Evaluation criterion for filling process of cryo-compressed hydrogen storage vessel

Cryo-compressed hydrogen (CcH₂) is a promising method for hydrogen storage. However, a lack of existing evaluation for the CcH₂ filling process has impeded the development of the CcH₂-related standards and future applications. In this study, a criterion based on linear scaling transformation was initiated to evaluate the filling process. The criterion scores important aspects of filling based on four normalized parameters: filling duration, gas consumption, and temperature rise in two parts of the liner. It is expected to facilitate a fast and intuitive assessment of the filling scheme. Two filling strategies for the CcH₂ vessels of 140 L and 210 L have been proposed to establish the combined condition of 77 K and 20 MPa. A comprehensive comparison of twenty-two different scenarios for both cylinder types, employing data obtained from numerical simulations with the SST k − ω turbulence model.

The results showed that the scenarios with progressive mass flow rates (PMFR) consistently outperformed those with constant mass flow rates (CMFR) by no less than 4.5 %, underscoring the superior storage efficiency of the PMFR filling strategy for the CcH₂ cylinder. Notably, the scheme featuring a mass flow rate change of 4 g/s² for the 140 L vessel and 6 g/s² for the 210 L vessel had the highest score, respectively. This research assists in the designing and decision-making process for the filling procedures and may inform the development of related standards.