Hydrodynamic analysis of spiral wound reverse osmosis membrane recovery fraction and permeate water flow rate

Nowadays spiral wound membrane modules are the most common type of modules used for reverse osmosis (RO) because its packing density is fairly high. This study focused on how geometric and operating parameters affect the two main SWM parameters: the recovery fraction and the permeate water flow rate. The hydrodynamics of flow was expressed by presenting an approximate model. The mathematical procedure yielded to the pressure equations for retentate and permeate channels. The permeability of the retentate channel was considered as a function of the spacer geometry and the Reynolds number. There is a certain membrane's length and width that the maximum recovery and the permeate flow rate is obtained but this cannot be always as a practical condition. For instance, according to RO module BW30-400 in considered operating conditions, the membrane length to the width ratio of about 3.6 is predicted for a maximum recovery. Finally, the sensibility analysis of main operating conditions on the permeate flow rate was pursued. The operating pressure, the retentate channel pressure drop and the spacer diameter influence the permeate flow rate and flux significantly. About 10% increase in permeate flux and flow rate is predicted for 15% increase in mentioned parameters.