Colloquia

Summary

By 2030, EU member states must ensure that hydrogen refuelling stations (HRS) are installed along the Trans-European Transport Network (TEN-T), with a maximum spacing of 200 km. Each HRS must provide at least 1 tonne of gaseous hydrogen per day and include a 70 MPa dispenser. Meeting these targets requires a large expansion of the current HRS network, which still faces significant technical and economic challenges.

One major bottleneck in hydrogen transport is pipelines. Due to the low density and high diffusivity of hydrogen, pressure variations during pipeline transport can be significant, especially during fast refuelling, when compressibility effects dominate. These conditions result in high flow velocities, making it difficult to accurately predict outlet pressure and temperature.

This research investigated the following question:

How can empirical, analytical, and numerical models be used to approximate hydrogen flow in pipelines of varying diameter, and to what extent are they suitable for predicting pressure and temperature under measured inlet conditions?

A selection of commonly used hydrogen pipeline diameters was studied. Experimental data was obtained using a custom-developed test setup and compared with the models. Additionally, shadowgraph imaging was performed at pipeline outlets to visualise flow phenomena.

The results showed that empirical and analytical models tend to underestimate the flow velocity of gaseous hydrogen, but correcting the outlet velocity towards the local speed of sound significantly improved accuracy. Numerical models proved to be highly capable even without real gas corrections. Shadowgraphs revealed shock patterns near the outlet, confirming the presence of sonic conditions.