Objective Hydrogen serves as a core medium for deep decarbonization as the global energy structure accelerates its shift toward green and low-carbon development. The large-scale transportation of hydrogen depends on safe and efficient pipeline infrastructure. Since the unique physical properties of pure hydrogen render existing natural gas venting models inapplicable, a tailored analytical framework is required to guide engineering practices.

Methods To identify the key influencing factors and characteristics of cold venting in pure hydrogen pipelines, a scaled experimental system is adopted.The system investigates the mechanisms by which venting pressure, pipe diameter, vent height, flame arresters, and proportional valve opening affect the dynamic characteristics of hydrogen venting. The prediction model for the maximum volume fraction of hydrogen is revised based on experimental data.

Results In the cold venting process of pure hydrogen pipelines, venting pressure serves as the dominant factor. Increasing venting pressure remarkably raises the driving pressure difference and system flow rate. This leads to significant growth in pipeline internal pressure, flow velocity, external noise, and the maximum hydrogen volume fraction. Conversely, vent height exerts only a slight effect on the flow field and volume fraction distribution, making it a non-critical safety parameter. Although increasing pipe diameter effectively reduces venting noise, the decreased outlet flow velocity causes hydrogen to diffuse horizontally at a lower height. This expands the distribution range of volume fraction and raises its peak value, bringing risks of local hydrogen accumulation. A prominent throttling effect occurs when the proportional valve opening is below 0.3, leaving the flow field unbalanced. When the opening reaches 0.3 or above, the system tends to be stable, and all parameters rise slowly with valve opening. Finally, installing flame arresters alters the distribution of pressure and flow velocity inside pipelines but has a relatively limited impact on the diffusion of hydrogen volume fraction.

Conclusion Venting pressure and proportional valve opening are the decisive factors affecting venting capacity and associated hazards during cold venting of pure hydrogen pipelines. It is recommended to regulate venting flow rate by adjusting the proportional valve opening under high venting pressure. In addition, the selection of vent pipe diameter should strike a balance between noise reduction and potential safety risks. Although vent height and flame arresters have minor effects on venting hazards, properly increasing vent height and installing flame arresters are recommended from the perspective of inherent safety. (8 Figures, 1 Table, 27 References)