Mass transfer takes place whenever there is a change from one phase to the another. Quiet often the mass transfer is by the simultaneous action of diffusion and convective mass transfer. Ex; Mixing of water vapor with air during evaporaton of water from the lake surface is partly due to convection and diffusion.We do not use the term mass transfer to describle gross or bulk fluid motion due to mechanical work such as motion of air induced  by a fan or motion of water forced through a pipe liner. Based on this information, you can use your software to get the values close to reality.           

Laminar 2 phase flow with a solute, soluble in both phases, experience Tylor Diffusion Effect, see Wikipedia. 

Maybe I need to clarify here that my question is  specifically about COMSOL capabilities. By the way, thank you for your inputs. 

I am wondering if you have solved the problem. Kindly let me know if such coupling is possible in comsol.