Performance evaluation of multi-stage vacuum membrane distillation: The effect of seawater-coolant feed arrangement

In this paper, a multi-stage vacuum membrane distillation (VMD) system has been developed for seawater desalination process where the feed seawater is employed as the coolant medium. A rigorous mathematical model for such system is formulated to investigate the performance in terms of distillate production with respect to the seawater-coolant feed flow configurations such as the backward feed and the parallel feed. The VMD model is developed based on the commercially available capillary membrane module (MD020CP2N, Mycrodyn), which consists of an array of porous hydrophobic membranes, assembled together in a shell-and-tube module. The proposed multi-stage VMD desalination system consists of 24 stages with multiple recoveries of condensation heat to the feed seawater, i.e., coolant for the condensation, with the shell diameter of 0.03 m, fiber length of 0.5 m and 100 hollow fibers. It is observed that total distillate production of multi-stage VMD system with parallel feed arrangement is relatively superior as compared to that with backward feed type