General Thermodynamic Model Research Articles

Criteria of Distribution Transitions in Dispersed Multiphase Systems Based on an Extended Lattice Model.

Dispersed multiphase systems are ubiquitous in biological systems, energy industries, and medical science. The distribution transition of the dispersed phase is critical to the properties and functions of the multiphase systems, among which the agglomeration, adsorption, and extraction processes are of most significance due to their impact on the colloidal stability, interface modification, and particle synthesis. To reveal fundamental correlations between the macroscopic particle distributions and the microscopic interactions, general thermodynamic models of the dispersed multiphase systems are needed. Here, based on Meyer's model, which is restricted to binary isotropic mixtures, we propose a novel extended lattice model that can be applied to multicomponent anisotropic mixtures with interfaces considered. For agglomeration, adsorption, and extraction processes, the approximate free energy differences between the initial distribution and the final distribution are obtained. Based on the minimum free energy principle, the above free energy differences are used to derive three criteria for the prediction of the preferable distribution of the system with given interparticle interaction potentials. While the quasi-uniform number density assumption is still required for all the previous lattice models, the long-range interactions neglected by previous lattice models are incorporated. The validity of our model and criteria is verified by many-body dissipative particle dynamics (mDPD) simulations. By tuning the interaction coefficients between mDPD particles, the simulated distribution transitions for all the agglomeration, adsorption, and extraction cases perfectly match the predictions from the three criteria. The good agreement between the theoretical predictions and the mDPD simulation results shows the great potential of our model for applications in various dispersed multiphase systems.

Analytical and numerical modelling of biomass gasification in downdraft gasifiers

The ever-growing energy demand and environmental pollution level have pushed research interest toward the development of new promising technologies to utilize bioenergy sustainably. In this scenario, biomass gasification has been regarded as a promising renewable energy resource that, if efficiently exploited, can contribute to the reduction of dependency on fossil fuel and CO2 emissions from the power sector. Nevertheless, exploitation of biomass gasification still requires to overcome technological and logistical issues. In this work, the authors propose a general thermodynamic model able to predict the steady operating conditions of biomass gasification. Assuming thermodynamic equilibrium, the model is able to predict temperature, mass flow rate and composition of produced syngas. Moreover, a numerical model of the biomass gasification system has been developed by using the commercial software Aspen Plus. It is a steady-state zero-dimensional equilibrium model, based on the mass and energy balances, assuming the Gibbs free energy minimization. Aspen Plus allows building models of customized operative units using the Fortran code. In order to assure the performance of both analytical and Aspen Plus models, numerical results are compared with experimental data available in the scientific literature for downdraft gasifiers.

The excess volumes of protic ionic liquids and its significance to their thermodynamic modelling

With the increasing number of applications being reported for protic ionic liquids (PILs), there is a demand for the development of thermodynamic models that can accurately describe their thermophysical properties and phase equilibria, with equations of state (EoS) derived from the Statistical Associating Fluid Theory (SAFT) being amongst the best.This work aims at discussing the development of such models and the advantages of not using the pseudo-pure component approach commonly adopted in literature, but instead using an individual component approach as previously proposed for Deep Eutectic Systems (DES). Although both PILs and DESs are highly non-ideal mixtures of Brønsted or Lewis acids and bases, PILs are shown to exhibit large negative excess molar volumes when compared to DESs that prevent the direct prediction of the PIL properties by modelling it as a mixture of its precursors, using an individual component approach. To overcome this limitation, and to highlight the importance of being aware of such characteristic of the PILs when developing new models, a simplified volume-shift type correction is applied in the framework of PC-SAFT EoS to provide a more accurate modelling of PILs density data. The implemented correction is shown to increase the accuracy and predictive ability of the model, and its limitations are discussed, suggesting the need for additional experimental data (e.g., on the quantification of the different species present) for the development of robust and general thermodynamic models for PILs

A general thermodynamic model for eutectics of phase change molten salts in concentrating solar power applications

• Development of a thermodynamic simulation tool • Design of innovative molten salts-based phase change materials • Practical modeling method to determine eutectic points • Calorimetric and theoretical investigation of ternary phase diagrams • Employment of NRTL and Wilson equations for activity coefficients

A general thermodynamic model for the long-period stacking ordered phases in magnesium alloys

Abstract A thermodynamic model Mgx(Xs, Mg)6(Xl, Mg)8 (Xs and Xl are elements smaller and larger than Mg) for long-period stacking ordered phases (LPSOs) was proposed based on two key factors: the Xs6Xl8-type L12 clusters and the variation of chemical compositions. In general, all available LPSOs can be described with this model. As a representative system, Mg-Y-Zn with three LPSOs was investigated using the CALPHAD (calculation of phase diagram) approach aided with first-principles calculations. Two new three-phase equilibria were predicted and were validated by key experiments. The model-based descriptions will be the basis for the research and development of magnesium alloys.

Massively parallel CRISPRi assays reveal concealed thermodynamic determinants of dCas12a binding

The versatility of CRISPR-Cas endonucleases as a tool for biomedical research has led to diverse applications in gene editing, programmable transcriptional control, and nucleic acid detection. Most CRISPR-Cas systems, however, suffer from off-target effects and unpredictable nonspecific binding that negatively impact their reliability and broader applicability. To better evaluate the impact of mismatches on DNA target recognition and binding, we develop a massively parallel CRISPR interference (CRISPRi) assay to measure the binding energy between tens of thousands of CRISPR RNA (crRNA) and target DNA sequences. By developing a general thermodynamic model of CRISPR-Cas binding dynamics, our results unravel a comprehensive map of the energetic landscape of nuclease-dead Cas12a (dCas12a) from Francisella novicida as it inspects and binds to its DNA target. Our results reveal concealed thermodynamic factors affecting dCas12a DNA binding, which should guide the design and optimization of crRNA that limits off-target effects, including the crucial role of an extended protospacer adjacent motif (PAM) sequence and the impact of the specific base composition of crRNA-DNA mismatches. Our generalizable approach should also provide a mechanistic understanding of target recognition and DNA binding when applied to other CRISPR-Cas systems.

Modelling non-equilibrium self-assembly from dissipation

Non-equilibrium self-assembly is ubiquitous in physico-chemical and biological systems, and manifests itself at different scales, ranging from the molecular to the cosmological. The formation of microtubules, gels, cells and living beings among many others takes place through self-assembly under nonequilibrium conditions. We propose a general thermodynamic non-equilibrium model to understand the formation of assembled structures such as gels and Liesegang patterns and at the same time able to describe the kinetics and the energetics of the structure formation process. The model is supported for a global mechanism to obtain self-assembled structures from building blocks via activation, deactivation, assembly, and disassembly processes. It is proposed that the resulting structures can be characterised by a structural parameter. Our model may contribute to a better understanding of non-equilibrium self-assembly processes and give deeper insight as to how to obtain a specific structural architecture to materials, such as hydrogels which are of great importance in the design of advanced devices and novel materials.

Modelling and experimental validation of advanced adiabatic compressed air energy storage with off‐design heat exchanger

Advanced adiabatic compressed air energy storage (AA-CAES) has been recognised as a promising approach to boost the integration of renewables in the form of electricity and heat in integrated energy systems. Nevertheless, the uncertainty and variability of renewables spark the consideration of the off-design thermodynamics of AA-CAES, particularly when the heat exchanger is equipped to collect and recycle air-compression heat. Here, the authors propose a general off-design thermodynamic simulation model of AA-CAES incorporating the part-load characteristics of heat exchangers, and validate the effectiveness of the proposed model on a practical AA-CAES demonstration pilot. The results indicate that the simulation model offers an acceptable approximation for the practical operation behaviour of AA-CAES facility and decreases the modelling error from 20.8 to 6.28% compared with the existing model. The proposed simulation model is expected to provide insights into the investigation of the dynamic characteristics of AA-CAES in the future integrated energy system.

A General Thermodynamic Model for the Long-Period Stacking Ordered Phases in Magnesium Alloys

A thermodynamic model Mgx(Xs, Mg)6(Xl, Mg)8 (Xs and Xl are elements smaller and larger than Mg) for long-period stacking ordered phases (LPSOs) was proposed based on two key factors: the Xs6Xl8-type L12 clusters and the variation of chemical compositions. In general, all available LPSOs can be described with this model. As a representative system, Mg-Y-Zn with three LPSOs was investigated using the CALPHAD (calculation of phase diagram) approach aided with first-principles calculations. Two new three-phase equilibria were predicted and were validated by key experiments. The model-based descriptions will be the basis for the research and development of magnesium alloys.

Hydrogen-rich syngas produced from co-gasification of wet sewage sludge and torrefied biomass in self-generated steam agent

A synergistic scheme of co-gasification of wet sewage sludge and torrefied biomass was proposed in order to get the hydrogen-rich syngas, which could avoid the dual energy input for drying of wet sewage sludge and steam generation. Co-gasification behavior of wet sewage sludge and torrefied biomass was evaluated by using a general non-stoichiometric thermodynamic equilibrium model developed based upon the Gibbs free energy minimization. The tenary plot of CHO system was used to evaluate the theoretical carbon formation performance at thermodynamic equilibrium state. The effects of mixing ratio and torrefaction severity on carbon conversion ratio, compositions of dry syngas, and H2 yield were also addressed. High mixing ratio of wet sewage sludge and high gasification temperature were required for the high carbon conversion ratio. The gasification temperature of 1100 K was a favorable level for the H2 yield and energy input. The optimal mixing ratio range of wet sewage sludge for low and middle temperatures torrefied biomass samples was between 30% and 40%, while that for high temperature ones was approximately 55%. This work could provide a feasible technical route and basic data for the resource and energy utilization of sewage sludge and biomass.

Roads to improve the performance of hybrid thermosolar gas turbine power plants: Working fluids and multi-stage configurations

This paper presents a general thermodynamic model for hybrid Brayton central tower thermosolar plants. These plants have been proved to be technically feasible but research and development efforts need to be done in order to improve its commercial interest. From the thermodynamic viewpoint it is necessary to increase its performance to get larger power production with reduced fuel consumption, and so reduced emissions. A model for multi-step compression and expansion is developed with that aim. The model is flexible and allows to simulate recuperative or non-recuperative plants, with an arbitrary number of stages and working with different subcritical fluids. The results for multi-step configurations are compared with those obtained for a plant with one turbine and one compressor. Different working fluids are analyzed, including air, nitrogen, carbon dioxide, and helium. Several plant layouts and the corresponding optimal pressure ratios are analyzed. Configurations with two-stages compression with intercooling combined with one or two expansion stages can significantly improve overall plant efficiency and lower fuel consumption. Power block efficiencies can reach 0.50 and overall plant efficiency can attain values about 0.40 working with air or carbon dioxide. For instance, comparing with a single-stage plant running with air, a plant working with subcritical carbon dioxide and two compression stages with intercooling can reach an overall efficiency about 19% larger and a fuel conversion rate around 23% larger. For such configuration, the specific fuel consumption is predicted to be about 108 kg/(MW h) at design point conditions.

Ni-Substituted Sr(Ti,Fe)O3 SOFC Anodes: Achieving High Performance via Metal Alloy Nanoparticle Exsolution

Summary Electrically conducting oxides have been proposed as alternatives to Ni-based cermet anodes for solid oxide fuel cells (SOFCs) to overcome issues such as coking and impurity poisoning, but their electrochemical performance is typically inferior to that of Ni-based cermets. Here we show that a new oxide composition, Sr 0.95 (Ti 0.3 Fe 0.63 Ni 0.07 )O 3−δ , yields anode polarization resistance competitive with Ni cermets, and substantially better than that of the corresponding Ni-free compound, SrTi 0.3 Fe 0.7 O 3−δ . Exposure to fuel results in exsolution and nucleation of Ni 0.5 Fe 0.5 nanoparticles uniformly dispersed on the Ni-substituted perovskite surface, whereas no nanoparticles are observed on SrTi 0.3 Fe 0.7 O 3−δ . A general thermodynamic model is developed that quantitatively predicts exsolved nanoparticle composition. The reduction in anode polarization resistance by the nanoparticles, by as much as 4 times, is most pronounced at cell operating temperatures below 800°C and low H 2 partial pressures, suggesting that the nanoparticles improve performance by promoting H 2 adsorption.

Toward Rational Design of Oxide-Supported Single-Atom Catalysts: Atomic Dispersion of Gold on Ceria.

We have constructed a general thermodynamic model of chemical potentials and applied ab initio electronic structure and molecular dynamics simulations, as well as kinetic Monte Carlo analysis, to probe the dynamical, reactive, and kinetic aspects of metal single-atom catalysts (SACs) on oxide support. We choose Au single atoms (SAs) supported on ceria as a typical example to demonstrate how our model can guide the rational design of highly stable and reactive SACs. It is shown that, under realistic conditions, various factors such as temperature, pressure, particle size, and the reducibility of the support can strongly affect both the stability and the reactivity of SACs by altering the relative chemical potentials between SAs and metal nanoparticles (NPs). The Au SAs at step sites of ceria support are rather stable, even at temperatures as high as 700 K, and exhibit around 10 orders of magnitude more reactivity for CO oxidation than the terrace sites. Remarkably, under reaction conditions, Au SAs can be dynamically created at the interface of small-size Au NPs on ceria support even without step sites, which accounts for the puzzling significant size effect in gold catalysis. Our work underscores an unrecognized critical role of Au SAs in gold nanocatalysis and provides a general methodology for designing the metal SACs on oxide supports.

Development of an oxide-dispersion-strengthened steel by introducing oxygen carrier compound into the melt aided by a general thermodynamic model.

In general, melting process is not a common method for the production of oxide dispersion strengthened (ODS) alloys due to agglomeration and coarsening of oxide particles. However, vacuum casting process has recently been employed as a promising process to produce micro-scale oxide dispersed alloys. In this paper, we report the process and characterization of in situ formation and uniform dispersion of nano-scale Y-Ti oxide particles in Fe-10Ni-7Mn (wt.%) alloy. The processing route involves a solid-liquid reaction between the added TiO2 as an oxygen carrier and dissolved yttrium in liquid metal leading to an optimal microstructure with nano-sized dispersed oxide particles. The developed thermodynamic model shows the independence of the final phase constituents from experimental conditions such as melting temperature or vacuum system pressure which offers a general pathway for the manufacture of oxide dispersion strengthened materials.

Crowding-Induced Mixing Behavior of Lipid Bilayers: Examination of Mixing Energy, Phase, Packing Geometry, and Reversibility.

In an effort to develop a general thermodynamic model from first-principles to describe the mixing behavior of lipid membranes, we examined lipid mixing induced by targeted binding of small (Green Fluorescent Protein (GFP)) and large (nanolipoprotein particles (NLPs)) structures to specific phases of phase-separated lipid bilayers. Phases were targeted by incorporation of phase-partitioning iminodiacetic acid (IDA)-functionalized lipids into ternary lipid mixtures consisting of DPPC, DOPC, and cholesterol. GFP and NLPs, containing histidine tags, bound the IDA portion of these lipids via a metal, Cu(2+), chelating mechanism. In giant unilamellar vesicles (GUVs), GFP and NLPs bound to the Lo domains of bilayers containing DPIDA, and bound to the Ld region of bilayers containing DOIDA. At sufficiently large concentrations of DPIDA or DOIDA, lipid mixing was induced by bound GFP and NLPs. The validity of the thermodynamic model was confirmed when it was found that the statistical mixing distribution as a function of crowding energy for smaller GFP and larger NLPs collapsed to the same trend line for each GUV composition. Moreover, results of this analysis show that the free energy of mixing for a ternary lipid bilayer consisting of DOPC, DPPC, and cholesterol varied from 7.9 × 10(-22) to 1.5 × 10(-20) J/lipid at the compositions observed, decreasing as the relative cholesterol concentration was increased. It was discovered that there appears to be a maximum packing density, and associated maximum crowding pressure, of the NLPs, suggestive of circular packing. A similarity in mixing induced by NLP1 and NLP3 despite large difference in projected areas was analytically consistent with monovalent (one histidine tag) versus divalent (two histidine tags) surface interactions, respectively. In addition to GUVs, binding and induced mixing behavior of NLPs was also observed on planar, supported lipid multibilayers. The mixing process was reversible, with Lo domains reappearing after addition of EDTA for NLP removal.

Domain-swap polymerization drives the self-assembly of the bacterial flagellar motor.

Large protein complexes assemble spontaneously, yet their subunits do not prematurely form unwanted aggregates. This paradox is epitomized in the bacterial flagellar motor, a sophisticated rotary motor and sensory switch consisting of hundreds of subunits. Here we demonstrate that Escherichia coli FliG, one of the earliest-assembling flagellar motor proteins, forms ordered ring structures via domain-swap polymerization, which in other proteins has been associated with uncontrolled and deleterious protein aggregation. Solution structural data, in combination with in vivo biochemical cross-linking experiments and evolutionary covariance analysis, revealed that FliG exists predominantly as a monomer in solution but only as domain-swapped polymers in assembled flagellar motors. We propose a general structural and thermodynamic model for self-assembly, in which a structural template controls assembly and shapes polymer formation into rings.

Thermodynamic optimization of three-thermal irreversible systems

Multi-temperature-level systems enlarge the prospects and degrees of freedom for an effective design and an environment-friendly use of energy. Based on a general thermodynamic model of three-thermal cycles and finite thermal capacity of the heat sources, this paper aims at the analysis and the performance optimization of these systems by considering the influence of irreversibility. Suitable dimensionless parameters for an overall optimization are introduced and their influence on the cycle efficiency is investigated. This approach identifies the limitations imposed to the physical processes by accounting for the inevitable dissipation due to their constrained duration and intensity, and constitutes a general thermodynamic criterion for the optimization of three-thermal irreversible systems. Dependence on the main factors is highlighted in a way that shows how to change them in order to improve the overall efficiency. Under this point of view, the analysis evaluates COP improvements and can be used to perform plant diagnostics, besides predicting the system performance. The use of this criterion is exemplified for the absorption chiller application case.

Causal Entropic Forces

Recent advances in fields ranging from cosmology to computer science have hinted at a possible deep connection between intelligence and entropy maximization, but no formal physical relationship between them has yet been established. Here, we explicitly propose a first step toward such a relationship in the form of a causal generalization of entropic forces that we find can cause two defining behaviors of the human "cognitive niche"-tool use and social cooperation-to spontaneously emerge in simple physical systems. Our results suggest a potentially general thermodynamic model of adaptive behavior as a nonequilibrium process in open systems.

Mechanistic Electron Transport Chain Model Explains ROS Production in Different Respiratory Modes

Reactive oxygen species (ROS) have been implicated in disorders ranging from neurodegenerative diseases to diabetes to heart disease. In cardiac myocytes mitochondria represent the predominant source of ROS, specifically complexes I and III. The model presented here endeavors to explore and elucidate the modulation of electron transport chain ROS production under state 3 versus state 4 respiration and the role of succinate as a substrate. A mechanistic complex III model was developed, driven by redox potential differences between adjacent redox centers. This model shows that ROS production increases exponentially with membrane potential when in state 4. Because the mechanism of ROS production from complex I remains unknown, a more general thermodynamic model was used to describe the influence of NADH/NAD+ and ubiquinone/ubiquinol redox potentials on complex I-derived ROS release. This release occurs in the presence of NADH and succinate, leading to a highly reduced ubiquinone pool, displaying the highest ROS production flux in state 4. Overall, total ROS production is moderate in state 3 and increases substantially under state 4 conditions. The ROS production model was combined with a minimal model of ROS scavenging. Since scavenging systems rely on the reduced form of NADPH, scavenging capacity decreases as the cellular environment becomes more oxidized. When the cellular redox status is modified by increasing mitochondrial inner membrane uncoupling, simulations with the combined model of ROS production and scavenging show that ROS levels initially decline as production drops off with decreasing membrane potential and then increase as the mitochondria become more oxidized and scavenging capacity is exhausted. Hence this mechanistic model of ROS production demonstrates how ROS levels are controlled by the cellular redox environment in agreement with the Redox-optimized ROS Balance hypothesis.

On the thermodynamics of biomolecule surface transformations

Biological surface science is receiving great and renewed attention owing the rising interest in applications of nanoscience and nanotechnology to biological systems, with horizons that range from nanomedicine and biomimetic photosynthesis to the unexpected effects of nanomaterials on health and environment. Biomolecule surface transformations are among the fundamental aspects of the field that remain elusive so far and urgently need to be understood to further the field. Our recent findings indicate that surface thermodynamics can give a substantial contribution toward this challenging goal. In the first part of the article, we show that biomolecule surface transformations can be framed by a general and simple thermodynamic model. Then, we explore its effectiveness by addressing some typical cases, including ligand–receptor surface binding, protein thin film machines, nanomechanical aspects of the biomolecule–nanoparticle interface and nanomechanical biosensors.