Thermodynamics and mass transport

Wen CJ, Boukamp BA, Huggins RA, Weppner W. Thermodynamic and mass transport properties of LiAl. J Electrochem Soc 1979 126 2258-2266. 

Whereas for reversible reactions only thermodynamic and mass-transport parameters can be determined, for quasi-reversible and irreversible reactions both kinetic and thermodynamic parameters can be measured. It should also be noted that the electrode material can affect the kinetics of electrode processes. 

The mechanism whereby drugs are absorbed from the GI tract is complex. Understanding the intestinal transport mechanism is crucial to the prediction of oral drug absorption. The physical model utilizes the basic principles of thermodynamics and mass transport. The physical model for the simultaneous passive and active membrane transport of drugs in the intestinal lumen is depicted in Fig. 7. The bulk aqueous solution with an aqueous boundary layer on the mucosal side is followed by a series of heterogeneous membranes consisting of parallel lipoidal and aqueous channel pathways for passive and active transport. Thereafter, a sink on the serosal side follows. 

The present model assumes that ingredients diffuse and evaporate independently, whereas thermodynamic and mass transport considerations dictate that interactions must occur in concentrated mixtures (Cussler, 1997). Careful analysis of the evaporation rates in Vuilleumier etal. (1995) shows this to be the case The musk ingredient, compound XII in Table 10.2, depressed the initial evaporation rates of... 

ALEX M. JAMIESON received his D. Phil, at the University of Oxford, England, and is currently professsor of macromolecular science at Case Western Reserve University, Cleveland, Ohio. His research interests are thermodynamic and mass transport of polymer fluids, quasielastic laser light scattering and structure-function relationships of biological polymers. 

The kinetic analysis of a complicated electrochemical process involves two crucial steps the validation of the proposed mechanism and the extraction of the kinetic parameter values from experimental data. In cyclic voltammetry, the variable factor, which determines the mass transfer rate, is the potential sweep rate v. Therefore, the kinetic analysis relies on investigation of the dependences of some characteristic features of experimental voltammograms (e.g., peak potentials and currents) on v. Because of the large number of factors affecting the overall process rate (concentrations, diffusion coefficients, rate constants, etc.), such an analysis may be overwhelming unless those factors are combined to form a few dimensionless kinetic parameters. The set of such parameters is specific for every mechanism. Also, the expression of the potential and current as normalized (dimensionless) quantities allows one to generalize the theory in the form of dimensionless working curves valid for different values of kinetic, thermodynamic, and mass transport parameters. 

This work offers a contribution to the understanding of some fundamental aspects of sorption and diffusion in glassy polymers. The research focuses on an extensive experimental study of sorption and mass transport in a specific polymeric matrix. A high free volume polymer, (poly l-trimethylsilyl-l-propyne) [PTMSP], has been used here in order to emphasise aspects of sorption and transport which are peculiar to polymer/penetrant mixtures below the glass transition temperature. The discussion of the experimental data presented in this work permits a clarification of concepts which are of general validity for the interpretation of thermodynamic and mass transport properties in glassy systems. 

The experimental results are briefly discussed in terms of thermodynamic and mass transport properties in the glassy polymer mixture. The aim of the discussion is to highlight peculiarities of solubility and difiusivity in polymeric systems below the glass transition temperature and to consider possible interpretations. The focus is on the effect of swelling on the thermodynamic and transport properties in glasses. Indeed, it is well known that, contrary to the case of rubbery systems, the solute partial specific... 

The scientific basis of extractive metallurgy is inorganic physical chemistry, mainly chemical thermodynamics and kinetics (see Thermodynamic properties). Metallurgical engineering reties on basic chemical engineering science, material and energy balances, and heat and mass transport. Metallurgical systems, however, are often complex. Scale-up from the bench to the commercial plant is more difficult than for other chemical processes. 

Estimation of parameters. Model parameters in the selected model are then estimated. If available, some model parameters (e.g. thermodynamic properties, heat- and mass-transfer coefficient, etc.) are taken from literature. This is usually not possible for kinetic parameters. These should be estimated based on data obtained from laboratory expieriments, if possible carried out isothermal ly and not falsified by heat- and mass-transport phenomena. The methods for parameter estimation, also the kinetic parameters in complex organic systems, and for discrimination between models are discussed in more detail in Section 5.4.4. More information on parameter estimation the reader will find in review papers by Kittrell (1970), or Froment and Hosten (1981) or in the book by Froment and Bischoff (1990). 

Like CVD units, plasma etching and deposition systems are simply chemical reactors. Therefore, flow rates and flow patterns of reactant vapors, along with substrate or film temperature, must be precisely controlled to achieve uniform etching and deposition. The prediction of etch and deposition rates and uniformity require a detailed understanding of thermodynamics, kinetics, fluid flow, and mass-transport phenomena for the appropriate reactions and reactor designs. 

The phenomenological coefficients are important in defining the coupled phenomena. For example, the coupled processes of heat and mass transport give rise to the Soret effect (which is the mass diffusion due to heat transfer), and the Dufour effect (which is the heat transport due to mass diffusion). We can identify the cross coefficients of the coupling between the mass diffusion (vectorial process) and chemical reaction (scalar process) in an anisotropic membrane wall. Therefore, the linear nonequilibrium thermodynamics theory provides a unifying approach to examining various processes usually studied under separate disciplines. 

The optimal Reynolds number defines the operating conditions at which the cylindrical system performs a required heat and mass transport, and generates the minimum entropy. These expressions offer a thermodynamically optimum design. Some expressions for the entropy production in a multicomponent fluid take into account the coupling effects between heat and mass transfers. The resulting diffusion fluxes obey generalized Stefan-Maxwell relations including the effects of ordinary, forced, pressure, and thermal diffusion. 

At this time, only a small number of nanoscale processes are characterized with transport phenomena equations. Therefore, if, for example, a chemical reaction takes place in a nanoscale process, we cannot couple the elementary chemical reaction act with the classical transport phenomena equations. However, researchers have found the keys to attaching the molecular process modelling to the chemical engineering requirements. For example in the liquid-vapor equilibrium, the solid surface adsorption and the properties of very fine porous ceramics computed earlier using molecular modelling have been successfully integrated in modelling based on transport phenomena [4.14]. In the same class of limits we can include the validity limits of the transfer phenomena equations which are based on parameters of the thermodynamic state. It is known [3.15] that the flow equations and, consequently, the heat and mass transport equations, are valid only for the... 

Because of the nature of the chip surface, BIA is a heterophasic technique like the GEMSA and filter binding assays discussed in the previous section. There have been careful analyses made of the potential effect of artefacts arising from the heterophasic nature of the chip, such as steric hindrance and mass transport effects, on the absolute values of rate and thermodynamic parameters (Schuck 1997). The conclusion appears to be that relative values of parameters, particularly equilibrium constants, obtained by this approach can be viewed with confidence, but careful experimental design is needed to determine reliable absolute values (Myska 2000). 

This article has described the Hall-Heroult cell that is the mainstay of the aluminum industry throughout the world. Emphasis has been on the electrochemistry and electrochemical engineering that govern cell performance. The cell operation, electrolyte chemistry, thermodynamics, and electrode kinetics have been reviewed. Some complexities, notably the anode effect and the environmentally important fluoride emissions and anode gas bubbles and their effect on cell voltage, flow, and CE, have been examined. The incorporation of these phenomena, along with current distribution, magnetic fields, electromagnetically driven flow, heat and mass transport, and cell instability into mathematical models was summarized. 

However, thermodynamic-based solubility data and its correlation with solvent properties (sub-H20) is only one facet in optimizing processes with sub-H20 - kinetic and mass transport factors must also be considered to receive maximum benefit in using this technique. Unfortunately, far less is known about the mass transport properties of solutes in sub-H20, but some useful correlations and experimental data do exist. These will be considered in the next section and how they can be utilized in conjunction with analyte solubility in optimizing and designing efficient experimental conditions. 

Rational reactor selection and design requires information on thermodynamics, chemical kinetics, heat and mass transport, and reactor hydrodynamics. In practice, a quantitative analysis is based on reactor models and engineering correlations. In this chapter we limit ourselves to a qualitative discussion, emphasizing principles rather than quantitative calculations. 

Taking account chemical reaction and mass transport differences between elements, then we can infer the distribution of secondary minerals by considering thermodynamic constraints, as well as kinetic and transport phenomena. Solubility (Shikazono, 1988) and mass transport coefficient of Ca is large at low temperature, and therefore Ca is readily dissolved in shallow zones and transported to deeper levels. As a result, Ca-bearing alteration minerals, such as Ca-montmorillonite, occur widely in a geothermal field. Solubility and mass transport coefficient of Ca decreases with increasing temperature, so Ca-zeolites precipitate in the active zones. 

The rate of corrosion will depend on a number of factors, including thermodynamic, kinetic, and mass-transport-related aspects. The first few sections of this volume will describe these influences on corrosion. 

Another important factor is the likelihood that the catalyst QX, QY) will partition between the aqueous and organic phases in liquid-liquid systems. Thus electrostatic interactions and mass transport tend to govern much of the thermodynamics and kinetics of the PTC cycle. 

Electrochemistry Thermodynamics and Electrified Interfaces, Vol 10 In Situ Imaging Interfadal Kinetics and Mass Transport, Vol 10 Electrochemical Nucleation and Growth Interfacial Kinetics and Mass Transport, Vol 10 Electrodeposition of nanoparticles Interfacial Kinetics and Mass Transport, Vol 10 Electrochemical AFM Instrumentation and Electroanalyt-ical Chemistry, Vol 10 Layer-by-layer Assemblies of Thin Films on Electrodes Modified Electrodes, Vol 10 Organic Polymer Modified Electrodes Modified Electrodes, Vol 10 AFM, In Situ Methods Modified Electrodes, Vol 10. 

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