Experimental Measurements of the Thermal Conductivity of Nanoparticle Packed Beds

Abstract

Experimental measurements of heat transfer across packed beds of ceramic and metallic nanoparticles are presented. Round disk-shaped cakes of nanoparticles approximately one millimeter thick and 6.75 millimeters diameter are produced by packing either copper or silica nanoparticles into a mold. The thermal conductivity of these packed beds are then determined using a Guard-Heated Calorimeter under steady state conditions. SEM imaging of the packed beds indicates that the copper nanoparticles are neither monosized nor entirely spherical while the silica nanoparticles, are both highly spherical and monosized. However, both packed beds were found to have very similar effective thermal conductivities. The thermal conductivity of the copper nanoparticle packed bed is found to be 0.054 ± 0.006 W/m°C, while the thermal conductivity of silica nanoparticle packed bed is found to be 0.018 ± 0.007 W/m°C. As a result, it is seen that, at least in this limited comparison, particle material and thermal conductivity (metal with high conductivity, or ceramic with low conductivity), as well as the regularity of the nanoparticle itself (size distribution and sphericity) appear to have a small effect on overall packed bed thermal conductivity.