Simulation of gas diffusion in highly porous nanostructures by direct simulation Monte Carlo

Dreyer, Jochen A.H.; Riefler, Norbert; Pesch, Georg R.; Karamehmedović, Mirza; Fritsching, Udo; Teoh, Wey Yang; Mädler, Lutz

doi:10.1016/j.ces.2013.10.038

Cited by 32 publications

(21 citation statements)

References 14 publications

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“…As a result, due to k=D < 0:01, using the continuum flow approach with no-slip boundary conditions is accurate to simulate flow fields inside the reactors [38,[42][43][44][45]. Therefore, the governing transport equations are as follows: @q @t þ r:ðq…”

Section: Governing Equationsmentioning

confidence: 98%

Investigating atomic layer deposition characteristics in multi-outlet viscous flow reactors through reactor scale simulations

Shaeri

Jen

Yuan

et al. 2015

International Journal of Heat and Mass Transfer

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Section: Governing Equationsmentioning

confidence: 98%

Investigating atomic layer deposition characteristics in multi-outlet viscous flow reactors through reactor scale simulations

Shaeri

Jen

Yuan

et al. 2015

International Journal of Heat and Mass Transfer

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“…In the present work, the DSMC method, which is the stochastic solution of the Boltzmann equation (Nanbu 1980), was used for numerical simulations of gas flows in porous media. The DSMC method has been used to simulate gas flow in micro-/nanoscale porous media (Saito et al 1995;Tomarikawa et al 2011;Kalarakis et al 2012;Oshima et al 2012;Dreyer et al 2014;Christou and Dadzie 2016).…”

Section: Methodsmentioning

confidence: 99%

“…They showed that the permeability of a porous medium obtained in the gas flow simulations by the lattice Boltzmann method incorporating the effective gas viscosity in the transition flow regime agrees well with that obtained by the DSMC simulations. Dreyer et al (2014) investigated the gas diffusion process in high-porosity nanoscale porous media by using the DSMC method and compared the DSMC results with those of the dusty gas model. Christou and Dadzie (2016) investigated the effect of the Knudsen number for the velocity profile in a Berea porous structure, which was obtained with micro-CT, by performing DSMC simulations.…”

Section: Introductionmentioning

confidence: 99%

A study on pressure-driven gas transport in porous media: from nanoscale to microscale

Kawagoe

Oshima

Tomarikawa

et al. 2016

Microfluid Nanofluid

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“…38 Previous application of the DSMC method on a 3D nano-particle model claimed that the empirical equation for the estimation of the tortuosity factor t = (e 1/3 ) À1 43 could cause aberrations in concentration distribution. 44 However, to our knowledge, few studies apply numerical methods like DSMC to extract the Knudsen tortuosity factor based on 3D reconstructed electrode microstructures obtained from X-ray computed tomography (X-ray CT), which provides a faithful description of the pore structures. The simulated Knudsen tortuosity factor at the pore-scale makes it possible to relate macroscopic transport properties to the underlying pore-scale physical process, which will be a breakthrough benefiting the study of multi-scale gas transport in porous media.…”

Section: Introductionmentioning

confidence: 99%

The application of hierarchical structures in energy devices: new insights into the design of solid oxide fuel cells with enhanced mass transport

Bertei

et al. 2018

Energy Environ. Sci.

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a Mass transport can significantly limit the rate of reaction and lead to concentration polarisation in electrochemical devices, especially under the conditions of high operating current density. In this study we investigate hierarchically structured micro-tubular solid oxide fuel cells (MT-SOFC) fabricated by a phase inversion technique and quantitatively assess the mass transport and electrochemical performance improvement compared to a conventional tubular SOFC. We present pioneering work to characterise the effective mass transport parameters for the hierarchically porous microstructures by an integrated computed fluid dynamics simulation, assisted by multi-length scale 3D X-ray tomography. This has been historically challenging because either imaging resolution or field of view has to be sacrificed to compensate for the wide pore size distribution, which supports different transport mechanisms, especially Knudsen flow. Results show that the incorporation of radially-grown micro-channels helps to decrease the tortuosity factor by approximately 50% compared to the conventional design consisting of a spongelike structure, and the permeability is also improved by two orders of magnitude. When accounting for the influence of Knudsen diffusion, the molecule/wall collisions yield an increase of the tortuosity factor from 11.5 (continuum flow) to 23.4 (Knudsen flow), but the addition of micro-channels helps to reduce it down to 5.3. Electrochemical performance simulations using the measured microstructural and mass transport parameters show good agreement with the experimental results at elevated temperatures. The MT-SOFC anode displays 70% lower concentration overpotential, 60% higher power density (0.98 vs. 0.61 W cm À2 ) and wider current density window for maximum power density than the conventional design. Broader contextHierarchical materials are a popular choice not only for electrochemical energy devices such as fuel cells and batteries, but also for a range of functional materials including catalysts, diffusion media and membranes for waste processing. This study qualitatively and quantitatively illustrates the effectiveness of hierarchically structured pores in reducing gas transport resistance, providing new insights into advanced microstructure optimisation. Moreover, it is a common mistake in the modelling of hierarchical materials to assume the flow to be governed by continuum physics irrespective of the length scale, whereas in the region of finest structure, the molecule/wall collisions become dominant, which cannot be addressed by continuum physics. It is also impossible to define a relevant average pore size to describe the mass transport in these materials due to the wide pore size distribution. The integrated computed fluid dynamics (I-CFD) technique proposed by us for the first time herein, aims to overcome this problem and accurately characterise the effective mass transport in these complex hierarchical structures. The concept and techniques used in this study are believed to be of wide inter...

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Simulation of gas diffusion in highly porous nanostructures by direct simulation Monte Carlo

Cited by 32 publications

References 14 publications

Investigating atomic layer deposition characteristics in multi-outlet viscous flow reactors through reactor scale simulations

Investigating atomic layer deposition characteristics in multi-outlet viscous flow reactors through reactor scale simulations

A study on pressure-driven gas transport in porous media: from nanoscale to microscale

The application of hierarchical structures in energy devices: new insights into the design of solid oxide fuel cells with enhanced mass transport

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