Dynamic modeling and analysis of LNG fuel tank pressurization under marine conditions

Abstract

In this paper, a fast and effective dynamic model was developed to predict and investigate the performance of liquefied natural gas (LNG) fuel tank pressurization under marine conditions. An extended sloshing Nusselt number was defined to quantitatively evaluate the heat transfer enhancement in horizontal tanks under resonant sloshing. The validity of the model was confirmed by the corresponding experimental data. The pre-pressurization process, the fuel gas supply process, and the cryogenic liquid sloshing were investigated for two types of LNG fueled ships. Parametric studies, including the tank size, the filling level, the rated power, the engine load, and the sloshing intensity were conducted. The results showed that the heat transfer between the vapor and tank wall dominates the pressurization process, while the vapor condensation at the liquid-vapor interface dominates the holding period and the sloshing process. Moreover, the sloshing has a severe impact on the tank pressure, especially when the resonance condition of the tank is met, which can cause the shut-down of gas engines in extreme situations.