Abstract
An experimental study focused on the identification of the flow regimes and quantification of the velocity field at pore scale in microporous media is presented and discussed. Transparent porous media are fabricated by removing a pore forming agent in slightly sintered glass beads of size 50 μ m between two glass slides, leaving typical pores with a size of 500 μ m . Pressure-drop measurements and particle image velocimetry measurements are conducted simultaneously in order to evaluate the flow regimes and flow behaviors at pore size based Reynolds numbers from 0.1 to 140. Four different regimes, pre-Darcy, Darcy, Forchheimer, and turbulent, are found and presented. Spatial distribution and characteristics of the time-averaged velocity in all regimes and fluctuation intensity in transitional and turbulent regimes are investigated. Critical Reynolds numbers are identified using both velocity and pressure-drop measurements and the results agree very well, providing direct evidence underpinning the transition. The effects of porosity on these flow properties are also studied, and finally the flow regime boundaries are compared with the literature. These data provide an insight into the flow properties in microporous media with various porosities and an improved understanding that could be further utilized to enhance the flow and heat transfer performance of microporous media. It also demonstrates that velocity and pressure measurements used in combination can be an effective method for studying microporous media.
Highlights
The transport of fluids through porous media is common in many engineering fields, such as solute diffusion in catalytic reactors in chemical engineering, oil flow in reservoirs in petroleum production, groundwater flow and migration of hazardous wastes in soil in subsurface hydrology, fluid movement in body tissue and blood flow through capillaries in biomedical research, and natural and forced convection in heat exchangers for equipment cooling
The understanding of fluid behavior in porous media, especially in microporous media, is very limited due to the restriction of techniques
Some studies have been conducted in the past, the porous media used in most previous studies are limited to packed beds and granular porous media with porosities in the range 0.3–0.5 [1,2], or a typical metal foam consisting of interconnected dodecahedral-like cells with porosity higher than 0.8 [3,4,5]
Summary
The transport of fluids through porous media is common in many engineering fields, such as solute diffusion in catalytic reactors in chemical engineering, oil flow in reservoirs in petroleum production, groundwater flow and migration of hazardous wastes in soil in subsurface hydrology, fluid movement in body tissue and blood flow through capillaries in biomedical research, and natural and forced convection in heat exchangers for equipment cooling. Studies [1,2,3,5,12] tried to find out the universal flow regime boundaries in a porous medium by a traditional method such as pressure-drop measurements. Sen et al [23] packed microglass spheres of size 200 μm inside a glass micromodel, with a typical pore size of 10–50 μm They studied velocity fields at different spatial locations having different pore structure and found that the statistical distribution of the velocity field agreed well with the available numerical and experimental results pertaining to macroporous media. The porous medium is fabricated by removing the pore forming agent in a matrix of packed glass spheres after slight sintering, leaving the same size pores in packed beds This method breaks the porosity limitations of packed beds and traditional typical metal foams. The flow regime boundaries obtained from pressure gradient measurements are compared with that obtained from μ-PIV measurement
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