Study on staged precooling heat transfer characteristics of large-diameter liquid hydrogen pipelines

doi:10.11949/0438-1157.20250779

Abstract

Abstract:

Cryogenic liquid hydrogen is a crucial chemical product and has garnered significant attention as a key carrier for future low-carbon energy. Precooling of liquid hydrogen pipelines is a critical step in ensuring efficient liquid hydrogen transportation. This study establishes a comprehensive one-dimensional liquid hydrogen flow model by incorporating a radial high-vacuum multilayer insulation heat transfer scheme, applying appropriate empirical correlations for pressure drop and heat transfer, and designing a staged precooling strategy suitable for large-diameter liquid hydrogen pipelines. In the simulation of the precooling process for a 300 m horizontal pipe with a nominal diameter of 314, the vapor cooling stage exhibits a gradual temperature reduction, with an inner metal pipe wall heat flux below 1 kW/m², taking 37 h to complete. During the liquid cooling phase, the cooling rate initially increased rapidly and then decreased, with the maximum two-phase wall heat flux reaching approximately 9.4 kW/m². The cooling process took approximately 0.45 h, reducing liquid hydrogen mass consumption by 55% compared to conventional constant-flow pre-cooling schemes. The maximum pressure drop inside the pipe reaches 60 kPa, displaying dynamic pulsating fluctuations that stabilize at 40 kPa as the flow becomes steadier. The findings of this study provide theoretical support for the development of efficient precooling technologies for long-distance liquid hydrogen transportation.

Key words: liquid hydrogen, pipeline precooling, flow boiling, two-phase flow, heat transfer characteristics

摘要：

低温液氢是重要的化工产品，作为未来低碳能源重要载体备受关注。液氢管道预冷是其液氢高效输运的关键一环。建立系统完善度较高的一维液氢流动模型，通过增加径向高真空多层绝热材料传热方案，应用合适压降、传热经验关联式，并设计适用大管径液氢输送管线的分阶段预冷方案。在对公称直径DN314、长度300 m的水平管预冷过程模拟中，气冷阶段降温平缓，内金属管壁面热通量低于1 kW/m²，预冷耗时37 h。液冷阶段降温速率先快后慢，两相流壁面热通量最大约9.4 kW/m²，耗时约0.45 h，对比常规恒流量预冷方案减小液氢质量消耗55%。管内最大压降60 kPa，呈现脉动动态变化，随流动趋于稳定脉动幅度减小稳定至40 kPa。研究结果可为长距离输运液氢高效预冷技术提供理论支撑。

关键词: 低温液氢, 管道预冷, 流动沸腾, 气液两相流, 传热特性

CLC Number:

TK 91

Xinyu LU, Shaolong ZHU, Haoran GAN, Kai WANG, Limin QIU, Shiran BAO. Study on staged precooling heat transfer characteristics of large-diameter liquid hydrogen pipelines[J]. CIESC Journal, 2025, 76(12): 6562-6572.

陆新宇, 朱少龙, 甘浩然, 王凯, 邱利民, 包士然. 大管径液氢输送管线分阶段预冷传热特性研究[J]. 化工学报, 2025, 76(12): 6562-6572.

Figures/Tables 18

Fig.1 Schematic diagram of insulation layer structure

Fig.2 Heat transfer calculations of inner pipe microelement

Fig.3 Discrete scheme for pipeline segment elements

Table 1 Staged chilldown process

预冷阶段		工质种类	工质温度	流量
气冷阶段	阶段一	氮气	110 K	196~2457 L/min
	阶段二	氢气	120 K	3000 L/min
	阶段三	氢气	50 K	523~1080 L/min
液冷阶段	阶段四	液氢	20.3 K	2.7547 kg/s

Table 2 Pipeline geometric parameters

几何尺寸与边界条件	数值
管道长度/m	300
管道内径/mm	314
管道外径/mm	348
环境温度/K	293.15
管道初始温度/K	293.15
管内初始压力/kPa	100
管内初始干度	1

Fig.4 Mesh irrelevance verification

Table 3 System parameters of liquid unloading process at LNG receiving terminal

预冷阶段	参数	数值
气冷阶段	体积流量/(L/min)	2000~8000
	来流温度/K	193.15~253.15
	管线初始温度/K	295.15
	管内初始压力/kPa	100
液冷阶段	质量流量/(kg/s)	0.55
	来流温度/K	115.15
	管内初始温度	气冷阶段最终温度
	管内初始压力/kPa	100

Fig.5 Natural gas chilldown: comparison between experimental and simulated values

Fig.6 LNG chilldown: comparison between experimental and simulated values

Fig.7 Temperature changes in different pipe sections during the vapor chilldown stage

Fig.8 Heat flux in different pipe sections during the vapor chilldown stage

Fig.9 Temperature changes in different pipe sections during the liquid chilldown stage

Fig.10 Vapor phase volume fraction change in different pipe sections

Fig.11 Heat flux in different pipe sections during the liquid chilldown stage

Fig.12 Boiling characteristic curve at 150 m pipe section

Fig.13 Mass flow rate in different pipe sections

Fig.14 Pressure in different pipe sections

Fig.15 Dynamic pressure drop in different pipe sections

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