Determining hydrogen pre-cooling temperature from refueling parameters

Compressed hydrogen storage has a requirement on the temperature: for safety reasons, the final gas temperature is not allowed to exceed 85 °C during filling. However, due to the short time and the fast filling rate in practice, the final gas temperature rises sharply. To solve the issue, the hydrogen could be pre-cooled sometimes, but setting the pre-cooling hydrogen temperature becomes a critical problem, we need to know whether the inflow hydrogen needs to be pre-cooled and what the pre-cooling temperature it should be. This paper proposes a new analytical solution of pre-cooling hydrogen temperature from a simplified lumped parameter model. The effects of initial temperature, initial pressure and the filling time on the inflow hydrogen temperature are studied, and three sets of equations are proposed correspondingly. Further we use these equations to fit the published reference data, the fittings show good agreement. The occasions where the hydrogen needs to be pre-cooled are presented. We suppose this study not only helps to choose the pre-cooling hydrogen temperature, but also ensure the safety during the hydrogen filling.