Thermodynamic analysis of a novel humidification–dehumidification desalination system enhanced by a thermally driven ejector cooling system

This study presents a novel humidification–dehumidification (HDH) desalination system integrated with a thermally driven ejector cooling system (ECS) to enhance energy utilization and freshwater productivity under solar-driven conditions. The proposed configuration employs R141b as the working fluid in the ejector loop, which operates solely on low-grade thermal energy without major mechanical work input. The ejector condenser rejects heat to preheat the feed water entering the humidifier, while the evaporator provides auxiliary cooling to improve condensation in the dehumidifier. A comprehensive thermodynamic model was developed and solved using Engineering Equation Solver (EES) based on steady-state mass and energy balances, and was validated against published HDH and ejector data with less than 5% deviation in GOR and a mean absolute percentage error of 7.7% for the entrainment ratio. Parametric analyses were conducted to evaluate the effects of mass ratio and component temperatures on system performance. Under representative operating conditions, integrating the ejector cycle increases the gained output ratio (GOR) from 3.15 for the standalone HDH cycle to 4.5, corresponding to an enhancement of about 42%, and raises the recovery ratio (RR) by approximately 12%. Across the investigated operating range, the maximum GOR reaches about 6.0 and the RR up to 2.5%. The entrainment ratio has a pronounced influence on the thermal performance of the system. These results demonstrate that the proposed thermally driven HDH–ECS configuration can significantly improve freshwater production from low-grade thermal energy.