Prediction of effective thermal conductivity of cellular and polymer composites

Theoretical expression has been developed to predict effective thermal conductivity (ETC) of cellular and polymer composites considering random flow of heat flux lines. The concept of averaging temperature field within different phases has been used. For heterogeneous materials, the parameter F has been introduced in place of physical porosity. Due to the randomness of the flux lines in heterogeneous materials, the laws of statistical mechanics have been used to derive the expression in terms of the ratio of thermal conductivity of the constituents and the physical porosity. Expression so obtained for F is used in the model and it has been found that the predicted results of effective thermal conductivity are quite close to the experimental values. A comparison of the proposed relation with different models has also been made.