[golshadi]

hi Dears
My work is about a catalytic reaction in porous media.I study the user guide of fluent but my mind is wandered to very things and I have very questions. (anyone that have good information) I would like guide me to best books, texts,sites, in this subject or even give me a case file and other things you think them help me.
in first stage I don't know how can determine permeability of porous media. And what is the best under-relaxation for a homogeneous porous media(because my case doesn't convergevery well).
also when can I use porous media model for packed bed catalysts(what is criterion?).
I have a non-Arrhenius rate equation (surface reaction in porous media) what is the best way to present it to fluent?
I appreciate you.
regards

[shk12345]

Try to use the Eurgun equation for inertial and viscous resistances for the packed bed.

SHK

[golshadi]

thanks shoeb khan.
now the problems are about two things:
1-I have in my case a non-Arrhenius rate equation, so for entering it in fluent should I do?
2- I have a principle problem: in my case the diameter of catalyst is about 0.06 mm, I dont know with this diameter, whether it is right to use porous model? or I should use multiphase model (granular , packed bed) ? ((what is the criterion??))

[Sixkillers]

You can define your custom reaction rate with UDF by using macro DEFINE_VR_RATE.

[golshadi]

DEFINE_VR_RATE or DEFINE_SR_RATE??
do you have any suggestion about my second problem?

[Sixkillers]

Hi. Sorry my bad, DEFINE_SR_RATE is definitely more suitable for your case. I have only used granular model for simulation solid-liquid system in a stirred tank. Speaking of convergence, I usually set under-relaxation of momentum to 0.2 and after simulation starts converging I return it to its default value, which is 0.7.

[golshadi]

Hi.
I want to express my gratitude for your suggestions. You've useful suggestions for me.

my case about gas (flow) and solid (catalyst). Do you have any comment about this case?

[Sixkillers]

From my point of view porous media model seems to be more rigorous, but on the other hand it requires much more input parameters, so it depends if you can provide suitable values to Fluent. By contrast granular & packed bed model requires only particle diameter and packing limit (i.e. 1 - void fraction). Packed bed model means that velocity field of solid phase is freezed and isn't floating in a reactor. From my simulation of solid-liquid phase I have found that granular model converge more rapidly for particles with smaller diameter (e.g. 1e-6 m) then for larger one (1e-3 m). So your particles (0.06 mm) shouldn't be be a problem for it.

[golshadi]

Originally Posted by Sixkillers

From my point of view porous media model seems to be more rigorous, but on the other hand it requires much more input parameters, so it depends if you can provide suitable values to Fluent. By contrast granular & packed bed model requires only particle diameter and packing limit (i.e. 1 - void fraction). Packed bed model means that velocity field of solid phase is freezed and isn't floating in a reactor. From my simulation of solid-liquid phase I have found that granular model converge more rapidly for particles with smaller diameter (e.g. 1e-6 m) then for larger one (1e-3 m). So your particles (0.06 mm) shouldn't be be a problem for it.

your comments really helped me.thank a lot.
If you have any reference about this problem please guide me to it.
thanks again