Terms Of Entropy Production Research Articles

Numerical study of the energy loss in the bulb tubular pump system focusing on the off-design conditions based on combined energy analysis methods

The unsteady flow characteristics of the low-head bulb tubular pump highly affects the operation efficiency and stability of the whole system. The purpose of this paper is to investigate the dominating loss area in a typical tubular pump using the combined energy analysis methods. The transient multi-condition flow through the pump system is simulated based on N–S equation integrating SST k-ω model. The power loss characteristics of each flow passage component are analyzed in terms of total pressure variation, entropy production and energy balance equation. The turbulent entropy generation power (PSD') in the entropy production and the turbulent kinetic energy production (PL3) of the energy balance equation are the primary source of power loss, indicating that the fully developed turbulent flow tends to generate considerable loss in the pump system, followed by the power loss of solid wall (PSW and PLW). The distribution of power loss in the impeller and diffuser was comprehensively exhibited and it was found that the undesirable flow patterns are mainly caused by blades and walls. The rim region in impeller domain with volume fraction of 15% induces the energy loss of approximately 45% due to the presence of solid wall and tip leakage vortex (TLV). Furthermore, the individual grid volume is considered to better locate and visualize regions with our great interest, and a number of typical vortex structures are identified under several flow rates showing that the positive attack angle is more likely to caused flow instability and energy loss at low flow rate condition.

Thermodynamic forces and flows between a thermal bath and a squeezed thermal bath: Application to optomechanical systems

When a quantum system is coupled to two thermal baths at different temperatures, the temperature gradient as a thermodynamic force causes stationary heat flow within the system. We present a theoretical model to study how quantum features of squeezed thermal reservoirs affect the classical formulation of entropy production in terms of generalized forces and flows. Applying the quantum phase-space method to calculate Wigner entropy production helps us identify heat and squeezing fluxes and their corresponding generalized forces in terms of input-noise correlations of both reservoirs. Our study highlights the essential role played by the correlation of the input-noise operators of the thermal squeezed bath, which are asymmetric (squeezed and unsqueezed) and far from thermal equilibrium. Using the framework for an optomechanical system, we find the regime in which heat flows from the cold squeezed thermal bath to the hot thermal bath without violating the second law of thermodynamics and the regime in which entropy production is purely a quantum-mechanical effect. The results can be useful for improving the performance of Gaussian heat engines operating with squeezed thermal reservoirs.

Upper bound for quantum entropy production from entropy flux.

Entropy production is a key quantity characterizing nonequilibrium systems. However, it can often be difficult to compute in practice, as it requires detailed information about the system and the dynamics it undergoes. This becomes even more difficult in the quantum domain and if one is interested in generic nonequilibrium reservoirs, for which the standard thermal recipes no longer apply. In this paper, we derive an upper bound for the entropy production in terms of the entropy flux for a class of systems for which the flux is given in terms of a system's observable. Since currents are often easily accessible in this class of systems, this bound should prove useful for estimating the entropy production in a broad variety of processes. We illustrate the applicability of the bound by considering a three-level maser engine and a system interacting with a squeezed bath.

Fluctuation and dissipation in memoryless open quantum evolutions

Von Neumann entropy rate for open quantum systems is, in general, written in terms of entropy production and entropy flow rates, encompassing the second law of thermodynamics. When the open-quantum-system evolution corresponds to a quantum dynamical semigroup, we find a decomposition of the infinitesimal generator of the dynamics, that allows to relate the von Neumann entropy rate with the divergence-based quantum Fisher information, at any time. Applied to quantum Gaussian channels that are dynamical semigroups, our decomposition leads to the quantum analog of the generalized classical de Bruijn identity, thus expressing the quantum fluctuation-dissipation relation in that kind of channels. Finally, from this perspective, we analyze how stationarity arises.

Thermodynamics of scale-dependent Friedmann equations

In this work, the role of a time-varying Newton constant under the scale-dependent approach is investigated in the thermodynamics of the Friedman equations. In particular, we show that the extended Friedman equations can be derived either from equilibrium thermodynamics when the non-matter energy momentum tensor is interpreted as a fluid or from non-equilibrium thermodynamics when an entropy production term, which depends on the time-varying Newton constant, is included. Finally, a comparison between black hole and cosmological thermodynamics in the framework of scale-dependent gravity is briefly discussed.

Different constructions and optimization of the irreversible quantum Carnot cycle

The irreversible Carnot cycle is designed, constructed and optimized for quantum systems with non-scalable energy levels. In the cycle, the thermalization strokes are interpreted as either energy conserving steps or quantum isochoric processes. It is found that the latter construction is necessary to optimize the irreversible cycle efficiency. A strict connection between the two interpretations is given in terms of the irreversible entropy production and the efficiency lag. Two spins 1/2 interacting within the Heisenberg XXX model under a tunable magnetic field are proposed as the working system of the irreversible cycle. It is found that the irreversible cycle efficiency is always below the classical Carnot efficiency and depends on the parameters of the working medium and the heat baths. The role of the reservoir temperatures and the interaction between the spins on the efficiency is revealed. Quantum coupling is found to have a destructive role on the cycle performance which decreases the efficiency and makes the Carnot cycle cease to operate as a heat engine after a critical value. System parameter regimes are revealed where the optimized cycle efficiency is close to or notably higher than the one that conserves the energy in the thermalization stages.

Thermodynamic uncertainty relation for energy transport in a transient regime: A model study.

We investigate a transient version of the recently discovered thermodynamic uncertainty relation (TUR) which provides a precision-cost trade-off relation for certain out-of-equilibrium thermodynamic observables in terms of net entropy production. We explore this relation in the context of energy transport in a bipartite setting for three exactly solvable toy model systems (two coupled harmonic oscillators, two coupled qubits, and a hybrid coupled oscillator-qubit system) and analyze the role played by the underlying statistics of the transport carriers in the TUR. Interestingly, for all these models, depending on the statistics, the TUR ratio can be expressed as a sum or a difference of a universal term which is always greater than or equal to 2 and a corresponding entropy production term. We find that the generalized version of the TUR, originating from the universal fluctuation symmetry, is always satisfied. However, interestingly, the specialized TUR, a tighter bound, is always satisfied for the coupled harmonic oscillator system obeying Bose-Einstein statistics. Whereas, for both the coupled qubit, obeying Fermi-like statistics, and the hybrid qubit-oscillator system with mixed Fermi-Bose statistics, violation of the tighter bound is observed in certain parameter regimes. We have provided conditions for such violations. We also provide a rigorous proof following the nonequilibrium Green's function approach that the tighter bound is always satisfied in the weak-coupling regime for generic bipartite systems.

Comparative Energy and Emission Analysis of Oxy-Combustion and Conventional Air Combustion

Carbon capture and storage and oxy-fuel combustion have recently become more significant due to global warming as well as green energy solutions. Oxy-combustion power plants fueled with natural gas are compatible with today’s clean energy policies. In this study, effects of oxygen content of reactant mixtures used in oxy-combustion on thermodynamic properties, adiabatic flame temperatures, combustion products and pollutant emissions are analyzed using a novel multi-feature equilibrium combustion model. Using natural gas from most important origins (Russia, USA, Iran, Australia) as fuel, results obtained from oxy-fuel combustion for three different O2 fractions are compared with the results of conventional air–fuel combustion for varying equivalence ratio, inlet temperature and pressure. The accuracy of the results is confirmed by two different popular combustion softwares. According to the results, oxy-fuel combustion of same oxygen content with air causes 24% less entropy production but 40 times less NOx emissions which is an indicator of significant decrease in carbon capture and storage costs. Comparison of natural gas of different origins shows that Russian natural gas is more advantageous in terms of NOx emissions where Australian natural gas is more advantageous in terms of entropy production.

Thermodynamic Uncertainty Relation for Time-Dependent Driving.

Thermodynamic uncertainty relations yield a lower bound on entropy production in terms of the mean and fluctuations of a current. We derive their general form for systems under arbitrary time-dependent driving from arbitrary initial states and extend these relations beyond currents to state variables. The quality of the bound is discussed for various types of observables for an interacting pair of colloidal particles in a moving laser trap and for the dynamical unfolding of a small protein. Since the input for evaluating these bounds does not require specific knowledge of the system or its coupling to the time-dependent control, they should become widely applicable tools for thermodynamic inference in time-dependently driven systems.

Unified approach to classical speed limit and thermodynamic uncertainty relation.

The total entropy production quantifies the extent of irreversibility in thermodynamic systems, which is nonnegative for any feasible dynamics. When additional information such as the initial and final states or moments of an observable is available, it is known that tighter lower bounds on the entropy production exist according to the classical speed limits and the thermodynamic uncertainty relations. Here we obtain a universal lower bound on the total entropy production in terms of probability distributions of an observable in the time forward and backward processes. For a particular case, we show that our universal relation reduces to a classical speed limit, imposing a constraint on the speed of the system's evolution in terms of the Hatano-Sasa entropy production. Notably, the obtained classical speed limit is tighter than the previously reported bound by a constant factor. Moreover, we demonstrate that a generalized thermodynamic uncertainty relation can be derived from another particular case of the universal relation. Our uncertainty relation holds for systems with time-reversal symmetry breaking and recovers several existing bounds. Our approach provides a unified perspective on two closely related classes of inequality: classical speed limits and thermodynamic uncertainty relations.

Entropy generation model to estimate battery ageing

Abstract Determining battery ageing is a key issue in predicting the available charge in battery-operated systems. Beyond the common use of voltage or current measurements, which have proved unsuccessful as general methods, we aim to determine battery ageing in terms of irreversible entropy production. On the one hand, entropy describes transformations, such as ageing, and on the other hand, entropy combines the benefits of voltage, current and temperature effects in a single magnitude. We develop a thermoelectrochemical model based on phenomenological equations to compute entropy generation rates as a function of internal parameters such as concentration, electrode porosity and conduction in NiMH batteries. We simulate ageing by changing internal parameters during battery cycling and we found a threshold in the entropy generation rate of 0.12 mW K−1 cm−2 and a normalized cumulated entropy of 40% for a capacity decrease of 20% in the studied cell. We conclude that entropy characterization is a promising tool to describe battery ageing because it allows a simultaneous approach to capacity and power fade during ageing.

Modification of the Electron Entropy Production in a Plasma.

A modified expression of the electron entropy production in a plasma is deduced by means of the Kelly equations of state instead of the ideal gas equations of state. From the Debye–Hückel model which considers the interaction between the charges, such equations of state are derived for a plasma and the entropy is deduced. The technique to obtain the modified entropy production is based on usual developments but including the modified equations of state giving the regular result plus some extra terms. We derive an expression of the modified entropy production in terms of the tensorial Hermitian moments by means of the irreducible tensorial Hermite polynomials.

Life Defined in Terms of Entropy Production: 20th Century Physics Meets 21st Century Biology.

Life Defined in Terms of Entropy Production: 20th Century Physics Meets 21st Century Biology.

Entropy production analysis in thermodynamic cavitating flow with the consideration of local compressibility

The objectives of this research are to apply entropy production theory into cavitating flows and investigate dynamic characteristics of entropy production rate (EPR). A thermodynamic cavitation model and a density corrected turbulence model was adopted to this simulation around NACA0015 hydrofoil. Entropy production as a new method for evaluating energy performance is applied on thermodynamic cavitating flows. Cavitation effects on entropy production are firstly derived and revealed. Different entropy production terms by direct dissipation (EPDD), turbulent dissipation (EPTD), wall shear stress (EPWS), mean and fluctuating temperature gradients (EPMT and EPFT) were established in unsteady cavitating flow at 343 K to understand the interactions between cavitation and entropy. The results indicates that entropy production has strong association with cavitation. And entropy production rate by cavitation (EPRC) was derived firstly to evaluate the effects of phase change on entropy production rate. The entropy production rate by cavitation mainly focuses on the interface of cavity where there has intensive mass transfer procedure. Total entropy production rate (TEPR) mainly focuses on leading edge of hydrofoil, rear of attached cavity, detached cavity. Direct and turbulent entropy production rate are two main part in thermal cavitating flows. Direct entropy production can better reflect how total entropy production is distributed. Velocity gradients and phase change are two dominate factors controlling entropy change. In one cycle, total entropy production firstly decreases to its minimum and keeps stable to the inception stage of detached cavity collapse, then increases and fluctuates with cavity collapse.

Unified formalism for entropy production and fluctuation relations.

Stochastic entropy production, which quantifies the difference between the probabilities of trajectories of a stochastic dynamics and its time reversals, has a central role in nonequilibrium thermodynamics. In the theory of probability, the change in the statistical properties of observables due to reversals can be represented by a change in the probability measure. We consider operators on the space of probability measures that induce changes in the statistical properties of a process, and we formulate entropy production in terms of these change-of-probability-measure (CPM) operators. This mathematical underpinning of the origin of entropy production allows us to achieve an organization of various forms of fluctuation relations: All entropy production has a nonnegative mean value, admit the integral fluctuation theorem, and satisfy a rather general fluctuation relation. Other results such as the transient fluctuation theorem and detailed fluctuation theorems then are derived from the general fluctuation relation with more constraints on the operator of entropy production. We use a discrete-time, discrete-state-space Markov process to draw the contradistinction among three reversals of a process: time reversal, protocol reversal, and the dual process. The properties of their corresponding CPM operators are examined, and the domains of validity of various fluctuation relations for entropy production in physics and chemistry are revealed. We also show that our CPM operator formalism can help us rather easily extend other fluctuation relations for excess work and heat, discuss the martingale properties of entropy production, and derive the stochastic integral formulas for entropy production in constant-noise diffusion process with Girsanov theorem. Our formalism provides a general and concise way to study the properties of entropy-related quantities in stochastic thermodynamics and information theory.

Entropy production analysis in two-phase cavitation flows with thermodynamic cavitation model

Entropy production is an important parameter for the design and optimization of turbo machines, which is short of intuitiveness in previous studies. The present article investigated the mechanisms of entropy production in cavitation flows around a hydrofoil. The objectives of this research are to (1) reveal the thermodynamic effects with advanced cavitation model, (2) investigate dynamic characteristics of different entropy production terms, (3) analyze the interactions between vorticity and local entropy production rate based on vorticity transport equation. Firstly, water from 298 K to 423 K is investigated around a NACA0015 hydrofoil to reveal thermodynamic effects on different temperatures. Then, in order to study the energy loss due to cavitation, the entropy production theory is firstly applied on two-phase cavitation flows with high temperature water based on homogenous model and its unsteady characteristics is revealed combining with cavity structure. The density corrected turbulence model (DCM) and advanced thermodynamic cavitation model adopted in this research are validate corresponding to experiment. The analysis of local entropy production rate (EPR) indicated that the entropy production rate induced by direct dissipation (EPDD) and turbulent dissipation (EPTD) has the characteristics of spatial and time delay compared with the evolution of cavity instabilities. Moreover, entropy production rate induced by temperature gradients and wall shear stress are slight, while entropy production rate induced by velocity gradients are main part toward total entropy production rate (TEPR).

Thermodynamics of switching in multistable non-equilibrium systems.

Multistable non-equilibrium systems are abundant outcomes of nonlinear dynamics with feedback, but still relatively little is known about what determines the stability of the steady states and their switching rates in terms of entropy and entropy production. Here, we will link fluctuation theorems for the entropy production along trajectories with the action obtainable from the Freidlin-Wentzell theorem to elucidate the thermodynamics of switching between states in the large volume limit of multistable systems. We find that the entropy production at steady state plays no role, but the entropy production during switching is key. Steady-state entropy and diffusive noise strength can be neglected in this limit. The relevance to biological, ecological, and climate models is apparent.

In pursuit of the framework behind the biosphere: S-curves, self-assembly and the genetic entropy paradox

The origins, evolution and functioning of the Biosphere have occupied humankind for as long as recorded history has existed. In this paper we examine the claims of thermodynamics to be the framework within which we can understand the evolution, functioning and development of the Biosphere, exploring the evidence from ecology, molecular science and evolutionary biology, and particularly focussing upon the maximum entropy production principle (MEPP), and its explanatory potential in terms of many of the logistic relationships found within the Biosphere. We introduce the genetic entropy paradox, where the DNA increases in terms of internal information entropy, as the genetic code is continuously randomized through mutation, and yet this leads to increasing external entropy production, as increasingly more complicated structures and functions are produced in the form of new protein morphologies and metabolic pathways (again determined by the bioenergetic context). We suggest that the central dogma acts as a form of entropy exchange mechanism, but at the core of this is change in information entropy, which increases within the genetic code, and decreases within the organism. This would appear to be a truly unique event, and highlights a key interaction between two levels of organization within the Biosphere, the genome and the proteome, in terms of entropy production. The Biosphere is seen as being composed of a series of self-organizing sub-groups, each maximizing entropy production within the constraints of time, feedback and system constraints. The entropic production of the Biosphere is thus an emergent property.

The kinetic exclusion process: a tale of two fields

We introduce a general class of stochastic lattice gas models, and derive their fluctuating hydrodynamics description in the large size limit under a local equilibrium hypothesis. The model consists of energetic particles on a lattice subject to exclusion interactions, which move and collide stochastically with energy-dependent rates. The resulting fluctuating hydrodynamics equations exhibit nonlinear coupled particle and energy transport, including particle currents due to temperature gradients (Soret effect) and energy flow due to concentration gradients (Dufour effect). The microscopic dynamical complexity is condensed in just two matrices of transport coefficients: the diffusivity matrix (or equivalently the Onsager matrix) generalizing Fick–Fourier’s law, and the mobility matrix controlling current fluctuations. Both transport coefficients are coupled via a fluctuation-dissipation theorem, suggesting that the noise terms affecting the local currents have Gaussian properties. We further prove the positivity of entropy production in terms of the microscopic dynamics. The so-called kinetic exclusion process has as limiting cases two of the most paradigmatic models of nonequilibrium physics, namely the symmetric simple exclusion process of particle diffusion and the Kipnis–Marchioro–Presutti model of heat flow, making it the ideal testbed where to further develop modern theories of nonequilibrium behavior.

Determination of Entropy Production for a Quantum System in the Presence of an Auxiliary System

A thorough understanding of entropy production, which can be used as a natural quantifier of the degree of irreversibility of a process, is both fundamentally relevant and technologically desirable. Recently, Esposito et al. (J. Phys. 12, 013013 2010), have derived an exact expression for the entropy production in terms of correlations between a system and its reservoir. However, evaluation of the mentioned correlations is virtually impossible to access in real world situations. Here, it is demonstrated that how we can overcome this problem by considering an auxiliary system and using the monogamy relations. To this aim, we consider a system A that is initially correlated with an auxiliary system B, which in turn interacts with the environment E. In the presence of the auxiliary system B, the amount of created classical and quantum correlations between the system A and the environment can be obtained by using existed monogamy properties and consequently the associated entropy production is determined. In addition, another situation is investigated in this work where only the system A is interacting with the environment E and the auxiliary system B evolves free of any direct interaction. As an example, this scenario is illustrated by considering the systems A and B as two-level systems undergoing an amplitude damping process and generalized amplitude damping process.