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Equilibrium condition for an identity pair

Posted 30.10.2012, 13:07 GMT-4 Chemical Reaction Engineering Version 4.2a, Version 4.3, Version 4.3a 6 Replies

Jorge Sánchez
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Hi.

I am new in COMSOL and I am checking for the software abilities. Currently I am using the identity pair in a mass transfer model. The idea is a fluid flowing on the surface of a slab, which is transfering any specie to the fluid. I would like to know if is possible to define an equilibrium condition for the specie (c_slab=K*c_fluid) on the surface in contact with the fluid?

By default the pair has Continuity, Concentration, Discontinuity, No-flux boundary conditions but I don´t know how to specify the equilibrium condition.

I appreciate any help in this topic.

Thanks a lot.

Jorge
6 Replies Last Post 02.11.2012, 12:53 GMT-4
Freddy Forero
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Posted: 1 decade ago 31.10.2012, 14:13 GMT-4
Hi

You can see the example about ... dialysis, in the model library, there used the equilibrium condition K.

Greetings ...
Hi You can see the example about ... dialysis, in the model library, there used the equilibrium condition K. Greetings ...
Jorge Sánchez
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Posted: 1 decade ago 31.10.2012, 15:36 GMT-4
Dear Freddy,

Thanks for your help. This was very useful.
I just have another question: When the geometry form a union it is not necessary specify both flux continuity and the equilibrium condition at the interphase? Or does the union implicitly consider the flux continuity?

I obtained a good result just considering the equilibrium condition.

Thanks.

Jorge
Dear Freddy, Thanks for your help. This was very useful. I just have another question: When the geometry form a union it is not necessary specify both flux continuity and the equilibrium condition at the interphase? Or does the union implicitly consider the flux continuity? I obtained a good result just considering the equilibrium condition. Thanks. Jorge
Freddy Forero
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Posted: 1 decade ago 31.10.2012, 19:57 GMT-4
Hello

The dialysis example, uses the variable c_all defined under .. model> definitions, to force continuity across the three domains ..

c_all is the variable representing concentrations, c1, c2, c3.

If you like you can share the model in this forum and help you improve it.

byee .....
Hello The dialysis example, uses the variable c_all defined under .. model> definitions, to force continuity across the three domains .. c_all is the variable representing concentrations, c1, c2, c3. If you like you can share the model in this forum and help you improve it. byee .....
Jorge Sánchez
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Posted: 1 decade ago 01.11.2012, 12:50 GMT-4
Hi Freddy.

Thanks for the explanation. But, why defining c_all as a variable representing concentrations, c1, c2, c3, ensure continuity? It this a recomendation of COMSOL or is just a "trick"?

Thanks.

Jorge

Hi Freddy. Thanks for the explanation. But, why defining c_all as a variable representing concentrations, c1, c2, c3, ensure continuity? It this a recomendation of COMSOL or is just a "trick"? Thanks. Jorge
Freddy Forero
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Posted: 1 decade ago 01.11.2012, 21:13 GMT-4
You can read the model doc for the full info.... the last part...
You can read the model doc for the full info.... the last part...
Jorge Sánchez
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Posted: 1 decade ago 02.11.2012, 12:53 GMT-4
Hi Freddy.

Thanks for the answer. I did not know about the stiff-spring method, but I see that is too useful where a jump in the dependent variable exist.

Thanks for all your help. Now is clear for me how to specify an equilibrium condition on a boundary.

Bye.
Hi Freddy. Thanks for the answer. I did not know about the stiff-spring method, but I see that is too useful where a jump in the dependent variable exist. Thanks for all your help. Now is clear for me how to specify an equilibrium condition on a boundary. Bye.

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