Theoretical And Experimental Study On Inhibition Mechanism Of Combustion And Explosive For Low-gwp Flammable Refrigerants

Environmental friendly refrigerants HC and HFC have good thermal performance and attention is increasingly paid to the research on these alternative refrigerants. The hidden insecure trouble produced by the flammability of most HC and HFC refrigerants is an important topic of the study on these alternative refrigerants. In this paper, the studies on the theory of explosion inhibition mechanisms and the experiments of explosion limits about the flammable mixed refrigerants with low-GWP are carried out.First, the combustion theory of chain reaction and the explosion limits theory were discussed. Besides, the risk assessment parameters on the system of flammable refrigerants were elaborated, including the flame propagation speed, the ignition energy, the refrigerant charge and the minimum operating space of refrigeration system. According to the analysis above, the effects of the risk assessment parameters on the safe use of flammable refrigerants were further discussed.Second, the chemistry and physics inhibition mechanisms of the halogen elements were discussed. In addition,based on the group contribution method theory, the inhibition efficiency on flame propagation speed and the estimated formula of the minimum inerting concentration of HFC flame retardant were established. The estimated results show that the inhibition efficiency of R134a,R245fa,R125 were gradually increased.Finally, as for the ternary mixture consisting of A, B and C, the flammable concentration range and the critical flammable concentration were estimated, the estimated results would give reference for our experiment research. The explosion limits of several flammable mixed refrigerants including three binary mixtures and a ternary mixture were measured by the experiments. A lot of available data were obtained from this experiment, and it provided the experimental basis on the safe use of flammable mixed refrigerants. The experimental results of the binary mixtures show as follows:⑴The flame retardant will increase the lower explosion limit and reduce the explosive limit range of the mixed refrigerants.⑵The effects of flame retardant on upper explosive limit of pure flammable refrigerants are greater than lower explosion limit. The upper explosive limit of pure flammable refrigerants drops quickly, but the lower explosion limit increases slowly.⑶Every flame retardant on flammable refrigerants has the minimum inerting concentration, and the mixed refrigerants become non-flammable and safe once the concentration of the flame retardant exceeds the minimum inerting concentration. For the experiment results of the ternary mixture, it shows that the more the concentration of B is, the more flammable it will be for the mixture, and the flame retardant will not inhibit it to be non-flammable refrigerants the moment B is excessive .