Comparative analysis of thermodynamic performance of CO ₂ cascade refrigeration system assisted with expander and mechanical subcooling

Abstract

Summary In order to discuss the feasibility of using R744/R744 cascade refrigeration system (CRS) instead of R744/R717 CRS, six configurations of R744/R744 CRS assisted with expander and mechanical subcooling system (MS) are analyzed. Based on the thermodynamic analysis, the results show that the high pressure, the condensing temperature of the low‐temperature cycle (LTC), and the degree of subcooling of LTC and the high‐temperature cycle (HTC) are three important operating parameters with an optimum value corresponding to the maximum coefficient of performance (COP). Compared with other CRSs, CRS with HTC throttling valve and MS of HTC (CTSH) and CRS with HTC expander and MS of HTC (CESH) show an excellent performance. CESH has the highest COP and is improved by an average of 13.8% compared with the COP of R744/R717 CRS. The COP of CTSH is improved by an average of 4.2% compared with the COP of R744/R717 CRS. In conclusion, it is an efficient way to improve performance that CRS combines MS in HTC and HTC expander. And it is possible R744/R744 CRS instead of R744/R717 CRS.

Thermodynamic, economic, and environmental analyses of various novel ejector refrigeration subcooled transcritical CO 2 systems

“…Liu et al 18 reported the COP amelioration up to 76% by utilizing a mechanical subcooler in a two‐stage CO 2 refrigeration system. Sun et al 19 theoretically observed that the mechanical subcooling in the high‐temperature cycle is effective for cascade devices. Nebot‐Andrés et al 20 experimentally optimized the gas cooler pressure of mechanical subcooled CO 2 refrigeration system.…”

Thermodynamic performance evaluation of the CO 2 parallel compression supermarket refrigeration system with a subcooler

“…20 Sánchez experimentally verified the feasibility of two types of subcoolers in a single-stage compression system. 6 Combining R717/R744 cascade system with a subcooler also is an efficient way to improve the overall performance put forward by Sun et al 22 However, to the best of the authors' knowledge, the investigation of subcooling by the liquid refrigerant itself in two temperature parallel compression trans-critical CO 2 refrigeration systems for supermarket refrigeration is lacking.…”