CFD modeling and simulation of concentration polarization reduction by gas sparging cross-flow nanofiltration

•Nanofiltration of MgSO4 solution was investigated by both a finite volume CFD model and an experimental procedure.•CP phenomenon was properly modeled implementing the CFD technique.•An Eulerian multiphase model was used to solve for filed variables within a spacer-filled membrane channel.•The bubbly flow had no effect on the permeate flux while moving the flow regime to slug flow increased the permeate flux. In this study, computational fluid dynamics (CFD) modeling of gas–liquid cross-flow spacer-filled nanofiltration was developed to simulate the process in a vertical flat-sheet module. Experiments were carried out using MgSO4 solution as the feed to validate the developed model. As the novelty of this research, the Eulerian based multiphase method was implemented to assess the effect of air sparging on the concentration polarization and to compute the Sherwood number. It was shown that in most cases air sparging led to a higher permeate flux since it could reduce the concentration polarization layer on the membrane surface up to 73% with the lowest occurring at the air flowrate of 0.4 l min−1. It was also proved that the bubbly flow (0.2, 0.4, and 0.6 l min−1) had no effect on the permeate flux while moving the flow regime to slug flow (0.8 and 1 l min−1) increased the permeate flux. Finally, a good agreement between CFD simulation results and experimental data was seen.