Experimental investigation on pressure and temperature evolution in a 5 m3 vacuum-insulated LNG storage tank under multiple operating conditions

LNG storage tanks, as core equipment for cryogenic energy storage, are being developed toward the integration of safety, economy, and resource conservation under the guidance of green manufacturing. This necessitates a detailed investigation of their pressure and temperature evolution under multiple operating conditions. In this study, a 5 m3 vacuum-insulated storage tank integrated with an experimental platform was developed for real-time monitoring of pressure, liquid level, and multi-point temperatures under multiple LNG operating conditions. Systematic tests were conducted, and an experimental database covering multi-condition operations was established. The pressure-temperature evolution, fluid-wall temperature relationships, and axial/circumferential wall temperature distributions were analyzed. The results show that wall cooling undergoes three stages (convection, boiling heat transfer, and stabilization) during replacement and filling. During pressurization and liquid discharge, a maximum wall temperature of −30.23 °C is observed at 0.31 MPa. The axial wall temperature distribution exhibits saturated/subcooled conditions in the bottom liquid-phase region, while the temperature increases with height in the upper region. Notably, the temperature gradient during storage gradually diminishes, exhibiting a linear profile at high liquid levels and a concave profile at low liquid levels. The wall temperature converges to the liquid temperature under stable liquid contact, while pressurization and discharge may induce abrupt medium temperature changes, with a maximum fluid-wall difference of 26.36 °C. The circumferential temperature distribution indicates that single-axis temperature data can reflect the overall temperature variation trends. These findings offer an experimental basis for the safe design, structural optimization, and monitoring system simplification of LNG storage tanks.