Optimizing hydrogen storage performance in Mg2Ni metal hydride reactors: The impact of phase change materials and heat transfer fluids

Efficient thermal management remains a critical challenge for enhancing hydrogen storage in Mg 2 Ni metal hydride (MH) reactors. To address this, we propose a novel hybrid approach integrating phase change materials (PCM) with geometrically optimized spiral heat transfer fluid (HTF) tubes. This study aims to: (1) Quantify performance gains from combining PCM/HTF configurations; (2) Identify optimal operating parameters; (3) Decipher heat contribution mechanisms. A three-dimensional numerical model was developed to analyze four reactor designs: straight HTF pipes, spiral HTF pipes, PCM-integrated straight HTF pipes, and PCM-integrated spiral HTF pipes. The PCM-spiral HTF configuration achieves 90 % hydrogen absorption 48.2 % faster than standalone spiral HTF systems, attributable to synergistic thermal regulation where PCM stores 35.8 % (98.59 kJ) of reaction heat through latent buffering, while spiral HTF enhances convective dissipation (64.2 % heat removal). Parametric optimization identifies a PCM/MH mass ratio of 1.06, HTF velocity of 20 m/s, and supply pressure of 2.4 MPa as optimal conditions maximizing system efficiency. This work establishes a design framework for efficient thermal management in next-generation hydrogen storage systems.