Design of a test apparatus to measure the thermal properties of insulators in cryogenic temperature field

Low-temperature conditions of potential propellant fluids, such as hydrogen or natural gas, could diminish the volume occupied for their storage, keeping a high energy content, since the density increases lowering their temperature. This aspect makes the cryogenic reservoirs attractive especially for the decarbonization of mobility sectors, in which it is important to minimize the occupied space maintaining the same energy content, maximizing the volumetric energy density. The research in this field is relatively new and has a huge potential for advancement in both technology and knowledge. A crucial role in cryogenic reservoirs is played by the insulation system working in cryogenic conditions, emphasising the importance of optimizing their thermal performance for the spread of cryogenic applications in the market. Indeed, good insulation is fundamental since it permits to save money and energy by limiting the amount of evaporated cryogenic fluid. For this reason, this work aims to conceive a test apparatus to enhance the understanding of the performances of the well-known insulation systems in cryogenic conditions, particularly considering multi-layer insulation ones since they are the best alternative in a high-vacuum environment. The design of a novel test apparatus to measure the thermal properties of different insulation systems is provided in this work, moving from the existing layouts patented for such measurements. The proposed apparatus has been sized through FEM analysis and the main components employed are described considering both the cryogenic and the high-vacuum working environment. Finally, the thermal performances of a multi-layer insulation system applied on this apparatus are predicted by a purposely-developed model, and the uncertainty analysis of the measurement of the thermal conductivity is provided based on an innovative experimental procedure proposed for the apparatus.