Computational fluid dynamics simulation of the stacked module in air gap membrane distillation for enhanced permeate flux and energy efficiency

Advancements in membrane distillation (MD) technology require the development of module designs to optimize system performance. This study established a computational fluid dynamics (CFD) model to assess the performance of an air gap membrane distillation (AGMD) system. The CFD model achieved an accuracy of approximately 96.43% through verification under various feed temperatures and flow conditions in an experimental AGMD system. CFD simulations demonstrated the importance of flow and temperature distribution within the module, and the response surface method was employed to investigate the influence of module size on system performance. The thickness of the air gap affected the permeate flux by >7 times the module length. The influence of the module length on the change in the gained output ratio was >11 times that of the feed temperature. In addition, graphical optimization enables the identification of optimal conditions that satisfy multiple variables simultaneously. The dual mode of the AGMD system based on optimization improved the performance of the model and demonstrated efficient operation compared with the single mode, indicating improvements of 14.36% and 13.64% in the permeate flux and gained output ratio, respectively.