Thermodynamic Research on Liquid Hydrogen (LH2) Refueling Processes: A Review

Liquid hydrogen (LH2) has been regarded as an ideal carrier for large-scale and long-distance hydrogen energy storage and transportation due to its high gravimetric hydrogen storage density, rapid refueling efficiency and favorable safety performance. However, the physical properties of LH2, such as low viscosity and high volatility at the ultra-low temperature of −253 °C, cause complex thermodynamic problems during the refueling process—including drastic phase transitions, concentrated thermal stress, and two-phase flow instability—which act as bottlenecks restricting the large-scale application of LH2. In this paper, research advances achieved domestically and internationally in recent years are reviewed in detail with respect to thermodynamic issues occurring in the ultra-low-temperature LH2 refueling process. Research achievements concerning the thermodynamics of LH2 refueling are classified, summarized and discussed from the perspectives of theoretical thermodynamic analysis, numerical simulation, experimental investigation and refueling process optimization strategies for LH2 refueling. The heat and mass transfer mechanisms involved in LH2 refueling are revealed, the variation in thermodynamic responses during the refueling process is described, the critical factors affecting the thermodynamic behaviors of LH2 refueling are clarified, the industry standards on LH2 refueling are critically assessed, and various refueling process management strategies are discussed. Finally, the future development directions of thermodynamic research on the LH2 refueling process are discussed and prospected on the basis of the development trends and potential prominent challenges faced by LH2 refueling technologies.