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The burning velocity plays an important role in determining the safety level of new refrigerants. Based on the self-designed test system for burning velocity characteristics of flammable refrigerants, the burning velocities of R152a with different concentration were studied by vertical glass tube method. And the maximum burning velocity of R152a was analyzed, which was close to the standard recommended value. R1234yf with environmental advantages and lower flammability may form a new alternative refrigerant mixture with R152a. Therefore, the flame propagation and burning velocity characteristics of R152a+R1234yf were studied under the conditions of different component ratio and different concentration. Based on the theoretical analysis, three calculation methods for predicting the burning velocity of binary mixed flammable refrigerant were proposed for the first time. Then, three groups of predicted burning velocity of R152a+R1234yf under different composition or concentrations were calculated. Compared with the experimental data, it was found that the prediction accuracy of the component equivalent simplified method is the highest among the three methods. It was of great significance for the prediction of burning velocity and the assessment of safety level of new mixed refrigerant or flammable gas. [ABSTRACT FROM AUTHOR]

In this study, experiments and analysis addressed the flammable difference between chemical isomers of 2,3,3,3-tetrafluoropropene (R1234yf) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)). All measurements of the flammability limits were conducted with a self-made apparatus system with temperature ranging from 5 to 55 °C and relative humidity of air ranging from 0 to 100% corrected for 25 °C. The temperature dependences of flammability limits of R1234yf and R1234ze(E) were larger than the predictions by White's rule, but they could be predicted by a linear model accurately. Meanwhile, the results revealed that water vapor expanded the flammability limits of both R1234yf and R1234ze(E), but the sensitivity of these two isomers is very different, especially for the lower flammability limits (LFLs). The humidity dependence for R1234yf was linear, while it was not for R1234ze(E). [ABSTRACT FROM AUTHOR]

As the key part of the refrigeration systems, heat pump systems, and Organic Rankine Cycle (ORC) systems, most working fluids with low global warming potential (GWP) are flammable. This paper proposed a novel method called indirect inhibition to mitigate their flammability to enhance the applicability of low-GWP working fluids. Firstly, the effect of lubricants oil, indirect flame retardants (IFR), and mixtures of the two on the flammability of propane were investigated. The experimental results showed that lubricating oil promoted the combustion of propane to a certain extent. The introduction of indirect flame retardant (CP-52) weakened the combustion intensity of propane. The lubricating oil, in conjunction with a flame retardant, could inhibit the combustion of propane. Secondly, the effects of the indirect flame retardant and mineral oil on the flammability of propane were theoretically analyzed using density functional theory (DFT). The theoretical calculation results showed that the ability of IFR to capture reactive free radicals was comparable to that of traditional flame retardants. The research results are of great significance for improving the safety of the cycle system and reducing the risk of accidents. [ABSTRACT FROM AUTHOR]