Computational study of sweeping gas membrane distillation process - Flux performance and polarization characteristics

Computational fluid dynamics simulations were conducted in a three-dimensional sweeping gas membrane distillation (SGMD) desalination module. The module flux performance and polarization characteristics were investigated for a wide range of flow rates spanning the laminar and turbulent flow regime in the feed and permeate channel. The membrane was treated as a functional surface with zero thickness, and the membrane permeability was determined by a combination of Knudsen and molecular diffusion using the Dusty Gas model. The mathematical model and numerical method was validated against existing experimental work. It was shown that low membrane thickness, high porosity, and low tortuosity yield high vapor flux. It was demonstrated that high vapor flux can be achieved in a SGMD module by increasing the permeate flow rate to avoid temperature and moisture polarization in the permeate channel. By increasing the feed flow rate, the flux also increased, and temperature and concentration polarization decreased. It was shown that the SGMD process, as effective as other MD processes, could be used as an alternative method for water desalination. The model developed here can be utilized for design and optimization of full-scale SGMD modules.