Applications in Porous Media

The flow through porous media of emulsions, foams and suspensions can be important in a number of applications ranging from fixed-bed catalytic reactors in the chemical process industries, to flows through soils environments, to flows in underground reservoirs. To understand the flow of dispersions in porous media, one needs a knowledge of the properties of not only the dispersion but also the porous medium. Pore characterization itself has been reviewed elsewhere [109, 110]. 

The ease with which any fluid can flow through a porous medium, the fluid conductivity, is measured as the permeability, k, of the porous medium, which is defined by Darcy s law as 

the relative permeability is the fraction by which the fluid conductivity of the porous medium has to be modified to account for the presence of the other fluid. For a given fluid, k increases with concentration, but is always less than or equal to 1. Since the porous medium will usually have a wetting preference for one fluid over others, there will be a distribution of fluids among the different sizes of pores. Some of the factors that can influence the relative permeability of a particular fluid include the following [111-114]  

The permeabilities themselves vary widely among natural materials, some approximate values being 

The flow of emulsions, foams and suspensions in porous media is more complex because of the nature of the particular dispersion itself. If the droplets, bubbles or particles are very small compared with the size of the flow channels, then the 

The flow of emulsions, foams, and suspensions in porous media is more complex due to the nature of the particular dispersion itself. If the droplets, bubbles, or particles are very small compared with the size of the flow channels, then the nature of the dispersed phases can be largely ignored, at least for as long as the dispersion is stable. In most practical cases, however, the sizes of the dispersed species are not much smaller than the pore sizes, if at all, and the the dispersions cannot, then, be treated as pseudo-single-phase. Much more detail is available elsewhere for the flow through porous media of simple fluids [133,420], emulsions [108,227,421], foams [422,423], and suspensions [419,424,425], See also Sections 11.2.2 and 15.3. 

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