Thermodynamic Tool Research Articles

Microstructural and thermal processing effects on adding 3 wt-%Ti to powder metallurgy processed Ni–Cr–Fe alloy

To investigate the effect of adding Ti to a Ni–Cr–Fe powder metallurgy alloy, a thermodynamic software package was used to predict the phase transformations that occurred during thermal processing. Specifically, the effect of adding 3 wt-%Ti to a 6 wt-%Al modified ternary Ni–Cr–Fe alloy (the quaternary) was simulated and the phase transformations that might occur in the material on sintering were obtained using the thermodynamic modelling tool. These predictions were subsequently compared with experimental results obtained by X-ray diffraction and metallography. For comparison, selected compacts were prepared containing only the ternary+3 wt-%Ti (no Al). Based upon compressibility curves, the optimum pressure for producing the new Ti compacts was 500 MPa versus 600 MPa for the quaternary composition with Ti. In each case, hardness of the base alloy was enhanced by the Ti addition, whereas the residual porosity remained relatively constant at ∼19%. Finally, although SEM/energy dispersive spectroscopy failed to confirm the presence of Ti in the gamma prime intermetallic, X-ray diffraction spectra showed a shift in lattice parameter on addition of Ti, suggesting that the intermetallic was of the form Ni3(Al,Ti).Afin d’étudier l’effet de l’addition de Ti à un alliage de Ni-Cr-Fe obtenu par métallurgie des poudres, on a utilisé un progiciel thermodynamique pour prédire les transformations de phase qui se produisent lors du traitement thermique. Spécifiquement, on a simulé l’effet d’une addition de 3% en poids de Ti à un alliage ternaire Ni-Cr-Fe modifié de 6% en poids d’Al (le quaternaire) et l’on a obtenu les transformations de phase qui pourraient se produire dans le matériau lors du frittage en utilisant l’outil de modélisation thermodynamique. On a subséquemment comparé ces prédictions aux résultats expérimentaux obtenus par diffraction des rayons X et par métallographie. Pour fin de comparaison, on a préparé des compacts choisis contenant seulement le ternaire avec 3% en poids de Ti (sans Al). En se basant sur les courbes de compressibilité, on a déterminé que la pression optimale pour produire les nouveaux compacts de Ti était de 500 MPa par rapport à 600 MPa pour la composition quaternaire avec le Ti. Dans chaque cas, la dureté de l’alliage de base était accrue par l’addition de Ti, alors que la porosité résiduelle demeurait relativement constante à 19%. Finalement, bien que le SEM/la spectroscopie à dispersion d’énergie n’ait pas réussi à confirmer la présence de Ti dans l’intermétallique gamma prime, les spectres de diffraction des rayons X ont montré un déplacement du paramètre de réseau lors de l’addition de Ti, suggérant que l’intermétallique était de la forme Ni3(Al,Ti).

Thermodynamic models and factual data banks - ideal tools for the development of chemical processes

The synthesis, design and simulation of chemical processes, in particular thermal separation processes is today carried out by solving the resulting balance equations of a mathematical model of the considered unit operation or the whole chemical plant using sophisticated commercial process simulation software. The reliability and correctness of the simulation results is mainly influenced by the reliability and correctness of the thermophysical property parameters used for the pure compounds and their mixtures. For the description of the required phase equilibria GE-models and equations of state were developed. These models allow the prediction of the phase equilibrium behavior of multicomponent systems using binary experimental data only. However, since the number of experimental binary data is limited, these methods often cannot be applied. Therefore in particular for process development reliable predictive models with a large range of applicability are most important. With the help of the worldwide largest factual data bank (Dortmund Data Bank (DDB)) for pure component properties, phase equilibria and excess properties, in the last 35 years powerful group contribution methods (UNIFAC, modified UNIFAC) have been developed in my research group. By combination of cubic equations of state with the group contribution concept, now even the phase equilibrium behavior with supercritical compounds can be predicted. At the same time other important properties (e.g. densities, enthalpies, heat capacities, etc.) can directly be predicted. With the development of an adequate electrolyte model (LIQUAC, LIFAC) the equation of state approach was even extended to systems with strong electrolytes. Today ideal predictive thermodynamic tools are available, which can be used in combination with factual data banks for the development of chemical processes. In the lecture the status of the factual data bank and the different predictive models will be shown. Furthermore important applications of industrial interest of the predictive thermodynamic models and the Dortmund Data Bank will be presented.

Development of thermodynamic and kinetic databases in micro-soldering alloy systems and their applications

Recent progress in the development of thermodynamic and kinetic databases of micro-soldering alloys, which were constructed within the framework of the Thermo-Calc and DICTRA software, was presented. Especially, a thermodynamic tool, ADAMIS (alloy database for micro-solders) was developed by combining the thermodynamic databases of micro-solders with Pandat, a multi-component phase diagram calculation software program. ADAMIS contains 11 elements, namely, Ag, Al, Au, Bi, Cu, In, Ni, Sb, Sn, Zn and Pb, and can handle all combinations of these elements in the whole composition range. The obtained thermodynamic and kinetic databases can not only provide much valuable thermodynamic information such as phase equilibria and phase fraction, but also shows the kinetics and the evolution of microstructures when they are combined with some appropriate software programs and models, such as the phase field method and ADSTEFAN software. From the viewpoints of computational thermodynamics and kinetics, some technical examples were given to demonstrate the great utility of these databases for the applications in the development of micro-soldering materials. These databases are expected to be powerful tools for the development of micro-solders and Cu substrate materials, as well as for promoting the understanding of interfacial phenomena and microstructure evolution between solders and substrates in electronic packaging technology.

Amyloid Features and Neuronal Toxicity of Mature Prion Fibrils Are Highly Sensitive to High Pressure

Prion proteins (PrP) can aggregate into toxic and possibly infectious amyloid fibrils. This particular macrostructure confers on them an extreme and still unexplained stability. To provide mechanistic insights into this self-assembly process, we used high pressure as a thermodynamic tool for perturbing the structure of mature amyloid fibrils that were prepared from recombinant full-length mouse PrP. Application of high pressure led to irreversible loss of several specific amyloid features, such as thioflavin T and 8-anilino-1-naphthalene sulfonate binding, alteration of the characteristic proteinase K digestion pattern, and a significant decrease in the β-sheet structure and cytotoxicity of amyloid fibrils. Partial disaggregation of the mature fibrils into monomeric soluble PrP was observed. The remaining amyloid fibrils underwent a change in secondary structure that led to morphologically different fibrils composed of a reduced number of proto-filaments. The kinetics of these reactions was studied by recording the pressure-induced dissociation of thioflavin T from the amyloid fibrils. Analysis of the pressure and temperature dependence of the relaxation rates revealed partly unstructured and hydrated kinetic transition states and highlighted the importance of collapsing and hydrating inter- and intramolecular cavities to overcome the high free energy barrier that stabilizes amyloid fibrils.

Thermodynamic Methods and Models to Study Flexible Metal–Organic Frameworks

Much attention has recently been focused on a fascinating subclass of metal-organic frameworks that behave in a remarkable stimuli-responsive fashion. These soft porous crystals feature dynamic crystalline frameworks displaying reversible, large-amplitude structural deformations under external physical constraints such as temperature, electric field or gas exposure. The number of reported syntheses of such materials is rapidly growing and they are promising for practical applications, such as gas capture, purification and fluid separation. Herein, we summarize the recently developed thermodynamic tools that can help understand the process of fluid adsorption and fluid mixture coadsorption in these flexible nanoporous materials. These tools, which include both molecular simulation methods and analytical models, can help rationalize experimental results and predict adsorption properties over a wide range of thermodynamic conditions. A particular focus is given on how these methods can guide the experimental exploration of a large number of materials and working conditions (temperature, pressure, composition) to help design efficient processes relying on fluid adsorption in soft porous crystals.

A THEORETICAL AND NUMERICAL MULTISCALE FRAMEWORK FOR THE ANALYSIS OF PATTERN FORMATION IN PROTEIN CRYSTAL ENGINEERING

The relevance of self-organization, pattern formation, nonlinear phenomena, and nonequilibrium behavior in a wide range of problems related to macromolecular crystal engineering calls for a concerted approach using the tools of statistical physics, thermodynamics, fluid dynamics, nonlinear dynamics, mathematical modeling, and numerical simulation in synergy with experimentally oriented work. The reason behind such a need is that in many instances of relevance in this field one witnesses an interplay between molecular and macroscopic-level entities and processes. Along these lines, two models are defined here and discussed in detail, one dealing with issues of complex behavior at the microscopic level and the other referring to the strong nonlinear nature of macroscopic evolution. Such models share a common fundamental feature, a group of equations strictly related from a mathematical point of view to the kinetic conditions used to model mass transfer at the crystal surface. Model diversification then occurs on the basis of the desired scale length; i.e., according to the level of detail required by the analysis (local or global). If the local evolution of the crystal surface is the subject of the investigation (distribution of the local growth rate along the crystal face, shape instabilities, onset of surface depressions due to diffusive and/or convective effects, etc.; i.e., all those factors dealing with the local history of the shape) the model is conceived to provide microscopic and morphological details. For this specific case a kinetic-coefficient-based moving boundary numerical (computational fluid dynamics) strategy is carefully developed on the basis of the volume-of-fluid methods (also known as the volume tracking methods) and level-set techniques, which have become popular in the last years as numerical techniques capable of modeling complex multiphase problems as well as for their capability to undertake a fixed-grid solution without resorting to mathematical manipulations and transformations. On the contrary, if the size of the crystals is negligible with respect to the size of the reactor (i.e., if they are small and undergo only small dimensional changes with respect to the overall dimensions of the cell containing the feeding solution), the shape of the crystals is ignored and the proposed approach relies directly on an algebraic formulation of the nucleation events and on the application of an integral form of the mass balance kinetics for each protein crystal. The applicability and the suitability of the different submodels are discussed according to some worked examples of practical interest. Pattern formation in these processes is described here with respect to crystal shapes, nuclei spatial discrete arrangements, and the convective multicellular structures arising as a consequence of buoyancy forces, thus enriching the discussions with some interdisciplinary flavor.

SusDesign – An approach for a sustainable process system design and its application to a thermal power plant

Abstract This paper presents a structured process design approach, SusDesign, for the sustainable development of process systems. At each level of process design, design alternatives are generated using a number of thermodynamic tools and applying pollution prevention strategies followed by analysis, evaluation and screening processes for the selection of potential design options. The evaluation and optimization are carried out based on an integrated environmental and cost potential (IECP) index, which has been estimated with the IECP tool. The present paper also describes a flowsheet optimization technique developed using different thermodynamic tools such as exergy/energy analysis, heat and mass integration, and cogeneration/trigeneration in a systematic manner. The proposed SusDesign approach has been successfully implemented in designing a 30 MW thermal power plant. In the case study, the IECP tool has been set up in Aspen HYSYS process simulator to carry out the analysis, evaluation and screening of design alternatives. The application of this approach has developed an efficient, cost effective and environmentally friendly thermal system design with an overall thermal efficiency of 70% and CO2 and NO emissions of 0.28 kg/kW h and 0.2 g/kW h respectively. The cost of power generation is estimated as 4 ¢/kW h. These achievements are significant compared to the conventional thermal power plant, which demonstrates the potential of the SusDesign approach for the sustainable development of process systems.

Modeling alcohol + water + hydrocarbon mixtures with the group contribution with association equation of state GCA-EoS

The growing interest on first- and second-generation biofuels requires the development of thermodynamic tools with predictive capacity for mixtures containing a wide variety of organo-oxygenated compounds, water and hydrocarbons. Modeling this type of mixtures is challenging due to the presence of association and solvation effects. In this work, we present a revision of the group contribution with association equation of state (GCA-EoS) parameters, with the purpose of extending and improving the predictive capacity of the model for systems containing water, alcohols and hydrocarbons.

Evaluation of Mn substitution for Ni in alumina-forming austenitic stainless steels

There has been increasing interest in the substitution of low-cost Mn for Ni in austenitic stainless steels due to the rising price of Ni. This paper investigates the possibility of such a substitution approach for the recently developed alumina (Al 2O 3)-forming austenitic (AFA) class of heat-resistant stainless steels. Computational thermodynamic tools were utilized to predict the alloy composition range to maintain an austenitic matrix microstructure when Mn is substituted for Ni in the presence of Al, which is a strong body-centered-cubic (BCC) phase stabilizer. Phase equilibria, oxidation behavior, and creep properties of Fe–(10–14)Cr–(5–15)Mn–(4–12)Ni–(2.5–3)Al–Cu–Nb–C–B (in weight percent) based alloys were studied. The alloys based on Fe–14Cr–2.5Al–(5–9)Mn–(10–12)Ni exhibited the best balance of oxidation and creep resistance, which represents approximately 50% reduction in Ni content compared to previously developed AFA alloys. These low-Ni, high-Mn AFA alloys formed protective Al 2O 3 scales up to 973–1073 K in air and at 923 K in air with 10% water vapor. Creep-rupture lives of the alloys under a severe screening condition of 1023 K and 100 MPa were in the 7.2 × 10 5–1.8 × 10 6 s (200–500 h) range, which is comparable to or somewhat improved over that of type 347 stainless steel (Fe–18Cr–11Ni base).

Evaluating Crystallization Risks in Liquefied-Natural-Gas (LNG) Production

Summary Liquefied natural gas (LNG) is anticipated to dominate world energy trade and fill the gap between production and energy demands in a few years, especially in the US. LNG is the liquefied version of dry natural gases at ultralow temperatures (approximately −160°C or −260°F at atmospheric pressure), which aims at minimizing storage volume requirements needed for overseas transportation. Within this context, it is clear that technology must continue to be developed to optimize the thermodynamic processes involved in the compression, liquefaction, and revaporization of LNG and associated operational challenges. One key challenge during the production of LNG is the presence of trace amounts of heavy components in the gas feed composition is known to induce the precipitation of a solid phase during the cooling process, which presents the risk of equipment plugging and associated hazards. However, there are very few general thermodynamic tools available for the prediction of solid-liquid equilibrium for very low-temperature conditions (<−200°F). In this study, available thermodynamic predictive tools are evaluated for the determination of LNG crystallization conditions. Previously presented crystallization prediction models are examined, and potential pitfalls identified. The results from this study are expected to provide a better understanding of the thermodynamics of LNG processes and provide a framework for subsequent work in the analysis of LNG refrigeration and liquefaction processes—typically considered the key elements of any LNG project.

Thermodynamic Analysis of Resources Used in Manufacturing Processes

In this study we use a thermodynamic framework to characterize the material and energy resources used in manufacturing processes. The analysis and data span a wide range of processes from "conventional" processes such as machining, casting, and injection molding, to the so-called "advanced machining" processes such as electrical discharge machining and abrasive waterjet machining, and to the vapor-phase processes used in semiconductor and nanomaterials fabrication. In all, 20 processes are analyzed. The results show that the intensity of materials and energy used per unit of mass of material processed (measured either as specific energy or exergy) has increased by at least 6 orders of magnitude over the past several decades. The increase of material/energy intensity use has been primarily a consequence of the introduction of new manufacturing processes, rather than changes in traditional technologies. This phenomenon has been driven by the desire for precise small-scale devices and product features and enabled by stable and declining material and energy prices over this period. We illustrate the relevance of thermodynamics (including exergy analysis) for all processes in spite of the fact that long-lasting focus in manufacturing has been on product quality--not necessarily energy/material conversion efficiency. We promote the use of thermodynamics tools for analysis of manufacturing processes within the context of rapidly increasing relevance of sustainable human enterprises. We confirm that exergy analysis can be used to identify where resources are lost in these processes, which is the first step in proposing and/or redesigning new more efficient processes.

On the stored and dissipated energies in heterogeneous rate-independent systems: theory and simple examples

The aim of the present work is to determine the amount of dissipated and stored energies in structures containing frictional cracks and elasto-plastic zones. The proposed theory combines micromechanical and thermodynamic tools to calculate both energies. Using simple examples, it is shown that the Taylor–Quinney coefficient is not a constant, and can be much less than the values usually considered (i.e. close to unity).

Exergy analysis of binary plate distillation column operations

This work developed the stage-exergy rate diagrams for determining feasible operating conditions in binary distillation columns and studied the effects of key process parameters on the stage-exergy rate diagrams, energy and exergy efficiencies, and irreversibility rate at various conditions. HYSYS (2003) process simulation software and Microsoft EXCEL spreadsheet were used for process analysis. The stage-exergy rate diagram was found to be a very useful thermodynamic tool, which should be used to compliment exergy efficiency results in exergy studies. Increase in reference temperature was found to decrease the exergy efficiency and to increase the irreversibility rate of the distillation unit.

Inconsistency of the judgment matrix in the AHP method and the decision maker’s knowledge

In this paper, we propose a method for a quantitative estimation of the decision maker’s knowledge in the context of the Analytic Hierarchy Process (AHP) in cases where the judgment matrix is inconsistent. We show that the matrix of deviation from the transitivity condition corresponds to the rate matrix for transaction costs in the financial market. For the quantitative estimation of the decision maker’s professionalism, we apply the Ising model and thermodynamics tools.

Microdomain Ca2+ dynamics in mammalian muscle following prolonged high pressure treatments

High pressure (HP) applications are an important thermodynamic tool to influence cellular processes. Especially processes that undergo large volume changes, e.g. opening or closing of ion channels, are in particular susceptible to HP treatments. Such volume changes are extremely difficult to assess for intracellular ion channels, like ryanodine receptors (RyR) residing in the membrane of organelles. In skeletal muscle, RyR act as Ca2+ release channels. We previously showed that plasmalemmal Na+ and Ca2+ ion channels were irreversibly altered after prolonged 20 MPa treatments. Here, changes in microdomain Ca2+ levels due to elementary Ca2+ release events (ECRE) were monitored using confocal fluorescence microscopy. We studied ECRE in mammalian skeletal muscle following 3 h HP treatments up to 30 MPa to clarify whether RyR induced intracellular microdomain Ca2+ dynamics was more susceptible to HP treatment compared to surface membrane ion currents. ECRE frequencies exponentially declined with pressure. ECRE amplitudes and rise times (RT) were quite robust towards HP treatments. In contrast, spatial and temporal ECRE extension showed a tendency towards larger values up to 20 MPa but declined for higher pressures. Activation volumes for pressure-induced persistent ECRE alterations were zero for RT but showed a bimodal behavior for event duration. It seems that although ECRE frequencies are markedly reduced, ECRE morphology is less affected by HP. In particular, RyR opening time is practically unaltered and the observed morphological ECRE changes might reflect alterations in local Ca2+ buffers and Ca2+ concentration profiles rather than involvement of RyR in mammalian skeletal muscle.

Countercurrent supercritical fluid extraction of different lipid-type materials: Experimental and thermodynamic modeling

This work presents the main results attained by our research group merging chemical reaction, supercritical fluid extraction, thermodynamic phase equilibrium modeling and chemical analysis to study alternative supercritical extraction processes related with oil-type materials. Different fatty oil raw materials were fractionated in a countercurrent packed column using supercritical carbon dioxide and following different process targets, such as the deacidification of lampante olive oil and the recovery of minor lipid compounds (squalene, tocopherols and phytosterols) from industrial byproducts and wastes. If necessary, in order to facilitate the concentration of the preferred minor lipids in the raffinate product, the raw material employed was previously esterified. The GC-EoS model was used as the thermodynamic tool to represent phase equilibria behavior of the multicomponent oil-type material + CO 2 mixture, and was employed to guide experiments so as to simulate and optimize the supercritical extraction processes. The coupling of thermodynamic modeling with experimental work has offered an efficient low-time consuming tool to analyze the viability of supercritical extraction processes.

Computational quantum mechanics: An underutilized tool in thermodynamics

AbstractIn this paper, we highlight the various ways computational quantum mechanics (QM) can be used in applied thermodynamics. We start with the most rigorous procedures of calculating the interactions between molecules that can then be used in simulation and progress, in steps, to less rigorous but easily used methods, including the very successful continuum solvation models.

Thermodynamic modeling and analysis of biomass gasification for hydrogen production in supercritical water

Abstract Biomass gasification in supercritical water is a promising technology for hydrogen production by utilizing wet biomass. A new experimental system of biomass gasification in supercritical water was built in SKLMF. In this paper, a comprehensive thermodynamic analysis, including chemical equilibrium in the reactor, gas–liquid equilibrium in the high-pressure separator, exergy and energy analysis of the whole system, was conducted. Chemical equilibrium model is based on minimizing Gibbs free energy. By chemical equilibrium analysis in the reactor, rules of the main parametric effects on biomass gasification in supercritical water are obtained. Simultaneously, a high-pressure gas–liquid equilibrium model was proposed based on modified universal functional activity coefficient (UNIFAC) model, Soave–Redlich–Kwong (SRK) equation of state and modified Huron–Vidal second-order (MHV2) mixing rule. Effects of pressure, temperature and water recycled ratio on gas–liquid equilibrium in high-pressure separation were discussed. Finally, results from energy and exergy analysis show that energy and exergy efficiencies of the whole system are in excess of 40% and increase with increasing heat transfer efficiencies. Energy loss of the system is caused mainly by heat transfer and exergy loss is mainly caused by heat transfer and chemical reaction. Our research provided a thermodynamic tool for improvement of design and operation optimization of biomass gasification system in SKLMF, which may be also applicable to other biomass gasification system.

Multicomponent transport studies of crude oils and asphaltenes in DSC program

Crude oils have matured during ages in reservoirs under obvious non-equilibrium conditions. The resulting stratification and phases present can be predicted only with non-equilibrium thermodynamics tools. Possibly, convection is present and enforced by the Soret effect. These parameters are the focus of the MAP DSC (Diffusion and Soret Coefficients) multicomponent studies. Theoretical and ground based studies are completed by measurements performed in the SCCO experiments (Soret Coefficients of Crude Oils), of the DSC experiment on SODI facility (Beginning 2008). The problem is presented here in a simplified manner using Maxwell-Stefan formalism, and is applied to some situations occurring in reservoirs and in the GATE experiment proposed for the study of growth conditions of asphaltenes.

Producing a Scale-Invariant Spectrum of Perturbations in a Hagedorn Phase of String Cosmology

We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.