Thermal dispersion in thick-walled tubes as a model of porous media

Abstract A theoretical study of thermal dispersion in porous media is presented. The contribution of pore level velocity distributions on dispersion is captured in an analysis of thermal transport in a thickwalled tube containing a flowing fluid. It is shown that the cases of an applied steady-state temperature gradient and a traveling temperature wave produce different thermal dispersivities. In both cases, the dispersion coefficient is defined by the static thermal conductivity plus a term due to dispersive flow. The dispersive term is proportional to the Peclet number squared. The proportionality coefficient is shown to be a function of porosity, fluid and solid thermal properties, and the temperature field. Through consideration of a bundle of tubes of various radii, the contribution of heterogeneities on thermal dispersion is evaluated. Variations of pore diameters are shown to cause orders of magnitude increases in dispersion. Satisfactory comparisons of the dispersion model with published experimental data are presented.

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