title: Limited options for low-global-warming-potential refrigerants.
abstract: 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. Here we show that only a few pure fluids possess the combination of chemical, environmental, thermodynamic, and safety properties necessary for a refrigerant and that these fluids are at least slightly flammable. We search for replacements by applying screening criteria to a comprehensive chemical database. For the fluids passing the thermodynamic and environmental screens (critical temperature and global warming potential), we simulate performance in small air-conditioning systems, including optimization of the heat exchangers. We 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 volumetric refrigeration capacity, but there are few fluids in this range.
authors.affiliation: Applied Chemicals and Materials Division, National Institute of Standards and Technology, 325 Broadway, Mailstop 647, Boulder, Colorado 80305, USA.
authors.forename: Mark O
authors.identifier: 0000-0002-1082-309X
authors.initials: MO
authors.lastname: McLinden
authors.affiliation: Department of Mechanical Engineering, The Catholic University of America, 620 Michigan Avenue, NE, Washington D.C., 20064, USA.
authors.forename: J Steven
authors.initials: JS
authors.lastname: Brown
authors.affiliation: Energy and Environment Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8631, Gaithersburg, Maryland 20899, USA.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Brignoli
authors.affiliation: Applied Chemicals and Materials Division, National Institute of Standards and Technology, 325 Broadway, Mailstop 647, Boulder, Colorado 80305, USA.
authors.forename: Andrei F
authors.initials: AF
authors.lastname: Kazakov
authors.affiliation: Energy and Environment Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8631, Gaithersburg, Maryland 20899, USA.
authors.forename: Piotr A
authors.initials: PA
authors.lastname: Domanski