Thermodynamic Work Research Articles

Stochastic heat engine using an active particle.

The topic of microscopic heat engine has undergone intensive research in recent years. Microscopic heat engines can exploit thermal as well as active fluctuations to extract thermodynamic work. We investigate the properties of a microscopic Stirling's engine that uses an active (self-propelling) particle as a working substance, in contact with two thermal baths. It is shown that the presence of activity leads to an enhanced performance of the engine. The efficiency can be improved by increasing the activity strength for all cycle time, including the nonquasistatic regime. We verify that the analytical results agree very well with our simulations. The variation of efficiency with the temperature difference between the two thermal baths has also been explored. The optimum region of operation of the engine has been deduced, by using its efficient power (product of efficiency and power) as a quantifier. Finally, a simple model is provided that emulates the behavior of a flywheel driven by this engine.

Representations and divergences in the space of probability measures and stochastic thermodynamics

Radon–Nikodym (RN) derivative between two measures arises naturally in the affine structure of the space of probability measures with densities. Entropy, free energy, relative entropy, and entropy production as mathematical concepts associated with RN derivatives are introduced. We identify a simple equation that connects two measures with densities as a possible mathematical basis of the entropy balance equation that is central in nonequilibrium thermodynamics. Application of this formalism to Gibbsian canonical distribution yields many results in classical thermomechanics. An affine structure based on the canonical representation and two divergences are introduced in the space of probability measures. It is shown that thermodynamic work, as a conditional expectation, is indicative of the RN derivative between two energy representations being singular. The entropy divergence and the heat divergence yield respectively a Massieu–Planck potential based and a generalized Carnot inequalities.

The Effect of Solvent Nature on the Adhesive Properties of Binary Styrene–n-Butyl Acrylate Copolymer Films Formed by Casting on Solid Substrates

A methodological approach has been proposed for studying the effect of solvent nature on the adhesive properties of films of binary copolymers with different chain microstructures. The approach is based on a complex analysis of the thermodynamic work of adhesion in polymer–liquid model systems and the results of mechanical tests in combination with quantum-chemical calculations. The approach has been used for the first time for copolymers of styrene and n-butyl acrylate having gradient and random distributions of comonomer units over the chains, with the copolymers being synthesized by radical polymerization with reversible chain transfer. The results obtained have shown that the adhesive properties of the binary copolymer films may be regulated by varying the chemical nature of solvents from which they are formed.

Application of the meta‐heuristics for optimizing exergy of a HT‐PEMFC

The aim of this study is to analyze the exergy efficiency of a high-temperature proton exchange membrane fuel cell. To do this purpose, meta-heuristic technique has been used. First, the model of a membrane fuel cell is simulated and the polarization diagram shows a potent agreement with empirical data. Then, a new improved version of collective animal behavior algorithm is utilized for evaluating and optimizing the thermodynamic irreversibility, exergy efficiency, and work of the fuel cell. The algorithm uses opposition-based learning and Lévy flight for improving the algorithm's premature convergence shortcoming. The result of this study shows that by comparison with standard collective animal behavior algorithm, genetic algorithm, and empirical results, the proposed algorithm has better achievements for both terms of optimal value finding and convergence strength.

No-go results in quantum thermodynamics

Thermodynamics is one of the fascinating branches of traditional physics to certify the occurrence of many natural processes. On the other hand, quantum theory is the most acceptable description of the microscopic world. In the present work, we have studied how the structure of quantum theory prohibits cloning or masking of several thermodynamic quantities, viz., work and energy stored in a quantum state. Our results have important consequences in quantum partial cloning, quantum masking and on the action of quantum channels.

Thermodynamic work in inline piston gasoline engines as a function of crank angle

The purpose of this research work is to identify the laws of thermodynamic operation in the theoretical cycles of four-stroke inline piston gasoline internal combustion engines (ICE). The main results: dependence of the thermodynamic operation of the working body of ICE in theoretical cycles of four-stroke inline piston gasoline engines as a function of the angle of rotation of the crankshaft; regularities of uneven generation of positive thermodynamic operation in the theoretical cycle of four-stroke inline one-, two-, three -, five-cylinder piston gasoline ICE; regularities of the alternating character of thermodynamic operation in the theoretical cycles of inline four-stroke one -, two -, three -, four - and five-cylinder gasoline piston ICE; regularities of positive thermodynamic operation during the entire theoretical cycle of four-stroke inline six-and eight-cylinder piston gasoline ICE; conditions for uniform pulsation of thermodynamic operation during the entire theoretical cycle of four-stroke inline piston gasoline ICE - the product of the crankshaft angle by the number of cylinders must be 720o (four-cylinder inline with a crankshaft angle of 180o, six-cylinder inline with a crankshaft angle of 120o, eight-cylinder inline with a crankshaft angle of 90o).

Extraction of the equilibrium pinning force on a contact line exerted from a wettability boundary of a solid surface through the connection between mechanical and thermodynamic routes.

By molecular dynamics (MD) simulations, we investigated the effects of chemical inhomogeniety of a wall surface on the equilibrium pinning behavior of a contact line (CL) of solid (S), liquid (L), and vapor (V) phases. We analyzed a quasi-two-dimensional LV-meniscus of Lennard-Jones fluid formed between two parallel flat solid walls, where the CL was located around the wetting boundary (WB) between lyophilic and lyophobic areas of the wall surface. Based on the relationship between the wall-tangential stress integral at the SL or SV interface and the corresponding thermodynamic work of adhesion WSL or WSV shown in our previous study [Y. Yamaguchi et al., J. Chem. Phys. 150, 044701 (2019)], the mechanical balance on the fluid around the CL was successfully described by the relation among WSL, WSV, the apparent contact angle, and the pinning force. In addition, the depinning force needed to move the CL across the WB was estimated as the difference between WSL values at lyophilic and lyophobic areas. Since the works of adhesion WSL and WSV can be easily calculated independently in simple systems through the thermodynamics integration, such a connection between the mechanical and thermodynamic routes provides a possible pathway toward the understanding of wetting including CL-pinning without the need of computationally demanding calculation of the local stress distributions.

The design and testing of a kW-class free-piston Stirling engine for micro-combined heat and power applications

This research paper describes the design methodology of the free-piston Stirling engine (FPSE) and its demonstration. The FPSE is equipped with a dual-opposed linear alternator. The design and experiment are mainly focused on understanding how the FPSE dynamically behaves. Based on the data obtained from experiments, the operational issues regarding the output and dynamic characteristics are discussed in detail. The FPSE can accept approximately 4.2 kW at the engine head with a temperature of 525 °C. As a heat source, city-supplied natural gas is used. The linear alternator stably produces 961 We-electricity at a resonance frequency of 60 Hz. The deduced efficiency of the linear alternator is 70–75% of the thermodynamic work generated by the engine. The integrated system, FPSE, has an overall efficiency of 23.0% when comparing the heat supplied to the electrical output. The FPSE was also proven with a direct connection to the grid, so it can generate and sell electricity back to the grid. The equipped resonant capacitor enables this by compensating for the power factor. The experiment results show that the design methodology is able to adequately explain the behavior of the FPSE.

Thermodynamic aspects of nanoscale friction

Developing the non-equilibrium thermodynamics of friction is required for systematic design of low friction surfaces for a broad range of technological applications. Intuitively, the thermodynamic work done by a material sliding along a surface is expected to be partially dissipated as heat and partially transformed into the change of the internal energy of the system. However, general non-equilibrium thermodynamic principles governing this separation are presently unknown. We develop a theoretical framework based on the transition state theory combined with the conventional Prandtl-Tomlinson model, allowing to set explicit expressions for evaluating the heat dissipation and internal energy change produced during the frictional stick-slip motion of a tip of a typical friction force microscope (FFM). We use the formalism to quantify the heat dissipation for a range of parameters relevant to materials in practical applications of nanoscale friction.

Assessment of sewage sludge gasification in supercritical water for H2-rich syngas production

The potential of sewage sludge for hydrogen-rich syngas production from supercritical water gasification (SCWG) was evaluated through thermodynamic analysis and experimental work. The thermodynamic analysis was conducted by using Aspen Plus simulator based on Gibbs free energy minimization. The effect of temperature (380–460°C), sludge concentration (5–30wt%), and activated carbon addition (2–8wt%) on SCWG was experimentally studied. The solid and liquid residues were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), and Total Organic Carbon (TOC) Analyzer. The results showed that higher temperature and lower sludge concentration favored syngas production, leading to higher hydrogen yield. While pressure had no significant effect on the SCWG performance. The TOC and FTIR analyses revealed that organic matters in sewage sludge were decomposed and hydrolyzed into syngas. The addition of activated carbon increased the syngas yield and enhanced the cold gas efficiency. A syngas yield of 6.44mol/kg containing 38.43% H2 was obtained from SCWG at 400°C with the activated carbon loading of 8wt%. Moreover, the analysis of heavy metals indicated that SCWG had a positive effect on the stabilization of heavy metals and reduced the leaching toxicity of heavy metals in sewage sludge.

Stochastic work extraction in a colloidal heat engine in the presence of colored noise

From synthetic active devices such as self-propelling Janus colloids to micro-organisms like bacteria, micro-algae, living cells in tissues, active fluctuations are ubiquitous. Thermodynamics of small systems involving thermal as well as active fluctuations are of immense importance. They can be employed to extract thermodynamic work. Here we propose a simple model system that can produce thermodynamic work exploiting active fluctuations. We consider a Brownian particle, trapped by an externally controlled harmonic confinement that contracts and expands time-periodically by modulating its spring constant e.g. optical tweezers. The system produces work by being alternately connected to two baths one passive and other active. The active bath provides exponentially time-correlated noise to the particle, that breaks the fluctuation dissipation relation. The average efficiency of the system is calculated exactly in quasistatic limit. Nonquasistatic regime is explored by numerics. Comparing with its passive counterpart, we also show that the active micro heat engine can be more efficient depending on the chosen parameter space. We also believe that our model can be realised experimentally with the help of bacterial baths.

PH Swing Cycle for CO2 Capture Electrochemically Driven through Proton-Coupled Electron Transfer

We propose and perform a thermodynamic analysis of the energetic costs of CO2 separation from flue gas using a pH swing created by electrochemical redox reactions involving proton-coupled electron transfer from molecular species in aqueous electrolyte. Electrochemical reduction of these molecules results in the formation of alkaline solution, into which CO2 is absorbed; subsequent electrochemical oxidation of the reduced molecules results in the acidification of the solution, triggering the release of pure CO2 gas. We examined the effect of buffering from the CO2-carbonate system on the solution pH during this pH swing cycle, and thus on the open-circuit potential of a hypothetical electrochemical cell in a 4-step CO2 capture-release cycle. The thermodynamic minimum work input varies from 16 to 75 kJ/molCO2 as throughput increases, for both flue gas and direct air capture, with the potential to go substantially lower if CO2 capture or release is performed simultaneously with electrochemical reduction or oxidation. These values are compared with those for other separation methods. We also discuss the properties required of molecules that would be suitable for such a cycle, and preliminary experimental data from a cycle run using one such molecule.

Convergence of thermodynamic quantities and work fluctuation theorems in the presence of random protocols

Recently, many results, namely the Fluctuation theorems (FT), have been discovered for systems arbitrarily away from equilibrium. Many of these relations have been experimentally tested. The system under consideration is usually driven out of equilibrium by an external time-dependent parameter which follows a particular protocol. One needs to perform several iterations of the same experiment in order to find statistically relevant results. Since the systems are microscopic, fluctuations dominate. Studying the convergence of relevant thermodynamics quantities with number of realizations is also important as it gives a rough estimate of the number of iterations one needs to perform. In each iteration, the protocol follows a predetermined identical/fixed form. However, the protocol itself may be prone to fluctuations. In this work, we are interested in looking at a simple nonequilibrium system, namely a Brownian particle trapped in a harmonic potential. The center of the trap is then dragged according to a protocol. We however lift the condition of fixed protocol. In our case, the protocol in each realization is different. We consider one of the parameters of the protocol as a random variable, chosen from some known distribution. We study the systems analytically as well as numerically. We specifically study the convergence of the average work and free energy difference with number of realizations. Interestingly, in several cases, randomness in the protocol does not seem to affect the convergence when compared to fixed protocol results. We study symmetry functions. The cases of a Brownian particle in a harmonic potential with sinusoidally changing stiffness constant, as well as a Brownian particle in a double well potential, are also studied. We believe that our results can be experimentally verified.

An irreversible Stirling cycle with temperature difference both in non-isothermal and isochoric processes

In this paper, an irreversible thermodynamic cycle working between two constant temperature external reservoirs is proposed to model the practical Stirling engine by applying finite time thermodynamics (FTT). To analyze the regenerative processes, the regenerator is assumed to consist of numerous smaller heat reservoirs with individual temperature, and the irreversible heat transfer occurs between the working fluid and these smaller heat reservoirs. To analyze the expansive and compressive processes, polytropic processes are adopted to model the expansive and compressive processes, and corresponding polytropic exponents are obtained by thermodynamics for the first time. Based on the proposed thermodynamic model, the expression of thermal efficiency and output power are derived. In addition, the effects of thermodynamic parameters on power and efficiency are investigated to evaluate the performance of the proposed model. To optimize the proposed Stirling cycle model, an intelligent optimization algorithm named multi-objective particle swarm optimization based on crowding distance (MOPSOCD) is adopted to optimize the output power and thermal efficiency simultaneously.

The temperature-dependence of the dynamic contact angle

HypothesisThe wetting of a solid by a liquid is a thermally-activated molecular rate process, which may be investigated by studying the temperature-dependence of the dynamic contact angle at standard experimental scales. ExperimentsWe use the plunging-tape method and a low-powered microscope to measure the dynamic contact angle of di-n-butyl phthalate (DBP) on poly(ethylene terephthalate) (PET) tape over a very wide speed range of 0.003–100 cm/s at 5 temperatures from 15 °C to 55 °C. The molecular-kinetic theory of dynamic wetting (the MKT) is then used to interpret the data, which span angles from 8° to near 180°. FindingsThe MKT successfully accounts for the temperature-dependence of the dynamic contact angle, yielding rational values for key parameters including the activation free energy of wetting. Arrhenius-like behavior is also demonstrated. These results would appear to confirm that, at the molecular-scale, dynamic wetting is a thermally-activated rate process and that the influence of temperature is not restricted simply to its effect on surface tension and viscosity. The data show a discontinuity at dynamic contact angles between 60° and 90° that implies a velocity-dependent change in the wetting mechanism. We attribute this to the chemical heterogeneity of the PET surface, which contains both polar and non-polar groups. The parameters obtained by applying the MKT suggest that the interactions of DBP with these groups determine, respectively, the dynamics observed below and above the transition. The sum of the activation free energies of wetting on either side of the transition is close to the total thermodynamic work of adhesion of DBP to PET.

CO2 regenerative battery for energy harvesting from ammonia-based post-combustion CO2 capture

Amine-based CO2 capture is considered the most mature technology for industrial application in coal-fired power stations, but its large energy requirement represents a major barrier to commercial deployment. Here, we introduce a novel approach involving a CO2 regenerative amine-based battery (CRAB), which harvests the chemical energy from amine-based CO2 capture through a metal-mediated electrochemical process. The CRAB process uses the dual ability of amines (i.e. ammonia) to reversibly react with CO2 and complex with metal ions (i.e. copper) to convert the CO2 reaction enthalpy into electrical energy. To determine how the CRAB process harvests energy from CO2 capture, we established a validated chemical model for CRAB system which was used to predict the electrode potentials, and conceive a CRAB cycle that links CO2 absorption/desorption with the electrochemical process. Modelling results indicate that CRAB could at best produce 8.4 kJe/mol CO2 from a copper/ammonia based energy harvesting system, while optimised CRAB experimentally discharged 6.5 kJe/mol CO2 of electrical energy with a maximum power density of 32 W/m2. When CRAB is coupled with an advanced ammonia process, the experimentally achieved energy output could reduce capture energy requirement to 0.177 MW h/tonne CO2 (including CO2 compression to 150 bar), with a high thermodynamic efficiency of CO2 capture of 62.1% (relative to thermodynamic minimum work of 0.11 MW h/tonne CO2). Our results demonstrate the technical feasibility of the CRAB system to harvest electrical energy from CO2 capture process, providing a pathway to significantly reduce capture energy requirement.

Interface Characterization Between Polyethylene/ Silica in Engineered Cementitious Composites by Molecular Dynamics Simulation.

Polyethylene is widely adopted in engineered cementitious composites to control the crack width. A clearer knowledge of the PE/concrete interfacial properties is important in developing engineered cementitious composites, which can lead to a limited crack width. Tensile failure and adhesion properties of the amorphous polyethylene/silica (PE/S) interface are investigated by molecular dynamics to interpret the PE/concrete interface. The influence of the PE chain length, the PE chain number and coupling agents applied on silica surface on the interfacial adhesion is studied. An increase of the adhesion strength of the modified silica surface by coupling agents compared with the unmodified silica is found. The failure process, density profile and potential energy evolutions of the PE/S interface are studied. The thermodynamic work of adhesion that quantifies the interfacial adhesion of the PE/S interface is evaluated. The present study helps to understand the interfacial adhesion behavior between ECC and PE, and is expected to contribute to restricting the crack width.

Thermodynamic Approach to Substantiating the Work and Potential for Separation of Multicomponent Mixtures

Equations for calculating the thermodynamic work of separation are proposed and generalized.

Quantum coherence, many-body correlations, and non-thermal effects for autonomous thermal machines

One of the principal objectives of quantum thermodynamics is to explore quantum effects and their potential beneficial role in thermodynamic tasks like work extraction or refrigeration. So far, even though several papers have already shown that quantum effect could indeed bring quantum advantages, a global and deeper understanding is still lacking. Here, we extend previous models of autonomous machines to include quantum batteries made of arbitrary systems of discrete spectrum. We establish their actual efficiency, which allows us to derive an efficiency upper bound, called maximal achievable efficiency, shown to be always achievable, in contrast with previous upper bounds based only on the Second Law. Such maximal achievable efficiency can be expressed simply in term of the apparent temperature of the quantum battery. This important result appears to be a powerful tool to understand how quantum features like coherence but also many-body correlations and non-thermal population distribution can be harnessed to increase the efficiency of thermal machines.

Extractable Work, the Role of Correlations, and Asymptotic Freedom in Quantum Batteries.

We investigate a quantum battery made of N two-level systems, which is charged by an optical mode via an energy-conserving interaction. We quantify the fraction of energy stored in the battery that can be extracted in order to perform thermodynamic work. We first demonstrate that this quantity is highly reduced by the presence of correlations between the charger and the battery or between the subsystems composing the battery. We then show that the correlation-induced suppression of extractable energy, however, can be mitigated by preparing the charger in a coherent optical state. We conclude by proving that the charger-battery system is asymptotically free of such locking correlations in the N→∞ limit.