Reference permeability

After experimental work, the value of the activation energy (EA) and the reference permeability (Qref) for a PVA-based (from GKSS) pervaporation membrane and mixture in use have been obtained (see tablel), and the model for the pervaporation process with and without heat integration has been successfully validated. The absolute error between the model and the experimental permeate fluxes is under 8% (see fig.4), and almost insignificant for the water purity in the permeate side (under 0.5%) obtaining a permeate stream with up to 99.9% in water. 

The reference permeability (k f) is the permeability at which the input adsorption parameters are specified. Eqs. 5.31 and 5.32 take into account the salinity, polymer concentration, and permeability. 

Figures 9 and 10 suggested that the continuum analyses modeled reasonably the trending of permeability responses to the heating process although there were obvious discrepancies between the estimated and the measured trends. One discrepancy was the variations in permeability estimated at the location of Pressure Sensor 1 (PSl) in Holes 57 and 59. The measured data at this location indicated a permeability reduction (smaller than the reference permeability) trend for the...

In the TH code the governing equations are split according to components, rather than phases. This choice was made in regard to phase changes. Hence, the general mass balance equation results in the component equation for air, and the component equation for water, which are our components in the TH model. Each component equation contains terms for both, the liquid and the gas phase. Equation (3) shows the governing equation for air or water, (k = a, w), where X [-] is the mass fraction, P [Pa] is pressure, k i [-] is the relative permeability, k [m j is the reference permeability, ft [Pas] is viscosity, [Pa] is capillary pressure, g... 

The pores between the rock components, e.g. the sand grains in a sandstone reservoir, will initially be filled with the pore water. The migrating hydrocarbons will displace the water and thus gradually fill the reservoir. For a reservoir to be effective, the pores need to be in communication to allow migration, and also need to allow flow towards the borehole once a well is drilled into the structure. The pore space is referred to as porosity in oil field terms. Permeability measures the ability of a rock to allow fluid flow through its pore system. A reservoir rock which has some porosity but too low a permeability to allow fluid flow is termed tight . 

Cross-linked versions of water-soluble polymers swollen in aqueous media are broadly referred to as hydrogels (52) and have a growing commercial utility in such apphcations as oxygen-permeable soft contact lenses (qv) (53) (Table 4) and controUed-release pharmaceutical dmg deflvery devices (54). Cross-linked PVP and selected copolymers fit this definition and are of interest because of the following stmcture/performance characteristics ... 

Permeability ( l), which is often used, albeit imprecisely, in referring to ferromagnetic substances, is the ratio of the magnetic-flux density to the magnetic-field density. 

Next refer to the normal magnetization eurves and seleet a value of H (magnetizing foree, oersteds (Oe)) that is below the point on the eurves where the permeability starts to drop due to the saturation of the eore material. From the ehart in figure 3-22 a value of 20 Oe is a good value. Choosing a permeability of 60 yields a reasonably low value of flux density. 

Reference to Figure 3-21 yields the part number 55310-A2 with a permeability of 125. This core has an AL of 90mH/l,000T. 

A microscopic description characterizes the structure of the pores. The objective of a pore-structure analysis is to provide a description that relates to the macroscopic or bulk flow properties. The major bulk properties that need to be correlated with pore description or characterization are the four basic parameters porosity, permeability, tortuosity and connectivity. In studying different samples of the same medium, it becomes apparent that the number of pore sizes, shapes, orientations and interconnections are enormous. Due to this complexity, pore-structure description is most often a statistical distribution of apparent pore sizes. This distribution is apparent because to convert measurements to pore sizes one must resort to models that provide average or model pore sizes. A common approach to defining a characteristic pore size distribution is to model the porous medium as a bundle of straight cylindrical or rectangular capillaries (refer to Figure 2). The diameters of the model capillaries are defined on the basis of a convenient distribution function. 

Shapes of inside objects which are only partly permeable to airflow (sometimes referred to as porous objects), such as inlet grills, vents, etc. 

Permeability is defined as a measure of a rock s ability to transmit fluids. In addition to a rock s being porous, sedimentary rock can also be permeable. Permeability refers to the property of a rock that allows fluids to flow through its pore network at practical rates under reasonable pressure differentials. The quantitative definition of permeability was first given in an empirical relationship developed by the French hydrologist Henry D Arcy who studied the flow of water through unconsolidated sands [31]. 

Deposits of sand, dirt or permeable corrosion products on the metal surface (a type of crevice corrosion that is referred to as deposit attack). 

Although the 3 - and 5 -polyphosphate derivatives mentioned above exhibit exquisite inhibitory potency these compounds are not cell permeable. To take advantage ofthepotency of such derivatives for studies with intact cells and tissues, there are two possibilities. One is chemically to protect the phosphate groups from exonucleotidases that also allows the compound to transit the membrane intact. The other is to provide a precursor molecule that is cell permeable and is then metabolized into an inhibitor by intracellular enzymes. The general term for such a compound is prodrug nucleotide precursors are also referred to as pronucleotides. Families of protected monophosphate derivatives were synthesized, based on (3-L- and 3-D-2, 5 -dd-3 -AMP, 3-L-2, 3 -dd-5 -AMP, and the acyclic 9-substituted adenines, PMEA and PMPA. Protective substituents were (i) -( -pivaloyl-2-thioethyl) ... 

FIGURE 6-15 Schematic representation of the ion permeability modulation for cation-responsive voltammetric sensors based on negatively charged lipid membranes. Complexation of the guest cation to the phospholipid receptors causes an increase of the permeability for the anionic marker ion. (Reproduced with permission from reference 49.)... 

Fluorinated poly(arylene edier)s are of special interest because of their low surface energy, remarkably low water absorption, and low dielectric constants. The bulk—CF3 group also serves to increase the free volume of the polymer, thereby improving various properties of polymers, including gas permeabilities and electrical insulating properties. The 6F group in the polymer backbone enhances polymer solubility (commonly referred to as the fluorine effect ) without forfeiture of die thermal stability. It also increases die glass transition temperature with concomitant decrease of crystallinity. 

The term chlor-alkali refers to those products obtained from the commercial electrolysis of aqueous sodium chloride. These are chlorine, sodium hydroxide, and sodium carbonate. The first two are produced simultaneously during the electrolysis while the latter is included because it is also produced in small quantities and shares many of the end uses of sodium hydroxide. Perfluorinated ionomer membranes are permeable to sodium ions but not the chloride ions, and hence they are useful for these electrolytic cells. The arrangement of a typical membrane cell is shown in Figure 10.2. 

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