Experimental study on self-pressurization and active pressure management in a horizontal liquid hydrogen tank

Abstract

Liquid hydrogen (LH2) storage offers significant advantages in storage density and operating pressure, particularly for mobile applications where horizontal tanks are preferred due to their favorable geometry and integration capabilities. However, detailed experimental studies under actual operating conditions for horizontal LH2 tanks remain limited. A multifunctional liquid hydrogen test platform was developed, incorporating a 500-L horizontal storage tank and liquefaction systems, to investigate storage performance under various operating conditions. Results show that the vapor-cooled-shield (VCS) operation reduced the average daily boil-off rate from 7.8% to 6.2%, improving efficiency by 20.4%. During steady-state evaporation, distinct temperature discontinuities were observed at the liquid-vapor interface, enabling supplementary liquid level detection through temperature sensors. Self-pressurization tests revealed a mechanism where the interface transitions from condensation to evaporation during storage cycle durations. Four consecutive cycles were recorded, lasting 16.23 h, 13.18 h, 10.83 h, and 10.34 h, respectively. Temperature sensor data indicates that vapor-phase dynamics, rather than direct liquid hydrogen evaporation, primarily govern self-pressurization rates. For lossless storage, the system effectively condensed boil-off gas (BOG) and reduced tank pressure from the rated 557 kPa to atmospheric levels (104 kPa) within 45 h, demonstrating the feasibility of lossless storage. An intermittent gravity-driven liquid hydrogen self-circulation process was observed with a period of approximately 7.45 min. A subsequent 10-day cycling test further validated the feasibility of the lossless storage concept. This work provides valuable experimental data for horizontal LH2 storage optimization and offer practical insights for both vehicle applications and long-term storage solutions.