CHARACTERISTICS OF HEAT TRANSFER DURING COOLING DOWN PROCESS IN A SINGLE CARGO TANK OF LNG CARRIER

A deep understanding of heat transfer characteristics is essential in evaluating risk and putting forward any option for the Liquefied Natural Gas (LNG) tank cooling down process. A novel Computational Fluid Dynamics (CFD) model was built to perform the flow and heat transfer simulation of the process. The predicted results agreed well with the test data from a prototype LNG tank. Then the heat transfer characteristics of the process were analysed. It was found that the vapour temperature and density were linearly varying and became stable after 2.3 hours. A sudden pressure drop risk was identified during the process, which will cause the inwards collapse risk of the invar membrane. Then the proposals to prevent the risks of the inwards collapsing membrane are presented. The heat transfer characteristics of the vapour and different membrane layers were analysed in detail, and if the suggested option was to be implemented this could save about 39% of LNG consumed.