Test facility to study the chilldown and pressurization of cryogenic storage systems

The storage of cryogenic fluids represents a critical issue in various industrial sectors, including the medical, food, manufacturing, energy, and aerospace fields. In the aerospace sector specifically, the use of hydrogen is key to reducing the environmental impact of air transport. However, under standard temperature and pressure conditions, its volumetric energy density is extremely low, necessitating excessively large storage volumes. An effective way to reduce the required volumes is to liquefy hydrogen, making it cryogenic. This poses significant operational and design challenges, including the need for advanced insulation systems, efficient safety systems, and the management of phenomena such as boil-off, i.e., the evaporation of liquid hydrogen due to heat absorption. The purpose of this thesis is to carry out an experimental investigation of two-phase flow heat transfer in cryogenic fluids for the study of low-temperature storage and transportation of liquid hydrogen. Particular attention is given to the chilldown and pressurization phases, which are critical for efficiency and safety, by experimentally analyzing the phenomena involved and the influence of operating parameters, validating previous results and testing new configurations. The research is carried out through the development of a dedicated LabVIEW-based control and acquisition software, interfaced with a CompactRIO-9503 embedded platform developed by National Instruments. The experimental setup consists of a feed box, a transfer section, and a return box, equipped with valves and sensors suitable for studying the behavior of cryogenic fluids under different operating conditions. In particular, liquid nitrogen is used as a simulant for liquid hydrogen due to its similar cryogenic properties, lower complexity and cost, and relatively minor safety concerns. The results provide valuable insight into the thermal behaviors of cryogenic fluids during the chilldown and pressurization processes, highlighting the influence of the operating parameters on the efficiency of the system. The outcomes of this work contribute to the development of new technologies for the storage of cryogenic fluids and a better understanding of the management of their systems in hydrogen-powered aircraft, supporting the design of innovative and efficient architectures for sustainable aviation.