Characterization of Powder Beds by Thermal Conductivity: Effect of Gas Pressure on the Thermal Resistance of Particle Contact Points

Abstract

The thermal conductivity of ceramic powder packed beds was measured at temperatures below 100 °C for various powder sizes and compositions and under different gas atmospheres. Measurements at low pressures (down to 10 Pa) combined with a theoretical model allowed the elucidation of geometrical and thermal resistance parameters for the contact points between granules. The gap thickness and contact point size were found to be well correlated with the mean particle size. The thermal conductivities of all powders at low pressure were found to differ at most by a factor of two, whereas the solid‐phase conductivities of the powder materials differed by more than one order of magnitude. A theoretical model accounting for the size‐dependence of contact point conductivity is incorporated to rationalize this trend.

Experimental measurements of the effective thermal conductivity of a lithium titanate (Li2TiO3) pebbles-packed bed

“…In 2004 Shapiro et al [6] published their model for predicting effective thermal conductivity of ceramic powder packed beds. In this model, the pebble bed is assumed to be composed of identical pebbles that contact each other over area of πa 2 .…”

Polystyrene colloidal crystals: Interface controlled thermal conductivity in an open-porous mesoparticle superstructure

“…Thermal transport in these materials is governed by the porosity, the mutual contact points and the environment. [5][6][7] Of major importance is the interfacial contribution, 4 which consist of geometric constriction due to the contact area and the grain boundary thermal resistance. 8 In particular for inorganic powders micro-roughness on the particle interface can severely reduce the actual contact area leading to a reduced effective thermal conductivity.…”

A preliminary assessment of beryllium dust oxidation during a wet bypass accident in a fusion reactor

“…However, during operating conditions of a tokamak reactor, initially very little gas will be present in such gaps; and during accident conditions, this gas pressure could increase up to about 150 kPa before the ITER vacuum vessel (VV) pressure suppression system actuates and limits the VV pressure. In order to simulate this transition from vacuum to a collisional gas in this gap, the formula for effective gas conductivity in powder beds, cited in Reference [16], is used in Equation 9.…”