Thermodynamic, environmental, and thermoeconomic analysis of CO2 ejector expansion supermarket refrigeration systems in Türkiye climatic conditions

The use of carbon dioxide (CO2) in refrigeration systems has gained importance as a result of legal restrictions applied to refrigerants with high global warming potential. Although CO2 is an environment-friendly refrigerant, its low critical temperature and high operating pressure lead to high energy consumption, especially in commercial refrigeration. In this thesis, five different transcritical supermarket refrigeration cycle configurations, two without ejector and three with ejector expansion were theoretically modeled, optimum values for the gas cooler pressure, intermediate pressure in cycles without ejector, suction nozzle pressure drop in ejector expansion cycles were determined, performance of the cycles was compared under different conditions, annual energy analysis by deriving current bin-hour data for 11 provinces from 7 regions of Türkiye, environmental impact analysis with total equivalent warming impact (TEWI) method, exergy analysis, and thermoeconomic analysis with specific exergy costing (SPECO) method were carried out. The applicability of multi-ejectors to the ejector expansion cycles was also investigated. Up to 37% performance increase was achieved in ejector expansion cycles compared to cycles without ejector at the investigated ambient temperatures, and it was observed that ejector expansion cycle configurations with different secondary circuits perform quite close to each other. Improvement up to 17% in terms of annual energy consumption and TEWI, up to 28% in terms of specific exergy cost were determined in the investigated provinces. In the exergy analysis, it was observed that the highest irreversibilities occur in high-pressure compressor, gas cooler, and high-pressure valve in cycles without ejector.