Thermofluidynamic modelling of hydrogen absorption in metal hydride beds by using multiphysics software

Abstract

In this study, a performance analysis of metal hydride reactors (MHRs) based hydrogen storage during absorption process is presented. The study shows the effect of using heat pipe and fins for enhancing heat transfer inside MHRs at various hydrogen supply pressures. Three different cylindrical MHR configurations using LaNi5 as a storage media were adopted including: i) reactor cooled by means of natural convection, ii) reactor equipped with a heat pipe along its central axis, iii) reactor equipped with finned heat pipe. A 3-D mathematical model is developed and utilized to simulate the thermofluidynamic behaviour of a metal hydride bed. The simulation study is conducted by solving simultaneously the energy, mass, momentum, and kinetic differential equations of conservation by using COMSOL multiphysics 5.2a software. Parameters such as hydrogen stored capacity, internal temperature distribution for the reactor, and their duration have been optimized. The model was validated against experimental result which have been previously published by the authors. The obtained results confirmed that the simulation and experimental results reasonably match where the maximum error vlaue was less than 8% at 10-bar hydrogen supply pressure, which proves that the model has efficiently captured the key experimental trends. On the other hand, the MHR design, which is equipped with a finned heat pipe is shown a superior performance as compared to all the other tested configurations in terms of charging time and storage capacity. Therefore, the model can be used as a helpful tool in the optimization of the MHR designs and performance.