Mathematical Models for Effective Thermal Conductivity
Different mathematical models for effective thermal conductivity are described and discussed in view of experimental results for porous materials.
Models which apply the porosity of the solid as the only structural information are found not to be satisfactory. The degree of continuity in the phases is identified as an important structural parameter. Consequently, such a parameter is included in the models.
Model I: A solid lattice is assumed.
Model II: No specific structure of the solid is assumed, but a distribution in space is anticipated for the porosity.
Model III: An extended use of the EMA-model (Effective Medium Approximation for calculation of dielectric constants) to predict effective thermal conductivity leads to a model which involves a factor interpreted as a measure of the degree of continuity in the solid phase.
It is concluded that models II and III are the most promising models.
KeywordsThermal Conductivity Effective Thermal Conductivity Solid Lattice Equal Volume Fraction Heat Conduction Path
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