Monday August 26, 2019 from 10:30 to 12:10
Replacements for R410A with GWPs less than 300
1Ingersoll Rand, La Crosse, United States
The recent Kigali amendment to the Montreal Protocol will require the phase-out of R410A used in air conditioning systems in developed countries by the late 2020s. This will require the industry to begin using R410A replacements by the middle 2020s. Lower global warming potential (GWP) refrigerant replacements for R410A have been studied extensively over the past few years. The main hurdle is that all of the candidates have been classified as flammable.
R32 has been given consideration as an alternative to R410A. R32’s GWP is 675 and has served as the benchmark for setting the upper limit of 750 GWP in various proposed rules and regulations targeting the phase-out of R410A. However, analyses indicate that reaching the Kigali targets will require a weighted average GWP of <300. The large volume of R410A used in HVAC applications makes this difficult to achieve if the GWPs of its replacements are allowed to be 675 to 750.
Three new recently introduced molecules offer opportunities to formulate blends with GWPs well less than 675, even achieving GWPs less than 300. R13I1 (trifluoroiodomethane, CF₃I) has GWP <1 and is a flame suppressant. R13I1 has properties similar to R1234yf and so can be substituted for R1234yf in blends to reduce flammability. R1123 (trifluoroethene, F₂C=CHF) has properties similar to R32 and forms near-azeotropic mixtures across the full range of compositions. With a GWP <1, R1123 can be used to displace R32 in blends to reduce GWP while maintaining capacity. R1132a (1,1-difluoroethene, F₂C=CH₂) also offers a GWP <1 while potentially enhancing capacity.
This paper investigates the thermodynamic properties of blends using these new molecules and identifies several specific blend compositions that could serve as lower GWP replacements for R410A. Compromises between a number of important factors are considered, including capacity (match to R410A), efficiency, temperature glide, compressor discharge temperature, and operating pressures. Beyond their thermodynamic properties, these new molecules present challenges in chemical stability and materials compatibility (R13I1 and R1123 more so) that are beyond the scope of this paper.