Viable solutions to increase efficiencies of transcritical CO2 systems for commercial refrigeration.

CO2 offers inherently good performances for commercial refrigeration due to its heat transfer properties resulting in higher evaporating temperatures showing increased cycle efficiencies at low/medium ambient temperatures compared to conventional HFC systems. Over a thousand applications have been implemented in the market using mostly a two-stage expansion process and installing them in Europe, where average temperatures are below 15°C. However, CO2 also offers great opportunities to raise efficiencies at high ambient temperatures above 23°C (Finckh 2011), where it currently has disadvantages compared to conventional HFC systems. This paper presents an analysis of different concepts to enhance performance of CO2 commercial refrigeration systems for high ambient temperature applications. Additionally, it gives an outlook when this technology is available for product insertion.