Viscosity estimation methods

Multicomponent Mixtures No simple, practical estimation methods have been developed for predicting multicomponent hquid-diffusion coefficients. Several theories have been developed, but the necessity for extensive activity data, pure component and mixture volumes, mixture viscosity data, and tracer and binaiy diffusion coefficients have significantly limited the utihty of the theories (see Reid et al.). 

Key material properties for SOFC, such as the ionic conductivity as a function of temperature, are available in refs 36—39. In addition, Todd and Young ° compiled extensive data and presented estimation methods for the calculation of diffusion coefficients, thermal conductivities, and viscosities for both pure components and mixtures of a wide variety of gases commonly encountered in SOFCs. Another excellent source of transport properties for gases and mixtures involved in a SOFC is the CHEMKIN thermodynamic database. ... 

The book by Reid et al. [9] is an excellent source of information on properties such as thermal conductivities, diffusion coefficients and viscosities of gases and liquids. Not only are there extensive tables of data, but many estimation methods and correlations are critically reviewed. 

In order to calculate the numerical values of transfer coefficients, values of the molecular properties are required. In the next section, we present estimation methods for viscosity, diffusivity, thermal conductivity and surface tension, for the high-pressure gas. 

For a gas, the effect of pressure on the viscosity depends on the region of P and T of interest relative to the critical point. Near the critical state, the change in viscosity with T at constant pressure can be very large. The correlation of Uyehara and Watson [15] is presented for the reduced viscosity estimated from the corresponding-states method. The critical viscosities of a few gases and liquids are available [15]. These are necessary to calculate the... 

There is a wide-spread literature on methods for temperature-dependent viscosity estimation. Their discussion and further references can be found elsewhere [1,2,17,18,19,20,21], Usually, these methods are based on various input data, such as density, boiling point, and critical point. Dynamic viscosities of most gases increase with increasing temperature. Dynamic viscosities of most liquids, including water, decrease rapidly with increasing temperature [18]. 

The strain-rate estimates suggest that the microstructures were formed by flow in the mantle related to large-scale tectonic processes. In the case of the Voltri peridotites, Drury et al. (1990) have related this deformation to extension and rifting of a continental lithospheric plate. The high-temperature deformation occurred under asthenospheric conditions, whereas the low-temperature deformation occurred within the lithosphere. The estimates of upper mantle viscosity obtained from the study of microstructures are lower than those for average viscosity obtained independently from other methods, such as analysis of glacial rebound of land surfaces (Nakada and Lambeck 1987), which are also based on a number of assumptions. All the samples studied are derived from the uppermost part of the mantle, so the viscosity estimates obtained from the microstructural study are consistent with the presence of a low viscosity zone between the... 

Gardas RL, Coutinho JAP (2008) A group contribution method for viscosity estimation of ionic liquids. Fluid Phase Equilib 266 195-201... 

Most of the theoretically based estimation methods for viscosity of dense gases rely on modified Enskog theory. Corresponding states based methods are also popular but should be used with care due to their empiric nature. 

As a rule of thumb, the author estimates an accuracy of 10%. For the quantum gases helium and hydrogen, a modified equation is given in [76]. Figure 3.23 gives an example of the performance of Eq. (3.127). The pressure dependence of the dynamic viscosity of gaseous n-pentane is quite significant for the 498.15 K isotherm due to its vicinity to the critical temperature. The estimation method of Lucas [76] works remarkably well. 

An additional role in my professional life is a Honorar) Professor position in Durban, South Africa. Currently, my group there consists of 4 MSc students, all highly motivated. We developed and published estimation methods for a number of important properties like vapor pressure, liquid viscosity, water and alkane solubility, etc. The first of our methods on normal boiling point estimation is already generally regarded as the primary and best method available. 

The Petersen et al. model also allows extrapolations to high pressures and to mixtures as will be discussed later, but it is of limited accuracy for hydrocarbons heavier than C,o and for cyclic compounds. For example, AAD in viscosity estimates for hydrocarbons up to C 2 is about 10%, whereas it increases to 39% for C g and to 47% for cyclohexane. Thus, none of the available corresponding states methods are better than the simpler Andrade-type equations of the previous section. 

The one-fluid approach can be used with some of the models presented earlier. In the method of Mehrotra [II], the one-fluid model can be used to obtain the needed normal boiling temperature, T, from = [ZxjT y ], if the mixture is well defined. This proposal has not been tested in that method. However, Orbey and Sandler [ 13] found this boiling-point estimation method to be suitable for use in their viscosity model as discussed later. 

Grain, C.F., Liquid Viscosity, in Handbook of Chemical Property Estimation Methods, McGraw-Hill, New York, 1982. 

Several estimation methods have been published since 1987. A method to estimate liquid viscosities over a temperature range from the freezing point up to reduced tenq>er-atures of 0.95 has been presented by Sastri and Rao (1992). It is based on the supposition that the liquid viscosity is related to the vapor pressure, / > by... 

HeXe gas mixture thermal conductivity estimates are not as consistent as the mixture viscosity estimates and do not compare as well to empirical data. TTie Wassiljewa formnlation and the method of Chnng were veiy inaccurate. The Chapman (DIPPR) method stayed within 5.7% of INL provided empirical data, while the Mason (DIPPR) method was less accurate. 

Van Velzen s method provides an estimation of hydrocarbon viscosities and their variation with temperature ... 

At atmospheric pressure, hydrocarbon viscosities can be estimated by two methods the ASTM method and that of Mehrotra (1990). 

The viscosity of a liquid increases with pressure. This behavior is relatively small for liquids of high molecular weight and low compressibility the effect can be estimated by Kouzel s method (1965) ... 

The traditional, essentially phenomenological modeling of boundary lubrication should retain its value. It seems clear, however, that newer results such as those discussed here will lead to spectacular modification of explanations at the molecular level. Note, incidentally, that the tenor of recent results was anticipated in much earlier work using the blow-off method for estimating the viscosity of thin films [68]. 

Solution Polymers. Methacryhc solution polymers are usually characterized by thek composition, soHds content, viscosity, molecular weight, glass-transition temperature, and solvent type. The compositions of methacryhc polymers are most readily determined by physicochemical methods such as spectroscopy, pyrolytic gas—Hquid chromatography, and refractive index measurements. The soHds content is determined by dilution followed by solvent evaporation to constant weight. Solution viscosities are most conveniendy determined with a Brookfield viscometer. Methods for estimating molecular weights by intrinsic viscosity are available (103). 

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

The electrokinetic effect is one of the few experimental methods for estimating double-layer potentials. If two electrodes are placed in a coUoidal suspension, and a voltage is impressed across them, the particles move toward the electrode of opposite charge. For nonconducting soHd spherical particles, the equation controlling this motion is presented below, where u = velocity of particles Tf = viscosity of medium V = applied field, F/cm ... 

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