Thermal Performance Analysis of LaNi₅ Metal Hydride Reactors Using Multiple Heating-Tube Configurations and Fin Enhancements

Abstract

Metal hydrides such as LaNi₅ offer a compact and intrinsically safe hydrogen-storage solution for PEM fuel cells, but their endothermic desorption reaction requires efficient heat delivery to maintain acceptable release rates. This study numerically investigates the thermal performance of a cylindrical LaNi₅ metal hydride reactor heated using waste heat from an 80 °C PEMFC coolant stream. A three-dimensional slice of a 500 mm-diameter tank was modeled in SolidWorks and Space-Claim, and transient CFD simulations were conducted in ANSYS Fluent using an Arrhenius-based temperature-dependent volumetric heat sink to represent desorption. Twelve aluminum tubes were arranged in square, triangular, and radial patterns, each examined with and without 10 mm fins. Temperature uniformity, heat absorbed, and statistical indicators were compared across six configurations. Results show that the square pattern yields the most uniform temperature field and the highest heat absorption, while the radial arrangement performs the poorest. In the un-finned cases, the square configuration showed the lowest temperature non-uniformity, with approximately 9% lower standard deviation and coefficient of variation compared to the radial arrangement, along with a marginal (~1%) increase in heat absorption The finned square configuration achieved up to 24% higher heat absorption compared to its un-finned counterpart and approximately 0.3% improvement over the finned triangular arrangement and about 1.5% over the finned radial arrangement, maintaining the lowest temperature non-uniformity between all the configurations. Validation against previous study trends and a grid-independence study confirm the reliability of the numerical model, offering guidance for optimizing metal hydride tank heating-tube configurations.