Passive Enhancement of Air Gap Membrane Desalination Using Finned Condensation Surfaces: Numerical and Experimental Evaluation

Air gap membrane desalination (AGMD) is an emerging energy-efficient desalination technology, but its freshwater production rate is limited by the high resistance of mass and heat transfer across the air gap. To overcome this limitation in AGMD, a passive finned design is used to effectively increase the total available surface area for condensation. Three types of fins—pin fins, trapezoidal fins, and rectangular fins—were developed and investigated via the COMSOL Multiphysics coupled model and were then prototyped. The results from the experimental test were consistent with the coupled model analysis and proved the rectangular fin to be the best option. The rectangular fin attained a flux of 12.04 kg m−2 h−1, while the flat-plate fin had a flux of 2.70 kg m−2 h−1. In addition, the rectangular fin had continuous channels to allow for better water drainage and therefore was able to reduce the film resistance. The passive fin increases freshwater production and reduces specific energy consumption (SEC) per unit volume of freshwater produced. Ultimately, the findings demonstrate that finned condensation plates offer a scalable and thermodynamically viable approach to optimizing AGMD systems without requiring complex active components or additional energy input.