Design and performance enhancement of a dual-purpose ejector system for integrated cooling and desalination applications

This work addresses the need for sustainable solutions that simultaneously provide cooling and freshwater, particularly for off-grid and water-stressed regions. A dual-purpose ejector-based system integrating refrigeration and desalination is proposed, designed to operate on low-grade waste heat or renewable energy. The novelty of this study lies in establishing a comprehensive design framework that couples subsystem performance with the underlying ejector flow physics, going beyond earlier works that considered these applications separately. The methodology combines analytical system modeling with detailed computational fluid dynamics (CFD) simulations to investigate ejector performance under varying geometric and operating parameters, followed by integrated system-level analyses. CFD results show that ejector entrainment behavior depends strongly on diameter ratio and primary pressure. Entrainment ratio increases and then decreases with diameter ratio, with an optimum of 2.25, while primary pressure exhibits a similar trend with an optimum at 5 bar. The physical mechanisms behind these trends were identified through shock structure and mixing field visualizations. Subsystem-level results reveal that desalination performance depends primarily on primary jet pressure, with distillate production improving by 65% (45.37 $\to$ 71.20 g/s) as pressure increases, while specific energy consumption decreases from 16.32 to 10.78 kWh. In contrast, refrigeration performance depends on primary pressure, secondary pressure, and discharge pressure, achieving a maximum cooling capacity of 9.36 kW and a peak Coefficient of Performance (COP) of 0.21 under optimal conditions. Importantly, the integrated system exhibits strong thermal synergy, with overall COP remaining stable between 3.02 and 3.18 despite variations in individual subsystems. These findings confirm that ejector-based integration of refrigeration and desalination is both feasible and efficient, providing a stable, low-grade energy-driven solution for combined cooling and freshwater generation.