Comparison of combustion and interaction mechanisms of mixed working fluids R152a and R1270: A theoretical and experimental study

In the background of global efforts to reduce carbon emissions, mixed working fluids could mitigate flammability concerns of low global warming potential (GWP) working fluids for organic Rankine cycles (ORCs) and compression refrigeration cycles. In this study, the combustion and interaction mechanisms of R152a/R1216 and R1270/R1216 were investigated. Density functional theory (DFT) and ReaxFF molecular dynamics (MD) methods were employed to analyze the combustion processes of the two binary working fluids and the formation pathways of the toxic substance HF. Additionally, the influence of R1216 on the combustion of R152a and R1270 was evaluated and compared at different reaction temperatures and component ratios. The results showed that, R1216 did not inhibit but rather promoted the consumption of R152a and R1270. Corresponding experiments demonstrate that the combustion of R152a and R1270 becomes more complete and occurs more quickly after the addition of low proportions of R1216. Subsequently, the flammability limits of the two binary working fluids were determined through experiments at different ambient temperatures. The experimental results indicated that the rise in ambient temperature expands the flammability limit ranges of both binary working fluids, and the higher the proportion of R1216, the more sensitive the flammability is to changes in ambient temperature.