wall surface reaction

vculiu

Thanks you for your time and reply.

I have a species transport model with wall surface reaction A+B-->C. The reaction is diffusion controlled, so I set pre-exp k at large value (>1E10) (activation energy 0). I found when k is large enough (such as >1E10 in my case), the surface concetration of A and B (CA and CB) as well as the reaction rate R(kg/m2s) are no longer changing. But the definition of surface reaction is R=k*CA*CB. When R is maintained same and k is increasing, CA and CB should decrease. Anyone can explain this?

Thanks