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Low-GWP Alternative Refrigerant Blends for HFC-134a: Interim Report



Piotr A. Domanski, Mark O. McLinden, Valeri I. Babushok, Ian Bell, Tara Fortin, Michael Hegetschweiler, Mark A. Kedzierski, Dennis Kim, Lingnan Lin, Gregory T. Linteris, Stephanie L. Outcalt, Richard A. Perkins, Aaron Rowane, Harrison M. Skye


This project addresses the objectives of the Statement of Need number WPSON-17-20 "No/Low Global Warming Potential Alternatives to Ozone Depleting Refrigerants." Its goal is to identify and demonstrate performance of low global-warming-potential (GWP), non-flammable refrigerants to replace HFC-134a in military environmental control units (ECUs). This project is a follow-on to the limited-scope project WP-2740, which used thermodynamic cycle simulation models alone to screen over 100 000 refrigerant blends and identified over 20 candidate HFC-134a replacements. In this study we narrow the pool of blend candidates down to three 'best' fluids, verify experimentally their flammability behavior, demonstrate their performance through tests in a military ECU in environmental chambers at a wide range of operating conditions, and extrapolate the laboratory measured performance to ECUs equipped with optimized heat exchangers through first-principles-based simulations combined with machine-learning optimization methods. This Interim Report documents the preliminary work leading to the selection of three 'best' blends. This work included refrigerant blend tests in a laboratory mini-breadboard heat pump apparatus, fundamental measurements and modeling of thermophysical properties, two-phase heat-transfer performance, and flammability behavior.
NIST Interagency/Internal Report (NISTIR) - 8395
Report Number


Air conditioning, Coefficient of performance, Cycle simulation, Flammability, Refrigerants, Vapor compression, Volumetric capacity


Domanski, P. , McLinden, M. , Babushok, V. , Bell, I. , Fortin, T. , Hegetschweiler, M. , Kedzierski, M. , Kim, D. , Lin, L. , Linteris, G. , Outcalt, S. , Perkins, R. , Rowane, A. and Skye, H. (2021), Low-GWP Alternative Refrigerant Blends for HFC-134a: Interim Report, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed April 16, 2024)
Created October 13, 2021, Updated November 29, 2022