Stress analysis of cyclic sorption-desorption in metal hydride vessels

An axisymmetric finite element analysis (FEA) model based on a typical prototype of metal hydride (MH) storage vessel was established to investigate the thermal-mechanical behaviors during cyclic hydrogenationdehydrogenation processes. The FEA results were compared with the experimental data from a previous study. Good agreement between the FEA simulation and experimental results was obtained. Geometrical parameter and packing fraction exploration was carried out to predict wall deformation induced and to evaluate the performance of such MH alloy vessels under long-term cyclic hydrogenation-dehydrogenation. Numerical results indicated that the hoop stresses induced increase with the numbers of hydrogenation-dehydrogenation cycles, packing fraction, and slenderness ratio of MH storage vessels. The largest deformation tends to concentrate at the bottom of vessels caused by the progressive pulverization and agglomeration mechanism. With a packing fraction of 70 %, the hoop stresses induced tend to increase to a saturation point after 60 hydrogenationdehydrogenation cycles correlated with the saturated densification of MH alloy powders. It was found that the packing fraction and slenderness ratio (h/d) should be maintained lower than values of 60 % and 3.3, respectively, in order to assure safety performance.