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Research Papers

Structure Effects on Electro-Osmosis in Microporous Media

[+] Author and Article Information
Moran Wang1

School of Aerospace,Tsinghua University, Beijing 100084, China;  Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545moralwang@gmail.com

1

Corresponding author.

J. Heat Transfer 134(5), 051020 (Apr 13, 2012) (6 pages) doi:10.1115/1.4005711 History: Received July 30, 2010; Revised July 02, 2011; Published April 11, 2012; Online April 13, 2012

The structure effects on electro-osmosis in microporous media have been studied by modeling the multiphysical transport using our numerical framework. The three-dimensional microstructures of porous media are reproduced by a random generation-growth method, and then the nonlinear governing equations for the electrokinetic transport are solved by a highly efficient lattice Poisson–Boltzmann method. The simulation results indicate that the porous structure type (granular, fibrous, or network) influences the electro-osmotic permeability significantly. At the low porosity regime (<0.4), the network structure exhibits the highest electro-osmotic permeability because of its highest surface–volume ratio among the three types of structure at the same porosity. When the porosity is high (>0.5), the granular structure leads to the highest electro-osmotic permeability due to its lower shape resistance characteristics. The present modeling results improve our understanding of hydrodynamic and electrokinetic transport in geophysical systems, and help guide the design of porous electrodes in micro-energy systems.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Microstructure generation strategy

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Figure 2

The lattice direction system (α) for the three-dimensional 19-speed (D3Q19) model

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Figure 3

The electro-osmotic permeability as functions of porosity at different porosity ranges (a) for the low porosity regime (0, 0.38) and (b) for the high porosity regime (0.5, 0.9)

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Figure 4

Velocity fields for three types of structures for different porosities. The porosity of structures for a1, b1, and c1 is 0.1 and that for a2, b2, and c2 equals 0.73. The vectors denote the three-dimensional velocity field. The contours shows the values of velocity in x-direction at mid-plane (y = 0.5). The scales for vector and contour are same for the three structures, respectively. For the contour maps, the solid parts are blocked for clear show.

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