Study on variation of thermodynamic parameters in vehicle-mounted LNG gas cylinder under static state

Abstract

To study the variation regularities of the mass, evaporation, temperature, and pressure of LNG in the gas cylinder with time, LNG was used as the working medium, and three specifications of LNG gas cylinders (150L, 330L, and 450L) were selected for heat transfer calculation. For the liquefied medium in the LNG gas cylinders, a saturated homogeneous model was adopted. For the heat transfer calculation of the adiabatic layer of LNG gas cylinders, a multilayer insulation structure model of radiation and heat conduction was adopted. According to the thermodynamic relations in the saturated state, the relations between the temperature and the physical parameters of the liquefied medium were fitted. The calculation method and calculation model were verified by the experimental data of liquid nitrogen for three specifications of LNG cylinders (150L, 330L, and 450L). According to the calculation model, the variation regularities of LNG thermodynamic parameters with time were obtained at a normal temperature. In the initial period of evaporation, the increasing temperature rate of LNG, the evaporating rate of LNG, and the pressure-boost rate of LNG in the gas cylinder are slow, and then these rates increase. The final mass of boil-off gas (BOG) produced by the phase change finally reaches 0.68% of the total mass of the medium in the gas cylinder.