Experimental study on the influence of flame retardants under high-temperature conditions on the flammability of R1234ze(E) and R290

The development of alternative refrigerants with low global warming potentials (GWP) has become a trend in response to the increasing demands for environment protection. R1234ze(E) and R290 have extremely low GWP values and are potential substitutes. However, their flammability limits their applications under hightemperature conditions. In this study, R134a was experimentally investigated for its flame-retardant effect on R1234ze(E) and R290 refrigerants at 60 degree celsius. The flammability ranges of pure flammable refrigerants were measured, and the variations in the flammability limits of binary mixtures, namely, R134a/R1234ze(E) and R134a/R290, formed at different concentrations of R134a, were explored. The critical explosion suppression ratios for R134a/R1234ze(E) and R134a/R290 were 0.315 and 17.3, respectively. Theoretical predictions were made to study the flammability limit range of the ternary refrigerant mixture R1234ze(E)/R290/R134a, revealing a very narrow non-flammable range, and experimental validation confirmed the accuracy of this prediction. This was primarily due to the poor flame-retardant effect of R134a on R290, which hindered effective synergy formation. This study provided important combustion safety data for R1234ze(E) and R290 mixed refrigerants under high -temperature conditions, and laid an experimental foundation for the future development of new low-GWP mixed refrigerants.