Determination of effective thermal conductivity from geometrical properties: Application to open cell foams

The thermo-physical behavior of open-celled metal foams depends on their microscopic structure. An ideal periodic isotropic structure of tetrakaidecahedron shape i.e. Kelvin cell is studied. The geometrical parameters of casted metal foams are obtained using iMorph (in-house code). We have proposed an analytical model in order to obtain geometrical parameters correctly as they have substantial influence on thermal and hydraulic phenomena, where strut geometry is of primary importance. Various relationships between different geometrical parameters and porosities are presented. The analytical results are fully compared with the experimental data in the literature and measured morphological data. The relationship of geometrical parameters with physical properties such as effective thermal conductivity is equally important. The range of solid to fluid phase conductivity ratios (λs/λf) studied is from 10 to 30,000 and for different porosities (80-95%). A modified correlation term, F is introduced in order to take account of thermal conductivities of constituent phases using electrical resistor model. An excellent agreement has been observed between the predicted correlation and experimental data.