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 high-temperature conditions. In this study, R134a was experimentally investigated for its flame-retardant effect on R1234ze(E) and R290 refrigerants at 60 °C. 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.