Leakage And Diffusion Mechanism Of R290 In Refrigeration System And Safety Assessment

Based on the needs of environmental protection,the replacement of refrigerants is an urgent problem to be solved recently in the air-conditioning industry.Existing studies have found that HCFCs and HFCs refrigerants have disadvantages of high ODP and GWP values and can not be used for long.R290 has good environmental protection and excellent thermal properties,and can be used as a direct substitute for R22.But the safety hidden danger brought by the fire and explosion limits its application.If the problem of safety can be solved,the application prospect of R290 will be very wide.Therefore,this paper studies the leakage and diffusion process of R290 in the limited space,analyzes the diffusion law,the concentration distribution in the room,and the safety of the room in the case of leakage..On the basis of studying the characteristics of R290,the mechanism of R290 leakage and diffusion is analyzed.It is found that the leakage of R290 refrigerant from small holes to the environment can be regarded as the free flow of small holes,which is suitable for small hole leakage models.The diffusion process of R290 after leakage can be divided into natural diffusion driven by concentration difference ancd convection diffusion with air.In the condition of air conditioning is shut down,the diffusion of R290 is mainly dominated by gravity.The R290 diffusion is greatly influenced by air turbulence when the ventilation exists.In order to study the security problem of R290 after leaking in the room,the physical model and grid are established by Gambit,and the leakage and diffusion process of R290 in the limited space is simulated with Fluent.First,the law of leakage and diffusion under the condition of air conditioning is studied.It is found that the R290 concentration on the ground is larger when the leakage angle is closer to the vertical downward and the leakage speed is slow.When the R290 leaks in the room,it will only form a combustion and explosion area near the leakage port,and the explosion range will disappear quickly after the leakage is stopped.On this basis,the diffusion of R290 in the air conditioning system is simulated,and the influence of air supply speed and air supply angle on the concentration distribution of R290 is studied.It is found that the air supply air has a great influence on the concentration distribution of R290,and the R290 concentration in the main air supply area is larger.In the end,the diffusion and concentration distribution of R290 under the action of natural ventilation and mechanical ventilation are analyzed.The results show that ventilation can rapidly reduce the concentration of R290 in the room,and the greater the ventilation intensity,the faster the indoor R290 is diluted.