液氢低温输送管道环空绝热技术研究进展

Research progress of annulus insulation technology for cryogenic liquid hydrogen pipelines

【目的】液氢因其体积密度大、氢纯度高等优势而备受关注,但其极低的沸点导致在输送过程中易蒸发而造成氢损失,低温绝热技术是实现液氢管道输送的关键手段。【方法】从热传递的3种方式(固体导热、气体导热、辐射换热)对管道环空间的漏热进行分析,固体导热主要来源于环空间绝热支撑结构,总结了不同类型支撑结构的导热性能;同时,维持环空间夹层真空度可以有效减少因气体导热引起的漏热。真空多层绝热材料对低温绝热技术的影响是研究热点,在此从真空多层绝热材料预测模型、绝热材料布置方式、定密度多层绝热、变密度多层绝热等方面分别进行了讨论。【结果】在保证应力强度的前提下改善支撑形状,最大限度缩短传热路径、减少支撑与内外管的接触点个数及接触面积能够有效减少支撑的漏热量。同时,加快研制低成本与高效率的吸气剂是维持真空度最直接的有效方法。真空多层绝热技术在低温设备中应用广泛,可有效减少固体导热、气体导热及辐射换热。定密度多层绝热和变密度多层绝热都存在使漏热最低的最佳层密度排布方式,且变密度多层绝热具有更好的绝热性能及重量优势。【结论】合理优化环空间几何结构与热传递方式、研制高效吸氢剂,对优化液氢低温输送管道环空绝热技术、有效降低液氢输送过程中的氢损失具有重要意义。(图5,表2,参85)

[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 heat-conducting 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.(5 Figures,2 Tables,85 References)