Membrane distillation. I. Module design and performance evaluation using vacuum membrane distillation

Abstract

Pure water vacuum membrane distillation (VMD) experiments were performed to evaluate the heat and mass transfer boundary layer resistances in a new laboratory-scale membrane module. The membrane module designed for this work is unique in that it can use flat-sheet membranes without a support. Additionally, the membrane module and associated apparatus were designed to achieve relatively high feed and permeate Reynolds numbers within the module. These two factors led to a dramatic reduction in boundary layer resistances, which resulted in improved VMD fluxes. This paper also examines a new complete VMD model based on the dusty-gas model, which accounts for both Knudsen and viscous mass transport across the membrane. The new model was used to predict the performance of VMD with pure water and ethanol-water solutions.