Gas flow in a permeable medium

Socio, L. M. de; Marino, Luca

doi:10.1017/s0022112006009621

Cited by 23 publications

(16 citation statements)

References 20 publications

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“…Using the same pressures for all cases ensures that the permeabilities are being measured at the same Knudsen numbers; this is required for a fair comparison as, unlike permeability to a liquid, it has been shown [13,15] that the permeability to a gas is a function of rarefaction. The simulations were run on the ARCHIE-WeSt supercomputer facility 3 at the University of Strathclyde.…”

Section: Porosities Numerical Meshing and Simulation Parametersmentioning

confidence: 99%

“…de Socio and Marino [13] created an experimental set up consisting of glass spheres arranged randomly in a stainless steel cylinder, with a mean final porosity of 0.33. Their experimen-tal sample was then subjected to a pressure differential with a nitrogen-fed flow-meter upstream and a vacuum pump downstream; the flow rate could be controlled manually.…”

Section: Introductionmentioning

confidence: 99%

“…there is a distinct minimum in permeability against gas rarefaction, with it being greater both below and above this critical Knudsen number. The DSMC method presented in the paper of de Socio and Marino [13] features a modified collision routine to emulate particles striking the surface of the packed spheres (the actual porosity is not physically modelled) and is only valid for a tortuosity that is characteristic of their experiment.…”

Section: Introductionmentioning

confidence: 99%

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Permeability of Ablative Materials Under Rarefied Gas Conditions

White

Scanlon²,

Brown³

2016

Journal of Spacecraft and Rockets

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Numerical meshes of both cork and carbon fibre ablative materials in their virgin and pyrolised states, with realistic porosity and tortuosity, have been created from micro-computed tomography (µCT) scans. The porosity of each material has been calculated from the µCT scans and used to extract smaller representative sample volumes to perform numerical simulations on.Direct simulation Monte Carlo simulations of rarefied gas flow through these materials have been performed to find the permeability of each material to argon gas and to a gas mixture. The method has been validated by comparing the measured permeability for a Berea sandstone material to previously published experimental values. For the specific pressure conditions investigated here, the cork-phenolic material becomes around ten mores permeable after being pyrolised, while the carbon-phenolic material only becomes five times more permeable than its virgin form. The permeability to the gas mix- * Corresponding author Email addresses: craig.white.2@glasgow.ac.uk (Craig White), tom.scanlon@strath.ac.uk (Thomas J. Scanlon), richard.brown@strath.ac.uk (Richard E. Brown) Preprint submitted to Journal of Spacecraft and RocketsJuly 24, 2015 ture is found to be greater than to argon for most of the samples, showing the importance of choosing the correct gas for rarefied permeability studies.The form of the pressure and Mach number profiles through the materials is indepedent of the applied pressure gradient.Keywords: permeability, rarefied gas, ablation, re-entry, CT scan, DSMC

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Section: Porosities Numerical Meshing and Simulation Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Permeability of Ablative Materials Under Rarefied Gas Conditions

White

Scanlon²,

Brown³

2016

Journal of Spacecraft and Rockets

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“…37 The method has been well validated by comparing the numerical simulation either with the experimental permeability 38 or the established analytical solution. 39 DSMC has been widely applied to the permeability study for Knudsen gas flows in various structures such as fibrous materials, 39,40 channels filled with packed spheres 41,42 and ablative materials. 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.…”

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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“…Bear 1972;Wu et al 2001), relies on the molecular kinetics of fluids (De Socio and Marino 2006) and finds application in silicon-based micro-fluidic devices which consists of rectangular ducts on the micro-scale (Barber and Emerson 2002). Many experiments have been performed (Tanikawa and Shimamoto 2006;Wu et al 1998), numerical simulation techniques developed (De Socio and Marino 2006) and analytical solutions proposed (Carman 1950;Skjetne and Auriault 1999;Chastanet et al 2004;Wu et al 1998) to verify the Klinkenberg effect. Numerous experimental measurements for determining the permeability of sandstones have been performed on Fontainebleau sandstone (e.g.…”

Section: Introductionmentioning

confidence: 99%

Predicting the Permeability of Very Low Porosity Sandstones

Woudberg

Plessis

2007

Transp Porous Med

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The permeability predictions of two geometric pore-scale models, one being predominantly granular and the other consolidated with tube-like pores, are compared with experimental results for Fontainebleau sandstones and the results interpreted. Percolation thresholds are determined from experimental data and applied in the modelling exercise by means of cut-off asymptotes on porosity. It is found that, although both granular and foamlike models yield plausible results, the granular model appears to be superior, at least for the sets of data considered. The Klinkenberg correction is analytically derived and incorporated into the models to relate gas and liquid permeabilities and an analytical expression for the Klinkenberg factor is proposed for each model. The permeability predictions are promising and yield an effective manner to correlate sandstone percolation data.

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Gas flow in a permeable medium

Cited by 23 publications

References 20 publications

Permeability of Ablative Materials Under Rarefied Gas Conditions

Permeability of Ablative Materials Under Rarefied Gas Conditions

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

Predicting the Permeability of Very Low Porosity Sandstones

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