Dehydrogenation performance of metal hydride container utilising MgH2-based composite

Mg-based hydrides have gained formidable interest for hydrogen storage applications due to their high intrinsic hydrogen capacity up to 7.6 wt%. However, their ability to absorb/desorb hydrogen is limited by their slow inherent kinetics and the heat and mass transfer within the storage container. The dehydrogenation of the metal hydride material in the container becomes important when coupling with a fuel cell, since the fuel cell requires a constant H-2 flow rate to provide constant power output. In this study, we investigate numerically the dehydrogenation performance of a cylindrical container filled with 300 g of ball milled Mg90Ti10 + 5 wt% C with the objective to identify the operating conditions at which the H-2 flow rate is higher or equal to the threshold for a proper functioning of a fuel cell. The heat exchange in the container is improved by a combination of internal basin-like and external annular fins. The heat transfer characteristics used in the numerical model are determined from the experimental work conducted in our laboratory. The results show that during the dehydrogenation process, at low convective heat transfer coefficient of 5-35 W/m(2) K, the hydride container can supply H-2 to a fuel cell with different power rating from 100 to 250 W for a long period of time with nearly constant flow rate.

Automated summary

Mg-based hydrides have high intrinsic hydrogen capacity, but their hydrogen absorption and desorption kinetics are limited by slow reactions and heat and mass transfer. This study numerically investigates the dehydrogenation performance of a cylindrical container filled with ball milled Mg90Ti10 + 5 wt% C and suggests operating conditions that can meet the hydrogen flow rate requirement for a fuel cell.