Study on thermodynamic response in liquefied natural gas storage tanks under static pressurization and sloshing conditions

Liquefied natural gas (LNG) is becoming a potential power fuel in ocean transport and will be widely utilized in the near future. However, severe thermodynamic imbalance issues, caused by environmental heat leakage and external sloshing disturbances, must to be efficiently addressed to improve the operation reliability and safety storage of LNG fuel tanks. In this paper, a comprehensive theoretical model is developed to investigate the thermal response in a type C LNG storage tank, with consideration of composition migration, heat penetration, liquid evaporation, fluid sloshing, and vapor pressure rise. The prediction accuracy of the theoretical model is validated by comparing with selected tank pressurization experiments, with deviation limited within 5.0%. Based on the theoretical model, the aging process of LNG is first involved. The variations of composition migration in vapor and liquid regions are specially considered and discussed. During static pressurization, the thermal physical performance, including tank pressure rise, vapor temperature change, and boil-off gas (BOG) generation, is detailedly researched under heat penetration. Finally, the effect of external sloshing excitation on thermal behavior in LNG fuel tanks is explored. Compared to static pressurization, external sloshing excitation causes obvious influences on thermodynamic performance of LNG tanks, including promotion on tank pressure and enhancement of heat and mass transfer. With some valuable conclusions achieved, this work is significant to comprehensive understanding on the thermal response of LNG storage tanks under different operation conditions.