Experimental measurements and theoretical predictions of the thermal conductivity of two phases glass beads

Abstract

Effective thermal conductivities of dry and water saturated glass beads have been measured with the transient thermal probe method. The glass beads used in the experiments have particles with diameters ranging from 0.07 mm to 6 mm. The thermal probe used for the measurements has an external diameter of 1.2 mm. The effective thermal conductivities of dry and water saturated glass beads, with diameters smaller than 1.2 mm, are well predicted by a theoretical model, proposed by the first author, which uses the experimentally measured porosity. If the diameter of the glass beads is 3 and 6 mm, i.e. it is higher than the probe one; the porosity of the porous medium is higher near the probe than in the core of the medium. The effective thermal conductivity of the porous medium is then lower because air and water have a lower thermal conductivity than the solid particles of the beads. A theoretical approach has been used in order to take into account the increase of porosity near the probe. The theoretical models use the corrected porosity, which account for the probe presence, and provide good agreement with the experimental measurements.