Thermodynamic analysis of the humidification-dehumidification-adsorption (HDHA) desalination process

The process of Air Humidification-Dehumidification (HDH) for water desalination and purification can play an important role in the field of low-carbon water production from non-conventional sources. Our research group presented a novel process scheme consisting of a multiple extraction HDH with vapour adsorption (HDHA) and brine recirculation, able to approximate a closed-air closed-water loop with bottom temperature below the environmental one. This novel work presents the strategy of process optimization through the variance analysis and a mathematical algorithm of thermodynamic balancing adapted to this novel process. The results point out the optimization strategies and allow the literature comparison to show how HDHA can overcome the performances of conventional processes at similar conditions, also reaching acceptable values of second law efficiency. In fact, HDHA can overcome the GOR of similar “balanced” water heated HDH reaching GOR around 10 even at acceptable enthalpy pinch (around 15 kJ kg⁻¹) with three air extractions.