A multiphysics numerical model of oxidation and decomposition in a uranium hydride bed

Kanouff, Michael P.; Gharagozloo, Patricia E.; Salloum, Maher; Shugard, Andrew D.

doi:10.1016/j.ces.2012.05.005

Cited by 19 publications

(19 citation statements)

References 28 publications

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“…In practice, we can first use the particle model to verify that this assumption is appropriate. The following set of PDEs are applied, starting with a form of Darcy's law to provide a semi-empirical relationship between pressure and flow (Kanouff et al, 2013):…”

Section: Coupled Surface Reaction-gas Flow Modelmentioning

confidence: 99%

Effects of surface thermodynamics on hydrogen isotope exchange kinetics in palladium: Particle and flow models

Salloum

James

Robinson

2015

Chemical Engineering Science

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A detailed surface reaction is incorporated into models of hydrogen isotope exchange in palladium. Surface hydride stability causes a large activation barrier and strong temperature dependence. The transition between solid-phase diffusion-and surface-limited reactions is delineated. The model identifies conditions for optimal performance of isotope exchange columns. a b s t r a c tPalladium is an important material for separation of hydrogen from other gases, separation of hydrogen isotopes, and for hydrogen storage. Its main advantages are its high selectivity and rapid, highly reversible uptake and release of hydrogen at near-ambient temperatures and pressures. Toward a more comprehensive understanding of its behavior, we present particle and continuum multiphysics mathematical models of the coupled reactive transport of hydrogen isotopes in the context of a single palladium sphere, and of flow in a packed palladium hydride bed. The models consider rates of chemical reactions and mass transport within a hydride bed, and incorporate a multistep reaction mechanism involving the metal bulk, metal surface, and gas phases. A unique feature in this formulation is that the chemical reaction model accounts for all absorption, adsorption, and diffusion activation energies. In particular, the adsorption energy is believed to depend strongly on the composition and atom-scale structure of the surface. We perform a parametric study to evaluate the effects of temperature, surface adsorption energy, and hydride particle radius on the isotope exchange kinetics. The models are useful in designing optimal hydride beds operating at various temperatures, with varied hydride particle size, and surface conditions.

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Section: Coupled Surface Reaction-gas Flow Modelmentioning

confidence: 99%

Effects of surface thermodynamics on hydrogen isotope exchange kinetics in palladium: Particle and flow models

Salloum

James

Robinson

2015

Chemical Engineering Science

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“…Note that the second term on the left-hand side describing convection uses the density and specific heat of the gas because it is the phase that is in motion. The thermal inertia term (first term on left-hand side) and the conduction term (first term on right-hand side) use the properties of the solid phase because they are much larger than the corresponding gas phase values [10]. The source term accounts for heat absorbed by the UH 3 bed in order to produce the H 2 gas which transport occurs by convection and diffusion, as described by [45]:…”

Section: Governing Equationsmentioning

confidence: 99%

“…The model aims to understand the different physical phenomena involved in the process, such as the pressure buildup in the powder bed, the bed permeability, the morphological changes in the bed, etc., and their effects on the H 2 extraction rate. The model relies on the decomposition kinetics extracted from the physics-based model in Section 4 and comprises the governing equations for momentum, energy and mass transport, and the chemical reactions [10]. Unless otherwise stated, the units of the variables are CGS.…”

Section: Continuum Modelmentioning

confidence: 99%

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Empirical and physics based mathematical models of uranium hydride decomposition kinetics with quantified uncertainties.

Salloum

Gharagozloo

2013

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Metal particle beds have recently become a major technique for hydrogen storage. In order to extract hydrogen from such beds, it is crucial to understand the decomposition kinetics of the metal hydride. We are interested in obtaining a a better understanding of the uranium hydride (UH 3 ) decomposition kinetics. We first developed an empirical model by fitting data compiled from different experimental studies in the literature and quantified the uncertainty resulting from the scattered data. We found that the decomposition time range predicted by the obtained kinetics was in a good agreement with published experimental results. Secondly, we developed a physics based mathematical model to simulate the rate of hydrogen diffusion in a hydride particle during the decomposition. We used this model to simulate the decomposition of the particles for temperatures ranging from 300K to 1000K while propagating parametric uncertainty and evaluated the kinetics from the results. We compared the kinetics parameters derived from the empirical and physics based models and found that the uncertainty in the kinetics predicted by the physics based model covers the scattered experimental data. Finally, we used the physics-based kinetics parameters to simulate the effects of boundary resistances and powder morphological changes during decomposition in a continuum level model. We found that the species change within the bed occurring during the decomposition accelerates the hydrogen flow by increasing the bed permeability, while the pressure buildup and the thermal barrier forming at the wall significantly impede the hydrogen extraction. 3 AcknowledgmentThe authors would like to acknowledge Andrew Shugard for providing valuable discussions and feedback that were helpful to accomplish this work.

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“…We assume the porous catalyst bed to be isotropic and homogeneous [11], so the energy conversion equation was as follows:…”

Section: Multiphysics Coupling Model Of the Mltsrrmentioning

confidence: 99%

A Two-Dimensional Multiphysics Coupling Model of a Middle and Low Temperature Solar Receiver/Reactor for Methanol Decomposition

et al. 2017

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Abstract:In this paper, the endothermic methanol decomposition reaction is used to obtain syngas by transforming middle and low temperature solar energy into chemical energy. A two-dimensional multiphysics coupling model of a middle and low temperature of 150~300 • C solar receiver/reactor was developed, which couples momentum equation in porous catalyst bed, the governing mass conservation with chemical reaction, and energy conservation incorporating conduction/convection/radiation heat transfer. The complex thermochemical conversion process of the middle and low temperature solar receiver/reactor (MLTSRR) system was analyzed. The numerical finite element method (FEM) model was validated by comparing it with the experimental data and a good agreement was obtained, revealing that the numerical FEM model is reliable. The characteristics of chemical reaction, coupled heat transfer, the components of reaction products, and the temperature fields in the receiver/reactor were also revealed and discussed. The effects of the annulus vacuum space and the glass tube on the performance of the solar receiver/reactor were further studied. It was revealed that when the direct normal irradiation increases from 200 W/m 2 to 800 W/m 2 , the theoretical efficiency of solar energy transformed into chemical energy can reach 0.14-0.75. When the methanol feeding rate is 13 kg/h, the solar flux increases from 500 W/m 2 to 1000 W/m 2 , methanol conversion can fall by 6.8-8.9% with air in the annulus, and methanol conversion can decrease by 21.8-28.9% when the glass is removed from the receiver/reactor.

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A multiphysics numerical model of oxidation and decomposition in a uranium hydride bed

Cited by 19 publications

References 28 publications

Effects of surface thermodynamics on hydrogen isotope exchange kinetics in palladium: Particle and flow models

Effects of surface thermodynamics on hydrogen isotope exchange kinetics in palladium: Particle and flow models

Empirical and physics based mathematical models of uranium hydride decomposition kinetics with quantified uncertainties.

A Two-Dimensional Multiphysics Coupling Model of a Middle and Low Temperature Solar Receiver/Reactor for Methanol Decomposition

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