Effects of suction are included in the mass transfer coefficient to predict the performance of spiral wound and tubular modules under the turbulent flow conditions. The analysis is valid for the osmotic pressure controlled filtration. Dextran is selected as the model solute. Variations of bulk concentration, bulk velocity, retentate channel pressure, permeate flux, permeate concentration, etc., along the module length are obtained after solving the design equations numerically. The results are compared with the standard module design using mass transfer coefficient without including suction and the film theory. The results indicate that without including suction in the mass transfer coefficient leads to gross underprediction of the length averaged permeate flux (about 70-75%) and overprediction of the average permeate of concentration (about 8-10%) for various operating conditions studied herein (for a 10 m long module). On the other hand, calculations using film theory leads to underprediction of average permeate flux in the range of 30-35%. (c) 2006 Elsevier B.V. All rights reserved.