Experimental comparison of direct contact membrane distillation (DCMD) with vacuum membrane distillation (VMD)

Membrane distillation (MD) is a thermally driven membrane process using porous hydrophobic membranes. MD has been investigated as an alternative desalination technology due to its advantages over multi-stage flash (MSF) and reverse osmosis (RO). Nevertheless, it is difficult to design and optimize the MD systems under various conditions, because both thermal and hydrodynamic effects play an important role. Therefore, this study focused on performance analysis of MD systems in different configurations. Direct contact MD (DCMD) and vacuum MD (VMD) were experimentally compared using laboratory-scale systems. A simple model was also applied to analyze the difference between two configurations theoretically. Experimental results indicated that permeate flux in DCMD and VMD were sensitive to the operating conditions. Using same membranes, two MD systems showed different flux behaviors. The influences of operating parameters for DCMD and VMD on overall efficiency were also investigated. The model results also confirmed the difference between these two systems theoretically.