Reversible Thermodynamic Processes Research Articles

Comment on “Reversible superconducting-normal phase transition in a magnetic field and the existence of topologically protected loop currents that appear and disappear without Joule heating” by Koizumi Hiroyasu

This comment is written on the article by Hiroyasu Koizumi, in which an alternative theory of superconductivity is proposed. No Joule heating is predicted in this theory unlike the conventional BCS-London theory of superconductivity. The theory is based on the author's opinion that the kinetic energy for the supercurrent is converted into the energy of the magnetic field during the transition of a bulk superconductor into the normal state in the presence of a magnetic field. The Comment indicates that this opinion cannot be correct, since the kinetic energy is much less than the energy of the magnetic field and both of these energies decrease during the transition to the normal state, according to the generally accepted point of view. It is briefly explained how a reversible thermodynamic process differs from an irreversible process.

Thermomechanical modeling of nonlinear internal hysteresis due to incomplete phase transformation in pseudoelastic shape memory alloys

This paper presents a thermomechanical model for pseudoelastic shape memory alloys (SMAs) accounting for internal hysteresis effect due to incomplete phase transformation. The model is developed within the finite-strain framework, wherein the deformation gradient is multiplicatively decomposed into thermal dilation, rigid body rotation, elastic and transformation parts. Helmholtz free energy density comprises three components: the reversible thermodynamic process , the irreversible thermodynamic process and the physical constraints of both. In order to capture the multiple internal hysteresis loops in SMA, two internal variables representing the transition points of the forward and reverse phase transformation, $$\phi _s^f$$ and $$\phi _s^r$$ , are introduced to describe the incomplete phase transformation process. Evolution equations of the internal variables are derived and linked to the phase transformation. Numerical implementation of the model features an Euler discretization and a cutting-plane algorithm. After validation of the model against the experimental data, numerical examples are presented, involving a SMA-based vibration system and a crack SMA specimen subjected to partial loading–unloading case. Simulation results well demonstrate the internal hysteresis and free vibration behavior of SMA.

From entanglement to thermodynamics and to gravity

Here we develop the connection between thermodynamics, entanglement, and gravity. By attributing thermodynamics to timeslices of a causal diamond, we show that the Clausius relation $T\Delta S_{\text{rev}}=Q$, where $\Delta S_{\text{rev}}$ is the reversible entropy change, gives rise to the non-linear gravitational equations of motion for a wide class of diffeomorphism invariant theories. We then compare the Clausius relation to the first law of causal diamond mechanics (FLCD), a geometric identity and necessary ingredient in deriving Jacobson's entanglement equilibrium proposal -- the entanglement entropy of a spherical region with a fixed volume is maximal in vacuum. Specifically we show that the condition of fixed volume can be understood as subtracting the irreversible contribution to the thermodynamic entropy. This provides a "reversible thermodynamic process" interpretation of the FLCD, and that the condition of entanglement equilibrium may be regarded as equilibrium thermodynamics for which the Clausius relation holds. Finally, we extend the entanglement equilibrium proposal to the timelike stretched horizons of future lightcones, providing an entanglement interpretation of stretched lightcone thermodynamics.

Entransy analysis of reversible thermodynamic cycles based on the conservation of entransy equation and its application

Entropy analyses and entropy generation analyses have been widely used to analyze and optimize thermal processes. For instance, the entropy generation minimization principle has been used to optimize heat transfer processes, heat transfer systems and thermodynamic cycles. However, some studies have reported that the entropy generation minimization principle cannot derive the optimal results for pure heat transfer processes and heat transfer systems without heat-work conversion processes. The concept of entransy and the principle of the least entransy dissipation-based thermal resistance were proposed for these problems, and they have been widely applied to optimize pure heat transfer processes and systems. Besides, the concept of work entransy was developed for irreversible thermodynamic cycles involving heat-work conversion processes, and it is defined as the product of the work and the temperature. This concept was then used as the entransy analysis approach to optimize thermodynamic cycles. However, previous studies applying the work entransy concept mainly focused on (1) the relation between the work entransy loss and the endoreversible thermodynamic cycle efficiency, and (2) the optimization of practical thermodynamic cycles involving irreversible processes. There have been few such studies of reversible thermodynamic cycles or combined cycles. This article analyzes reversible thermodynamic cycles and combined thermodynamic cycles using the entransy analysis method with a derivation of the conservation of entransy equation. First, the entransy conservation equation for a reversible thermodynamic process is derived, which introduces the concept of heat entransy and heat-work entransy flow. They are both process dependent physical quantities. The corresponding entransy conservation equation is then derived for a reversible thermodynamic cycle. The equation shows that there are two different conservation equations for reversible thermodynamic cycles, i.e. the energy conservation equation (1st law of thermodynamics) and the entransy conservation equation. Meanwhile, according to thermomass theory, the entransy is nothing else but the relative energy. The entransy conservation equation can be used to analyze the performance of reversible thermodynamic cycles. On the other hand, since the entropy returns to the initial value in a reversible thermodynamic cycle, an entropy analysis cannot evaluate the performance of reversible thermodynamic cycles. Second, a combined heat engine-heat pump cycle is taken as an example application of entransy analysis. In the philosophy of entransy analyses, the performance indicator of the combined cycle is its net heat entransy flow. For the properly chosen parameters, the combined cycle can be regarded as an ideal voltage transformer. Therefore, this kind of combined cycle can be referred to as a temperature transformer, which is different from the absorption temperature transformer. A diagram is introduced to show the total effect of the combined cycle to help understand the combined cycle. Finally, two practical cases, i.e. combined cycles for heating and refrigeration, are chosen to show applications of this entransy analysis approach. The concept of entransy efficiency of combined cycles is introduced to evaluate the performance of the combined cycles.

Work entropy and work exergy

Clausius proposed a reversible thermodynamic cycle made up of three isothermal processes and three adiabatic processes to establish the theorem of the equivalence of the transformation of heat to work and the transformation of heat at a higher temperature to a lower temperature. Then, he derived the Clausius equality and the concept of entropy (later called thermal entropy to prevent confusion). Similarly, this study uses a reversible reversed thermodynamic cycle made up of three isobaric processes and three isochoric processes to establish the theorem of the equivalence of the transformation of work to heat and the transformation of work at a higher pressure to a lower pressure, and then derives a corresponding equality for a reversed thermodynamic cycle and the concept of work entropy. The work entropy is shown to be equal to the system volume which is the core physical quantity of a reversed thermodynamic cycle. Although this is not a new quantity, the work entropy gives the volume a new physical interpretation corresponding to thermal entropy. Next, by analogy with the definition of exergy (later called thermal exergy to prevent confusion), the work exergy is defined as the maximum heat output that can be transformed from the work in a system at pressure p though a reversed p - V cycle under ambient pressure. Furthermore, the work exergy of the working medium is defined as the sum of the heat that the working medium outputs though a series of reversed p-V cycles and the heat that the working medium outputs directly as the temperature varies, as the working medium changes reversibly from any state to the state in balance with the environment. The physical meanings of the work entropy and the work exergy are illustrated with comparisons to the thermal entropy and the thermal exergy. When it changes reversibly from any state to the state in balance with the environment, the working medium with more thermal entropy will have more unavailable energy T 0( ST – S T0) and, thus, less thermal exergy, if the system outputs work through a reversible thermodynamic cycle. In contrast, the working medium with more work entropy will have less unavailable energy p 0( V 0– V ) and, thus, more work exergy, if the system outputs heat through a reversible reversed thermodynamic cycle. Thus, the work entropy can measure the unavailable energy of the working medium while the work exergy can measure the available energy of the working medium. The pressure-work entropy diagram can be used to intuitively analyze a reversed thermodynamic cycle. Finally, a least action principle is proposed for reversible thermodynamic processes. When the heat-to-work action, Δ S / Q reaches a minimum, the optimal heat-to-work process is obtained that is the combination of an isothermal process and an adiabatic process. When the work-to-heat action, Δ V / W reaches a maximum, the optimal work-to-heat process is obtained that is the combination of an isobaric process and an isochoric process.

Reply to the Comments on: Tian Zhao et al. The Principle of Least Action for Reversible Thermodynamic Processes and Cycles. Entropy 2018, 20, 542.

The purpose of this reply is to provide a discussion and closure for the comment paper by Dr. Bormashenko on the present authors’ article, which discussed the application of the principle of least action in reversible thermodynamic processes and cycles. Dr. Bormashenko’s questions and misunderstandings are responded to, and the differences between the present authors’ work and Lucia’s are also presented.

Comments on "The Principle of Least Action for Reversible Thermodynamic Processes and Cycles", Entropy 2018, 20, 542.

The goal of this comment note is to express my concerns about the recent paper by Tian Zhao et al. (Entropy 2018, 20, 542). It is foreseen that this comment will stimulate a fruitful discussion of the issues involved. The principle of the least thermodynamic action is applicable for the analysis of the Carnot cycle using the entropy (not heat) generation extrema theorem. The transversality conditions of the variational problem provide the rectangular shape of the ST diagram for the Carnot cycle.

The Principle of Least Action for Reversible Thermodynamic Processes and Cycles.

The principle of least action, which is usually applied to natural phenomena, can also be used in optimization problems with manual intervention. Following a brief introduction to the brachistochrone problem in classical mechanics, the principle of least action was applied to the optimization of reversible thermodynamic processes and cycles in this study. Analyses indicated that the entropy variation per unit of heat exchanged is the mode of action for reversible heat absorption or heat release processes. Minimizing this action led to the optimization of heat absorption or heat release processes, and the corresponding optimal path was the first or second half of a Carnot cycle. Finally, the action of an entire reversible thermodynamic cycle was determined as the sum of the actions of the heat absorption and release processes. Minimizing this action led to a Carnot cycle. This implies that the Carnot cycle can also be derived using the principle of least action derived from the entropy concept.

Crystal Growth of Ag3MOxF6−x (M = V, x = 2; M = Mo, x = 3)

Understanding the complex relationship between synthesis conditions, in particular temperature and composition led to single crystals of the cryolite type phases Ag 3 MoO 3 F 3 and Ag 3 VO 2 F 4 . These crystals form in a reversible thermodynamic process from dissolved species when the solution is heated. Single crystal structural data reveal the Mo 6+ cation distorted toward facially coordinated oxides for Ag 3 MoO 3 F 3 , and the V 5+ cation toward the edge of the cis-oxide positions for Ag 3 VO 2 F 4 . Local ordering of oxide and fluoride ligands is observed for both structures.

“TERPI” AS A QUANTITY OF THERMODYNAMIC POTENTIAL ENERGY SUPPLEMENTARY TO THE CONCEPT OF WORK AND HEAT

Isothermal reversible thermodynamic processes were studied, where there will not occur flow of heat (q) in the system in accord with the second law of thermodynamic. It appear that the energy flow in the system cannot be explained adequately by considering the flow of P,V - work, usually indicated by w, in accordance with the first law, that is, ΔU = q + w with q = 0. Therefore, it is necessary to have another kind of work energy (potential) which is not electrical to explain such as the experiment of Boyle that results in the formula PV = C for a close ideal gas system undergoing an isothermal and reversible process. In this paper, a new work potential which is called ";;terpi";; is introduced, and is abbreviated as τ (tau) and defined as: dτ ≡ - T dSrev = - dqrev. Therefore, dt is also not an exact differential as dw and dq. For any isothermal reversible process, it can be written: τ = -TΔSrev, and for redox reaction, such as an electrochemical cell, it is noteworthy to distinguish between τ system (τsyst) and τ reaction (τr) which combine together to become an electrical work flow, (wel) done by the system on the surrounding, so that: ΔGr = τsyst + τr = v F E Furthermore, the studies of phase transitions, which occur isothermally, were also considered, e.g. the evaporation of a liquid into vapour at a certain T. The heat given to this process cannot freely flow isothermally, but first it must be changed into terpy and then added to the enthalpy of the vapour following the equation: τvap = -TΔSvap = -ΔHvap. Keywords: thermodynamics, heat, work, isothermal, reversible

An introduction to endoreversible thermodynamics

Reversible thermodynamic processes are convenient abstractions of real processes, which are always irreversible. Approaching the reversible regime means to become more and more quasistatic, letting behind processes which achieve any kind of finite transformation rate for the quantities studied. On the other hand studying processes with finite transformation rates means to deal with irreversibilities and in many cases these irreversibilities must be included in a realistic description of such processes. Endoreversible thermodynamics is a non-equilibrium approach in this direction by viewing a system as a network of internally reversible (endoreversible) subsystems exchanging energy in an irreversible fashion. This material provides an introduction to the subject.

An availability approach to thermal energy recovery in vehicles

Availability is a well-established and widely recognized way of describing the work-producing potential of energy systems. A first-law analysis is helpful in setting the energy context and ensuring that energy flows balance, but it is a second-law analysis based on availability that places an upper bound on the potential work output. In this analysis a new approach to thermal management intended for vehicle propulsion is examined and developed. Starting with a simple analysis of the chemical energy flow, a realistic heat exchange performance is introduced to establish a practical architecture. Within this framework, the availability analysis shows that effective thermal efficiencies of between 25 and 30 per cent are feasible. With a spark ignition engine operating at a high load condition, and the thermal recovery system at an operating pressure of 100 bar, the maximum efficiency possible with a steady flow work-producing device is 37 per cent (with fully reversible thermodynamic processes). In a water-based thermal recovery system, work could only reasonably be produced with heat transfer from a reservoir at the saturation temperature corresponding to the operating pressure. At 100 bar the maximum efficiency would be 33 per cent. In a different mode of operation, where heat is transferred incrementally to a thermal accumulator and work produced as required, the efficiency is 32 per cent at only 20 bar operating pressure. These efficiency values apply to work production to supplement a combustion engine at any operating condition. An analysis of a reciprocating expander as the work-producing device shows substantial flexibility in operation. Control of system operating pressure is shown to be of value in that periodic adjustments enhance the availability content of the thermal reservoir. The operating pressure of a fluid power system is related to the temperature of operation, and therefore the heat transfer processes. Choice of too high a pressure leads to reduced heat transfer, and ultimately a reduction in work output. There is an optimum condition that can be selected at design time and maintained during the running of the system.

Methodology for Predicting the Phase Envelope of a Heavy Crude Oil and Its Asphaltene Deposition Onset

We have presented general ideas to develop a new theoretical methodology, based on molecular simulation and equations of state, for obtaining the phase envelope and to predict pressure, volume, temperature (PVT) conditions of asphaltene precipitation by only taking into account the composition of the heavy crude oil and an asphaltene average molecular structure. Those results show that asphaltene precipitation is a reversible thermodynamic process. The precipitated phase is a liquid phase which consists of mainly asphaltene and some heavy fractions from the crude. This methodology can be applied to find complete phase diagrams of different crude oils based on an asphaltene average molecular structure and the composition of crude oil.

Status of the Fundamental Laws of Thermodynamics

We describe recent progress towards deriving the Fundamental Laws of thermodynamics (the 0th, 1st, and 2nd Law) from nonequilibrium quantum statistical mechanics in simple, yet physically relevant models. Along the way, we clarify some basic thermodynamic notions and discuss various reversible and irreversible thermodynamic processes from the point of view of quantum statistical mechanics.

Nonequilibrium quantum statistical mechanics and thermodynamics

The purpose of this work is to discuss recent progress in deriving the fundamental laws of thermodynamics (0th, 1st and 2nd-law) from nonequilibrium quantum statistical mechanics. Basic thermodynamic notions are clarified and different reversible and irreversible thermodynamic processes are studied from the point of view of quantum statistical mechanics. Special emphasis is put on new adiabatic theorems for steady states close to and far from equilibrium, and on investigating cyclic thermodynamic processes using an extension of Floquet theory.

Facilitando a compreensão da segunda lei da termodinâmica

A idéia central desse artigo é chamar a atenção para o uso do diagrama T x s na descrição das máquinas térmicas reversíveis. Este diagrama mostra-se extremamente adequado e eficaz no ensino da segunda lei da tertermodinâmica dos processos reversíveis, no entanto uma escolha mostra-se mais apropriada que a outra quando se pretende salientar a universalidade dessa lei e não restringir a análise a uma substância de operação específica com é gás ideal.

Thermodynamics of Crawford’s energy equipartition journeys

Energy equipartition ‘‘journeys’’ proposed originally in the context of relativistic mechanics [F. S. Crawford, Am. J. Phys. 61, 317–326 (1993)] are examined thermodynamically. Equipartition is between ideal gases separated by an insulating piston. Each journey alternates slow adiabatic volume changes and zero-work adiabatic piston resettings effected by a benevolent Maxwell’s demon until temperature and pressure equalities exist. For the systems considered, reversible adiabatic thermodynamic processes are equivalent to slow mechanically adiabatic, constant-action processes. Because phase space mixing is assumed implicitly in thermodynamics, the piston jiggling step needed in Crawford’s mechanics-based treatment is unnecessary. Zero-work journeys maximize the gas system’s entropy change, and maximum work output journeys leave that entropy unchanged. Thermodynamics confirms Crawford’s result for the piston’s effective spring constant, and statistical mechanics enables rigorous justification of his interesting recursion relation for the moments of q=momentum×velocity.

The nature of amorphization in crystalline systems

The conditions of the transition from the crystalline to amorphous state and the process of amorphization of crystalline systems under cold plastic deformation have been studied. Two concepts of crystalline system amorphization are considered. Fusion and amorphization in the solid state are analysed, particularly in terms of the thermodynamics of reversible processes of the transition from the crystalline to the amorphous state. The mechanism of amorphization of a crystalline alloy is considered when it undergoes deformation or low-temperature annealing. The emphasis is on the system of Fe-B alloys.

Kinetic and Thermodynamic Effects in the Formation of Amphiphilic Colloidal Particles

AbstractLiposomes as well as many other colloidal particles are normally formed in a kinetic rather than in a reversible thermodynamic process. In order to explain their stability and the mechanism of formation a qualitative model which couples kinetic and thermodynamic factors is proposed. It is speculated that due to their membraneous structure various gradients across the bilayer(s) can be imposed and that these gradients locally cause the breakdown of planar symmetry and induce curvature proportionally to the bending elasticity of the bilayer. In some cases this prevents the energy released into the system by some exothermic reactions from dissipating randomly as heat, and stores part of it in the states with higher conformational free energy, such as selfclosed curved bilayers.

An Analysis of the Conditional Instability of the Tropical Atmosphere

Abstract The ice phase is included in thermodynamic calculations of convective available potential energy (CAPE) for a large number of soundings in the tropical atmosphere, at both land and ocean stations. It is found that the positive-buoyancy contribution to CAPE resulting from the latent heat of fusion more than offsets the negative-buoyancy contribution due to water loading in the reversible thermodynamic process. The departure from moist neutrality in much of the tropical atmosphere exhibits a threshold in boundary-layer wet-bulb potential temperature of 22°–23°C. The corresponding sea surface temperature is approximately 26°C, close to the empirical threshold for hurricane formation, which suggests that conditional instability plays an important role in the latter phenomenon. The simultaneous presence of finite CAPE and infrequent deep convection in the tropics is tentatively attributed to the convective inhibition energy (CINE) and to the mixing process that destroys positive buoyancy in incipient ...