Research progress of annulus insulation technology for cryogenic liquid hydrogen pipelines

Abstract

[Objective] Liquid hydrogen has garnered significant interest for its high volumetric density and hydrogen purity. However, it easily evaporates during transportation due to its low boiling point, thus causing hydrogen loss. In this case, cryogenic insulation technology becomes essential for facilitating liquid hydrogen pipeline transportation. [Methods] The analysis of heat leakage in the pipeline's annulus considered three modes of heat transfer: solid heat conduction, gas heat conduction, and radiant heat exchange. Since the solid heat conduction primarily arises from the thermal insulation support structure within the annulus, an overview was provided on the heatconducting properties of various support structures. In addition, maintaining the vacuum level of annulus interlayer can effectively weaken the heat leakage caused by gas heat conduction. The impact of vacuum multilayer insulation on cryogenic insulation is a current focus of research. The prediction model and arrangement mode of vacuum multilayer insulation, as well as uniform density multilayer insulation(UD-MLI) and variable density multilayer insulation(VD-MLI) were examined and analyzed in this study. [Results] By optimizing support shape and minimizing heat transfer paths while reducing contact points and areas between the support and inner/outer pipe, heat leakage can be effectively decreased while ensuring stress intensity. Further study on cost-effective and high-efficiency getters is the most direct and effective approach to maintaining vacuum levels. Vacuum multilayer insulation technology has been extensively utilized in cryogenic equipment to significantly diminish solid and gas heat conduction as well as radiant heat exchange. Both UD-MLI and VD-MLI feature the optimal layer density configuration to minimize heat leakage, with VD-MLI offering superior insulation performance and a weight advantage. [Conclusion] Optimizing annulus geometry and heat transfer modes, along with developing high-efficiency hydrogen getters, are vital for advancing annulus insulation technology in cryogenic liquid hydrogen transportation pipelines and minimizing hydrogen loss during transportation.

Keywords

• liquid hydrogen
• cryogenic transportation pipeline
• cryogenic insulation technology
• insulation support
• vacuum multilayer insulation