3D-CFD simulation of hollow fiber direct contact membrane distillation module: Effect of module and fibers geometries on hydrodynamics, mass, and heat transfer

Abstract

For achieving a successful membrane distillation operation, not only the properties of the membrane but also the module design must be optimized. Computational Fluid Dynamics (CFD) is a practical tool for investigating the transport phenomena in a membrane module. Thus this research aimed to investigate the momentum, heat, and mass transfer by means of a 3D-CFD simulation for a hollow fiber membrane module applied for direct contact membrane distillation (DCMD) of saline water. Momentum, heat, and mass transfer equations in three dimensions were coupled and solved using the finite volume method by the Comsol Multiphase® software, and the effects of feed and permeate flow rates, number of fibers, and fiber length on DCMD performance are examined. The results demonstrated that the number of fibers has a significant effect on the permeate flux through flow channeling. The impact of feed flowrate on the increase of permeate flux is much more considerable than the permeate side. The longer fibers resulted in lower average fluxes due to the development of a thermal boundary and concentration layers. The temperature profile shows abnormal deflections at feed entry and reject exit ports due to the fluid entrance effects. Finally, it could be concluded that enhancing the feed-side hydrodynamics is an easy and affordable technique for attaining considerable improvement in DCMD performance.