Influence of the gas injector configuration on the temperature evolution during refueling of on-board hydrogen tanks

In this article we show a refueling strategy analysis using different injector configurations to refuel a 70 MPa composite reinforced type 4 tank. The gas has been injected through single openings of different diameters (3 mm, 6 mm and 10 mm) and alternatively through multiple small holes (4 × 3 mm). For each injector configuration, slow (12 min) and faster (3 min) fillings have been performed. The gas temperature has been measured at different positions inside the tank, as well as the temperatures of the wall materials at various locations: on the external surface and at the interface between the liner and the fiber reinforced composite. In general, the larger the injector diameter and the slower the filling, the higher the chance that the gas develops vertical temperature gradients (a so-called gas temperature stratification), resulting in higher than average temperatures near the top of the tank and lower than average at its bottom. While the single 3 mm opening injector causes homogeneous gas temperatures for both filling speeds, both the 6 mm and 10 mm opening injectors induce gas temperature stratification during the 12 min fillings. The injector with multiple holes has an area comparable to the 6 mm single opening injector: in general, this more complex geometry tends to limit the inhomogeneity of gas temperatures during slow fillings. When gas temperature stratification develops, the wall materials temperature is also locally affected. This results in a higher than average temperature at the top of the tank and higher the slower the filling.