Limited options for low-global-warming-potential refrigerants

Hydrofluorocarbons, currently used as refrigerants in air conditioning systems, are potent greenhouse gases, and their contribution to climate change is projected to increase. Future use of the hydrofluorocarbons will be phased down and, thus replacement fluids must be found. Finds that only a few pure fluids possess the combination of chemical, environmental, thermodynamic, and safety properties necessary for a refrigerant and these fluids are at least slightly flammable. Searches for replacements by applying screening criteria to a comprehensive chemical database. For the fluids passing the thermodynamic and environmental screening (critical temperature and global warming potential), simulates their performance in small air conditioning systems, including optimization of the heat exchangers. The results show that the efficiency-versus-capacity trade-off that exists in an ideal analysis disappears when a more realistic system is considered. The maximum efficiency occurs at a relatively high unit volumetric refrigeration capacity, but there are few fluids in this range.