To supply hydrogen to the geographically decoupled demand sites, efficient hydrogen transport is necessary. The existing natural gas pipelines represent a promising transport solution, with the blended hydrogen content expected to steadily increase. An open issue of hydrogen blending is the mixing behavior. Therefore, the effects of different geometric parameters (diameters, angles), operating conditions (velocities, concentrations), and injection layouts (single- and multi-point) on the mixture quality during direct injection of hydrogen into a natural gas pipeline are studied using 3D CFD. The main goal is to find parameters and layouts leading to sufficient mixing quality over a range of operating conditions. The mixing quality is determined based on the coefficient of variation (COV). The results show that the momentum flux ratio is a key parameter governing the mixing behavior. However, a high momentum flux ratio alone does not guarantee sufficient uniformity for all operating conditions. For the investigated range, single-point injection cannot ensure reliable mixing quality, whereas multi-point layouts with higher hydrogen inlet velocities achieve sufficient uniformity.

To facilitate the adoption of hydrogen-based applications in the mobility sector, a reduction of the filling time is needed. However, faster filling times of compressed gaseous hydrogen (CGH2) tanks lead to a rapid temperature increase, whereby exceeding 85°C poses a safety risk due to the possibility of material failure. To prevent this, various filling protocols were developed by the SAE (e.g., J2601–5). To optimize the filling speed, infrared communication of the tank temperature between the vehicle and filling station is proposed, with the temperature measurement most likely taking place at the on-tank valve. Our experiments and simulations with filling Type III and IV tanks in the 60–320 liter range indicate a strongly inhomogeneous temperature field. By calculating the average tank temperature based on the measured tank pressure and mass, it was observed that the temperature sensor at the on-tank valve greatly underpredicts the actual tank temperature. Furthermore, the location of the hot spots within the tank depends on tank size, geometry, as well as filling parameters. Consequently, sensor placement is key for reliable measurement of the tank temperature. Similarly, the reliable temperature measurement is needed for the validation or parameter fitting of model-based approaches for predicting the tank temperature.