A computational fluid dynamics study on TPMS-based spacers in direct contact membrane distillation modules

Abstract

Feed spacers are incorporated in membrane modules to enhance fluid mixing, thereby enhancing membrane flux. Previous experimental work showed that triply periodic minimal surfaces (TPMS)-based spacers induce significant improvements in membrane distillation (MD) performance, which was attributed to the suppression of membrane boundary layer, reducing heat and mass transfer resistance. To corroborate those findings, in this study, we assess the performance of TPMS spacers in direct contact MD (DCMD) modules using computational fluid dynamics (CFD). Results showed that the Fischer-Koch S TPMS spacer topology achieved twice the flux of the empty channel case and exhibited a 13 % increment in flux compared to the net-type spacer, but this improvement was accompanied by a higher pressure drop in the feed channel. Therefore, a normalized power ratio (NPR) was used to evaluate the overall performance of spacers. For Reynold number (Re) ranging between 200 and 1200, Fischer-Koch S spacer had a 12 % improvement in NPR compared to the net-type spacer and resulted in higher shear stress near the membrane surface, indicating a promising mean for mitigating fouling in membrane distillation. This research highlights the importance of utilizing novel spacers in membrane distillation and showcases the power of CFD tools in optimizing the process.