Hydrofluorocarbons which are widely used as working fluids for air-conditioners and refrigerators have been shifted to ones with low environmental impact due to worldwide efforts to reduce CO₂ by the Montreal Protocol and the Paris Agreement. However, since the refrigerants with low environmental impact have flammability, it is essential to understand their iginiton and combustion characteristics for safety use. However, refrigerants produce corrosive burned gas and are not as flammable as gasoline fuels, therefore it is extremely difficult to evaluate the ignition and combustion characteristics of refrigerant using conventional methods.

In this study, the oxidation of hydrofluorocarbon refrigerants is tested using a micro flow reactor with a controlled temperature profile (MFR) and gas sampling analysis using a FTIR. The MFR can examine the samples with low flammable and it is easy to replace the reactor, therefore it is possible to repeatedly test corrosive samples. Previous studies have clarified the reactivity and detailed reaction pathway of some refrigerants. It has also been identified that there is a region where fluorinated combustion intermediates react slowly on the downstream of major heat release for the first time in the world. For the future tasks, we will summarize the relationship between the molecule structure of fluorohydrocarbons and their reactivity, and compare them with general combustion characteristics, leading to a comprehensive evaluation of fluorohydrocarbon refrigerants.

Weak flames of R32(CH₂F₂), R410A(CH₂F₂/C₂HF₅) and R125(C₂HF₅) observed in MFR

Reaction pathway of the R32 (CH₂F₂) oxidation in MFR