TED-AJ03-606 NUMERICAL MODELING OF STRATIFICATION AND ROLLOVER IN LNG AND THE IMPROVEMENTS TO BATES-MORRISON MODEL

概要

論文の詳細を見る
Liquefied natural gas (LNG) has become an important part of the world energy market. Stratification may occur in LNG tank due to density difference of the different contents in the tank, and rollover may happen at the end of the evolution. There have been several rollover accidents since LNG found its important roles in the modern world. The over-pressure of storage tank when rollover happens jeopardizes the safety of tank and produces severe waste and pollution. A lot of researches on LNG stratification and rollover have been carried out since the first LNG rollover accident happened. Vorticity-stream function method is often employed for numerical simulation because it is suitable for natural convection. The authors of this paper have done similar work, including taken the situation of both side wall and bottom heat loss of the tank into consideration. The numerical simulation is successful because all key stages and phenomena of the evolution of LNG stratification have been simulated. In the light of the numerical simulation, it has been verified that entrainment is the factor playing the most important role in stratification evolution. The Bates-Morrison model is by far the most successful model to demonstrate the LNG stratification and rollover evolution process. In this model, the full evolution process from the beginning of stratification to the accomplishment of rollover is divided into three stages : (1) immobile interface; (2) moving interface; (3) rollover of LNG. The results of experiments on entrainment have been employed into study of theoretical model in the paper. On the basis of improving the Bates-Morrison model, an advanced four-stage model has been developed. The four stages proposed are : (1) immobile interface; (2) entrainment of the top fluid; (3) penetration to the lower layer by center efflux; (4) rollover of LNG. After stage 1,the interface falls at increasing speed, rather than falling at a constant speed predicted by the Bates Morrison model. By taken entrainment into consideration, the simulation result agrees with the reported experimental data fairly well when the improved model is employed to predict the process with small initial density difference. If the initial density difference of top and bottom fluid is large, the main heat and mass transfer type is penetrating of boundary layer rather than entrainment at the early period of stage 2. If the initial density difference of two layers is small, entrainment becomes the dominant heat and mass transfer type, so the advantage of the new model is evident.[figure]
一般社団法人日本機械学会の論文

TED-AJ03-606 NUMERICAL MODELING OF STRATIFICATION AND ROLLOVER IN LNG AND THE IMPROVEMENTS TO BATES-MORRISON MODEL

スポンサーリンク

概要

著者

関連論文

スポンサーリンク