale, they look like a porous media.
If the particle ar moving with the flow, we have a granular flow - there are some models and approaches in Fluent ( euler-euler, euler-lagrange, kinetic-theory, Populational Balance, etc).
All chemistry must be included as a source for the particles or porous medium through an UDF.
There is also the possibility of a DEM + CFD coupling. Fluent works with Rocky DEM, but MFIX has DEM models and is free for download.
If you have a particle diffusion model with a mass transfer at the surface, adsorption in the porous matrix and chemical reaction. Yau cannot model like this, due to the CFD scale is higher than this level. It is common use the bottleneck step as a source to article process ( k.a(C-C*), dq/dt =f(C), etc)
It is a hard problem to model and to solve.
Thanks a lot ,
Because of non uniform void area of catalyst of packed bed its sounds, i should use DEM but cpu time and computation cost goes alot.
You said for defining heterogeneous reaction i should use UDF, chempetkin module is not efficient?
Please help more about DEM and UDF part for defining chemistry.
Thanks again
Ali Zakeri the porous media is nonuniform, but the equations do not see this morphology. They are volume averaged, hence, the reactions can be homogeneous on AVERAGE. see Whitaker, 1999 "
The Method of Volume Averaging" to understanding better how to see a porous media on a macroscopic scale.
DEM is a discrete Element model when the particle cannot be considered as a material point. I never used DEM in FLUENT.
Regarding Reactions and UDF seek to DEFINE_SOURCE macros for UDF in Fluent. There is no easy recipe. Each case is unique.
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