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Laminar burning velocity in R290/R32, R290/R1234yf, and R290/HFO-1123 binary mixtures: comparing experimental results to mixing rule calculations.

Number: 2494

Author(s) : ZHANG Z., ITO M., HIHARA E.

Summary

Trifluoroethylene (HFO-1123) emerges as a promising candidate for next-generation refrigerants in refrigeration and air-conditioning applications, attributable to its extremely low global warming potential (GWP) of less than one and zero ozone depletion potential (ODP). However, HFO-1123 is known to cause a thermal decomposition called disproportionation reaction. Inhibitors like R290 are added to suppress the reaction propagation. Considering the high flammability of R290, which has a laminar burning velocity (LBV) of approximately 38 cm/s, it is crucial to determine the appropriate composition of binary mixtures that can limit the LBV to below ten cm/s. Achieving this lower flammability level, as classified by ASHRAE as 2L, is essential for developing next-generation refrigerants. Typically, substances rich in hydrogen (H) atoms like R290 show high flammability, while substances rich in fluorine (F) atoms like fluorocarbons show low flammability. Existing studies have focused on the H/F balance of the mixture and proposed various mixing rules for predicting the LBV of refrigerant combinations. However, the applicability of these mixing rules to mixtures with significant differences in LBV like HFO-1123 and R290 remains unverified. The following mixing rules are selected as the mixing rules for comparison: Linear correlation which is a weighted average by mass/mole fraction; Le Chatelier’s law which is used for the lower flammability limit (LFL) prediction in flammability studies; Oxford correlation, an extension of Le Chatelier’s law concerning combustion heat of each component. This study experimentally investigated the LBVs of binary mixtures of strongly flammable R290 and weakly flammable R32, R1234yf, or HFO-1123. Experimental results indicated a significant deviation in the LBV of binary mixtures from the prediction by proposed mixing rules. This phenomenon was notably evident in binary mixtures of substances rich in H and substances rich in F. The deviation was significant when the H/F ratio of the mixture was approximately one. The discrepancy between the experimental results and mixing rule prediction was attributed to an additional exothermic reaction between combustion products. This finding revealed complex interactions in such mixtures not reflected in the existing mixing rules. Additionally, this study examines the correlation between LBV, product composition, and adiabatic temperature, offering new insights into refrigerant mixture developments.

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  • Original title: Laminar burning velocity in R290/R32, R290/R1234yf, and R290/HFO-1123 binary mixtures: comparing experimental results to mixing rule calculations.
  • Record ID : 30033047
  • Languages: English
  • Subject: Technology
  • Source: 2024 Purdue Conferences. 20th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2024/07/17

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