# Diffusion problem

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 November 18, 2002, 12:27 Diffusion problem #1 ravi varma Guest   Posts: n/a 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?

 November 21, 2002, 00:56 Re: Diffusion problem #2 Thitikorn Guest   Posts: n/a 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.

 November 24, 2002, 01:58 Re: Diffusion problem #3 mahdi saniee nezhad Guest   Posts: n/a Dear sir I have a problem with this title. If it's possible for you please send me your received responses. Very thanks for your attention to my request. With the best regards. Mahdi saniee nezhad

 November 24, 2002, 12:51 Re: Diffusion problem #4 ravi varma Guest   Posts: n/a hi Thitikorn, how many grid cells are you using for the reaction modelling in porous media?

 November 30, 2002, 03:50 Re: Diffusion problem #5 Thitikorn Guest   Posts: n/a 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/

 December 3, 2002, 14:54 Re: Diffusion problem #6 ravi varma Guest   Posts: n/a 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?

 December 9, 2002, 00:10 Re: Diffusion problem #7 Thitikorn Guest   Posts: n/a 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,

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