Papers by Keyword: Thermodynamic Model

Abstract: A thermodynamic model for cellular glass pore-formation has been developed on the basis of natural volcanic silicate and aluminosilicate glasses. The energy expenses for heating the materials, chemical reactions, breaking the structural bonds of water hydrates, evaporation of the released water, and pore formation of the glass mass are determined sequentially. The enthalpy and Gibbs energy of the complex gas-forming agent HNO₃ + SiC are calculated.

Abstract: The size and distribution of nanoscale precipitate particles in Ti-Mo ferrite matrix microalloyed steel under three different final rapid cooling temperatures were studied by scanning electron microscopy(SEM), transmission electron microscope(TEM) and microhardness test. The results show that the interphase precipitation could be weakened by the excessive final rapid cooling temperature. A higher supersaturated solid solubility and high-density dislocation in ferrite matrix can be obtained under a relatively lower final rapid cooling temperature, which makes it easier to precipitate in ferrite. The related thermodynamic analysis indicated that the precipitation behavior was influenced by the final rapid cooling temperature during austenite/ferrite region. It is not conducive to get a large amount of small size precipitates in Ti-Mo ferrite matrix microalloyed steel when the final rapid cooling temperature is too high or low.

Abstract: Solubilities of the quaternary system containing lithium, sodium, magnesium and chloride at 273.15 K were calculated using Pitzer ion-interaction model and its extended HW model. The values of the Pitzer single-salt parameters β⁽⁰⁾, β⁽¹⁾, β⁽²⁾ and C^φ for LiCl, NaCl, and MgCl₂, the mixed ion-interaction parameters θ_Li,Mg, θ_Li,Na, θ_Na,Mg, ψ_Li,Mg,Cl, ψ_Li,Na,Cl and ψ_Na,Mg,Cl, and the Debye–Hückel parameter A^φ in the quaternary system at 273.15K were derived. Based on the Jänecke indexes, the phase diagram was plotted. This study affords the necessary parameters for solubility predictions of complicated systems and establishes a theoretical basis for the separation of these valuable minerals from salt lake brine.

Abstract: Heap bioleaching of sulfide ores (geotechnology) simulates naturally occurring processes when sulfides convert to oxides. This process is environmentally-friendly. Gold-bearing sulfide ore from a Russian deposit was studied. The samples were composed of quartz (38-48%), feldspars (22-24%) and micaceous minerals (18-21%). Carbonates occurred as ankerite, calcite, dolomite and siderite. The host minerals were pyrite (2.2-2.3%) and arsenopyrite (1.2-1/7%). The grade of gold was 1.6-2.0 g/t. Russian software package Selector was used to develop the model. Thermodynamics of the reaction pathway for the conversion of the gold-bearing sulfide ore in H₂SO₄ environment with and without using bacteria was calculated. Phases and their components which are able to form in these given conditions were selected during modeling. Modeling of irreversible evolution of the rocks caused by bacteria was carried out in the three reservoir system. They are interconnected by the flows of three movable phases: gases, solid phase and liquid phase. In this case, the composition of the solutions which were obtained under steady state conditions without bacteria and metastable equilibrium using bacteria can be compared. Bacterial oxidation occurs under acidic conditions. Oxidation without using bacteria occurs under more alkaline conditions. Bacteria increase the rate of sulfides oxidation and retard the formation of mixed-layer aluminum silicates (illites, montmorillomonites) and carbonates (magnesian calcite). It was found that bacteria have the potential to achieve the required destruction of sulfides in favorable environment. Bacteria make the rate of sulfide oxidation higher. In the presence of bacteria, the rate of aluminosilicates oxidation is slower compared to the conditions without using bacteria. Mineralogical analyses of the leach products confirmed this. Results show that thermodynamic approach can be successfully used for the modeling of bacterial-oxidation circuits and geology of the rocks and ores.

Abstract: A thermodynamic model of calculation of sulfur distribution ratio between B₂O₃-containing slag and molten steel has been developed on the basis of the ion and molecule coexistence theory. Based on the model, the effects of B₂O₃ content and slag basicity on the sulfur distribution ratio in 1873K were investigated respectively. The results indicate that the sulfur distribution ratio decreased with increasing the content of B₂O₃, and when the content of B₂O₃ exceeds 6%, the sulfur distribution ratio was lower than 2.0. Therefore, in order to ensure the desulphurization ability of slag, the content of B₂O₃ should be controlled at about 6%. Moreover the sulfur distribution ratio can be increased by increasing the slag basicity.

Abstract: This paper proposes a hypothesis of hydration. It assumes that the solute in the electrolyte solution exists as molecules, and each solute molecule is surrounded by h water molecules. On this basis, this paper deduces the activity coefficient formulas, and the model is applied to binary electrolyte solutions at room and elevated temperatures.

Abstract: An improved model for heat transfer process is established to study the ice accretion on airfoil, which takes into consideration the influence of conduction through ice and water film compared with the classical Messinger model. Incorporating the calculation of collection efficiency by the Eulerian two-phase theory, ice accretion in specific condition on a NACA0012 airfoil is simulated with the classical model and the improved model respectively. It is shown that the simulation result with the improved model agrees well with experiment data, and the model is demonstrated to be valid in ice shape prediction and complement the shortage of the Messinger model in the estimation of freezing fraction in glaze ice condition, especially in the initial stage of ice accretion.

Abstract: Many researchers have shown a great deal of interest in the effects that magnetic fields have when applied in chemical reactions, crystallization, magnetic separation of materials, magnetic levitation, materials processing, and wastewater treatment. However, surprisingly little research has been done on the effects of magnetic fields on the vapor-liquid equilibrium and the thermodynamic model for vapor-liquid phase equilibrium. The influence of magnetic fields on vapor-liquid equilibrium of binary heterogeneous azeotrope was investigated with ethanol-water in this paper. It was found that the vapor-liquid equilibrium of an ethanol-water system is influenced by the external magnetic field, but that the azeotropic point of the ethanol-water system is not changed by the magnetic field when the magnetic intensity reaches 0.8 T. Rather, the exerted magnetic field reduces the equilibrium temperature and shortens the distance between T-x curve and T-y curve in T-x-y diagram of the vapor-liquid equilibrium of the ethanol-water system. A thermodynamic model for vapor-liquid phase equilibrium in the exerted magnetic field was derived theoretically, based on the fundamental thermodynamic theory. The results show that the logarithm value of the ratio of the composition of the certain component in a magnetic field to that without the magnetic field is proportional to the magnetic susceptibility of the solution, and to the square of magnetic field intensity. This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text.

Abstract: To study the thermal effects on pollutant dispersion in the street canyon, a thermodynamic model is developed in this paper to predict surface temperature in street canyon environment, which can offer boundary conditions for CFD model. This model considered the shielding effect of buildings on solar radiation, the multi-reflection of radiation between building surfaces and the road. Furthermore, sensible heat exchange between the canyon space and the overlaying atmosphere was also modeled based on the classical theory of dynamics of atmospheric boundary layer. The reliability of this model is validated through a field measurement. Based on the thermodynamic model, a coupled calculation method is presented to predict traffic-related pollutants dispersion in urban street canyons under low wind speed conditions.

Abstract: A thermodynamic model of the microalloy precipitation elements in austenite region for Fe-C-N-Al-Ti-Nb steel has been established. Through calculating the action of the microalloying element in austenite, it can be found that carbon in steel accelerates the precipitation of Nb greatly, Nb in solution decreases quickly and the precipitation of Nb increases quickly with the increase of carbon. When the C in steel is low, the main constituent of the precipitation is TiN in high temperature, and TiN guadually turns to be NbC with the decrease of tempertature. When the carbon in steel is high，the main constituent in the precipitation is NbC even though the temperature is higher. The nitrogen in steel has a slight effect on NbN precipitation.