Computational Study of Crossflow Patterned Hollow Fiber Vacuum Membrane Distillation

Abstract

Large Eddy Simulations (LES) were conducted to investigate transport phenomena in hollow fiber Vacuum Membrane Distillation (VMD) modules. Most previous studies have investigated VMD, where the feed flow is in the same axial direction and the boundary layers remain attached to the membranes, resulting in a gradual decline in driving force and a decrease in flux toward the outlet. A crossflow-patterned hollow fiber module (HF-VMD), in which the feed enters across the bundle, moving orthogonal to the fibers from top to bottom, is considered in this research. Key performance indicators included permeate flux, temperature polarization coefficient (TPC), and concentration polarization coefficient (CPC). The results demonstrate that crossflow geometry outperforms parallel flow, enhancing flux by nearly 40% while suppressing polarization. Medium to high packing densities (50–75%) provide an effective balance between compact module design and stable flux, as indicated by the merit number. Increasing the Reynolds number improved mixing and mass transfer, peaking at Re = 1500 by 35%. A higher feed temperature was confirmed as the dominant driver of vapor transport, boosting flux by more than 55% at 353 K compared to 333 K. In contrast, extending the module length degraded performance by 14% due to accumulated polarization. Overall, this dissertation advances the understanding of heat and mass transfer in HF-VMD systems and provides practical guidelines for module optimization using high-resolution LES simulations. The findings identify crossflow HF-VMD modules as a promising pathway for next-generation desalination technology, particularly for large-scale applications.