A non-equilibrium multilayer thermodynamic model is developed to predict the thermal stratification and rollover phenomena in liquefied natural gas (LNG) storage tanks. This model considers the boundary layer formation along the tank walls and uses an adaptive mesh to accommodate the changes in the LNG level in the tank over time. The accuracy of the model is verified against experiment data available in the literature to predict the thermal stratification and rollover in cryogenic storage tanks. The parametric study is conducted to investigate the key factors affecting the rollover start time. The results indicate that in an atmospheric LNG storage tank, the ratio between the amount of fresh LNG loaded to the tank (cargo) and the amount of LNG left in the tank (heel) prior to the loading of cargo, and the methane concentration in the cargo layer have direct effects on the rollover start time. The amount of heat transfer to the tank, the tank aspect ratio, and the nitrogen concentration in the heel or cargo layers affect the LNG evaporation rate. The results recommend that the cargo to heel ratio should be determined with caution to prevent the rollover in LNG storage tanks.

开发了一种非平衡多层热力学模型来预测液化天然气 (LNG) 储罐中的热分层和翻滚现象。该模型考虑了沿罐壁形成的边界层，并使用自适应网格来适应罐中 LNG 液位随时间的变化。该模型的准确性根据文献中可用的实验数据进行了验证，以预测低温储罐中的热分层和翻滚。进行参数研究是为了调查影响翻转开始时间的关键因素。结果表明，在常压 LNG 储罐中，装载到罐中（货物）的新鲜 LNG 量与装载货物之前留在罐中（跟部）的 LNG 量之比，货物层中的甲烷浓度对翻滚开始时间有直接影响。传递到储罐的热量、储罐纵横比以及尾部或货物层中的氮浓度会影响 LNG 蒸发率。结果建议应谨慎确定货跟比，以防止 LNG 储罐翻滚。