Carnot Engine Research Articles

Von Neumann Entropy and Evolution

In this paper I outline a hypothesis where quantum information in the form of von Neumann entropy provides a universal driving force for increasing complexity of systems and for evolutionary processes. Interference between quantum states of interacting systems allows storage of free energy that can be used to overcome kinetic barriers and accelerate reactions. This informational work cycle is analogous to entanglement in quantum Carnot engines where energy is stored as phase or so-called phaseonium fuel. The von Neumann entropy subadditivity and Araki-Lieb inequality properties of combined states can lower effective entropy and favour routes to increasing complexity of systems. It is proposed that observed macroscopic evolutionary processes are the emergent manifestation of this microscopic informational drive to complexity.

Temperature fluctuations in mesoscopic systems.

Temperature is a fundamental concept in thermodynamics. In macroscopic thermodynamics, systems possess their own intrinsic temperature which equals the reservoir temperature when they equilibrate. In stochastic thermodynamics for simple systems at the microscopic level, thermodynamic quantities other than temperature (a deterministic parameter of the reservoir) are stochastic. To bridge the disparity in the perspectives about temperature between the micro- and macroregimes, we assign a generic mesoscopic N-body system an intrinsic fluctuating temperature T in this work. We simplify the complicated dynamics of numerous particles to one stochastic differential equationwith respect to T, where the noise term accounts for finite-size effects arising from random energy transfer between the system and the reservoir. Our analysis reveals that these fluctuations make the extensive quantities (in the thermodynamic limit) deviate from being extensive. Moreover, we derive finite-size corrections, characterized by heat capacity of the system, to the Jarzynski equality. A possible violation of the principle of maximum work that scales with N^{-1} is also discussed. Additionally, we examine the impact of temperature fluctuations in a finite-size Carnot engine. We show that irreversible entropy production resulting from the temperature fluctuations of the working substance diminishes the average efficiency of the cycle as η_{C}-〈η〉∼N^{-1}, highlighting the unattainability of the Carnot efficiency η_{C} for mesoscopic heat engines even under the quasistatic limit. Our general framework paves the way for further exploration of nonequilibrium thermodynamics and the corresponding finite-size effects in a mesoscopic regime.

Atom-doped photon engine: Extracting mechanical work from a quantum system via radiation pressure.

The possibility of efficiently converting heat into work at the microscale has triggered an intense research effort to understand quantum heat engines, driven by the hope of quantum superiority over classical counterparts. In this work, we introduce a model featuring an atom-doped optical quantum cavity propelling a classical piston through radiation pressure. The model, based on the Jaynes-Cummings Hamiltonian of quantum electrodynamics, demonstrates the generation of mechanical work through thermal energy injection. We establish the equivalence of the piston expansion work with Alicki's work definition, analytically for quasistatic transformations and numerically for finite-time protocols. We further employ the model to construct quantum Otto and Carnot engines, comparing their performance in terms of energetics, work output, efficiency, and power under various conditions. This model thus provides a platform to extract useful work from an open quantum system to generate net motion, and it sheds light on the quantum concepts of work and heat.

Amended FRW universe: thermodynamics and heat engine

Thermodynamics of non-flat Amended Friedmann–Robertson–Walker (AFRW) universe with cosmological constant as thermodynamic pressure is studied. The unified first law of thermodynamics, the Clausius relation and the gravity equations yield entropy on the dynamic apparent horizon. Temperature, volume, pressure, enthalpy, Gibb’s free energy and Helmholtz’s free energies, and specific heat capacity with constant pressure of the universe are calculated in terms of surface area of dynamic apparent horizon. The study shows a non-negative Joule–Thomson coefficient, indicating the cooling nature of the AFRW universe. Inversion pressure and inversion temperature are expressed in terms of the surface area of the apparent horizon. Finally, the thermodynamical AFRW universe is considered as a heat engine. Work done for the Carnot engine is derived with maximum efficiency, and a new engine is also considered for which the work done, and its efficiency are calculated for AFRW universe.

Heat engines of the Kerr-AdS black hole

In this paper, we investigate three types of heat engines for the rotating Kerr-Anti de Sitter (Kerr-AdS) black hole. We first briefly review the thermodynamics and phase structure of the Kerr-AdS black hole and obtain the phase structure in the T–S chart. The thermal stability of Kerr-AdS black holes, along with their dependence on various parameters, is thoroughly examined. Then, by utilizing the phase diagram, we consider three types of heat engines: the maximal Carnot engine, Stirling engine, and Rankine engine. We calculate both the work and efficiency for these engines. The results indicate that angular momentum has a significant influence on these heat engines.

What Is Psychological Spin? A Thermodynamic Framework for Emotions and Social Behavior

One of the most puzzling questions in neuroscience is the nature of emotions and their role in consciousness. The brain’s significant energy investment in maintaining the resting state indicates its essential role as the ground state of consciousness, the source of the sense of self. Emotions, the brain’s homeostatic master regulators, continuously measure and motivate the recovery of the psychological equilibrium. Moreover, perception’s information-energy exchange with the environment gives rise to a closed thermodynamic cycle, the reversible Carnot engine. The Carnot cycle forms an exothermic process; low entropy and reversible resting state turn the focus to the past, causing regret and remorse. The endothermic reversed Carnot cycle creates a high entropy resting state with irreversible activations generating novelty and intellect. We propose that the cycle’s direction represents psychological spin, where the endothermic cycle’s energy accumulation forms up-spin, and the energy-wasting exothermic cycle represents down-spin. Psychological spin corresponds to attitude, the determining factor in cognitive function and social life. By applying the Pauli exclusion principle for consciousness, we can explain the need for personal space and the formation of hierarchical social structures and animals’ territorial needs. Improving intuition about the brain’s intelligent computations may allow new treatments for mental diseases and novel applications in robotics and artificial intelligence.

A review of the second law of thermodynamics and its application

Over thousands of years, many great physicists, such as Carnot, Boltzmann, Plank, Clausius, to name only a few, have put great endeavor into unwinding the mysteries of thermodynamic studies. In recent decades, many innovations have been made by groundbreaking modern technologies, such as refrigerators and air conditioning, and both recent findings and formerly discovered concepts of thermodynamics have been explained deeply by modern scientists. The paper briefly introduces the definition of the second law of thermodynamics and the relative concepts and their application. This paper delves into the history and definition of the Carnot Theorem, the Irreversible Carnot engine and refrigerator principle, as well as the Coefficient of Performance (COP). After that, this paper will introduce a few relative concepts, including entropy, exergy, and the Clausius-Duhem inequality. In summary, this paper covers a basic overall explanation of the aforementioned concepts, as well as drawing conclusions about the experimental achievements of the early explorers of thermodynamics.

Quantum Otto-type heat engine with fixed frequency.

In this work we analyze an Otto-type cycle operating with a working substance composed of a quantum harmonic oscillator (QHO). Unlike other studies in which the work extraction is done by varying the frequency of the QHO and letting it thermalize with a squeezed reservoir, here we submit the QHO to a parametric pumping controlled by the squeezing parameter and let it thermalize with a thermal reservoir. We then investigate the role of the squeezing parameter in our Otto-type engine powered by parametric pumping and show that it is possible to reach the Carnot limit by arbitrarily increasing the squeezing parameter. Notably, for certain squeezing parameters r, e.g., r=0.4, the quasistatic Otto limit can be reached even at nonzero power. We also investigated the role of entropy production in the efficiency behavior during the unitary strokes, showing that positive (negative) changes in entropy production correspond to increases (decreases) in engine efficiency, as expected. Furthermore, we show that under thermal reservoirs a work extraction process that is more efficient than the Carnot engine is impossible, regardless of the quantum resource introduced via the Hamiltonian of the system.

Laser fluctuation effects in an EIT engine

In contact with a hot and a cold reservoir, the three-level atom driven by a strong coupling field generates photons via a sequence of transitions that mimics the running process of a heat engine. The brightness of the output photon can be much larger than that of the hot reservoir, and its efficiency could be larger than that of the Carnot engine [Phys. Rev. A 94, 053859 (2016)PLRAAN1050-294710.1103/PhysRevA.94.053859]. The core element of the mechanism is an interference effect called electromagnetically induced transparency caused by the coupling field, which is commonly a perfect laser without any random change in the phase. In this paper, we investigate a more realistic model where the temporal fluctuation of the coupling field is considered. By applying the laws of thermodynamics in the analysis, we find that in addition to the reduced power of the engine, a relatively strong fluctuation changes the properties of the system radically, even making it lose the quality of being a heat engine. We have found the corresponding criteria for the maximal allowed fluctuation. The entropy changes when the engine works below the laser threshold suggest that the effect of the fluctuation is equivalent to increasing the temperature of the cold reservoir.

Comparative study of quantum Otto and Carnot engines powered by a spin working substance.

Quantum Otto and Carnot engines have recently been receiving attention due to their ability to achieve high efficiencies and powers based on the laws of quantum mechanics. This paper discusses the theory, progress, and possible applications of quantum Otto and Carnot engines, such as energy production, cooling, and nanoscale technologies. In particular, we investigate a two-spin Heisenberg system that works as a substance in quantum Otto and Carnot cycles while exposed to an external magnetic field with both Dzyaloshinsky-Moriya and dipole-dipole interactions. The four stages of engine cycles are subject to analysis with respect to the heat exchanges that occur between the hot and cold reservoirs, alongside the work done during each stage. The operating conditions of the heat engine, refrigerator, thermal accelerator, and heater are all achieved. Moreover, our results demonstrate that the laws of thermodynamics are strictly upheld and the Carnot cycle produces more useful work than that of the Otto cycle.

Optimal performance of the stochastic thermodynamic engine with a periodic heat bath

Stochastic thermodynamics provides a conceptual framework for describing the fluctuating behavior of small systems like colloids or biomolecules far from thermodynamic equilibriums but still contacted with a heat bath. In contrast to most literature focusing on the classical paradigm of Carnot engines, we herein study the optimal performance of the thermodynamic heat engine with a heat bath that periodically changes temperature, which is outside controllable by a time-dependent harmonic potential. Under reasonable assumptions on the control actuation, we derive the achievable upper bound for the maximal power and also the optimal control protocol. In addition, we also obtain the corresponding efficiency at maximal power, which only depends on the ratio of the minimal and maximal value of the temperature profile.

Mesin Carnot Quantum dengan Dua Partikel Tidak Berinteraksi dan Tidak Berdekatan

In this article, we study the quantum Carnot engine using a one-dimensional infinite well potential model in which two particles are non-interacting, indistinguishable and have the same mass. We find that the efficiency of this model is the same as that of the one-dimensional infinite potential well model in which there is one particle. Moreover, efficiency can be measured only when L_C/L_A≥2, where L_A and L_C are the potential well widths during isothermal and adiabatic expansion, respectively.

Carnot, Stirling, and Ericsson stochastic heat engines: Efficiency at maximum power.

This work uses the low-dissipation strategy to obtain efficiency at maximum power from a stochastic heat engine performing Carnot-, Stirling- and Ericsson-like cycles at finite time. The heat engine consists of a colloidal particle trapped by optical tweezers, in contact with two thermal baths at different temperatures, namely hot (T_{h}) and cold (T_{c}). The particle dynamics is characterized by a Langevin equationwith time-dependent control parameters bounded to a harmonic potential trap. In a low-dissipation approach, the equilibrium properties of the system are required, which in our case, can be calculated through a statelike equationfor the mean value 〈x^{2}〉_{eq} coming from a macroscopic expression associated with the Langevin equation.

A New Interpretation of the Newton´s Cooling Law: Two Features of Thermons: Their Elastic Volume and Their Angular Momentum

The Newton´s cooling law still attracts the attention of scholars in order to describe hidden features of heat particles (thermons) and the mechanism of the radiating heat into the surroundings with a lower temperature. The characteristic cooling constant of this process 1/τπ [min-1] was defined as the experimental parameter describing the contributions of the thermon elastic volume and thermon angular momentum. This experimental parameter τπwas found as the time needed to achieve the temperature Tπ = Tenv +(T0-Tenv)/π during the cooling of the studied object with the starting temperature T0 and the surrounding with temperature Tenv. The studied system was water in spherical flasks with the volumes 2000, 1000, 500, 250, and 100 mL and the starting temperatures 90° C, 80°C, and 70° C. The temperature of the surrounding was 24° C (laboratory temperature) and (4° ± 2°) C (outdoor temperature on March 5 2023 near Prague). There was one critical experimental parameter: where to place the thermometer in the spherical flask: 1. inside to the bottom wall, 2. in the center of spherical flask, 3. at the upper level of the water volume, 4. outside to the bottom wall. For all experimental runs we have found that the temperature Tπ measured at the inside bottom wall of the spherical flasks might be interpreted as the “true” Newtonian temperature while the characteristic cooling constant τπ is very close to the value of the slope in the semi-log graph of those cooling systems. This model was used to interpret the historical experimental data of Newton (1701) and the modern experimental data of Grigull (1984). This model opens a new view on the Carnot engine where the elastic volume of thermons can achieve the efficiency η1 = (THOT – Tπ)/(THOT – TCOLD) = 1-1/π ≈ 0.682. Moreover, the “waste heat” after the Carnot engine can be used in the Seebeck generator to convert the angular momentum of thermons into the electricity (thermoelectric generator) with the efficiency η2 = (Tπ –TCOLD)/(THOT – TCOLD) = 1/π ≈ 0.318. The combined Carnot (1824) – Seebeck (1825) engine can explore all available heat of the of thermons for the temperature difference THOT – TCOLD.

Functionalities of Ni–Ti Shape Memory Alloys and Their Efficiency as Event Actuators of Microelectromechanical Systems

The functionalities of Ni–Ti alloys subjected to different deformation treatments are studied. A critical stress corresponding to the onset of degradation of the functional properties were determined; it was found that this stress is about twice as low as the yield stress. The efficiency coefficients of virtual thermodynamic machines with a working body made of the investigated materials were calculated and compared with the efficiency of a Carnot engine based on the same materials; the ideality factor has been calculated under the condition of actuating at stresses no higher than critical ones. It has been established that, at the single actuation, the highest ideality factor (9.7%) is characteristic of a material consisting of bars 20 to 5 mm in diameter obtained by warm forging at 350°C. It has been determined that, at discontinuous operation under stresses lower than the critical ones by a factor of 1.2, the ideality factor is 7.4–7.7% for alloys subjected to hot forging or equal channel angular pressing combined with warm forging.

Thermodynamic overview and heat engine efficiency of Kerr–Sen–AdS black hole

This paper reflects a study on the thermodynamic features of charged rotating Kerr–Sen–AdS black holes discussed with an extended phase space, where the negative cosmological constant is accounted for pressure. Thermal stability/instability and dependency of the phase transition points on the parameters of a black hole have been discussed further. The authors have systematically studied the throttling process of the black hole considering its mass is identified by its enthalpy. Moreover, the phenomenon of Joule–Thomson expansion has been explored, and inversion temperature for the black hole has been investigated using a numerical approach. Next, a heat engine is constructed by considering the black hole as a working object and subsequently, its efficiency is calculated by considering a rectangular heat cycle in the [Formula: see text]–[Formula: see text] plane. Then the effects of the black hole parameters on its efficiency and their respective roles are studied, followed by a careful comparison of the efficiency with that of a Carnot engine so that the second law of thermodynamics holds true.

More on the demons of thermodynamics

Robertson replies: Daniel Sheehan, Garret Moddel, and James Lee draw attention to an interesting book, Challenges to the Second Law of Thermodynamics: Theory and Experiment, which provides a survey of recent work that throws doubt on the inviolability of the second law. Do those avenues resurrect Maxwell’s demon? Do they conjure new ones?Of course, no scientific law is immutably beyond reproach, no matter how many famous physicists have sworn by it. But in considering the avenues suggested in the book, it can be helpful to scrutinize what we mean by the “second law.”11. For more on this theme, see J. Uffink, in Time and History: Proceedings of the 28 International Ludwig Wittgenstein Symposium; Kirchberg am Wechsel, Austria 2005, F. Stadler, M. Stöltzner, eds., De Gruyter (2006), p. 275. If the second law is that entropy—of which there are many forms—cannot decrease, then it can surely be violated; the Boltzmann entropy decreases in macroscopically indeterministic processes. But if the second law is taken to be that no engine is more efficient than a Carnot engine, then at least the previous example is not necessarily a violation.As David Wallace said in a talk at the University of Cambridge in November 2015, the distinction is between whether we can find ingenious and cunning devices or whether we can solve the energy crisis! The faith in the implausibility of the latter—that we will not find a perpetual motion machine of the second kind—is what those aggrandizing thermodynamics attest to. I meant to have captured that distinction between different kinds of “violations” of the second law in my discussion of “deft illusionists” versus “true magicians.” But that may have sounded dismissive; to be clear, important insights are revealed by studying the cases that Sheehan, Moddel, and Lee highlight, especially with respect to how the macroscopic domain may differ from the mesoscopic and microscopic ones. And if there were a true magician, then that would be welcome news in the current energy crisis.Similarly, whether the spin-echo experiment counts as a violation depends on precisely what we mean by the second law—no one is expecting to create a greater-than-Carnot efficiency engine out of that scenario. The point is merely that a system “retracing its steps” may have seemed nigh on impossible to Josef Loschmidt, but the spin-echo case provides a nice illustration of its feasibility. I am sympathetic to Jean Jeener’s view that the spin echo is not a case of increasing and then decreasing entropy, but then again, if we just look at the unitary dynamics, then entropy is neither increasing nor decreasing.One feature absent from my original article—as rightly emphasized by Harvey Leff and Andrew Rex—is the connection between thermal physics and information forged by Maxwell’s demon. That is often the lynchpin or starting place for those interested in quantum thermodynamics (referenced as “quantum steampunk” in my article) and, as Leff and Rex emphasize, stochastic thermodynamics. That brings up a question though: If information is central to thermodynamics, does that raise the specter of anthropocentrism?ReferenceSection:ChooseTop of pageReference <<1. For more on this theme, see J. Uffink, in Time and History: Proceedings of the 28 International Ludwig Wittgenstein Symposium; Kirchberg am Wechsel, Austria 2005, F. Stadler, M. Stöltzner, eds., De Gruyter (2006), p. 275. Google Scholar© 2023 American Institute of Physics.

Carnot Cycles in a Harmonically Confined Ultracold Gas across Bose–Einstein Condensation

Carnot cycles of samples of harmonically confined ultracold 87Rb fluids, near and across Bose-Einstein condensation (BEC), are analyzed. This is achieved through the experimental determination of the corresponding equation of state in terms of the appropriate global thermodynamics for non-uniform confined fluids. We focus our attention on the efficiency of the Carnot engine when the cycle occurs for temperatures either above or below the critical temperature and when BEC is crossed during the cycle. The measurement of the cycle efficiency reveals a perfect agreement with the theoretical prediction (1-TL/TH), with TH and TL serving as the temperatures of the hot and cold heat exchange reservoirs. Other cycles are also considered for comparison.

Infinite spherical well as model of quantum carnot engine

The potential well is a simple example that generally used to present an understanding of quantum mechanics. In this article, we used infinite spherical well model to evaluate the thermodynamic processes in a quantum Carnot engine. The energy of the particles depended on the value of n and l lead to complex calculations. For simplicity we used the φ100 and φ200 quantum states to determine work and efficiency of a quantum Carnot machine. The results obtained show that efficiency depends on the value of which is the ratio of RC and RB.

Performance optimization on finite-time quantum Carnot engines and refrigerators based on spin-1/2 systems driven by a squeezed reservoir

We investigate the finite-time performance of a quantum endoreversible Carnot engine cycle and its inverse operation — Carnot refrigeration cycle, employing a spin-1/2 system as the working substance. The thermal machine is alternatively driven by a hot boson bath of inverse temperature β h and a cold boson bath at inverse temperature β c (>β h). While for the engine model the hot bath is constructed to be squeezed, in the refrigeration cycle the cold bath is established to be squeezed, with squeezing parameter r. We obtain the analytical expressions for both efficiency and power in heat engines and for coefficient of performance and cooling rate in refrigerators. We find that, in the high-temperature limit, the efficiency at maximum power is bounded by the analytical value , and the coefficient of performance at the maximum figure of merit is limited by , where η C = 1 – β h/β c and ε C = β h/(β c – β h) are the respective Carnot values of the engines and refrigerators. These analytical results are identical to those obtained from the Carnot engines based on harmonic systems, indicating that the efficiency at maximum power and coefficient at maximum figure of merit are independent of the working substance.