Relative permeability definition

The dimensionless partition coefficient K = cp/cl = Sr, also known as a relative solubility coefficient, is defined as the ratio of the concentration of a substance in the polymer cP to that in the liquid (food) cLat equilibrium. While D is practically independent of the liquid phase in contact with the polymer in these measurements, the K values are determined by the nature of the polymer and liquid contact phases. From the definition Sr = K, a relative peremeability coefficient can be calculated, Pr = Sr D, with the dimension D. Here, accordingly to Eq. (9-2) and the solubility constant in the polymer and in the liquid phases expressed as SP = cP/p and Sl = C Jp, respectively, the following relationship results between the absolute and relative permeability coefficients ... 

Basically, all of these closely related problems occur because gas-flood injection fluids have very small viscosities at the temperatures and pressures at which they are used. For example, the viscosity of CO2 at 13.8 MPa (2,000 psi) and 38°C (100°F) is about 0.066 cp, whereas the viscosities of reservoir oils are at least an order of magnitude greater (16). This produces a ratio of the mobility of the CO2 to the mobility of the oil that is much greater than one. (The mobility of a fluid is defined as its relative permeability divided by its viscosity for the definition of relative permeability, see equations below.)... 

Ransohoff and Radke found that for C <10 lamella generation occurred only by the leave-behind mechanism. The lamellae moderately increased the resistance to flow, raising it by about a factor of five (40). (Here p is the viscosity of the nonwetting phase, U is the total superficial velocity, R is the bead radius, K is the absolute permeability, k is the relative permeability, L is length, and Y is the interSacial tension.) The use of this definition of the capillary number, instead of the usual C = jU/y, with J the viscosity of the wetting phase, was justified in the heoretical analysis ( ). 

B is related to H at any given point by the equation B = p,H where p, is the permeability of the material. Note that later we will use the symbol p, for relative permeability, that is, the ratio of the permeability of the material to that of air. So in MKS units we should actually preferably write B = xcH, where xc is the permeability of the core (magnetic material). By definition, xc = nno. 

Next, determine the viscosity of the chemical slug. For this example, assume the chemical slug is a Newtonian fluid so that variations of viscosity with frontal-advance rate do not have to be considered. That is, the viscosity is a function of composition but does not change with shear rate. The viscosity of the chemical slug is obtained from the definition of mobility. It is first necessary to determine the relative permeability of the chemical slug in the presence of residual oil. The ROS to chemical flooding is 0.2. From... 

The permeability relative to a pure liquid, usually water, may be determined with the help of different devices that operate on the principle of measurement of filtrate volume obtained over a definite time interval at known pressure drop and filtration area. The permeability is usually expressed in terms of the hydraulic resistance of the filter medium. This value is found from ... 

The potential for the preservation of lipids is relatively high since by definition they are hydrophobic and not susceptible to hydrolysis by water, unlike most amino acids and DNA. A wide range of fatty acids, sterols, acylglycerols, and wax esters have been identified in visible surface debris on pottery fragments or as residues absorbed into the permeable ceramic matrix. Isolation of lipids from these matrices is achieved by solvent extraction of powdered samples and analysis is often by the powerful and sensitive technique of combined gas chromatography-mass spectrometry (GC-MS see Section 8.4). This approach has been successfully used for the identification of ancient lipid residues, contributing to the study of artifact... 

The values of for several similar bodies of a gas-permeable oxidatively-heating substance, having each a definite shape and a relatively small value of r, placed each in the atmosphere under isothermal conditions, are determined actually by performing a series of isothermal storage tests, respectively. 

Triton extracts of gastric mucosa contain apparently three materials which can produce channels in lipid bilayers with conductances of 2.5 X 10 ° mho. One material is apparently neutral and cation-selective, another charged, voltage-dependent and anion-selective, whilst the third is non-selective [41]. Material which produces K -selective channels in bilayers has been extracted from excitable tissue [42]. The data obtained so far with these natural channel formers are relatively crude compared with the elegant studies with channel-fdrming antibiotics. Therefore, it is, as yet, unclear whether these materials have definitive roles in biological membrane permeability. 

A competition experiment was carried out to determine whether the presence of added hercynine would decrease the incorporation of histidine-2-C into ergothioneine by N. crassa. No effect could be found. It was possible that this was due to impermeability of the cell wall to hercynine. Since W. Feldman in our laboratory had found that N. crassa in growing cultures is relatively impermeable to ergothioneine, but becomes more permeable when it is starved, the same technique was tried with hercynine. When the competition experiment was carried out with mycelium suspended in water rather than growth medium, a definite effect was observed, with a marked decrease in the uptake of histidine- -Ci in the presence of hercynine (Fig. 5). 

Gas permeability measurements were performed on the blended films as presented in Fig. 33.14. The blend shows a definite increase in permeability for all gases tested, relative to polyimide and the base form of polyaniline [60J. Ordinarily, there is an inverse relationship between permeability of two gases and the separation factor for those gases [61-64]. However, this blend does not hold to this axiom. Figure 33.15 illustrates the separation factors for the blend and the homopolymers. The separation factors for the blend are comparable to those of polyaniline (as-cast) for H2/N2 (a = 200) and O2/N2 (a = 9) and closer to that of polyimide for CO2/CH4 (a = 58). Thus, this blend appears to have achieved an improved combination of properties compared to its parent polymers, with enhanced permeability and good selectivity. 

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