Numerical investigation of fin-enhanced LaNi5 metal hydride reactors for improved hydrogen absorption and desorption

In this study, metal hydride reactors with differing fin configurations were investigated for hydrogen absorption and desorption processes. The simulations were performed using COMSOL Multiphysics V 6.3. To model the coupled heat and hydrogen transfer phenomena, heat transfer in porous media, Brinkman, and partial differential equation physics interfaces were employed. Metal hydride reactors with three geometrical configurations were considered: a reactor without fins, a reactor with fins 10 mm long and 2 mm thick attached at the center, and a reactor with fins of the same dimensions attached at the outer surface. The overall dimensions of the reactor were 50 mm in diameter and 80 mm in height. An expansion volume of 20 mm height was provided above the metal hydride bed and metal hydride of LaNi 5 was filled up to 60 mm height, and hydrogen was supplied at the top of the expansion volume. The heat and hydrogen transfer rates within the metal hydride bed were analyzed for different heat transfer fluid temperatures ranging from 293 K to 313 K. The results indicate that the outer-fin configuration provides the most effective enhancement of hydrogen absorption, exhibiting an absorption time of 1,140 s. In comparison, the inner-fin configuration requires 2,080 s, while the no-fin configuration takes 2,820 s to complete the absorption process. Thus, the use of inner fins reduces the absorption time by approximately 26.24%, whereas the outer-fin configuration achieves a substantially greater reduction of 59.57% relative to the no-fin configuration. These results demonstrate the superior effectiveness of the outer fin arrangement in accelerating hydrogen absorption.