Comparison and analysis on comprehensive performance of CO₂ multiphase refrigeration systems using liquefied natural gas cold energy.

This article focuses on the design and analysis of four types of carbon dioxide (CO₂) multiphase refrigeration systems that utilize liquefied natural gas (LNG) cold energy to improve refrigeration efficiency and reduce environmental impact. The systems—single-stage and double-stage compressed solid and gas or solid phase refrigeration cycles combined with a CO₂ liquid phase secondary refrigerant cycle—are evaluated through performance, exergy, economic, and CO₂ emission analyses. Results indicate that the double-stage compressed solid and solid phase system (DSCC2-RC) achieves the best overall performance, lowest exergy loss, and minimal CO₂ emissions, while the single-stage compressed solid and solid phase system (SSCC2-RC) offers the shortest payback period. Compared to an ammonia combined refrigeration system with equivalent capacity, the CO₂ multiphase systems demonstrate higher coefficient of performance (COP), lower power consumption, reduced equipment costs, greater annual revenue, shorter payback periods, and lower CO₂ emissions, though they exhibit higher exergy losses due to larger temperature differences in heat exchange.