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Boundary condition setting problem for electrode

Posted Jan 4, 2014, 11:10 a.m. EST Fluid & Heat Version 4.3a 3 Replies

Li Wang
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Hi!
I am using transport of diluted species to simulate particle movement in discharge but have some problems with the boundary condition setting for the electrode:
the electron move towards the electrode(anode),then it disappear when contacts the anode
how should I set the boundary condition for the electrode?
Hope someone can help me!
3 Replies Last Post Feb 8, 2016, 2:06 a.m. EST
Lasse Murtomäki
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Posted: 1 decade ago Jan 7, 2014, 4:10 a.m. EST
It depends on your experimental conditions. If you are passing current through the electrode, use the flux boundary condition through the Faraday's law. If you are controlling the potential of the electrode, you must use Butler-Volmer expression for the flux.

But why not to use the Electrochemistry module? There you have everything made ready?

Lasse
It depends on your experimental conditions. If you are passing current through the electrode, use the flux boundary condition through the Faraday's law. If you are controlling the potential of the electrode, you must use Butler-Volmer expression for the flux. But why not to use the Electrochemistry module? There you have everything made ready? Lasse
Abraham Mansouri
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Posted: 9 years ago Feb 8, 2016, 1:06 a.m. EST
Hi Li

were you able to solve this issue? what should we use for electrode boundary condition when
we are dealing with ion transport? I have the same problem

Regards
Abraham


Hi!
I am using transport of diluted species to simulate particle movement in discharge but have some problems with the boundary condition setting for the electrode:
the electron move towards the electrode(anode),then it disappear when contacts the anode
how should I set the boundary condition for the electrode?
Hope someone can help me!


Hi Li were you able to solve this issue? what should we use for electrode boundary condition when we are dealing with ion transport? I have the same problem Regards Abraham [QUOTE] Hi! I am using transport of diluted species to simulate particle movement in discharge but have some problems with the boundary condition setting for the electrode: the electron move towards the electrode(anode),then it disappear when contacts the anode how should I set the boundary condition for the electrode? Hope someone can help me! [/QUOTE]
Lasse Murtomäki
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Posted: 9 years ago Feb 8, 2016, 2:06 a.m. EST
Dear Abraham

For the consumed species the flux is negative and for the formed species positive. Let's say that you have a constant current experiment, current density being I (A/cm²). For the consumed species, the flux BC is -I/nF (assuming I > 0) where n is the number of electron and F Faraday constant. If you control the potential, you can express the flux via Butler-Volmer equation. If the reaction is reversible, the flux of the consumed species (here Cred) is

-M*(TH*Cred - Cox)

where M is an arbitrary but high enough mass transfer coefficient (say 100 cm/s) and

TH = exp[nF/(RT)*(E - E°)]. (Nernst equation)

For the formed species (here Cox), the BC is +M*(TH*Cred - Cox).

But the electroanalysis module includes all this.

Best regards
Lasse
Dear Abraham For the consumed species the flux is negative and for the formed species positive. Let's say that you have a constant current experiment, current density being I (A/cm²). For the consumed species, the flux BC is -I/nF (assuming I > 0) where n is the number of electron and F Faraday constant. If you control the potential, you can express the flux via Butler-Volmer equation. If the reaction is reversible, the flux of the consumed species (here Cred) is -M*(TH*Cred - Cox) where M is an arbitrary but high enough mass transfer coefficient (say 100 cm/s) and TH = exp[nF/(RT)*(E - E°)]. (Nernst equation) For the formed species (here Cox), the BC is +M*(TH*Cred - Cox). But the electroanalysis module includes all this. Best regards Lasse

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