Powder Geometry Based Models for Sintered Media Porosity and Effective Thermal Conductivity

Abstract

In this paper, the porosities of porous media fabricated from a copper powder sintering process were modeled and measured, aiming for use of the porosity as an input parameter for the prediction of the effective thermal conductivity of sintering porous media. An expression relating the porosity and the powder particle mean diameter, based on the arrangements of contacting spheres joined by necks, was obtained. The particle size distributions of the powders employed in this study were statistically analyzed. The atomized copper powder was sifted to reduce the size dispersion of the particles. The porosities of sintered media fabricated from powders with particle mean diameters ranging from 20 to 200 microns were measured by means of the image analysis method. Results from porosity literature models were compared with the present model and experimental data. A model to predict the effective thermal conductivity from the mean particle diameter was developed, based on an elementary porous media cell, which is physically represented by two metallic hemispheres in contact, surrounded by a thin film of liquid. The electrical circuit analogy is employed to determine the heat leaving the top and reaching the bottom of the cell. The effective thermal conductivity in a porous media, made of copper powder and saturated with distilled water, was used to compare with the effective thermal conductivity model. This comparison showed to be quite good.