Evaluation of binary and ternary refrigerant blends as replacements for R134a in an air-conditioning system

Conference Year

2018

Authors

Ian Bell, National Institute of Standards and Technology, United States of AmericaFollow
Piotr Domanski, National Institute of Standards and Technology, United States of AmericaFollow
Greg Linteris, National Institute of Standards and Technology, United States of AmericaFollow
M. O. McLinden, National Institute of Standards and TechnologyFollow

Keywords

mixtures, R134a, refrigeration, thermodynamics, screening

Abstract

We investigated refrigerant blends as possible low-GWP (global warming potential) alternatives for R134a in an air-conditioning application. We carried out an extensive screening of the binary and ternary blends possible among a list of 10 pure refrigerants comprising three hydrofluoroolefins (HFOs), six hydrofluorocarbons (HFCs), and carbon dioxide. The screening was based on a simplified cycle model, but with the inclusion of pressure drops in the evaporator and condenser. The metrics for the evaluation were nonflammability, low-GWP, high COP (coefficient of performance), and a volumetric capacity similar to the R134a baseline system. While no mixture was ideal in all regards, we identified 12 "best" blends that were nonflammable (based on a new estimation method by Linteris, et al., presented in a companion paper at this conference) and with COP and capacity similar to the R134a baseline; the tradeoff, however, was a reduction in GWP of, at most, 56% compared to R134a. An additional seven blends that were estimated to be "marginally flammable" (ASHRAE Standard 34 classification of A2L) were identified with GWP reductions of as much as 90%. These 19 "best" blends were then simulated in a more detailed cycle model.