CHARACTERISTIC OF EFFECTIVE THERMAL-CONDU CTIVITY IN POROUS MATERIALS

The effective thermal conductivities of porous materials are calculate d with a finite element method by the fundamental equation of heat con duction in porous materials in the case of void fraction, pore shapes and thermal conductivity ratio of two phases. Effective thermal conduc tivities in the porous materials with spherical pores are larger than those with cylindrical and parallelepipedic pores, and agree closely w ith the Maxwell-Eucken equation. Since effective thermal conductivitie s in the case of cylindrical and parallelepipedic pores are almost the same, a correlative equation is obtained by using the numerical resul ts for these pore shapes. To check these calculated results, the tempe rature distributions and effective thermal conductivities were measure d experimentally under the same operating conditions as those of the t heoretical analysis.