Dynamic boil-off characterization for discharge process of LNG vehicle tank

This study aims to find the optimal boil-off gas (BOG) recovery procedure during the regular LNG vehicle tank maintenance. The BOG discharge process links to rapid depressurization and other important physical characteristics. We set up a full-scale field prototype and test on different initial working conditions. A numerical model was developed accounting for fluid mechanics, interphase heat and mass transfer, which had been verified with the experiments. Based on experimental results and model predictions, we characterized the instantaneous thermodynamic properties of BOG and the relationship between discharge mass and discharge time. In practical situations, spending too much time in BOG recovering would affect the regular maintenances of the vehicle tank. Designing a reasonable recovery time for each tank is crucial to achieve the maximum BOG recovery efficiency. Finally, the mappings of recovery time and the equivalent recovery rate under different initial conditions are established to guide the design of practical operating scheme.