ON THE EFFECTIVE THERMAL CONDUCTIVITY OF POROUS PACKED BEDS WITH UNIFORM SPHERICAL PARTICLES

Point contact models for the effective thermal conductivity of porous media with uniform spherical particles have been briefly reviewed. The model of Zehner and Schlunder (1970) has been further validated with recent experimental data over a broad range of conductivity ratios from 8 to 1200 and over a range of solids fractions up to similar to 0.8. The comparisons further confirm the validity of the Zehner-Schlunder model, known to be applicable for conductivity ratios less than similar to 2000, above which area contact between the particles becomes significant. This validation of the Zehner-Schlunder model has implications for its use in the prediction of the effective thermal conductivity of water frost (with ice-to-air conductivity ratio similar to 100) which arises in many important areas of technology.