Transcritical carbon dioxide heat pump systems: A review

Carbon dioxide is a safe, economic and environmentally sustainable refrigerant which can be used in heat pump and refrigeration systems. Research into the performance and benefits of a transcritical heat pump cycle using carbon dioxide began in the early 1990s. Theoretical and experimental research, as well as commercial system development, has improved transcritical system performance to a level similar to that of conventional heat pump systems. This paper presents an overview of transcritical carbon dioxide heat pump systems. The paper begins with a summary of carbon dioxide's use as a refrigerant and the distinctions of the transcritical cycle, followed by a numerical analysis of transcritical cycle performance. The study will then present a review of research on transcritical carbon dioxide heat pump systems, which covers system components, configurations and modifications and how these factors affect overall system performance.