PEMFC Questions

LC

I am working on PEMFC modelling now, but met with the following problems. Hope someone can help me with this.

1) I would like to factor in the h2o mass source due to the combined effect of electro-osmotic drag and back diffusion. however, i would like to use values for the anode and cathode catalyst regions, which belong to different zones (threads) ( a membrane region in between(. May i know which udf and macro i can use?

2) from previous posts, i found out that i cannot enforce diffusion coeff terms to be zero for my electronic potential equation in regions such as my gas channel. in this case, can i set the diff coeff term to be extremely small?

3) I wish to prevent species other than h20 to enter the membrane. can i set the boundaries of the membrane to be well, and set the mass fraction of h2o to be 1 to prevent other species from entering the membrane?

Thank you