Exergy Analysis of Membrane Distillation Powered by Vortex Tube for Brackish Water Desalination

ABSTRACT Exergy analysis of a combined membrane distillation (MD) and vortex tube is numerically performed and presented in this work. The vortex tube generates a temperature difference between hot and cold streams that can operate the MD process with sufficiently hot feed and cold permeate. The heat and mass transfer as well as the exergy analyses corresponding to this integrated system have been modeled. The simulations indicated that the hybrid system exhibits an exergy loss of 212.5 kW and a low exergy efficiency of 1.5%. The vortex tube is found responsible for 97% of the exergy destruction. The other supplementary equipment shares the remaining 3% of the exergy loss. The supplementary equipment exhibits a high individual exergy efficiency of more than 80%. Increasing the inlet gas pressure improves the distillate production and exergy efficiency but worsens the irreversibility. Raising the air‐to‐water mass ratio enhances the distillate production but worsens the exergy destruction significantly and the exergy efficiency marginally. Escalating the cold mass ratio degrades the irreversibility slightly, but the exergy efficiency substantially. A modified hybrid structure can reduce the overall irreversibility by 9% and increase the exergy efficiency by 872%.