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Several membrane processes involve the convective velocityin the boundary layer due to high solubility and diffusivity in themembrane. The relatively high value of the convective velocity, asit can exist during gas separation, can cause convex concentrationdistribution in the boundary layer, and consequently, it can alterthe diffusive flow throughout the boundary layer, as well. How thePeclet number affects the diffusive flow is discussed in the firstpart of this study. It has been stated when the Pe> about 0.3–0.5, the diffusive mass transfer coefficientof the boundary layer obtained by prediction using dimensionless quantities,should be corrected by a factor depending on the Peclet number, obtainedby the exact solution of the boundary layer’s concentrationdistribution. The curvature effect of the concentration distributionis then taken into account by this factor. In the second part of thisstudy, the polarization modulus and enrichment are separately expressedby means of the mass transport parameters of the polarization andmembrane layer. Applying these explicit equations, the change of boththe polarization modulus and enrichment is shown as a function ofthe mass transport parameters, as mass transfer coefficient of thelayers, Peclet number, and solubility coefficient. These equationsenable the user to predict the value of enrichment and/or the polarizationmodulus under any operating conditions for gas separation using adense, polymeric membrane. [ABSTRACT FROM AUTHOR]