수소연료 자동차용 액화수소탱크의 열물성 성능 예측을 위한 3차원 수치모델 개발

Abstract

There is a worldwide understanding that hydrogen has a great potential as the fuel of the future. In addition to the challenge of developing appropriate hydrogen propulsion systems, however, the development of hydrogen storage systems is another big issue. The stored liquid hydrogen must be kept at a temperature of about 20 K. As such, the space between the outer jacket and the inner tank is mainly used for thermal insulation. The permanent heat input during the time when the vehicle is not used leads to pressure and temperature increases in the hydrogen fuel. This study thus focused on the development of a three-dimensional CFD model of liquefied hydrogen storage systems in view of boil-off management for controlled evaporation, pressurization in ullage, the flow characteristics of liquid and vapor, thermal stratification, and the evaporation characteristics on the free surface. Two-phase CFD-compressible VOF models with a Ranz-Marshall interfacial model using a customized in-house version of AVL, Fire®, for liquid hydrogen tank self-pressurization and pressure control were used to show the impact of interfacial and vapor phase turbulence on the evolution of the pressure and temperature in cryogenic storage tanks. The results show that the present CFD model has good adaptability in the prediction of pressurization behaviors, and is a useful tool for the design and optimization of a pressurization system.