Review of stationary and transport CO2 refrigeration and air conditioning technologies

• A review of stationary and mobile CO 2 refrigeration and AC is provided. • Thermodynamic justification for architectures and modifications is discussed. • Numerical and experimental analyses are summarized. • Exceptions, alternative approaches, and progressive findings are included. • Paths to overcome current challenges to broader acceptance of CO 2 refrigeration are identified. Since its resurgence as a refrigerant in the 1990s, Carbon Dioxide (CO 2 ) has grown in popularity and breadth of application. Its negligible global warming potential (GWP) eliminates the risk of being phased out due to legislation, and its non-toxicity, non-flammability, and low cost allows its use in many vapor compression cycle applications. However, the high critical pressure and low critical temperature require significantly more compressor power under moderate and high-ambient conditions and thus, necessitate the addition of cycle modifications to reach coefficient of performance (COP) values equal to or greater than those of other working fluids. This paper provides a review of research conducted on the use of CO 2 vapor compression cycles in refrigeration and air conditioning (AC) cycles for both transportation and stationary refrigeration. A primary intention of writing this review is to offer evidence and justification for many common cycle modifications, then connect these modifications to a broad array of applications. Thus, advanced cycles in mobile and stationary applications are shown and the individual modifications present have their own independent justification to create a complete picture of the topic. The designs of complete systems, as well as specific components within the system, are included, as are the relations between the thermo-physical properties of CO 2 and their benefits in these particular applications. Additionally, economic analyses of the feasibility of using CO 2 in place of existing fluids are reviewed. Challenges facing the use of CO 2 refrigeration cycles in stationary and transportation refrigeration are discussed, as are potential future advancements to overcome them.