Experimentally-validated computational simulation of direct contact membrane distillation performance

Abstract

A Direct Contact Membrane Distillation system using a flat-sheet membrane module was fabricated to experimentally study the effects of operating conditions (inlet temperatures and flow rates of feed and permeate streams and salt concentration) on its distilled water production. A two-dimensional Computational Fluid Dynamics (CFD) model considering transmembrane mass flux and heat conduction and associated phase change heat transfer (evaporation and condensation) was developed. It was found that the computational predictions of distilled water production agreed well with the experimental measurements. Furthermore, the CFD model analyzed the effects of filament spacing of a screen spacer in the flow channels and flow configuration (counterflow and parallel) on the water distillation performance. In this study, it is concluded that high water distillation is achieved by using low permeate temperature, high feed temperature, high feed and permeate flow rates, and less salt concentration in a counterflow configuration. The water distillation is more influenced by the feed temperature than the permeate temperature due to the water saturation pressure-temperature relation. The simulation results also showed that the convection thermal resistances in the feed and permeate channels are decreased by using screen spacers and therefore, the temperature and concentration polarization effects are decreased in the channels.