Experimental investigation on the inhibition of flame retardants on the flammability of R1234ze(E)

Owing to environmental friendliness, R1234ze(E) is considered as an alternative refrigerant, but the flammability restricts its use and promotion. To reduce the combustible risk, nonflammable refrigerants can be blended, while there is a lack of research on mixture flammability. In this paper, the inhibition effects of three typical refrigerants R744, R1336mzz(E) and R1233zd(E) on the flammability of R1234ze(E) were experimentally investigated under the condition of 23 °C and 50% relative humidity. The flammable limits at different concentrations were measured and the critical suppression concentrations of the three retardants were determined as 0.41, 0.2 and 0.4 respectively, by which the parameters of fitting equations to their flammable limits were obtained. The inhibition mechanisms were briefly analyzed in terms of both physical and chemical effects, and typical flame propagation phenomena were compared with further analyses. A model for estimating critical suppression concentrations of ternary blends was established. The critical suppression lines of ternary blends R744/R1234ze(E)/R1336mzz(E) and R744/R1234ze(E)/R1233zd(E) were obtained, by which the nonflammable zones of the two ternary blends were preliminarily determined. The results have provided complements for previous studies using R744/R1234ze(E) at flammable concentrations and will contribute to utilize R1234ze(E) and its blends in safety for both scientific researches and industrial applications.