Energy analysis and performance comparison of transcritical CO2 supermarket refrigeration cycles

Using carbon dioxide as a refrigerant gains importance as a result of restrictions applied to high-GWP (Global Warming Potential) refrigerants. Although CO2 is an environment-friendly refrigerant, its low critical temperature and high operating pressure lead to high energy consumption, especially in commercial refrigeration. As a result, research and improvements are being made to reduce the energy consumption of transcritical CO2 refrigeration cycles. This paper presents thermodynamic analysis and pressure optimizations to obtain maximum performance for transcritical booster, parallel compression, and ejector expansion supermarket refrigeration cycles. Effects of different operation conditions were also investigated and cycles were compared to each other in terms of performance. It was obtained that up to 47% Coefficient of Performance (COP) improvement can be achieved using ejector expansion cycle with the help of expansion work recovery in the ejector. It was also shown that ejector expansion cycle outperforms other CO2-only cycles without ejector in all conditions.