Optimization of optimal discharge pressure for a novel solar-assisted ejector subcooling CO2 transcritical refrigeration system based on NSGA-II

In recent years, due to the increasing energy consumption of buildings, energy saving and emission reduction have become the focus of attention in the field of refrigeration and air conditioning. This research proposes a novel system for the field of solar air conditioning: a solar-drive ejector subcooling CO2 transcritical refrigeration system (SESRS). The SESRS system both utilizes renewable solar energy and improves the energy efficiency of the system. This novel cascade cycle can effectively increase the COP of the system. But thermodynamic analysis using the Popt,dis reveals that although the COP of the system reaches the maximum value, the Asc also reaches the maximum value, and there is a problem of poor system economics. Therefore, in this study, a Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is used for multi-objective optimization of conflicting objectives COP and Asc. When Ta is 35 degrees C, the optimized discharge pressure (Pdis,optimized) obtained by thermodynamic calculation gives a COP of 2.19 and Asc of 8 m2. Although the COP is 12.34 % lower than that obtained after using the optimal discharge pressure (Popt,SESRS) calculation, the Asc is reduced by 65.57 %.When discharge pressures are adopted in terms of Pdis,optimized and Popt,TCRS, the performance and economy of the two discharge pressure calculations are closer. This multi-objective optimization approach considers both the coefficient of performance and the economics of SESRS, and integrating these criteria into the optimization process results in an environmentally friendly and economically viable SESRS cycle.