Experimental investigation of cryogenic tank chilldown and boil-off phenomena using liquid nitrogen

The transition to sustainable aviation has brought renewed focus to cryogenic fluid management, as liquid hydrogen emerges as a leading zero-emission fuel. Integrating cryogenic storage into aircraft, however, introduces significant operational challenges, particularly in refueling efficiency, chilldown behavior, and boil-off losses. Although these processes are well understood in space applications, aviation imposes distinct constraints, including rapid turnaround and compact system integration. As a result, experimental data representative of aviation-scale operations remain limited. This study presents an experimental investigation of chilldown and boil-off phenomena using a small-scale liquid nitrogen facility. The campaign examines tank filling, transfer line chilldown under gravity- and pressure-driven configurations, and boil-off at different fill levels. Results highlight a trade-off between speed and efficiency. High-pressure, fast chilldown reduces transfer time but causes substantial evaporative losses due to thermal inertia effects. In contrast, slower transfers combined with pre-cooling significantly improve propellant conservation. Boil-off tests further show that higher liquid inventories enhance thermal stability, reducing temperature rise in the vapor space. These findings provide practical guidance for optimizing cryogenic refueling and support the integration of liquid hydrogen storage in future aircraft.