Gaseous Tracer Techniques for Pore Structure Characterization of Granular Materials

摘要

The pore structure of granular materials influences several physical and chemical phenomena, including: 1) heat and mass transfer rates, 2) fluid dynamics, 3) mechanical response, and 4) heterogeneous chemical reaction rates. In many systems, these phenomena are coupled, and accurate pore structure characterization is important to developing reliable predictive models. Gaseous tracer techniques show promise as a rapid nondestructive method for characterizing pore structures. To provide a basis for developing a theoretical and experimental approach involving multiple tracer techniques, five characteristic parameters were defined to describe the major features of a macroscopically uniform pore structure. Those parameters are the following: 1) the portion of the total pore space that forms flow paths (flow porosity), 2) the fraction that forms relatively stagnant paths (stagnant porosity), 3) the tortuosity of the flow porosity, 4) the specific surface area of the pore space, and 5) the fraction of the specific surface area that is associated with the flow porosity. Initial experiments with samples having simple, known pore structures were conducted to evaluate the theory and experimental techniques. Agreement between known and experimentally determined parameter values was good. Furthermore, it appears that the tracer techniques can have broad application as nondestructive diagnostic tools for examining granular materials. (ERA citation 13:037365)