[khariel]

Hello everyone,

I'm currently modelling an ethanol fuel cell anode, and I need to add a boundary condition to an interface. This interface is between a porous region, where an ethanol solution permeates through, and a catalyst layer. Once the ethanol solution reaches the catalyst, a reaction happens.

This boundary condition will simply state that (ethanol diffusive flux)=(reactive flux) within the interface region.

How can I write an expression that includes this ethanol diffusive flux? I've only found the variables for the velocities, but those are for the bulk I presume.

Thanks in advance.

[ghorrocks]

I presume your ethanol is a mass fraction equation. So you just add a mass fraction source term at the interface.

[khariel]

Hi Glenn, thanks for the reply.

I'm aware I need to create a source for the ethanol mass fraction at the interface, but my question is how can I write an expression that would be equivalent to the stated BC (diffusive flux=reactive flux)?

I tried writing a source like this: -massFlowEth/areaInterface

But didn't quite work as intended.

[ghorrocks]

Are you modelling the chemistry to get the reactive flux? Or does it come from something else?

[khariel]

It is an electrochemical reaction. Put it simply, the reactive flux depends on the ethanol local concentration at the interface. So I guess I just need to declare the kinetics expression as the source term?

[ghorrocks]

Yes, that's right.