Diffusion problem
 

hi, i have modelled a porous media inside a domain. i am modelling reactions in the porous zone. when i solve for momentum and cold flow solution, i cannot see a change in the species concentration within the porous zone. although the velocity drops to a minimum within the porous zone, species mass fraction is hardly changing. could you explain why this is happening?

Re: Diffusion problem
 

If mass fraction slightly change. May be U must check parameter in reaction model. and if mass fraction not change. May be U forget to open option Volume reaction in species menu.

My work is simulate Fuel cell in 2D which have reaction in porous zone (cat. layer) and I use Fluent, it's work.

Re: Diffusion problem
 

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Re: Diffusion problem
 

hi Thitikorn, how many grid cells are you using for the reaction modelling in porous media?

Re: Diffusion problem
 

Hi, my model is Fuel cell 2 dimensions width 2 mm, height 0.26 mm and have grid 42 x 27 cells. Feed air and O2 is reacted on cat. layer But. If ur model have many porous zone and want rxn. at some zone (not all zone) I think u must defind species source term (UDF) in zone u want rxn occur. ======================== <-- cat. layer (porous zone 1) : width 0.01 mm I************************************************* ******I **\ I************************************************* ******I ***> porous zone 2 : width 0.25 mm. I************************************************* ******I **/ I - - - - - - =========== - - - - - - I air feed/

Re: Diffusion problem
 

i have defined the species source term. also, defined volumetric reaction term with UDF for porous zone. but, i see reaction occuring in the centre of my porous zone. ideally, i would like to the reaction at the face of the porous zone. what sort of results are you getting?

Re: Diffusion problem
 

I think you were definding UDF of species source term for volumetric rxn in porous zone, and now you can see rxn occor in center of porous zone.
But, I can't understand what is your model shape (2D or 3D).
If your model shape like me (2D picture). Rxn will occor at porous zone 1 (on top) coz, I defined species source term occor only in zone 1 not occor on porous zone 2.
May be I'll post my picture for you later. Sorry, about my English Skill. Best regard. Thitikorn,