Investigation of key parameters for optimizing high pressure in a single-stage transcritical CO2 system

Carbon dioxide is increasingly used as a refrigerant in modern refrigeration systems, especially in supermarkets and industrial cascade installations, where the efficiency of these systems at low temperatures represents a significant advantage. Innovations in this field highlight the sustainability of refrigeration systems that use CO2, effectively addressing various challenges arising from its (primarily poor thermodynamic) properties compared to conventional synthetic and other natural refrigerants. Controlling the high pressure in the gas cooler is the confirmed method for improving the operation of the CO2system in the transcritical region. Maintaining it at an optimal value achieves greater system efficiency and savings. This paper presents a single-stage transcritical CO2 system based on the as-built technical solution implemented in the Laboratory for Thermal Science at the Faculty of Mechanical Engineering, University of Belgrade. A thermodynamic analysis of the influence of various parameters on the optimal pressure and the coefficient of performance was carried out. Among these parameters, particular focus was given to the effect of the compressor’s isentropic efficiency, utilizing existing equations from the available literature and an equation derived from the analysis.