Abstract: Abstract:In storage process of LNG in large LNG storage tank, the stratification of filled LNG in the tank is the direct reason causing “rollover accident”. Taking the “rollover accident” of an Italian LNG storage tank as example, according to existing research model, it is believed that there is a transition layer between the upper layer and the under layer. Using the correlation of the naturalconvection heat transfer in large space, a method to calculate the heat and mass transferred through the interface was proposed. By programming calculation, the variation curves of density, temperature and components of the LNG in upper and under layers over time were obtained. The curves were analyzed, and the analysis result shows that when the densities of the upper and under layers are nearly equal, there is certain temperature difference between the upper a under layers, and the rollover accident may occur under this condition.

Key words: Keywords:liquefied nature gas (LNG), storage tank, layering, rollover, natural convection