Effective thermal conductivity of highly porous two-phase systems

A theoretical expression for predicting effective thermal conductivity (ETC) of highly porous two-phase systems has been developed. The porous system has been assumed to contain particles of irregular shape, being dispersed randomly within the continuous medium. The concept of averaging the temperature field within different phases has been used. Resistor model has been applied to determine ETC of two-phase porous systems, as a porous medium is neither composed of slabs parallel nor perpendicular to the heat flux. It is proposed to use slabs inclined at an angle θ with the heat flux lines. An effort is made to correlate angle of inclination θ in terms of the ratio of thermal conductivity of the constituent phases and the physical porosity. Best-fitted expression so obtained for θ is used in the derived model and found that the predicted values of ETC are quite close to the experimental results.