Properties, estimation transport

Experimentally determined effective transport properties of porous bodies, e.g., effective diffusivity and permeability, can be compared with the respective effective transport properties of reconstructed porous media. Such a comparison was found to be satisfactory in the case of sandstones or other materials with relatively narrow pore size distribution (Bekri et al., 1995 Liang et al., 2000b Yeong and Torquato, 1998b). Critical verification studies of effective transport properties estimated by the concept of reconstructed porous media for porous catalysts with a broad pore size distribution and similar materials are scarce (Mourzenko et al., 2001). Let us employ the sample of the porous... 

The parameters of a model can be estimated by fitting the model to experimental data [182,183]. Using the model of Section 4.7.3, two regression analysis procedures can be applied [43] transport properties estimation and transport properties equations estimation. 

It should be noted that the estimation of low-pressure gas viscosities is particularly important to the topic of transport property estimation because the low-pressure gas viscosity is often used in correlations for the other transport properties. Reichenberg s... 

The empirical data used as points of comparison for HeXe mixed gas transport property estimates were obtained by a literature search performed by Idaho National Laboratory (INL). Only a hmited amount of empirical mixture data has been found, especially for HeXe thermal conductivity. 

If these assumptions are satisfied then the ideas developed earlier about the mean free path can be used to provide qualitative but useful estimates of the transport properties of a dilute gas. While many varied and complicated processes can take place in fluid systems, such as turbulent flow, pattern fonnation, and so on, the principles on which these flows are analysed are remarkably simple. The description of both simple and complicated flows m fluids is based on five hydrodynamic equations, die Navier-Stokes equations. These equations, in trim, are based upon the mechanical laws of conservation of particles, momentum and energy in a fluid, together with a set of phenomenological equations, such as Fourier s law of themial conduction and Newton s law of fluid friction. When these phenomenological laws are used in combination with the conservation equations, one obtains the Navier-Stokes equations. Our goal here is to derive the phenomenological laws from elementary mean free path considerations, and to obtain estimates of the associated transport coefficients. Flere we will consider themial conduction and viscous flow as examples. 

In order to discuss electron transport properties we need to know about the electronic distribution. This means that, for the case of metals and semimetals, we must have a model for the Fermi surface and for the phonon spectrum. The electronic structure is discussed in Chap. 5. We also need to estimate or determine some characteristic lengths. 

Klopman, G., Zhu, H. Recent methodologies for the estimation of tt-odanol/water partition coeffidents and their use in the prediction of membrane transport properties of drugs. Minirev. Med. Chem. 2005, 5, 127-133. 

Transport Properties Although the densities of SCFs can approach those of conventional liquids, transport properties are more favorable because viscosities remain lower and diffusion coefficients remain higher. Furthermore, CO2 diffuses through condensed-liquid phases (e.g., adsorbents and polymers) faster than do typical solvents which have larger molecular sizes. For example, at 35°C the estimated pyrene diffusion coefficient in polymethylmethacrylate increases by 4 orders of magnitude when the CO2 content is increased from 8 to 17 wt % with pressure [Cao, Johnston, and Webber, Macromolecules, 38(4), 1335-1340 (2005)]. 

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. ... 

Little is known about the mass transport properties of reinforced-composite materials. Certainly, there are no new relations or concepts that govern estimations of diffusiv-ities that have not already been discussed. In most polymer-matrix composites, the transport properties of the polymer play an important role in diffusion through the composite. For example, hydrophilic polymers such as epoxy readily absorb water from the atmosphere. Thermoplastic polymers absorb relatively little moisture since they are more hydrophobic, but are more susceptible to uptake of organic solvents. 

This is in good agreement with the literature value of 355.41K (Daubert and Danner, 1992). There are nnmerous techniques which provide good accuracy for thermodynamic and transport properties. Techniques for estimating environmental properties and health effects have lower accuracy. 

Of a special astronomical interest is the absorption due to pairs of H2 molecules which is an important opacity source in the atmospheres of various types of cool stars, such as late stars, low-mass stars, brown dwarfs, certain white dwarfs, population III stars, etc., and in the atmospheres of the outer planets. In short absorption of infrared or visible radiation by molecular complexes is important in dense, essentially neutral atmospheres composed of non-polar gases such as hydrogen. For a treatment of such atmospheres, the absorption of pairs like H-He, H2-He, H2-H2, etc., must be known. Furthermore, it has been pointed out that for technical applications, for example in gas-core nuclear rockets, a knowledge of induced spectra is required for estimates of heat transfer [307, 308]. The transport properties of gases at high temperatures depend on collisional induction. Collision-induced absorption may be an important loss mechanism in gas lasers. Non-linear interactions of a supermolecular nature become important at high laser powers, especially at high gas densities. 

A means to find or estimate required constitutive properties that appear in the conservation equations. These can include equations of state, thermodynamic and transport properties, and chemical reaction rates. 

To apply kinetic theory for the quantitative evaluation of transport properties of low-density gases, one clearly needs the interaction parameters a and e/k. For common substances, these data are readily found in physical-chemistry references. Another good source is the NASA report by Svehla [389], which also provides estimation techniques. For example,... 

The Lennard-Jones interaction is often used as the intermolecular potential function to estimate transport properties. The form of the Lennard-Jones interaction between molecules i and j as a function of distance is... 

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