I want to know, kf (aqueous feed MTC) and kp ( aqueous permeate MTC) values of upstream and downstream side of flat sheet membrane, in order to calculate membrane diffusivity.
these coefficients following are usually computed from Sherwood Number correlations as functions of Reynolds and Schmidt number, as they depend on flow and substance properties on the respective side of the membrane.
Maybe this paper helps a little to start: http://doc.utwente.nl/70418/1/Berg89mass.pdf
You certainly find a lot more research on the topic at Google Scholar, Scifinder etc. Or just grab a text book on membrane filtration and its modelling.