Models for Metal Hydride Particle Shape, Packing, and Heat Transfer

TL;DR

This paper develops a comprehensive multiphysics model for heat transfer in metal hydride powders, incorporating particle shape, packing, and thermal conductivity, validated against experimental data.

Contribution

It introduces a statistical geometric model and packing simulation methods to accurately replicate particle distributions and predict thermal behavior in metal hydride powders.

Findings

Particles jam at higher densities than previously estimated

Thermal conductivity follows granular effective medium theory

Theoretical model aligns with experimental observations

Abstract

A multiphysics modeling approach for heat conduction in metal hydride powders is presented, including particle shape distribution, size distribution, granular packing structure, and effective thermal conductivity. A statistical geometric model is presented that replicates features of particle size and shape distributions observed experimentally that result from cyclic hydride decreptitation. The quasi-static dense packing of a sample set of these particles is simulated via energy-based structural optimization methods. These particles jam (i.e., solidify) at a density (solid volume fraction) of 0.665+/-0.015 - higher than prior experimental estimates. Effective thermal conductivity of the jammed system is simulated and found to follow the behavior predicted by granular effective medium theory. Finally, a theory is presented that links the properties of bi-porous cohesive powders to the present systems based on recent experimental observations of jammed packings of fine powder. This theory produces quantitative experimental agreement with metal hydride powders of various compositions.