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This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media. 4 ACKNOWLEDGMENTS

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Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. It is important for design applications to have an accurate, but relatively simple model for system analysis. We are interested in simulating the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. Our model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, we account for the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion. These expansions result in mechanical stresses which lead to bed deformation. To describe this, we develop a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation. We find that, by using this solid mechanics model, we improve the agreement between our reacting bed model and the experimental data.