Novel vacuum membrane distillation operated by air ejector and bubble column dehumidifier for sustainable water desalination-energetic, exergetic, and economic analysis

To address the challenge of energy-efficient water desalination, this study investigates a novel vacuum membrane distillation (VMD) operated by an air ejector and integrated with a bubble column dehumidifier (BCD). The novelty of the present study is emphasized by its comprehensive utilization of an air ejector instead of the vacuum pump of the conventional VMD module, reducing the production cost and enabling scalability for large-scale applications. The findings report an enhanced performance with a productivity of 210 kg/m2.h, at a specific energy consumption (SEC) of 760 kWh/m3 and gained output ratio (GOR) of 0.98, confirming the system's operational effectiveness. Economically, a unit production cost (UPC) of 22 $/m3 is achieved, reflecting a 30 % reduction compared to conventional thermal desalination systems. The influence of feed temperature is evident, increasing it from 50 °C to 90 °C amplifies flux roughly sevenfold and cuts the SEC by 25 %. Notably, while the air ejector enhances reliability by eliminating moving parts, it is responsible for about 45 % of the total exergy destruction, highlighting a key area for design optimization. The BCD efficiently condenses vapor by channelling warm, humid air through a cooled water column, promoting heat and mass transfer through the temperature gradient. This integrated VMD-ejector-BCD arrangement demonstrates a promising pathway toward scalable, energy-conscious desalination technologies.