Influence of MH Alloy Grain Fragmentation on Void Formation in an MNTZV-159 Pressure Vessel

Abstract

The presented article deals with degradation processes occurring in the metal hydride bed of an MNTZV-159 storage tank, with an emphasis on MH alloy grain fragmentation, redistribution of the active material, and void formation in the vicinity of the internal heat transfer intensifier. Particle fragmentation, induced by repeated hydriding–dehydriding cycles and mechanical loading, alters the granulometry of the bed, promotes vibrational compaction, and leads to the development of a locally non-homogeneous structure. These changes negatively affect permeability, flow path tortuosity, heat transfer, and hydrogen distribution within the porous medium. To evaluate material redistribution, a transient CFD model was developed in the ANSYS CFX environment. The fragmented MH bed was represented by an equivalent continuum phase with a finite effective dynamic viscosity. This simplified representation was used solely to estimate the limiting spatial redistribution of the material after prolonged gravitational and vibrational loading and was not intended to reproduce the detailed rheology or settling kinetics of individual particles. The results therefore represent a qualitative upper-bound scenario of long-term bed redistribution rather than a quantitative prediction of the actual settling kinetics.