A comparative investigation on the inhibition effects of CF3I/C3F6 on combustion of 1,1-Difluoroethane mixtures

Abstract

Despite its good environmental properties, the application of 1,1-Difluoroethane (R152a) is hindered by its flammability. So, an accurate instrument is required to solve the safety issues of R152a. In this study, the combustion characteristics of R152a mixtures with non-flammable CF3I/C3F6 were measured using the vertical tube method by ISO-817. It could be found that the maximum burning velocity (Su,max) of R152a decreased from 21.163 cm/s to 7.805 cm/s (with R13I1) or 7.675 cm/s (with R1216) at concentration of 15.403%(with R13I1) and 11.508%(with R1216) at an ambient temperature. By adding non-flammable retardants to R152a from volumetric concentration of 10% – 40%, the flammability of the mixtures was lowered. And Su,max of both were reduced by more than 60%, leading the mixture to reach A2L. According to the Su,max data, the dilution effect of the three refrigerants is: R1216 > R13I1 > R227ea. Meanwhile, the density functional analysis theory was used to study the relationship between the molecular bonds of these refrigerants. The results showed that the refrigerants containing higher F/H ratio and the molecules with -CF3 and -I groups were more prone to inhibit combustion.