Prediction of state property during hydrogen leaks from high-pressure hydrogen storage systems

In an actual hydrogen leakage process, heat exchange occurs between the gas in a high-pressure storage system and its surroundings. Therefore, the predictions of models that are established based on the isentropic process assumption have large errors. In this study, a high-pressure gas leakage process model including heat exchange (the HEC model) is established. It includes two parts; one is a high-pressure gas storage model without the isentropic process assumption, and the other is a leakage orifice model with the isentropic process assumption. Formulas for the pressure variation and temperature variation based on the mass and energy conservation equations, the Abel-Noble equation of state, and an enthalpy formula based on the Helmholtz free energy are used to establish the gas storage model. The leakage orifice model is built using a mass flow rate formula based on the van der Waals equation of state and Perry's flow coefficient formula. Finally, the proposed high-pressure gas leakage process model including heat exchange is compared with high-pressure hydrogen leakage process models with the isentropic process assumption based on the Abel-Noble and van der Waals equations of state. The results show that the proposed model can yield more promising results in predicting the gas leakage mass flow rate, gas pressure, and temperature inside hydrogen storage systems compared with previous models. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.