EXPERIMENTAL INVESTIGATION OF HIGH EFFICIENCY SINGLE-STAGE MEMBRANE DISTILLATION CONFIGURATIONS

Abstract

A novel single-stage membrane distillation (MD) configuration, known as conductive gap membrane distillation (CGMD), has been suggested by numerical modeling results to achieve up to two times higher energy efficiencies than conventional air gap MD systems. CGMD consists of an MD module with a high thermal conductivity material in the gap region between the membrane and condensing plate, increasing the effective thermal conductivity of the gap. Such systems, if realized practically, could make MD competitive as a large scale thermal desalination technology that is not restricted only to specialized waste heat applications and could also make a stronger case for MD’s use in waste-heat applications. In this study, an experimental comparison of different MD configurations is carried out on a bench scale system keeping membrane area constant, and results are compared to model predictions. The role of energy recovery within the module on improving CGMD efficiency is illustrated. A system with a simple copper woven mesh introduced in the gap in the place of plastic spacers is found to have 40% to 60% higher GOR than AGMD. The potential for further improvements in GOR and issues associated with studying MD efficiency at a laboratory bench scale are also discussed.