[sami1991]

I want to introduce a mass source or sink term in my model at the wall-3 of geometry, how can I do that ?
The fluent case file and mass source udf are attached here for your reference.In my understanding, source term can be defined only in volume zone, so how can we define it for wall ? I have hydrogen consumption and water generation at constant rate of 0.03 mol/m2-sec at wall 3.
wall 2 and 4 are zero flux wall, and at wall-1 mass fraction of diffusing species given, diffusivity values are provided in model.