Inhibition Performance Research Of The Low Environmental Hazard Flammable Refrigerants

In recent years,global warming has intensified,and climate change also has threatened people’s production practices.In response to the environmental hazards caused by climate change,countries around the world have reached an agreement on greenhouse gas reduction with the common goal of peak carbon dioxide emissions and carbon neutralization.In the refrigeration and heat pump field,due to the severe environmental situation and the restrictions of policies and regulations,the refrigerants that are harmful to the environment are gradually being phased down or even out.Meanwhile,the options for refrigerants with low environmental hazards will be very limited.In the face of the deepening of policies and regulations,the flammable working fluids with the excellent environmental property and system performance are gradually marching towards the market,which will be the main trend of future applications.Therefore,the research on the flammability characteristics and flame inhibition methods is the core task for the safe use of these flammable substitutions.In this work,the commonly used working fluids about hydrocarbons(HCs),hydrofluorocarbons(HFCs),etherate,and hydrofluoroolefins(HFOs)were mainly used as the research objects.Starting from the microscopic combustion mechanism,the flame inhibition methods of the flammable working fluids were focused on.The flame inhibition experiments of various types of flame retardants on flammable working fluids were carried out.And the inhibition mechanism of these retardants was analyzed and calculated.Secondly,based on the chain reaction theory and transition state theory of gas combustion reactions,the pyrolysis mechanism and preliminary combustion reaction path of R290,R152 a,and RE170 were calculated by DFT(density functional theory).The generation paths of active groups and the energy barrier of the reaction processes for the above flammable working fluids were explored in combustion reactions.And the change law about the collision and detachment of atomics and the dissociation of the bonds was also discussed.Thirdly,Screening of environmentally friendly gas-phase flame retardants with application potential,the flame inhibition effect of R1234 yf,R1216,R1233zd(E),and R13I1 was experimentally studied.According to the microstructure of the flame retardant molecules,the generation paths,reaction energy barriers,and reaction rates of the main flame retardant groups were deeply investigated in the process of combustion pyrolysis,and the inhibition mechanism was also discussed.Finally,by analyzing the actual situation when the flammable working fluid leaked in the refrigeration system,a novel inhibition method that used the lubricating oil as the retardant carrier was proposed.A set of experiment systems,which was suitable for the liquid flame retardants,was designed and improved,according to the flammable gas test standards ASTM E 681 and ASHRAE 34.To verify the feasibility of the above inhibition method,the flame inhibition characteristics of the liquid flame retardants on combustible working fluids were experimentally studied,and the inhibition mechanism was analyzed.Through this work,there will be an in-depth understanding of the flammable characteristics of combustible working fluids and the inhibition mechanism of the flame retardants.It is helpful to guide the promotion of the safety application of flammable working fluids.