Flux enhanced water gap membrane distillation process-circulation of gap water

A New process and design of flux-enhanced and energy-efficient water gap membrane distillation (WGMD) module is experimentally tested and evaluated. The gap water is circulated in a separate closed loop to enhance the heat and mass transfer characteristics inside the MD module. A fundamental investigation is conducted to compare the performance of WGMD system with and without gap circulation at different operating conditions. Results showed that circulation of the gap water increases the system flux by 80 to 96% compared to without gap circulation, at the expense of some increase in energy consumed as indicated by the changes in feed and coolant water temperatures through the module. With gap circulation, a reduction in the electric specific energy consumption (SEC) between 15% and 25% was measured, associated with an increase in the gain output ratio (GOR) between 5 and 22%, compared to the case of no gap circulation. The energy utilization efficiency increase with increasing feed temperature. Higher circulation flow rates enhanced the flux while gap width showed marginal effects with circulation due to dominating forced convection inside the gap.