Evaluation of flammability characteristics of mixed refrigerants R134a/R1270, R134a/R170, and R170/R1270

Abstract

Hydrocarbons (HCs) are considered promising alternative refrigerants due to their excellent thermodynamics, transport properties, and environmental friendliness. However, hydrocarbons are flammable. Conversely, R134a is a widely used non-flammable refrigerant but was listed in the Montreal Protocol-Kigali Amendment due to its relatively high global warming potential (GWP). Therefore, in order to reduce the GWP of R134a and inhibit the flammability of hydrocarbon refrigerants, this study investigated the flammability characteristics of mixed refrigerants R134a/R1270, R134a/R170, and R170/R1270. The flammability limits of different concentrations of R170/R1270, R134a/R1270, and R134a/R170 were measured under standard conditions, and the inhibition mechanism of R134a was briefly analyzed. Additionally, the flammability limits of R170/R1270, R134a/R1270, and R134a/R170 were predicted using the polynomial fitting method. Subsequently, the flame propagation speed and the flame color of R1270 and R170, with and without R134a, were compared and analyzed. Furthermore, the cycle performance of R134a/HCs was calculated. The research results are expected to provide guidance for the safe and effective utilization of R1270, R170, and their mixtures in refrigeration systems.