Heat And Mass Transfer Analysis For Spreading And Diving Of Cryogenic Luiquid Spilled On Water

The heat and mass transfer characters of cryogenic liquid released on water have been gaining attention increasingly so as to avoid and predict the damage of spilled cryogenic liquid. As the damage is depend on the heat and mass transfer characters of cryogenic liquid which exists in the processes of spilling, evaporation, pool spreading and diving of cryogenic liquid, the heat and mass transfer characters of cryogenic liquid spilled on water have been investigated and discussed in detail.The phenomena of cryogenic liquid released on water have been theoretically divided into two parts: the process of cryogenic liquid spreading on water and the process of cryogenic liquid diving into water. A simulation methodology has been developed based on shallow water theory to simulate cryogenic liquid spilled from tanks and cryogenic pool spreading on water. Different scenarios of cryogenic liquid spilled from various tanks has been analysed with the concern of the influence of the tank type, the size and the position of breach hole, the shape of the cryogenic pool and the condition of spilling site. Flow and heat transfer behavior of cryogenic liquid vertically diving into a relatively large pool of water was investgated. The level set method was introduced to track the interface and flow characteristic which was adopted to simulate the phase change process of luiquid nitrogen injection by adapting the source terms of conservation equations.After simulating 12500 m3 LNG(liquefied natural gas) spilled on water which are supposed to be released from tanks, some conclusions have been made. The surface of cryogenic liquid fluctuates with a hydraulic jump. Breach diameters show a Boltzmann nonlinear relation with pool maximum radius. After contrastive analysis of the pool shape and tank configuration, it is found that substituting cubic tank for spherical tank has lillte influence on the spreading process, while substituting semi-circular pool for circular pool will affect the spreading speed with little influence on maximum pool size. The simulation results showed that the stabe liquid nitrogen in the water looks like a baseball bat. Both the diameter and the velocity have a great influence on penetration of liquid nitrogen. For the injection with a relatively small diameter, all liquid nitrogen evaporates in water and a cryogenic pool will form for a rough one with violent flow rising up to water surface.The methodology and simulation method based on improved shallow water equations have revealed the mechanism of the heat and mass transfer characters of cryogenic liquid with more details and the multiphase flow model based on level set equations has covered the shortage of research of cryogenic liquid diving into water vertically which both provided the hazard control research work with guiding significance.