New insights into hydrogen flow could make pipelines safer

Using advanced measurement techniques, researchers at Luleå University of Technology have developed new knowledge about flow phenomena in hydrogen pipelines. The results show how small vortex movements can affect the lifespan and safety of pipelines. This new understanding can contribute to the development of safer standards for future hydrogen infrastructure.

As demand for hydrogen increases, so does the need for pipelines that can transport the gas safely over long distances. But hydrogen’s unique properties mean its flow behavior differs from that of other gases, and knowledge about how these flows affect pipeline durability is still limited.

In the project Hydrogen Transport in Pipelines, Sofia Larsson, Associate Professor of Fluid Mechanics at Luleå University of Technology, has investigated how flows behave in pipe bends and what mechanical stresses may arise over time. The results increase understanding of so-called swirl switching, a phenomenon where vortices in the flow alternate between two states, creating repeated stress cycles in the pipe material.

"This study shows that vortex switching in pipe bends can occur up to ten times per second, which over a pipeline’s lifetime corresponds to billions of load cycles. Understanding how these affect material strength is crucial for ensuring that pipelines can be used safely over long periods," says Sofia Larsson, Associate Professor of Fluid Mechanics at Luleå University of Technology.

Sofia Larsson, associate professor in fluid mechanics at Luleå University of Technology.

Safer methods and better understanding

Because experimenting with hydrogen is both risky and complex, the researchers developed a method using water as a model fluid. Through optical measurements and simulations, results from water flows can be transferred to hydrogen flows with high precision.

The experimental setup, based on tomographic Particle Tracking Velocimetry (PTV), makes it possible to visualize flows in three dimensions and represents, as far as the researchers know, the first 3D measurements of their kind for a pipe bend.

"By using water, we can safely and cost-effectively study the flow mechanisms that are central to hydrogen transport. This gives us a solid scientific foundation before proceeding to experiments with hydrogen on a larger scale," says Sofia Larsson.

Foundation for future standards

The knowledge generated by the project is important for designing future hydrogen infrastructure. Over time, the results can be used to develop national and international standards for how pipelines should be designed and tested, particularly with regard to cold climates.

In northern Sweden, both ground and air temperatures vary greatly. The cold climate especially affects above-ground distribution pipelines, which often contain many bends. For these constructions, robustness and precise design are crucial for safe operation.

"The cold climate in northern Sweden places special demands on the design of hydrogen pipelines. Our results can help create safer and more reliable standards for how these systems should be built and tested," says Sofia Larsson.

The project has also resulted in a scientific review article published in the International Journal of Hydrogen Energy, which has gained wide recognition and been classified as Highly Cited by Web of Science – a sign of its impact within the research field.

The next step is to validate the simulation results against experimental measurements. In the longer term, the researchers aim to conduct tests in real hydrogen pipelines, including at the upcoming H2-Lab test facility in Piteå. To make this possible, continued funding and long-term research investments will be required.

• Fluid Mechanics