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Water–Energy Nexus in Membrane Distillation: Process Design for Enhanced Thermal Efficiency

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journal contribution
posted on 09.03.2021, 23:43 by Paula G. Santos, Cíntia M. Scherer, Adriano G. Fisch, Marco Antônio S. Rodrigues
A drawback of membrane distillation is the excessive use of heat, which is neither cost-effective nor environmentally effective considering the water–energy nexus. The present paper reports on the analysis and optimization of a bench-scale membrane distillation unit regarding thermal efficiency and transmembrane flux. The research work was developed using a phenomenological mathematical model which was validated against the experimental data. With the optimized process, the heat lost by conduction through the membrane from the retentate side is minimized by a proper design of the membrane properties. With the optimal set of membrane thickness, porosity, and thermal conductivity, the heat conduction across the membrane skeleton was null but retaining the heat transferred by water vapor flux (about 30%), which is intrinsically associated with the membrane distillation phenomenon. Additionally, the transmembrane flux increased by 2-fold using the optimal design for the cell, confirming that thermal efficiency is not in contradiction to water productivity.