A semi-empirical model has been proposed to predict the permeate flux and permeate concentration during the cross flow nanofiltration of a dye solution. The model includes laminar flow regime as well as flow assisted by the turbulent promoters. Membrane hydraulic resistance, osmotic pressure resistance and the gel type layer resistance are considered in series. The gel type layer resistance is correlated to the operating conditions, namely, the feed concentration, the transmembrane pressure difference and the cross flow velocity for a set of selected experiments. For the rest of the experiments, the permeate flux values are predicted using the developed correlation and are found to be in good agreement with the experimental results. It has been found that the gel type layer resistance decreases up to 68% due to the presence of the turbulent promoters leading to an enhancement of the permeate flux by about 109%. (C) 2004 Elsevier B.V. All rights reserved.