Porous media, flow through

Porous media, flow through, 11 330-332, 766-767 25 290-291 Porous pipes, cross-flow filtration in,... 

Normally, the permeability of a porous medium can be related to other porous medium properties through a model of the porous medium structure. Pragmatically, the complexity of the flow rules out any rigorous analytical attempts to resolve the problem. Ideally, one would like to use heuristic arguments to derive an expression for k or F in terms of universal constants and easily measurable properties of the porous material and the flowing fluid. Such attempts have been made by many researchers in the past. A large collection of these studies has been... 

Polymer adsorption at a liquid/solid interface is a very well-established phenomenon and has an enormous associated literature (Lipatov and Sergeeva, 1974 Parfitt and Rochester, 1983). On the evidence from porous medium flow experiments it appears that mechanical entrapment is also a reasonably well-established mechanism for polymer retention in flow through porous media. Hydrodynamic retention is a rate-dependent effect which is rather less well understood. However, this retention mechanism is not a very large contributor to the overall levels of polymer retention in porous media and, although interesting, is probably not a very important effect in field-scale polymer floods. The important point to note is that it must be understood sufficiently well in laboratory floods so that core flood results can be interpreted correctly concerning polymer adsorption and entrapment retention mechanisms. 

The Structure of a Reservoir Simulator A reservoir simulator is software for solving the porous medium flow equations with detailed models of the spatial distribution of rock properties, detailed models of the thermodynamics of phase behaviour, of the wells and how the wells coimect with each other through surface networks. Further, a reservoir simulator will have built-in support for optimisation software in that derivatives of specified flow diagnostics, such as well rates, or masses of chemical components in specified volumes, with respect to a variety of parameters can be computed. 

In situations where a low concentration of suspended solids needs to be separated from a liquid, then cross-flow filtration can be used. The most common design uses a porous tube. The suspension is passed through the tube at high velocity and is concentrated as the liquid flows through the porous medium. The turbulent flow prevents the formation of a filter cake, and the solids are removed as a more concentrated slurry. 

A simple law, known as Darcy s law (1936), states that the volume flow rate per unit area is proportional to the pressure gradient if applied to the case of viscous flow through a porous medium treated as a bundle of capillaries,... 

When a pure gas flows through a channel the accompanying fall in pressure is accounted for partly by acceleration of the flowing stream and partly by momentum transfer to the stationary walls. Since a porous medium may be regarded as an assembly of channels, similar considerations apply to flow through porous media, but in the diffusional situations of principal interest here accelerational pressure loss can usually be neglected. If more than one molecular species is present, we are also interested in the relative motions of the different species, so momentum transfers by collisions between different types of molecules are also important. 

Though by no means a complete theory, this is at least a reasonable explanation of the Knudsen minimum, and it then remains to explain why the minimum is not observed for flow through porous media. Pollard and Present attributed this to the limited length/diameter ratio of the channels in a typical porous medium and gave a plausible argument in favor of this view. 

The technique just described requires the porous medium to be sealed in a cell, so It cannot be used with pellets of irregular shape or granular material. For such materials an alternative technique Introduced by Eberly [64] is attractive. In Eberly s method the porous pellets or granules are packed into a tube through which the carrier gas flows steadily. A sharp pulse of tracer gas is then injected at the entry to the tube, and Its transit time through the tube and spreading at the exit are observed. A "chromatographic" system of this sort is very attractive to the experimenter,... 

The governing flow equation describing flow through as porous medium is known as Darcy s law, which is a relationship between the volumetric flow rate of a fluid flowing linearly through a porous medium and the energy loss of the fluid in motion. 

From an industrial viewpoint, the objective of the unit operation of filtration is the separation of suspended solid particles from a process fluid stream which is accomplished by passing the suspension through a porous medium that is referred to as a filter medium. In forcing the fluid through the voids of the filter medium, fluid alone flows, but the solid particles are retained on the surface and in the... 

The characteristics of the pump relate the applied pressure on the cake to the flowrate at the exit face of the filter medium. The cake resistance determines the pressure drop. During filtration, liquid flows through the porous filter cake in the direction of decreasing hydraulic pressure gradient. The porosity (e) is at a minimum at the point of contact between the cake and filter plate (i.e., where x = 0) and at a maximum at the cake surface (x = L) where sludge enters. A schematic definition of this system is illustrated in Figure 2. 

B. Polymer chain in a flow through a porous medium... 

B. Polymer Chain in a Flow through a Porous Medium... 

V. Yamakov, A. Milchev. Polymer chain in a flow through a porous medium A Monte Carlo simulation. Phys Rev E 5(5 7043-7052, 1997. 

Ideally, cross-flow microfiltration would be the pressure-driven removal of the process liquid through a porous medium without the deposition of particulate material. The flux decrease occurring during cross-flow microfiltration shows that this is not the case. If the... 

In chemical micro process technology with porous catalyst layers attached to the channel walls, convection through the porous medium can often be neglected. When the reactor geometry allows the flow to bypass the porous medium it will follow the path of smaller hydrodynamic resistance and will not penetrate the pore space. Thus, in micro reactors with channels coated with a catalyst medium, the flow velocity inside the medium is usually zero and heat and mass transfer occur by diffusion alone. 

The flowing sensor medium as an integral part of remote detection naturally leads to the study of flow through porous media [40, 41]. In addition to carrying the... 

Permeability (k) is the transport coefficient for the flow of fluids through a porous medium and has the units of length squared. NMR measures the porosity and the... 

Experiment B is also a non-adsorption experiment in which flow through the capillary tube is used. The sample medium used is the surfactant solution prepared in the 1% acidified brine. Results will be combined with those from Experiment C to get the information on the permanent or irreversible adsorption on the porous medium by measuring peak areas. 

Because the fluid in a porous medium follows a tortuous path through channels of varying size and shape, one method of describing the flow... 

The permeability of a porous medium (K) is defined as the proportionality constant that relates the flow rate through the medium to the pressure drop, the cross-sectional area, the fluid viscosity, and net flow length through the medium ... 

Consider the flow of an incompressible fluid through a two-dimensional porous medium, as illustrated in Fig. 13-2. Assuming that the kinetic energy change is negligible and that the flow is laminar as characterized by Darcy s law, the Bernoulli equation becomes... 

Laminar flow through a porous medium is described by Darcy s laws... 

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