Unraveling fluid dynamics in full-scale hollow fiber nanofiltration membrane modules: From a perspective of CFD study

The fluid dynamics in hollow fiber nanofiltration (HFNF) modules have crucial impacts on the separation performance and energy efficiency during application process. Herein, full-scale computational fluid dynamics (CFD) analyses of the structural parameters and operational conditions of membrane modules were performed, revealing the vorticity, turbulent kinetic energy, and turbulence dissipation rate distribution within the modules. CFD results show that an overly large inlet open area reduces flow dispersion, while an elevated packing fraction increases hydraulic losses, both of which negatively affect the vorticity distribution. Additionally, shell-side fluid dynamics exhibit nonlinear dependence on packing fraction (Φ) with a sharp transition at Φ = 0.4619. Beyond this value, the hydraulic loss suddenly increases and low vorticity zone near the membrane surface significantly expands. Critically, while operating conditions primarily affect turbulence and vorticity, the module's structural design is the dominant factor in determining the resulting vortex structure. Collectively, this work provides fundamental understanding of the fluid dynamics within the modules and gives initial guidance for both the design and application of HFNF membrane modules.