Assessment and Modeling of Air Gap Membrane Distillation Unit

Abstract This research presents an extensive thermodynamic and transport model for an Air Gap Membrane Distillation (AGMD) system, aimed at assessing thermal efficiency. This research presents an extensive thermodynamic and transport model for an (AGMD) system, aimed at assessing thermal efficiency. under varying operational conditions. The MATLAB-implemented model incorporates essential heat and mass transfer processes, such as Knudsen-molecular diffusion and conductive heat losses, to calculate key performance metrics like permeate flux, thermal efficiency, (GOR), and (STEC). The AGMD configuration utilizes a hydrophobic polytetrafluoroethylene (PTFE) membrane featuring a 5 mm air gap, a pore dimension of 0.45 µm and a surface thickness of 150 µm. Experimental simulations investigate operational parameters, with feed temperatures varying from 40°C to 70°C and coolant temperatures fluctuating between 10°C and 25°C. Research demonstrates that elevating the feed temperature improves system efficiency, resulting in a peak permeate flow rate of 12.77 kg/m²·h, a thermal efficiency of 50.62%, and a minimum (STEC) of 29.04 kWh/m³ at a feed temperature of 70°C and a coolant temperature of 10°C. These results highlight AGMD’s potential as an energy-efficient desalination method, supporting sustainable freshwater generation in regions facing water scarcity. Future studies could explore optimizing membrane materials, minimizing thermal losses, and coupling with renewable energy to enhance performance and scalability. The model’s accuracy is validated by a ~ 60% increase in GOR, closely matching experimental outcomes. A custom built, solar integrated AGMD test rig equipped with a flat-plate solar collector and Arduino-based real-time monitoring was used to verify the model. Predictions showed strong alignment with experimental data and existing literature, confirming the system’s scalability and robustness. With an advantageous freshwater production expense of $2.52 per cubic meter, the system emerges as a practical solution for decentralized, off-grid applications. This research establishes a validated MATLAB modeling framework to guide AGMD design optimization, promoting its adoption as an affordable, renewable energy-powered desalination technology.