A GENERAL ANALYTICAL APPROACH TOWARD THE THERMAL-CONDUCTIVITY OF POROUS-MEDIA

A general analytical approach to the thermal conductivity of porous media is developed which leads to theoretically sound expressions having a wide range of applicability and easily fitted to available empirical data. Specifically, practical expressions are derived for pore distributions of any concentration, randomly oriented pores of arbitrary shape, pores of any conductivity, radiant heal transfer within pores, and fibrous media. Most results transfer freely to electrical conductivity or any other general area where Laplace's equation applies. Fundamental limitations of the approach restrict its use to random pore distributions and heat transfer through the continuous medium by conduction. Examples are chosen from selected problem areas of current interest, spanning a wide range of pore types, volume fractions, and conductivities.