In line with currently imposed environmental legislation,
1-3 restricting the usage of hydrofluorocarbons (HFCs) as working fluids in refrigeration and air-conditioning applications (RAC), low global warming potential (GWP) alternatives are in dire need. To tackle this issue, the polar soft-SAFT molecular-based equation of state has been used in a predictive manner to screen and design sustainable drop-in replacements for the most commonly used HFC refrigerants in RAC today, R134a (GWP=1300) and R410A (1924). The modeling framework is applied in a systematic manner for assessing compliance of drop-in replacements towards ensuring retrofitting scenarios based on a multi-criteria assessment (3E analysis) on energy, environmental, and economic variables, in addition to a thorough examination of safety and technical features. This involves the thermodynamic characterization of a long list of hydrofluorocarbons and hydro(chloro)fluoroolefins with polar- soft-SAFT.
4 Vapor-liquid equilibria, derivative properties and binary systems are calculated at a coarse-grain level to validate the parametrization. Such systematic and holistic approach is seen to be valid at a broad spectrum of working conditions and system configurations, emphasizing the applicability, transferability and accuracy of the accomplished methodology. Results indicate that near-azeotropic mixtures 90
wt.% R1234yf + R134a / R152a (130, 14) constitute the optimal screened systems by reason of its high efficiency, constrained extra cost, highlighted environmental (direct and indirect) and thermophysical properties, in addition to avoiding compressor retrofitting in self-designed R134a circuits. The compatibility metrics are also reproduced for R513A (608) and R450A (682), the best-known domestic and commercial drop-ins for R134a. Alternatively, R32 (677) and 90
wt.% R1123 + R32 (70) present the closest affinity to R410A by means of considerably similar drop-in key performance indicators at settled requirements. It should be noted that partial retrofitting may be demanded with regard to the latter set of replacements, while null or insignificant re-scaling is ensured for selected energy-efficient R134a drop-in alternatives. Overall, this work demonstrate the value of using an accurate molecular-based equation of state on the hunting for low GWP refrigerants in a reliable and robust manner.
Acknowledgments
This research is supported by the Spanish Ministry of Science and Innovation (project STOP-F-Gas, PID2019-108014RB-C21) and by Khalifa University of Science and Technology (project RC2-2019-007). CGA acknowledges a FI-SDUR fellowship granted by the Catalan Government.
References
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(4) Albà , C. G.; Alkhatib, I. I. I.; Llovell, F.; Vega, L. F. Assessment of Low Global Warming Potential Refrigerants for Drop-In Replacement by Connecting Their Molecular Features to Their Performance. ACS Sustain. Chem. Eng. 2021, 9 (50), 17034–17048. https://doi.org/10.1021/acssuschemeng.1c05985.
