(183b) A CFD Study of System Vibration's Effect on LNG Boil-Off in a Transportation Vehicle

Liquefied Natural Gas (LNG) takes up 1/600 the volume of its gas form at normal temperature and pressure, which is suitable for long-distance transportation. However, as a cryogenic fluid, the very low temperature of LNG makes it very easy to evaporate and generate boil-off gas (BOG). For economic and environmental considerations, BOG should be minimized during transportations if possible. Lots of studies have been reported on the root causes and impacts of BOG. However, most of them focus on the factor of heat leakage into the cryogenic facilities to generate BOG. Actually, mechanical vibrations can also contribute to BOG generations, where quantitative studies are still lacking, especially on BOG generation effects during LNG vehicle transportations.

In this work, the vibration of LNG trucks has been considered to study BOG generations. The study with computational fluid dynamics (CFD) is performed to investigate the cylindric tank of an LNG truck, which was filled with LNG. The commercial CFD software, ANSYS Fluent V18, has been employed to develop the multiphase mixture model. Specifically, a user-defined function(UDF) has been programmed to model the vibration effect due to LNG truck transportation. The simulation has studied the effect of BOG generation under different vibration scenarios in terms of their frequency and magnitude. Based on the CFD simulation study, cost-effective BOG minimization methods during LNG vehicle transportations would be suggested.