Study On Performance Optimization Potential Of Solar-Driven Cascade Ejector System With Heat And Cold Storage Based On Advanced Exergy Analysis Method

With the implementation of the"dual carbon"strategy,solar energy is widely favored as a clean energy source.Solar refrigeration technology has become one of the research hotspots in the field of refrigeration due to its good seasonal matching.In this paper,we propose a solar-driven cascade ejector system with heat and cold storage consisting of solar-driven ejector heat storage subsystem and the transcritical CO₂ ejector expansion refrigeration subsystem.By establishing thermodynamic model of the system and components,the performance optimization potential of the system is studied based on conventional and advanced exergy analysis methods.Firstly,this paper selects three environment-friendly refrigerants R744（CO₂）,R290,R1234yf and a common refrigerant R134a to apply to the transcritical CO₂ ejector expansion refrigeration subsystem for research.By discussing the conventional and advanced exergy characteristics of different refrigerants,the best refrigerant is selected to lay the foundation for the exergy analysis of the whole system.The research shows that when CO₂ is used as refrigerant,the system has higher system exergy performance and good matching,and it is more in line with the current strategic goal of"carbon peak and carbon neutralization"in our country,so CO₂ is the best choice as refrigerant.Secondly,this paper reveals the internal relationship between the interaction of the system components,and then evaluates the dependency between the system components,and quantifies the improvement potential of the system and each component.The results show that R290 ejector has the greatest potential for improvement,followed by solar collector.88.90%of system exergy destruction is endogenous,while 41.68%of system exergy destruction is avoidable.At the same time,improving the performance of CO₂ ejector and CO₂ evaporator can decrease the exergy destruction of compressor,and 65.94%of exergy destruction of middle heat exchanger is caused by compressor and CO₂ ejector.Meanwhile,CO₂ evaporator is not affected by other components.Overall,the CO₂ ejector and the R290 ejector have the highest improvement priority of the two subsystems respectively.Finally,the impact of the efficiency of key components and typical parameters on the exergy performance is discussed.To investigate the influence of CO₂ side pressure of middle heat exchanger on the exergy performance of R290 ejector,CO₂ ejector and compressor.The research results show that system exergy efficiency can be increased significantly by improving the performance of R290 ejector,CO₂ ejector and compressor,especially R290ejector.When compressor efficiency increased from 0.5 to 0.9,avoidable endogenous and exogenous exergy destruction of compressors decreased by 94.15%and 93.37%,respectively.The system has an optimal middle heat exchanger CO₂ side pressure of 8.5MPa.Under this pressure,the system exergy efficiency reaches the highest,and the R290 injector can avoidable endogenous exergy destruction to the minimum.In this paper,through an in-depth analysis of the exergy performance of the solar-driven cascade ejector system with heat and cold storage,the key parameters that quantify the interaction relationship between the components in the system and the performance improvement potential are obtained.This study provides the theoretical basis for efficient control,thermal enhancement and improvement of regulation strategies of cascade systems.