Non-equilibrium thermodynamics and entropy production spectra: A tool for the characterization of ferrimagnetic materials

2013 ◽  
Vol 38 (2) ◽  
Author(s):  
Silvina Boggi ◽  
Adrián C. Razzitte ◽  
Walter G. Fano
Keyword(s):  
Entropy Production ◽  
Equilibrium Thermodynamics ◽  
Non Equilibrium

Local Entropy Production Rates in a Polymer Electrolyte Membrane Fuel Cell

2017 ◽  
Vol 42 (1) ◽  
pp. 1-30 ◽  
Author(s):  
Marc Siemer ◽  
Tobias Marquardt ◽  
Gerardo Valadez Huerta ◽  
Stephan Kabelac
Keyword(s):  
Fuel Cell ◽  
Entropy Production ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Local Entropy ◽  
Equilibrium Thermodynamics ◽  
Electrolyte Membrane ◽  
Non Equilibrium

AbstractA modeling study on a polymer electrolyte membrane fuel cell by means of non-equilibrium thermodynamics is presented. The developed model considers a one-dimensional cell in steady-state operation. The temperature, concentration and electric potential profiles are calculated for every domain of the cell. While the gas diffusion and the catalyst layers are calculated with established classical modeling approaches, the transport processes in the membrane are calculated with the phenomenological equations as dictated by the non-equilibrium thermodynamics. This approach is especially instructive for the membrane as the coupled transport mechanisms are dominant. The needed phenomenological coefficients are approximated on the base of conventional transport coefficients. Knowing the fluxes and their intrinsic corresponding forces, the local entropy production rate is calculated. Accordingly, the different loss mechanisms can be detected and quantified, which is important for cell and stack optimization.

scholarly journals Dissipated work, stability and the internal flow structure of granular snow avalanches

2005 ◽  
Vol 51 (172) ◽  
pp. 125-138 ◽  
Author(s):  
Perry Bartelt ◽  
Othmar Buser ◽  
Martin Kern
Keyword(s):  
Steady State ◽  
Entropy Production ◽  
Dissipative Systems ◽  
Momentum Balance ◽  
Granular System ◽  
Snow Avalanches ◽  
Equilibrium Thermodynamics ◽  
Layer System ◽  
Constitutive Parameters ◽  
Non Equilibrium

AbstractWe derive work dissipation functionals for granular snow avalanches flowing in simple shear. Our intent is to apply constructive theorems of non-equilibrium thermodynamics to the snow avalanche problem. Snow chute experiments show that a bi-layer system consisting of a non-yielded flow plug overriding a sheared fluidized layer can be used to model avalanche flow. We show that for this type of constitutive behaviour the dissipation functionals are minimum at steady state with respect to variations in internal velocity; however, the functionals must be constrained by subsidiary mass- continuity integrals before the equivalence of momentum balance and minimal work dissipation can be established. Constitutive models that do not satisfy this equivalence are henceforth excluded from our consideration. Fluctuations in plug and slip velocity depend on the roughness of the flow surface and viscosity of the granular system. We speculate that this property explains the transition from flowing avalanches to powder avalanches. Because the temperature can safely be assumed constant, we demonstrate within the context of non-equilibrium thermodynamics that granular snow avalanches are irreversible, dissipative systems, minimizing – in space – entropy production. Furthermore, entropy production is linear both near and far from steady-state non-equilibrium because of the mass-continuity constraint. Finally, we derive thermodynamic forces and conjugate fluxes as well as expressing the corresponding phenomenological Onsager coefficients in terms of the constitutive parameters.

scholarly journals The maximum entropy production principle: two basic questions

2010 ◽  
Vol 365 (1545) ◽  
pp. 1333-1334 ◽  
Author(s):  
Leonid M. Martyushev
Keyword(s):  
Statistical Mechanics ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Statistical Physics ◽  
Overwhelming Majority ◽  
Equilibrium Thermodynamics ◽  
Maximum Entropy Production ◽  
Environmental Systems ◽  
Thermodynamics And Statistical Mechanics ◽  
Non Equilibrium

The overwhelming majority of maximum entropy production applications to ecological and environmental systems are based on thermodynamics and statistical physics. Here, we discuss briefly maximum entropy production principle and raises two questions: (i) can this principle be used as the basis for non-equilibrium thermodynamics and statistical mechanics and (ii) is it possible to ‘prove’ the principle? We adduce one more proof which is most concise today.

scholarly journals Minimization of a free-energy-like potential for non-equilibrium flow systems at steady state

2010 ◽  
Vol 365 (1545) ◽  
pp. 1323-1331 ◽  
Author(s):  
Robert K. Niven
Keyword(s):  
Free Energy ◽  
Steady State ◽  
Entropy Production ◽  
Equilibrium Thermodynamics ◽  
Turbulent Fluid Flow ◽  
System A ◽  
Flow Heat ◽  
Observed Behaviour ◽  
New Formulation ◽  
Non Equilibrium

This study examines a new formulation of non-equilibrium thermodynamics, which gives a conditional derivation of the ‘maximum entropy production’ (MEP) principle for flow and/or chemical reaction systems at steady state. The analysis uses a dimensionless potential function ϕ st for non-equilibrium systems, analogous to the free energy concept of equilibrium thermodynamics. Spontaneous reductions in ϕ st arise from increases in the ‘flux entropy’ of the system—a measure of the variability of the fluxes—or in the local entropy production; conditionally, depending on the behaviour of the flux entropy, the formulation reduces to the MEP principle. The inferred steady state is also shown to exhibit high variability in its instantaneous fluxes and rates, consistent with the observed behaviour of turbulent fluid flow, heat convection and biological systems; one consequence is the coexistence of energy producers and consumers in ecological systems. The different paths for attaining steady state are also classified.

scholarly journals Pitfalls of Exergy Analysis

2017 ◽  
Vol 42 (2) ◽  
Author(s):  
Petr Vágner ◽  
Michal Pavelka ◽  
František Maršík
Keyword(s):  
Fuel Cells ◽  
Steady State ◽  
Entropy Production ◽  
Exergy Analysis ◽  
Thermodynamic Optimization ◽  
Exergy Destruction ◽  
Equilibrium Thermodynamics ◽  
Useful Power ◽  
Non Equilibrium

AbstractThe well-known Gouy–Stodola theorem states that a device produces maximum useful power when working reversibly, that is with no entropy production inside the device. This statement then leads to a method of thermodynamic optimization based on entropy production minimization. Exergy destruction (difference between exergy of fuel and exhausts) is also given by entropy production inside the device. Therefore, assessing efficiency of a device by exergy analysis is also based on the Gouy–Stodola theorem. However, assumptions that had led to the Gouy–Stodola theorem are not satisfied in several optimization scenarios, e.g. non-isothermal steady-state fuel cells, where both entropy production minimization and exergy analysis should be used with caution. We demonstrate, using non-equilibrium thermodynamics, a few cases where entropy production minimization and exergy analysis should not be applied.

scholarly journals Nonlinear Non-Equilibrium Thermodynamics Based on the Ehrenfest–Klein Model

Entropy ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 293
Author(s):  
Gleb A. Zhernokleev ◽  
Leonid M. Martyushev
Keyword(s):  
Entropy Production ◽  
Fluctuation Theorem ◽  
Equilibrium Thermodynamic ◽  
Equilibrium Thermodynamics ◽  
Thermodynamic Entropy ◽  
Klein Model ◽  
Non Equilibrium

Nonlinear non-equilibrium thermodynamic relations have been constructed based on the generalized Ehrenfest–Klein model. Using these relations, the behavior of the entropy and its production in time at arbitrary deviations from equilibrium has been studied. It has been shown that the transient fluctuation theorem is valid for this model if a dissipation functional is treated as the thermodynamic entropy production.

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