Thermal regeneration of a ZrCoHx packed getter bed: CFD analysis of conductive enhancement strategies

Getter beds based on zirconium-cobalt hydride, ZrCoH x , are being considered as alternatives to cryogenic molecular sieve beds for hydrogen-isotope removal from helium purge loops in fusion blanket tritium extraction systems. During regeneration, the hydrided getter must be heated to elevated temperature under vacuum or near-vacuum conditions, where gas-phase convection inside the packed bed is negligible and the thermal response is governed mainly by the low effective thermal conductivity of the packed ZrCoH x ​ material. In this work, a representative three-dimensional CFD model was developed in ANSYS Fluent to assess conductive heat-transfer enhancement strategies for a chunk-/flake-form ZrCoH x packed bed heated by hot helium circulation through an internal pipe. The packed bed was represented as a homogenized solid domain using effective thermophysical properties measured for chunk-form ZrCoH x ​. Two enhancement approaches were compared: distributed conductivity enhancement by adding 10 and 20 vol.% copper spheres, and structured conductive enhancement using stainless-steel fins or copper fins with a copper support pipe. Simulations were performed for a helium inlet temperature of 450 °C and helium velocities of 2 and 10 m/s. The results confirm that the regeneration process is controlled primarily by internal heat diffusion through the packed hydride, while increasing helium velocity has only a secondary effect. At 2 m/s, the time required for the area-averaged outer ZrCoH x surface temperature to reach 400 °C decreased from 4.7 h for the plain bed to 3.3 h for the 20 vol.% Cu-sphere case and to 2.8 h for the Cu-fin configuration. At 10 m/s, the corresponding time decreased from 4.2 h to 2.6 h and 2.2 h, respectively. These results show that distributed copper addition improves the bulk thermal response, but connected conductive pathways provide the strongest transient heating enhancement by reducing the effective conduction length. The model is a comparative parametric screening tool and not a complete thermo-chemical regeneration model, since hydrogen desorption kinetics and the endothermic desorption heat load were not included. The results provide preliminary guidance for the thermal subdivision and internal conductive design of ZrCoH x ​ getter beds for fusion tritium extraction applications.