Thermal models for self-pressurization prediction of liquid hydrogen tanks: Formulation, validation, assessment, and prospects

With the growing demand for hydrogen as a clean fuel to power vehicles and aircraft, liquid hydrogen (LH2) is a promising choice for hydrogen storage with the advantages of large volumetric energy density, high purity, and low operating pressure. Safe operation and storage of LH2 rely on accurate prediction of the self-pressurization process inside LH2 tanks by thermal models. To avoid taking weeks or longer in the self-pressurization prediction by computational fluid dynamic models, thermal models with fewer nodes and faster calculation speed have attracted interest. This paper systematically reviews the progress in physical assumptions, theories, formulations, and state-of-the-art applications of thermal models. Faced with the lack of indicators to evaluate the modeling comprehensiveness of self-pressurization, five key indicators describing the effect of vapor–liquid mass transfer, temperature evolution, nonideality, temperature stratification, and compressibility of the vapor are proposed for the first time in this paper based on analyzing the real gas equation of vapor. The five indicators as well as calculation speed are adopted in assessing the precision of current thermal models. Some insights and outlooks for clarifying the mechanism of self-pressurization and upgrading thermal models with higher accuracy are discussed.