Principles Of Equilibrium Thermodynamics Research Articles

Oxidation and Fume Formation from Liquid Silicomanganese Alloys Exposed to Atmospheres Containing Moisture

In industrial applications and laboratory studies, it has been shown that the use of water spray may significantly reduce the amount of fume generated from the oxidation process of liquid high carbon ferromanganese alloy. However, in our recent study, it was shown that the oxidation rate of liquid silicon alloy increases with increasing water content in the atmosphere. Therefore, in this paper, the effect of moisture on the oxidation and fume formation of a liquid silicomanganese alloy was investigated. The fuming rate, fume characteristics, and experimental observations from wet air experiments on the silicomanganese melt were compared with those obtained from dry air experiments, and with the results of wet air experiments conducted on high carbon ferromanganese and silicon melts. In addition, the oxidation process of the silicomanganese and high carbon ferromanganese melts was modeled under the experimental conditions, using FactSage 8.1 thermochemical software, to better understand the equilibrium thermodynamic principles of the experimental results. In general, there was good agreement between the simulated and experimentally observed oxidation behavior of silicomanganese and high carbon ferromanganese melts under moist air conditions.

Kinetic partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions: New insights into clinopyroxene sector zoning and concentric zoning

Within subvolcanic plumbing systems, along volcanic conduits and post-eruptive emplacement, mineral textures and compositions are governed by complex kinetic (undercooling) and dynamic (convective) processes that deviate from theoretical models and equilibrium criteria. In this perspective, we have investigated the partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions at high degrees of undercooling (−ΔTnominal = 30–60 °C) and atmospheric pressure. We have integrated this novel data set with conventional static (no physical perturbation) clinopyroxene-melt compositions obtained under interface- and diffusion-controlled growth regimes. Results show that clinopyroxene growth kinetics and diffusion boundary layers caused by melt supersaturation are partly mitigated by the homogenizing effects of stirring. Because of continuous supply of fresh melt to the advancing crystal surface, the partitioning of major and trace cations is governed by local equilibrium effects, which are interpreted as the extension of equilibrium thermodynamic principles to non-equilibrium bulk systems. Major cations are incorporated into the clinopyroxene structure via the coupled substitution [M1Mg, TSi] ↔ [M1Ti, TAl] and in conformity with the thermodynamic mixing properties of CaMgSiO2, CaAl2SiO6, and CaTiAl2O6 components. The complementary relationship between lattice strain (ΔGstrain) and electrostatic (ΔGelectrostatic) energies of heterovalent substitutions is the most appropriate thermodynamic description for the accommodation of trace cations in the clinopyroxene lattice site (i.e., ΔGpartitioning = ΔGstrain + ΔGelectrostatic). The excess energy of partitioning ΔGpartitioning changes principally with Al in tetrahedral coordination and determines the type and number of charge-balanced and -imbalanced configurations taking place in the structural sites of clinopyroxene. An important outcome from dynamic stirring experiments is that superimposition of convective mass transfer on melt supersaturation phenomena causes the formation of Cr-rich concentric zones under closed system crystallization conditions. However, these Cr-rich zones do not correlate with enrichment in other compatible elements and depletion in incompatible elements, as would be expected in natural open systems characterized by input of more primitive magmas. While the convective transport acts to reduce the diffusive length scale of chemical species in the experimental melt, fresh Cr cations are more easily incorporated into the concentric zones due to crystal field effects. Together, our findings reveal that during magma ascent and emplacement, convective stirring may promote clinopyroxene crystallization and minimize kinetic effects on clinopyroxene zoning.

On the theory of constitutive equations for composites with different resistance in compression and tension

The paper proposes a new approach to the construction of nonlinear constitutive equations for the description of elastic deformation of fibrous composites with different resistance in compression and tension. The framework of the approach is the generalized rheological method of constructing constitutive equations of the uniaxial stress–strain state. Transition to the tensor equations uses the hypothesis of existence of a special cone of all possible compression states in the space of strains. The cone structure is governed by the reinforcement pattern of a composite. When imposed with strains in the cone, the composite behaves as a linearly elastic medium, while beyond the cone, the composite is nonlinear, with higher stiffness conditioned by tension of high-modulus reinforcement fibers. It is highly critical that the constitutive equations obtained using this approach belong to the theory of hyperelasticity. The elastic potentials of stresses and strains are obtained for these equations, which guarantees implementation of fundamental principles of equilibrium thermodynamics. Application of the developed general theory is exemplified by construction of the constitutive equations for the plane stress state of a thin unidirectional fiber reinforced composite plate and for a multilayer plate with different-direction reinforcement of layers. Using the finite element method in combination with the initial stress method, the stress and strain patterns are analyzed in rectangular one-, two- and three-layer carbon fiber reinforcement polymer plates with a circular cut under the action of external stresses at the boundary.

Active engines: Thermodynamics moves forward

The study of thermal heat engines was pivotal to establishing the principles of equilibrium thermodynamics, with implications far wider than only engine optimization. For nonequilibrium systems, which by definition dissipate energy even at rest, how to best convert such dissipation into useful work is still largely an outstanding question, with similar potential to illuminate general physical principles. We review recent theoretical progress in studying the performances of engines operating with active matter, where particles are driven by individual self-propulsion. We distinguish two main classes, either autonomous engines exploiting a particle current, or cyclic engines applying periodic transformation to the system, and present the strategies put forward so far for optimization. We delineate the limitations of previous studies, and propose some future perspectives, with a view to building a consistent thermodynamic framework far from equilibrium.

Mathematical Modeling of Plants for the Combined Production of Liquid Hydrocarbons and Electricity Based on Coal

Various aspects of the synthesis of gasoline fraction hydrocarbons from methanol obtained at power-engineering plants for the synthesis of methanol from coal are considered. The methods and approaches used in the modeling of hydrocarbon synthesis processes based on the principles of equilibrium thermodynamics and phase separation processes of multifraction mixtures are substantiated and described. Conditions for combining a hydrocarbon synthesis unit with power-engineering plants for the synthesis of methanol from coal are considered. Based on the results of studies of the unit for the synthesis of hydrocarbons from methanol, including detailed material and thermal balances, the economic efficiency conditions of the conversion of methanol produced from coal into liquid hydrocarbons at a single plant are estimated.

ЗАКОНОМЕРНОСТИ ИЗМЕНЕНИЙ ПАРАМЕТРОВ ПРОЦЕССОВ ПЕРЕНОСА МНОГОКОМПОНЕНТНЫХ УГЛЕВОДОРОДНЫХ ГАЗОВЫХ СРЕД В УСЛОВИЯХ СЕПАРАЦИИ

A detailed study of the evolution of local and integral parameters of momentum, heat, and mass transfer processes in hydrocarbon gas mixtures under separation conditions at given temperature and pressure values in working media is carried out within the framework of the principles of equilibrium thermodynamics using the Aspen HYSYS software package, namely, the Peng-Robinson equation of state for real gas mixtures, the principles of statistical mechanics, the approaches of corresponding states, the Chapman-Enskog and the Golubev methods, and the theory of similarity and dimensional analysis. The limits of similarity method applicability in quantitative estimates and qualitative forecasts of the mechanisms and configurations of convective heat and mass transfer in oil treatment units are established. The paper also discusses results of the analog method application in separation process modeling for momentum, heat and mass transfer processes in the problems of oil and gas industry. The conclusions about the aspects of property changes in complex mixtures and about heat and mass transfer intensity during separation, which violate a triple analogy in non-isothermal homogeneous and heterogeneous media, are recommended to take into account when designing real equipment.

Prediction of dynamic contact angles and bubble departure diameters in pool boiling using equilibrium thermodynamics

A model is proposed for predicting dynamic contact angles and bubble departure diameters in pool boiling based on principles of equilibrium thermodynamics. The method is shown to give good agreement with experimental measurements for pool boiling over a wide range of pressures, liquid superheats and working fluids.The model suggests that for fast-growing bubbles associated with boiling at high Jakob Numbers (>100) the bubble shape is dominated by fluid drag forces rather than surface tension forces, resulting in the bubbles having a predominantly hemispherical shape during growth. For slower-growing bubbles associated with lower Jakob numbers (<50) surface tension forces appear to dominate over fluid drag forces, resulting in the bubbles adopting a spherical cap shape with a contact angle that remains close to the thermodynamic contact angle. This observation is in accordance with experiment.The model implies that in high pressure boiling the thermodynamic contact angle for the system has a controlling influence on bubble departure sizes. Analysis of departure diameters in high pressure boiling of water supports the view that the thermodynamic contact angle is strongly dependent on temperature, and that it is this temperature dependence that is responsible for the small bubble departure sizes observed in high pressure boiling. Previous models of bubble departure have been unable to explain the pressure dependence of bubble departure size. A correlation of the thermodynamic contact angle against temperature for water is proposed.The current model of bubble departure requires a means of calculating the bubble growth rate, as the latter determines the fluid drag forces acting on an attached bubble. A new predictive method for bubble growth is developed for this purpose, based on Scriven’s solution for conduction controlled bubble growth, with corrections to take account of non-uniform liquid superheat, microlayer evaporation, the effect of growth rate on the bubble shape, and the cooling effect of the microlayer on the heated surface. The predictive method gives satisfactory agreement with bubble growth data for a wide range of pool boiling experiments and also with results of microscale CFD simulations of the growth of individual bubbles.

Isosteric Heat of Potential Confinement in the Hydrogen Storage Material

In the hydrogen storage problem, if an attractive potential well is formed inside the void space of porous materials, the storage gas density is expected to increase significantly compared to the H2 gas density outside the material. Actually, the overall H2 density inside the material is enhanced basically by a Boltzmann factor of exp[[Formula: see text]/[Formula: see text]] where U ([Formula: see text][Formula: see text]0) is some averaged potential energy. Corresponding to this negative potential energy, latent heat is released in the H2 gas confinement process. We theoretically investigate the energetics involved during the H2 storage in the potential well and, from the equilibrium thermodynamic principles, we derive a formalism for the isosteric heat of potential confinement of the H2 gas. Since the gas density inside the potential well increases tremendously, the van der Waals equation is adopted to describe the nonideal gas behavior of H2. We compare our results to the well-known expression for the isosteric heat of adsorption where, unlike our case, the molecules are bound to specific adsorption sites in the material.

Homo-FRET imaging highlights the nanoscale organization of cell surface molecules.

Several models have been proposed to understand the structure and organization of the plasma membrane in living cells. Predicated on equilibrium thermodynamic principles, the fluid-mosaic model of Singer and Nicholson and the model of lipid domains (or membrane rafts) are dominant models, which account for a fluid bilayer and functional lateral heterogeneity of membrane components, respectively. However, the constituents of the membrane and its composition are not maintained by equilibrium mechanisms. Indeed, the living cell membrane is a steady state of a number of active processes, namely, exocytosis, lipid synthesis and transbilayer flip-flop, and endocytosis. In this active milieu, many lipid constituents of the cell membrane exhibit a nanoscale organization that is also at odds with passive models based on chemical equilibrium. Here we provide a detailed description of microscopy and cell biological methods that have served to provide valuable information regarding the nature of nanoscale organization of lipid components in a living cell.

The thermochemistry library Thermochimica

Progress in numerical methods in computing thermodynamic equilibria is presented that is particularly well suited to large multicomponent multiphase systems and is incorporated in the thermochemistry library Thermochimica. The method described in this paper exploits fundamental principles of equilibrium thermodynamics that results in simplifying the numerical approach. The chemical potentials of all species and phases are defined by the chemical potentials of the component elements and the objective is to systematically partition the Gibbs energy of the system in a manner that diminishes the residuals of the mass balance equations. Several numerical advantages are obtained through this simplification that improve the rate of convergence while simultaneously promoting numerical stability. The resulting software library Thermochimica is described with an overview of the numerical methods that it employs.

Bentonite stability, speciation and migration behaviour of some critical radionuclides

The contribution is focused on chemical, geochemical and mineralogical research of bentonite stability with the aim to determine the effect of saturation medium composition and loading by heat on bentonite stability. The main part of the research is directed to the experimental results of bentonite and bentonite leachate samples obtained for the bentonite interaction under laboratory experiments. Computer-modeling methods were used to calculate equilibrium thermodynamic principles, the distributions of predominant aqueous species, and potential solubility controls for the environmentally important oxidation states of each investigated radioactive contaminants. The Eh–pH diagrams of individual chemical species of the tested radionuclides were calculated by the geochemical software tool Geochemist’s Workbench that included the actual chemical compositions of the solid–liquid systems under the given experimental conditions. It was confirmed that smectites are transformed to more stable silicate phases, such as illite/smectite mixed layers, illite. The data obtained from the model calculations conform with experimental results. The effect of the variable aqueous phase composition on bentonite stability using Ca–Mg and Na–Ca bentonites for the experiments was studied. The synthetic granitic waters with the higher concentration of the K+ and Mg2+ cations were applied for the study of bentonite stability.

Heterogeneous equilibria in systems MII(AsUO6)2·nH2O-aqueous solution (MII = Mg2+, Ca2+, Sr2+, Ba2+)

A comprehensive study of the state of alkaline-earth metal uranoarsenates in saturated aqueous solutions in a wide range of solution acidity was made. A physicochemical model based on the experimental solubility data and on principles of equilibrium thermodynamics was suggested for quantitative description of the state of the heterogeneous system crystalline uranoarsenate MII(AsUO6)2·nH2O-aqueous solution. The model was applied to calculation of the solubility products and Gibbs energies of formation of alkaline-earth metal uranoarsenates, and also of distribution diagrams of equilibrium aqueous solutions and bottom phases.

Solubility of uranoarsenates MAsUO6·nH2O in water and aqueous HClO4 (M = H+, Li+, Na+, K+, Rb+, Cs+, NH 4 + )

The solubility of poorly soluble uranoarsenates MAsUO6·H2O in water and aqueous HClO4 was determined. The solubility products and Gibbs energies of formation of these compounds were evaluated from the experimental data using the principles of equilibrium thermodynamics. The state of uranoarsenates in aqueous solutions in the range not studied experimentally was estimated.

Predicting the composition of acidic, ionic liquids in contact with HCl gas

AbstractThe acidic, chloroaluminate ionic liquid (IL) derived from the combination of 1‐ethyl‐3‐methyl‐1H‐imidazolium chloride (EMIM‐Cl) and aluminum chloride complex (AlCl3) in contact with HCl gas was modeled using the principles of equilibrium thermodynamics of chemically reacting systems as a means to understand better the reactivity of arene formylations in these IL's. The concentration of an HCl‐chloroaluminate species, ClHAl2Cl that has been characterized as a super acidic Brønsted species, increases with increasing HCl partial pressure. Another chloroaluminate species Al2Cl, which has been characterized as a strong Lewis acid, showed concentrations that decreased with increasing HCl gas phase partial pressures. The ultimate conversion of toluene to tolualdehyde could be correlated with the sum of the predicted molar amounts of ClHAl2Cl and Al2Cl, by assuming that each ClHAl2Cl combined with 1 tolualdehyde and each Al2Cl sequestered a single tolualdehyde molecule. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Multilevel regulation of protein–protein interactions in biological circuitry

Protein–protein interactions are central to biology and, in this ‘post-genomic era’, prediction of these interactions has become the goal of many computational efforts. Close inspection of even relatively simple biological regulatory circuitry reveals multiple levels of control of the contributing protein interactions. The fundamental probability that an interaction will occur under a given set of conditions is difficult to predict because the relationship between structure and energy is not known. Layered on this basic difficulty are allosteric control mechanisms involving post-translational modification or small ligand binding. In addition, many biological processes involve multiple protein–protein interactions, some of which may be cooperative or even competitive. Finally, although the emphasis in predicting protein interactions is based on equilibrium thermodynamic principles, kinetics can be a major controlling feature in these systems. This complexity reinforces the necessity of performing detailed quantitative studies of the component interactions of complex biological regulatory systems. Results of such studies will help us to bridge the gap between our knowledge of structure and our understanding of functional biology.

Viscous flow of a volatile liquid on an inclined heated surface.

We investigate the effects of evaporation on a gravity-driven flow of a viscous liquid on a heated solid surface. Vapor molecules are adsorbed on the dry areas of the solid and form a microscopic adsorbed film. The thickness of this film is calculated from the formulas for disjoining pressure and the principles of equilibrium thermodynamics. A lubrication-type approach is used to derive an evolution equation capable of describing both the macroscopic shape of the vapor-liquid interface and the adsorbed film on the vapor-solid interface. Under the conditions of negligible evaporation, the numerical solution of the evolution equation predicts translational motion and formation of capillary ridge, in agreement with previous investigations. Moderate evaporation is shown to slow down the flow and decrease the height of the capillary ridge, which implies a stabilizing effect of evaporation on the well-known instability observed in gravity-driven thin film flows. We also study the combined effects of evaporation and thermocapillary stresses and show that the latter act to reduce the velocity of the downward motion, but increase the height of the capillary ridge. Apparent contact angles are found from the solution and shown to increase with evaporation and contact line speed. For strong evaporation, steady state solutions are found such that evaporation balances the downward motion of the interface under the action of gravity.

A mathematical approach to cytoskeletal assembly.

The cytoskeleton is a fundamental and important part of cell's structure, and is known to play a large role in controlling the shape, function, division, and motility of the cell. In recent years, the traditional biological and biophysical experimental work on the cytoskeleton has been enhanced by a variety of theoretical, physical and mathematical approaches. Many of these approaches have been developed in the traditional frameworks of physicochemical and statistical mechanics or equilibrium thermodynamic principles. An alternative is to use kinetic modelling and couch the analysis in terms of differential equations which describe mean field properties of cytoskeletal networks or assemblies. This paper describes two such recent efforts. In the first part of the paper, a summary of work on the kinetics of polymerization, fragmentation, and dynamics of actin and polymers in the presence of gelsolin (which nulceates, fragments, and caps the filaments) is given. In the second part, some of the kinetic models aimed at elucidating the spatio-angular density distribution of actin filaments interacting via crosslinks is described. This model given insight into effects that govern the formation of clusters and bundles of actin filaments, and their spatial distribution.

Use of ionic detergents for enterovirus recovery from waste water

Virus recovery from poliovirus-seeded waste water was attempted after treatment of the samples with ionic detergents in the presence of acoustic energy. Viral titers strongly fluctuated depending upon concentration and chemical structure of the detergent as well as upon the dissolved organic content of the aqueous samples. Supplementation of the cellular monolayers with an additional amount of cell culture medium or with a nonionic detergent in a subcytotoxic concentration 48 h after inoculation partly induced cytopathic effects in silent dilution steps. Since, in the presence of the same detergent, viral recovery rates varied with the type of waste water, titer-conditioning activity of detergents was suggested to depend upon their effective critical micellization concentration. Especially for virus recovery from concentrated waste water, treatment with strongly disruptive detergents such as sodium dodecylsulfate revealed to be much more efficient than with the less hydrophilic sodium N-laurylsarcosine, sodium glycodeoxycholate or lauryldimethylamine-oxide, whereas the opposite seemed to be the case if virus recovery from filtrate samples were to be optimized. The mechanisms by which viral particles become infectious for the cell appear to be triggered by general principles of equilibrium thermodynamics, which means that interactions between viral surface proteins and cellular receptor molecules seem to reflect the tendency of these reagents to assume the energetically most favored orientation.

Bonding, Structure and Properties of Metal/Ceramic Interfaces

AbstractThis paper reviews the effects of chemical bonding, reaction, interfacial structure, fabrication, specimen geometry and testing conditions on the strength and fracture behavior of metal/ceramic interfaces. It is shown that a number of important properties of metal/ceramic interfaces such as the wetting behavior and work of adhesion can be qualitatively predicted from simple bonding models based on the elements in the metal and ceramic. In addition, the interfacial structure can often be predicted from principles of equilibrium thermodynamics and minimization of interfacial energy for relatively thick metal/ceramic layers. More quantitative description of interfacial structure employing atomistic calculations has been performed for simple interfaces and this area is progressing. The fracture behavior of metal/ceramic interfaces is a complicated process which depends on many factors such as the specimen geometry and loading conditions, strength of the interfacial bond, thermal, elastic and fracture properties of the metal and ceramic, thickness of the metal layer and testing environment. Advances in this area include the development of favorable specimen geometries for measuring interface properties and an understanding of the relationship among the phase angle of loading, crack trajectory and interface fracture energy for these geometries. Conversely, little is known about the stress corrosion and fatigue behavior of metal/ceramic interfaces although data on these time dependent failure modes are beginning to appear in the literature. Much progress has been made but considerably more work isneeded to understand the properties of metal/ceramic interfaces.

Solidification of an alloy cooled from above Part 1. Equilibrium growth

The interaction between the solidification and convection that occurs when a melt is cooled from above is investigated in a series of three papers. In these papers we consider a two-component melt that partially solidifies to leave a buoyant residual fluid. The solid forms a mushy layer of dendritic crystals, the interstices of which accommodate the residual fluid. The heat extraction through the upper boundary, necessary to promote solidification, drives convection at high Rayleigh numbers in the melt below the mushy layer. The convection enhances the heat transfer from the melt and alters the rate of solidification. In this paper the various phenomena are studied in a series of laboratory experiments in which ice is frozen from aqueous solutions of isopropanol. The experiments are complemented by the development of a general theoretical model in which the mush is treated as a continuum phase with thermodynamic properties that are functions of the local solid fraction. The model, which is based upon principles of equilibrium thermodynamics and local conservation of heat and solute, produces results in good agreement with the experimental data. Careful comparisons between this theory and experiments suggest the need to explore non-equilibrium effects, which are investigated in Parts 2 and 3.