Thermophysical properties of binary fluorinated mixtures FC-72/FC-770 and FC-72/HFE-649 for heat transfer applications

¹ Kielce University of Technology, Faculty of Environmental Engineering, Geomatics and Renewable Energy, al. Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland
² Warsaw University of Technology, Faculty of Civil Engineering, Mechanics and Petrochemistry, Łukasiewicza 17 St., 09-400 Płock, Poland

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Published online: 12 March 2026

Abstract

Fluorinated fluids are widely used in electronics cooling and compact heat exchangers due to their chemical stability, dielectric strength, and safety. A major advantage of these compounds is the ability to form binary mixtures, enabling adjustment of thermophysical properties for specific applications. This study presents experimental results for two mixtures, FC-72/FC-770 and FC-72/HFE-649, examined at three mass fractions (25/75, 50/50 and 75/25). The investigated properties included specific heat capacity, thermal conductivity, density, viscosity, and boiling point. The results show that specific heat capacity increases with temperature but exhibits clear non-linearity with composition, deviating from ideal additivity. Thermal conductivity decreases with temperature, yet positive deviations were observed for intermediate compositions, suggesting synergistic effects. Both mixtures remained stable and homogeneous throughout the tested range. FC-72/FC-770 demonstrated higher thermal conductivity and stronger deviations from ideal mixing, making it suitable for enhanced heat transfer applications. In contrast, FC-72/HFE-649 displayed more stable behaviour and very low global warming potential, providing an environmentally attractive alternative. Overall, the study confirms that fluorinated binary mixtures offer flexible control of thermophysical properties, allowing tailored performance for advanced cooling and heat exchanger systems.