Detailed numerical analysis of air gap membrane distillation performance using different membrane materials and porosity

Abstract

The motivation of this computational research is to comprehensively analyze the performance of the air gap membrane distillation (AGMD) process by varying the membrane porosity at different inlet feed temperatures (Tfeed) in counter-current and co-current flow regimes. This computational study also includes the comparative study of different membrane materials with different porosities. In this research work, a detailed theoretical model for porous medium with phase change is formulated and presented to evaluate the permeate mass flux, heat flux, and evaporation efficiency of the AGMD technique. Additionally, a CFD numerical model is successfully developed and validated with the previously published data.The results reveal that high evaporation efficiency is achieved at about 90 %, 92 %, and 94 % with 90 % membrane porosity at different inlet feed temperatures of 50 °C, 60 °C, and 75 °C, respectively, in both flow regimes. Also, transported mass flux was enhanced by 43 % at Tfeed, 50 °C with high porosity, while it increased by 65 % at Tfeed, 75 °C. The AGMD thermal performance using PVDF and PTFE flat sheet membranes is comparable with the same membrane thickness and at the same porosity; however, PTFE offers relatively high evaporation efficiency and mass flux, especially at low inlet feed temperature (50 °C).