Theoretical and Experimental Validation of Water Gap MembraneDistillation

摘要

Theoretical and experimental validation of a water gap membrane distillation (WGMD)process has been proposed and successfully tested for seawater desalination. It has been observedthat, employing water in the air gap between the membrane and condensation plate of an air gapmembrane distillation (AGMD) module, there is a significant enhancement of the water vaporflux, reaching 800 %. A detailed investigation on the influence of thickness of the water gap hasbeen carried in this study. Water vapor flux enhancement in the WGMD process has beendescribed with the help of a theoretical explanation of heat and mass transfer mechanismsthrough the membrane and water gap. Heat and mass transfer resistance in the air gap during anAGMD process is the major limiting factor for the lower water vapor flux. It was observed thatemploying water in the air gap of an AGMD module eliminates the heat and mass transferresistance in the air gap and results in increased water vapor flux. Temperature polarization isanother phenomenon which adversely affects all MD processes and causes a significant decreasein the water vapor flux. During the WGMD process, occurrence of natural convection in thewater gap helps to decrease the temperature polarization and provide a synergistic effect alongwith the sensible heat transfer to enhance the water vapor flux. A theoretical explanation of thenatural convection during the WGMD process will be described in this paper.