Computational investigation of thermo-kinetic limitations during metal-hydride hydrogen charging with open-cell metal-foam inserts of different alloys

Effective thermal management remains a critical limitation for fast hydrogen charging in metal-hydride reactors because the exothermic LaNi₅ absorption reaction produces temperature overshoot, spatial non-uniformity, and loss of kinetic driving force. This study presents a validated transient CFD investigation of a cylindrical LaNi₅ reactor operated as a conventional packed bed and as an open-cell metal-foam-enhanced MH–MF composite. Three practical foam alloys, AlSi10Mg, CuCr1Zr, and 316 L stainless steel, are compared at porosities of εmf = 0.89–0.93. The simulations cover Pₛ = 10–30 bar, T f = 293 K, and h = 10–2000 W·m −2 ·K −1 . Metal-foam insertion improves internal heat spreading, suppresses hot-core persistence, and promotes more uniform hydrogenation. CuCr1Zr gives the strongest enhancement: at εmf = 0.89, the near complete hydrogenation time, t₉₉, decreases from 38 min for the no-foam bed to 19 min, corresponding to a 50% reduction. AlSi10Mg provides intermediate improvement, whereas 316 L stainless steel remains limited by its lower thermal conductivity. Reducing porosity strengthens the conductive network but introduces a trade-off with foam mass and available hydride volume. Increasing h reduces t₉₉ from 35.0 min at 10 W·m −2 ·K −1 to 16.0 min at 500 W·m −2 ·K −1 , with diminishing returns beyond about 1000 W·m −2 ·K −1 . Increasing Pₛ accelerates uptake, reducing t 99 from 11.0 min at 15 bar to 8.0 min at 30 bar, while raising the peak average bed temperature from about 357 to 379 K. A conductivity-sensitivity analysis confirms that the enhancement trend remains valid even under reduced effective foam conductivity. These results provide practical guidance for balancing foam alloy, porosity, pressure, and cooling intensity to achieve faster and more uniform hydrogen charging.