An integrated model based on the finite volume formulation to numerically simulate the fluid flow of the feed phase in nanofiltration systems is presented. This model accounts for the transport phenomena occurring inside the membrane through the use of appropriate boundary conditions. It allows for predictions of developing laminar flows hydrodynamics and mass transfer of aqueous solutions in slits with permeable walls. The experimental cell (200 mm x 30 mm x 2 mm) simulates the two-dimensional conditions of flows in spiral-wound modules channels. Experimental data validate predictions of apparent rejection coefficients and permeate fluxes. Correlations for the concentration/hydrodynamic boundary layers thickness ratio, delta(omega)/delta(u) = 2.92Sc(-0.37) Re-p(-0.17) [(x/h)Re-1 + 0.013Sc(0.45)Re(p)(0.75)](0.5) and for the permeation Stanton number, St= 1.3(l/h)(-0.2RepRep-0.4Sc-0.1)-Re-0.05(1-f')/f', are proposed, in the range 250 < Re < 1000, 0.02 < Re-p < 0.1 and 570 < Sc < 3200.