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

Activity carried out by Riccardo Susini (tutored by Laura Savoldi), in collaboration with HMV, Eng. Giovanni Fatigati.

Framework of the activity:

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 due to the low-temperature conditions of the stored fluid with respect to the typical ones of the environment. Therefore, the optimization of the thermal insulation of cryogenic tanks is important for the spread of cryogenic applications in the market. A good insulation is fundamental since it permits to save money and energy by limiting the amount of evaporated cryogenic fluid. For this reason, in this work, commissioned by HVM company, leader in manufacturing of cryogenic tanks, a test apparatus is designed to compare the best-performing insulation systems under cryogenic conditions.  In particular, this work focuses on the performance analysis of the multi-layer insulation (MLI) systems since they are the best insulators under cryogenic and high-vacuum environment. Once the layout is sketched, the MLI thermal performances, composed in this work by successive layers of fibreglass and aluminium foils, are predicted by a purposely-developed model based on experimental data. Then, the effects introduced by the variable density multi-layer insulation (VDMLI) technique have been estimated qualitatively to compare how much the insulation performance changes with respect to other MLI configurations with the same total volume.