Research advances of heavy gas dispersion

Large quantities of hazardous substances are produced,transported and stored in industries.Gases such as chlorine,ammonia,carbon dioxide and liquefied natural gas(LNG) are often heavier than air when accidently released.These gases will fall down to the floor and then disperse along the ground when leaked from pipelines or other storage facilities,which is quite different from neutral gas diffusion.It could cause incidents of human poisoning and even other widespread explosion accidents once ignited or detonated.Thus considerable numbers of research on this topic have been undertaken.This paper summarized the current work,including theoretical analysis,experiments and mathematical simulations where the contributing factors of heavy gas,the diffusion process and influencing parameters on dispersion were investigated respectively according to the mechanism of heavy gas dispersion.To get a better understanding of the internal mechanism of heavy gas dispersion,series of experiments done in worldwide studies and mathematical models for heavy gas dispersion were also discussed.Several field experiments were conducted abroad in the last century,including full scale and reduced scale field tests.The data obtained were beneficial and some noteworthy phenomena were observed,for instance,the concentration branching.However,the study was financial and manpower consuming and suffered from some strict limitations on the atmospheric and topography conditions. Therefore,wind tunnel in laboratory serves as another popular alternative in which the experimental parameters can be easily controlled.In addition,the mathematical models and mathematical simulations on different kinds of dangerous gases which have been rapidly developed during the last forty years compliment the application of wind tunnel.Above all,the author suggested that the following research should focus on some specific influencing factors of gas diffusion such as initial release state,multiphase components of heavy gas,thermal effect and etc.as well as the establishment of more precise mathematical models,which could reflect real flowing process of complex system.