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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

MULTIPHYSICS SIMULATION OF PALLADIUM HYDRIDE ISOTOPE EXCHANGE IN NON-UNIFORM PARTICLE BEDS

DOI: 10.1615/TFESC1.prm.012710
pages 2237-2249

Patricia E. Gharagozloo
Sandia National Laboratories, Livermore, CA 94551, USA

Mehdi Eliassi
Sandia National Laboratories, Albuquerque, NM 87185, USA

Bradley L. Bon
Sandia National Laboratories, Livermore, CA 94551, USA


KEY WORDS: thermal fluid flow porous media hydride simulation model multiphysics particle bed exchange reaction

Abstract

It has long been known that hydrogen and its isotopes (e.g., H, D, and T) readily dissolve in certain metals, notably palladium (Pd). Due to small differences in thermochemistry, one isotope is generally stored preferentially over the other, thereby making separations possible. Alternatively, storage itself may be the primary goal, with one isotope being used to flush out another. Measured and controlled hydrogen isotope exchange with Pd is routinely carried out, but the physical and chemical aspects of this process are not fully understood. Packed particle beds suffer from particle density variations due to the packing process, which causes non-uniform fluid and thermal bed-flow properties. These non-uniformities affect pressure and temperature distributions both of which have direct impacts on hydride stoichiometry and isotope exchange. This work develops a computational model and studies simulation results for a series of isotope exchange dynamics experiments including long and thin isothermal beds and larger non-isothermal beds. The multiphysics 2D axisymmetric model simulates the temperature and pressure dependent exchange reaction kinetics, pressure and isotope dependent stoichiometry, heat generation from the reaction, reacting flow through porous media, and non-uniformities in particle density. The model is able to replicate experimentally observed curved reaction fronts and asymmetry of exit mass fractions over time. The improved understanding of the exchange process and its dependence on non-uniform bed properties and temperatures in these larger systems is critical to the future design of such systems.

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