Hasil untuk "Thermodynamics"

U. F. Kocks

W. G. McMillan, J. Mayer

T. Fichefet, M. Maqueda

H. Callen, H. L. Scott

C. Borgnakke, R. Sonntag

R. Wald

We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of black hole entropy. We conclude with a discussion of some unresolved open issues.

R. Astumian

M. Grmela, H. C. Öttinger

R. Guillaumont, F. Mompeán

Shu-Kun Lin

For readers interested in the Prigogine school of thermodynamics, this book is the first choice because it is a textbook.[...]

M. Horodecki, J. Oppenheim

The relationship between thermodynamics and statistical physics is valid in the thermodynamic limit—when the number of particles becomes very large. Here we study thermodynamics in the opposite regime—at both the nanoscale and when quantum effects become important. Applying results from quantum information theory, we construct a theory of thermodynamics in these limits. We derive general criteria for thermodynamical state transitions, and, as special cases, find two free energies: one that quantifies the deterministically extractable work from a small system in contact with a heat bath, and the other that quantifies the reverse process. We find that there are fundamental limitations on work extraction from non-equilibrium states, owing to finite size effects and quantum coherences. This implies that thermodynamical transitions are generically irreversible at this scale. As one application of these methods, we analyse the efficiency of small heat engines and find that they are irreversible during the adiabatic stages of the cycle. The usual laws of thermodynamics that are valid for macroscopic systems do not necessarily apply to the nanoscale, where quantum effects become important. Here, the authors develop a theoretical framework based on quantum information theory to properly treat thermodynamics at the nanoscale.

M. Bazant

Advances in the fields of catalysis and electrochemical energy conversion often involve nanoparticles, which can have kinetics surprisingly different from the bulk material. Classical theories of chemical kinetics assume independent reactions in dilute solutions, whose rates are determined by mean concentrations. In condensed matter, strong interactions alter chemical activities and create variations that can dramatically affect the reaction rate. The extreme case is that of a reaction coupled to a phase transformation, whose kinetics must depend not only on the order parameter but also on its gradients at phase boundaries. Reaction-driven phase transformations are common in electrochemistry, when charge transfer is accompanied by ion intercalation or deposition in a solid phase. Examples abound in Li-ion, metal-air, and lead-acid batteries, as well as metal electrodeposition-dissolution. Despite complex thermodynamics, however, the standard kinetic model is the Butler-Volmer equation, based on a dilute solution approximation. The Marcus theory of charge transfer likewise considers isolated reactants and neglects elastic stress, configurational entropy, and other nonidealities in condensed phases. The limitations of existing theories recently became apparent for the Li-ion battery material LixFePO4 (LFP). It has a strong tendency to separate into Li-rich and Li-poor solid phases, which scientists believe limits its performance. Chemists first modeled phase separation in LFP as an isotropic "shrinking core" within each particle, but experiments later revealed striped phase boundaries on the active crystal facet. This raised the question: What is the reaction rate at a surface undergoing a phase transformation? Meanwhile, dramatic rate enhancement was attained with LFP nanoparticles, and classical battery models could not predict the roles of phase separation and surface modification. In this Account, I present a general theory of chemical kinetics, developed over the past 7 years, which is capable of answering these questions. The reaction rate is a nonlinear function of the thermodynamic driving force, the free energy of reaction, expressed in terms of variational chemical potentials. The theory unifies and extends the Cahn-Hilliard and Allen-Cahn equations through a master equation for nonequilibrium chemical thermodynamics. For electrochemistry, I have also generalized both Marcus and Butler-Volmer kinetics for concentrated solutions and ionic solids. This new theory provides a quantitative description of LFP phase behavior. Concentration gradients and elastic coherency strain enhance the intercalation rate. At low currents, the charge-transfer rate is focused on exposed phase boundaries, which propagate as "intercalation waves", nucleated by surface wetting. Unexpectedly, homogeneous reactions are favored above a critical current and below a critical size, which helps to explain the rate capability of LFP nanoparticles. Contrary to other mechanisms, elevated temperatures and currents may enhance battery performance and lifetime by suppressing phase separation. The theory has also been extended to porous electrodes and could be used for battery engineering with multiphase active materials. More broadly, the theory describes nonequilibrium chemical systems at mesoscopic length and time scales, beyond the reach of molecular simulations and bulk continuum models. The reaction rate is consistently defined for inhomogeneous, nonequilibrium states, for example, with phase separation, large electric fields, or mechanical stresses. This research is also potentially applicable to fluid extraction from nanoporous solids, pattern formation in electrophoretic deposition, and electrochemical dynamics in biological cells.

N. Altamirano, D. Kubizňák, R. Mann et al.

Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran* Author to whom correspondence should be addressed; E-Mail: rbmann@sciborg.uwaterloo.ca;Tel.: +1-519-882-1211.Received: 9 January 2014; in revised form: 6 February 2014 / Accepted: 7 February 2014 /Published: 3 March 2014Abstract: In this review we summarize, expand, and set in context recent developmentson the thermodynamics of black holes in extended phase space, where the cosmologicalconstant is interpreted as thermodynamic pressure and treated as a thermodynamic variablein its own right. We specifically consider the thermodynamics of higher-dimensionalrotating asymptotically flat and AdS black holes and black rings in a canonical (fixedangular momentum) ensemble. We plot the associated thermodynamic potential—theGibbs free energy—and study its behavior to uncover possible thermodynamic phasetransitions in these black hole spacetimes. We show that the multiply-rotating Kerr-AdSblack holes exhibit a rich set of interesting thermodynamic phenomena analogous to the“every day thermodynamics” of simple substances, such as reentrant phase transitions ofmulticomponent liquids, multiple first-order solid/liquid/gas phase transitions, and liquid/gasphase transitions of the van der Waals type. Furthermore, the reentrant phase transitions alsooccur for multiply-spinning asymptotically flat Myers–Perry black holes. These phenomenado not require a variable cosmological constant, though they are more naturally understoodin the context of the extended phase space. The thermodynamic volume, a quantity conjugateto the thermodynamic pressure, is studied for AdS black rings and demonstrated to satisfy thereverse isoperimetric inequality; this provides a first example of calculation confirming the

Martha Fernanda Mohedano-Castillo, Carlos Díaz-Delgado, Boris Miguel López-Rebollar et al.

Micro-hydropower technologies are increasingly attracting attention due to their potential to contribute to sustainable energy generation. With the growing global demand for electricity, it is essential to research and innovate in the development of devices capable of harnessing hydroelectric potential through such technologies. In this context, the Archimedes screw generator (ASG) stands out as a device that potentially offers significant advantages for micro-hydropower generation. This study aimed, through a simplified yet effective method, to analyze and determine the simultaneous effects of the number of blades, inclination angle, and flow rate on the torque, mechanical power, and efficiency of an ASG. Computational Fluid Dynamics (CFD) was employed to obtain the torque and perform the hydrodynamic analysis of the devices, in order to compare the results of the optimal geometric and operational characteristics with previous studies. This proposal also helps guide future work in the preliminary design and evaluation of ASGs, considering the geometric and flow conditions that take full advantage of the available water resources. Under the specific conditions analyzed, the most efficient generator featured three blades, a 20° inclination, and an inlet flow rate of 24.5 L/s, achieving a mechanical power output of 117 W with an efficiency of 71%.

Stefan Heinz

The Terra Incognita (or gray-zone) problem seen in atmospheric flow simulations causes serious consequences: it implies, e.g., significantly incorrect flow predictions and results that often simply depend on flow simulation settings as the computational grid applied. There is definitely the need for a robust gray-zone modeling to ensure that research and technology decisions are based on reliable results. As a matter of fact, solution approaches to deal with this problem in atmospheric and engineering type simulations reveal remarkable differences. In contrast to atmospheric flow simulations, there exists a broad spectrum of solution concepts for engineering applications. Driven by these conceptual differences, the paper presents an analysis of the Terra Incognita problem and corresponding solution concepts. Specifically, the paper presents a modeling approach that overcomes the core problem of currently applied methods. A new method of providing a resolution-aware turbulence length scale (one of the major problems in atmospheric flow simulations) is presented. This approach is capable of seamlessly covering the full range of microscale to mesoscale simulations, and to appropriately deal with mesoscale to microscale couplings.

Zonglin Yi, Yi Zhou, Hao Liu et al.

Abstract Accurate prediction of practical reduction electrode potentials (E red) of electrolyte solvents of electrochemical energy storage devices relies on calculating the Gibbs free energy in their reduction reaction. However, the emergence of new electrolyte solvents and additives leaves most of the reaction mechanisms unveiled. Here, we provide a machine-learning-assisted workflow of thermodynamically quantified E red prediction for electrolyte solvents. A computational hydrogen electrode model based on density functional theory calculation is generalized for calculating the reaction free energy of electrochemical elementary steps. Machine-learning models are trained based on the organic and inorganic electrolyte solvents that possess experimentally identified reduction mechanisms. Validation of the best-scoring model is conducted by experimental validation of 6 additional solvents. Multiple thermodynamics features are found impactful on E red through different chemical bonding with reaction intermediates. This workflow enables accurate E red prediction for electrolyte solvents without identified reduction mechanisms, and is widely applicable in the electrochemical energy storage area.

Lamya Almaghamsi, Samah Horrigue

In this work, we establish the existence of at least one solution for a <i>p</i>-Laplacian Langevin differential equation involving the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ψ</mi></semantics></math></inline-formula>-Hilfer fractional derivative with antiperiodic boundary conditions. More precisely, we transform the studied problem into a Hammerstein integral equation, and after that, we use the Schafer fixed point theorem to prove the existence of at least one solution. Two examples are provided to validate the main result.

C. Broeck, M. Esposito

We revisit stochastic thermodynamics for a system with discrete energy states in contact with a heat and particle reservoir.

Masaki Kato, Teruki Ando, Cho Rong Kim et al.

Gas separation technology is crucial for addressing environmental issues like CO2 capture to mitigate climate change. While membrane separation is often cited for its efficiency, accurate estimations are scarce. We present estimations based on classical thermodynamics for very lean CO2 composition (400 ppm), revealing rich details in simple systems and deriving guiding principles. Our main conclusion emphasizes the critical necessity of a high membrane separation ratio, and we discuss candidates for achieving this goal.

B. Eslam Panah, M. E. Rodrigues

Abstract Motivated by the impact of the phantom field (or anti-Maxwell field) on the structure of three-dimensional black holes in the presence of the cosmological constant, we present the first extraction of solutions for the phantom BTZ (A)dS black hole. In this study, we analyze the effect of the phantom field on the horizon structure. Furthermore, we compare the BTZ black holes in the presence of both the phantom and Maxwell fields. Additionally, we calculate the conserved and thermodynamic quantities of the phantom BTZ black holes, demonstrating their compliance with the first law of thermodynamics. Subsequently, we assess the effects of the electrical charge and the cosmological constant on the local stability in the canonical ensemble by considering these fields with respect to the heat capacity. We then investigate the global stability area of the BTZ black holes with phantom and Maxwell fields within the grand canonical ensemble using Gibbs free energy. In this analysis, we evaluate the influence of the electrical charge and the cosmological constant on this area.