Thermal Conductivity of Porous Media and Soils: A Review of Soviet Investigations
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
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Thermal conductivity of soils and other dispersed porous materials of natural and artificial origin depends on the composition and geometric microstructure of a system. Besides structure and composition, thermal conductivity is influenced by interphase intercomponent interactions. Heat transfer occurs primarily by conduction in systems with pores of conventional size. 0.0001 m, with temperatures ranging from -50 to 100 C and subject to ordinary temperature gradients. Convective and radiative heat exchange in pores can be estimated and is generally negligible, except in materials with large pores, such as thermal insulation, and some structural construction materials, notably the large-celled concrete found in the Soviet Union. Porous media and soils belong to a large class of Heterogeneous Media HM, for which the theory of heat transfer allows the investigator to take an approach typical of continuous media first, introduction of averaged characteristics of the medium and the process volume content of components, temperature, heat flow, heat capacitance and thermal conductivity, and second, formulation of principal physical laws in terms of these characteristics.