Fluorobenzene as new working fluid for high-temperature heat pumps and organic Rankine cycles: Energy analysis and thermal stability test

• Fluorobenzene is proposed as working fluid for high-temperature heat pumps and ORC. • Thermal stability of the fluid is tested with improved method and chemical analysis. • The presence of non-condensable gases removal system is simulated during the test. • Excellent stability is found as annual degradation is lower than 4 % at 350 °C. • At 180 °C heat sink temperature, COP of 3.25 is achieved for 100 °C temperature lift. Industrial high-temperature heat pumps and Organic Rankine Cycles play a pivotal role in reducing CO 2 emissions of the industrial sector. While several eco-friendly refrigerants have been explored for subcritical heat pumps below 150 °C, above this threshold only a few fluids can be adopted. In this article, fluorobenzene (C 6 H 5 F) is proposed for the first time as a versatile working fluid suitable for both HTHP and ORC systems. Notably, it possesses a near-zero Global Warming Potential, null Ozone Depletion Potential, low cost, and low toxicity. The thermo-chemical stability of fluorobenzene is experimentally investigated with an advanced procedure, simulating the presence of the non-condensable-gases removal system in real plant operating conditions. The yearly rate of unimolecular decomposition is estimated less than 4 % at 350 °C, and even after 400 h of thermal stress no decomposition products have been detected in the liquid phase through Fourier Transform Infrared Spectroscopy. In a direct heat exchange case study, coupled with exhaust gases at 390 °C, fluorobenzene achieves a net power production higher than other commercial fluids adopted in high-temperature units. In subcritical two-stage throttling heat pump condensing at 180 °C fluorobenzene shows a good Coefficient of Performance of 3.25 at 100 °C temperature lift.