NUMERICAL-ANALYSIS OF EFFECTIVE THERMAL-CONDUCTIVITY OF MIXED SOLID MATERIALS

This paper presents a new method, called the numerical element method, to determine the effective thermal conductivity of mixed solid materials. It has the following distinctive features: high accuracy, there is no need for any hypothesis and it is suitable for calculating the effective thermal conductivity of mixed solid materials with discrete phases of different shapes. Based upon the numerical results, two new formulae relating the effective thermal conductivity of a mixed solid material to the weight percentage and density of the discrete phases are presented. The effective thermal conductivity of mixed solid media is influenced by the weight (or volume) fraction of the doped material rather than by the size or dimension of each discrete phase. For illustration purposes, the effective conductivities of some phase change materials and plastics doped with metal powders are calculated.