Efficiency Of Heat Engine Research Articles

Irreversible entropy production rate in a parametrically driven-dissipative system: The role of self-correlation between noncommuting observables

In this paper, we explore the emergence of the Wigner entropy production rate in the stationary state of a two-mode Gaussian system. The interacting modes dissipate into different local thermal baths. Also, one of the bosonic modes evolves into the squeezed-thermal state because of the parametric amplification process. Using the Heisenberg-Langevin approach, combined with quantum phase space formulation, we get an analytical expression for the steady-state Wigner entropy production rate. It contains two key terms. The first one is an Onsager-like expression that describes heat flow within the system. The second term resulted from vacuum fluctuations of the baths. Analyses show that self-correlation between the quadratures of the parametrically amplified mode pushes the mode towards the thermal squeezed state. It increases vacuum entropy production of the total system and reduces the heat current between the modes. The results imply that, unlike other previous proposals, squeezing can constrain the efficiency of actual non-equilibrium heat engines by irreversible flows.

Non-Markovianity and efficiency of a q-deformed quantum heat engine

We consider a qubit as a working medium in a deformed quantum Otto cycle using Tsallis statistics. To analyze the engine, we obtain the time evolution of the deformed density matrix in different steps of the cycle using the Lindblad equation. We calculate deformed work done, exchange heat, and cycle efficiency. We present a new and exact formula for the dependence of the above parameters with the non-Markovianity of the system, based on mutual information. It finds that the non-Markovian effects can be a resource to extract work from an Otto cycle.

Influence of an indefinite causal order on an Otto heat engine

The quantum effect plays an important role in quantum thermodynamics, and recently the application of an indefinite causal order to quantum thermodynamics has attracted much attention. Based on two trapped ions, we propose a scheme to add an indefinite causal order to the isochoric cooling stroke of an Otto engine through reservoir engineering. Then, we observe that the quasi-static efficiency of this heat engine is far beyond the efficiency of a normal Otto heat engine and may reach one. When the power is its maximum, the efficiency is also much higher than that of a normal Otto heat engine. This enhancement may originate from the non-equilibrium of the reservoir and the measurement on the control qubit.

Thermal stability, $$P{-}V$$ criticality and heat engine of charged rotating accelerating black holes

In this paper, we study thermodynamic features of the charged rotating accelerating black holes in anti-de Sitter spacetime. First, we consider these black holes as the thermodynamic systems and analyze thermal stability/instability through the use of heat capacity in the canonical ensemble. We also investigate the effects of angular momentum, electric charge and string tension on the thermodynamic quantities and stability of the system. Considering the known relation between pressure and the cosmological constant, we extract the critical quantities and discuss how the mentioned parameters affect them. Then, we construct a heat engine by taking into account this black hole as the working substance, and obtain the heat engine efficiency by considering a rectangle heat cycle in the $P-V$ plane. We examine the effects of black hole parameters on the efficiency and analyze their effective roles. Finally, by comparing the engine efficiency with Carnot efficiency, we investigate conditions in order to have a consistent thermodynamic second law.

Electrolyte engineering can improve electrochemical heat engine and refrigeration efficiency

The rational engineering of electrolytes can dramatically improve electrochemical heat engines and heat pumps (refrigerators), which are emerging, low-cost, high-efficiency thermal energy conversion technologies. We discuss the key parameters that make electrolytes attractive for thermal energy conversion, provide new insight into the trade-offs, and suggest approaches to circumvent these trade-offs.

Experimental investigation on heavy duty engine radiator using cerium oxide nano fluid

The goal of this work is to improve the heat transfer capacity of vehicle radiators by adding cerium oxide-based nanofluid, as well as to compare the performance analysis of radiators employing nanofluid with base fluid. By increasing heat transmission, this enhances heat transfer performance and engine efficiency of the radiator. Nanofluids are made by combining 3:2 water and ethylene glycol with 1% cerium oxide nanoparticles. This analysis has been performed in three distinct nanoparticle concentrations: 1%, 1.5%, and 2% by volume with different flow rate of 0.04, 0.05, 0.06, 0.07 and 0.08 kg/s. These modifications potentially increased the heat transfer rate by around 20% above the fluid (water). As a result, this demonstrates the usage of nanofluid in habitation of base fluid in boosting heat transfer rate by 6.2%, which aids in overall radiator performance enhancement. The experimental results showed a maximum enhancement of the “Nu” Nusselt numberby 13.39 percent with an inlet temperature of 60 °C, 2% Ceo2 nanomaterials, and a mass flow rate of 0.09 kg/s. The maximum increase in heat transfer rate is 6.2% with an inlet temperature of 60 °C, 2% Ceo2 nanoparticles, and a mass flow rate of 0.09 kg/s.

Thermodynamic Stability and Holographic Heat Engine Efficiency of a Kerr-Newmann-Nut-Kiselev-Ads Blackhole in Rastall Gravity

Thermodynamic Stability and Holographic Heat Engine Efficiency of a Kerr-Newmann-Nut-Kiselev-Ads Blackhole in Rastall Gravity

Maximum power and corresponding efficiency of an irreversible blue heat engine for harnessing waste heat and salinity gradient energy

Maximum power and corresponding efficiency of an irreversible blue heat engine for harnessing waste heat and salinity gradient energy

Energy breakeven in thermonuclear fusion. An advanced concept for efficient energy input with positive implications for energy saving and the geoscience of climate change

The motivation of the present study is energy generation with thermonuclear fusion. Specifically, it is the attainment of breakeven conditions with a fusionable plasma whereby the output fusion energy is at least equal to the energy expended in creating the plasma and bringing it to fusionable conditions. This objective has eluded the physics community for the past seven decades. It is here suggested that perhaps the reason is that ever-bigger fusion machines are built, which unfortunately have brought results not in line with the expectations, in terms of desired fusion output. The opposite view is taken here, where attention is paid to the energy input, with the objective of minimizing the energy losses. One of the most important losses is a consequence of the limited thermodynamic efficiency of conventional engines that convert heat to work, thus generating the electricity involved in the energy input. This preliminary study shows that the efficiency can be improved if a novel thermodynamic cycle is used with heat recovery and recirculation. No attention is paid in the present study to the applicability of the novel cycle to a working engine but only to its feasibility. After the delineation of the concept, we use a simulation program to confirm that such approach is promising, and the objective of improving the thermodynamic efficiency of conventional heat-engines by at least 10% is realistic. Finally, the economic benefits are quantified of such substantial efficiency improvement on a world-wide scale. Mitigation of the damage to our environment due to the reduced heat rejection is also quantified.

A thermodynamic probe of the topological phase transition in epitaxial graphene based Floquet topological insulator

One can use light to tune certain materials from a trivial to a topological phase. A prime example of such materials, classified as Floquet topological insulators (FTIs), is epitaxial graphene. In this paper, we probe the topological phase transition of a FTI via the efficiency and work output of quantum Otto and quantum Stirling heat engines. A maximum/minimum in the efficiency or work output invariably signals the phase transition point. Furthermore, both engines’ work output and efficiency are markedly robust against the polarization direction of light.

Regular AdS black holes holographic heat engines in a benchmarking scheme

In this work, we explore some properties of holographic heat engines with Regular Anti-de Sitter black holes as the working substances in a benchmarking scheme. Namely, the Hayward, Bardeen and Maxwellian classes which are solutions of Einstein gravity coupled to a non-linear electromagnetic field. We also examine how the nonlinear electrodynamics parameter, the size of the benchmark circular cycle, and the charge of such black holes can influence the efficiency of the cycle. In the end, a cross-comparison of the efficiencies of different black hole heat engines suggests that the Hayward class is the more efficient one, and the constraint μ<1 also increases the efficiency and renders it more sensitive as the charge varies.

The Quantum Otto Heat Engine with a Relativistically Moving Thermal Bath

We investigate the quantum thermodynamic cycle of a quantum heat engine carrying out an Otto thermodynamic cycle. We use the thermal properties of a moving heat bath with relativistic velocity with respect to the cold bath. As a working medium, we use a two-level system and a harmonic oscillator that interact with a hot and cold bath respectively. In the current work, the quantum heat engine is studied in the high and low temperatures regime. Using quantum thermodynamics and the theory of open quantum systems we obtain the total produced work, the efficiency and the efficiency at maximum power. The maximum efficiency of the Otto quantum heat engine depends only on the ratio of the minimum and maximum energy gaps. On the contrary, the efficiency at maximum power and the extracted work decreases with the velocity since the motion of the heat bath has an energy cost for the quantum heat engine. Furthermore, the efficiency at maximum power depends on the nature of the working medium.

Higher-order efficiency bound and its application to nonlinear nanothermoelectrics.

Power and efficiency of heat engines are two conflicting objectives. A tight efficiency bound is expected to give insights on the fundamental properties of such a power-efficiency tradeoff. Here, we derive an upper bound on the efficiency of steady-state heat engines, which incorporates higher-order fluctuations of power. In a prototypical model of nonlinear nanostructured thermoelectrics, we show that the obtained bound is tighter than a well-established efficiency bound derived from the thermodynamic uncertainty relation, demonstrating that the higher-order terms have rich information about the thermodynamic efficiency in the nonlinear regime. In particular, we find that the higher-order bound is exactly achieved if the tight coupling condition is satisfied. The obtained bound gives a consistent prediction with an observation that nonlinearity enhances the power-efficiency tradeoff, and would also be useful in a variety of nanoscale engines.

Multicriteria optimization of Brayton-like pumped thermal electricity storage with liquid media

A multi-objective and multi-parametric optimization of a Pumped Thermal Electricity Storage system based on Brayton cycles is presented by the calculation of different Pareto fronts and the associated Pareto optimal sets for energetic and design analysis, respectively. A large range of internal and external irreversibilities and the thermodynamic properties of the storage media are taken into account. The analysis shows that the heat capacity of the working fluid and the heat capacity of the storage media should be the same in the contact with the hot reservoirs and in the contact with the cold reservoir in the heat pump, but in the contact with the cold reservoir for the heat engine the ratio should be 0.33, this offers information regarding the mass flow increasing significantly the achievable values for the round-trip efficiency, power output and the heat engine efficiency in the discharge process. Optimal values are given in terms of the degree of irreversibilities in the system and a comparison is made with extreme cases of infinite and minimum sizes for the storage system. Round-trip efficiencies in the so-called optimum scale/mass-flow-ratio design point exhibits noticeably larger values compared to previously reported results including the so-called endoreversible limit, where no internal irreversibilities are considered and where the improvement can achieve 49% over the endoreversible case in the most ideal scenario. Explicit numerical values of the maximum round trip efficiency, power output, and efficiency are given for a broad range of both internal and external irreversibilities.

Space-fractional quantum heat engine based on level degeneracy

In order to examine the work and efficiency of the space-fractional quantum heat engine, we consider a model of the space-fractional quantum heat engine which has a Stirling-like cycle with a single particle under infinite potential well as an example. We numerically compute the work and efficiency for various fractional exponents. We show the work and the efficiency of the engine depending on the length of the potential well and fractional exponent of the engine. Furthermore, we show that fractional exponent plays a substantial role in the operating range of the quantum heat engine. Thus, we conclude that the fractional parameter can be used as a tuning parameter to obtain positive work and efficiency for the large size of the quantum heat engine. Additionally, the numerical results and model imply that the size of the engine can be enlarged in the nano-scale by using fractional deformations. As a result, in this study, we have not only shown that fractional deformations in space play an important role on the work and efficiency of the quantum heat engines but also introduced the concept of fractional quantum heat engines to the literature.

Quantum Otto thermal machines powered by Kerr nonlinearity

We study the effect of Kerr nonlinearity in quantum thermal machines having a Kerr-nonlinear oscillator as working substance and operating under the ideal quantum Otto cycle. We first investigate the efficiency of a Kerr-nonlinear heat engine and show that by varying the Kerr-nonlinear strength the efficiency surpasses in up to 2.5 times the efficiency of a quantum harmonic oscillator (QHO) Otto engine. Moreover, the Kerr-nonlinearity makes the coefficient of performance of the Kerr-nonlinear refrigerator to be as large as three times the performance of QHO Otto refrigerators. These results were obtained using realistic parameters from circuit quantum electrodynamics devices formed by superconducting circuits and operating in the microwave regime.

Holographic heat engine efficiency of hyperbolic charged black holes* *Project supported by the National Natural Science Foundation of China (Grant No. 11875184).

We consider a four-dimensional charged hyperbolic black hole as working matter to establish a black hole holographic heat engine, and use the rectangular cycle to obtain the heat engine efficiency. We find that when the increasing of entropy is zero, the heat engine efficiency of the hyperbolic black hole becomes the well-known Carnot efficiency. We also find that less charge corresponds to higher efficiency in the case of . Furthermore, we study the efficiency of the flat case and spherical case and compare the efficiency with that of the hyperbolic charged black holes. Finally, we use numerical simulation to study the efficiency in benchmark scheme.

Quantum cycle in relativistic non-commutative space with generalized uncertainty principle correction

Quantum heat cycles and quantum refrigerators are analyzed using various quantum systems as their working mediums. For example, to evaluate the efficiency and the work done of the Carnot cycle in the quantum regime, one can consider the harmonic oscillator as a working medium. For all these well-defined working substances (which are analyzed in commutative space structure), the efficiency of the engine is not up to the mark of the Carnot efficiency. So, one inevitable question arise, can one observe a catalytic effect on the efficiency of the engines and refrigerators when the space structure is changed? In this paper, two different working substances in non-commutative spacetime with relativistic and generalized uncertainty principle corrections have been considered for the analysis of the efficiency of the heat engine cycles. The efficiency of the quantum heat engine gets a boost for higher values of the non-commutative parameter with a harmonic oscillator as the working substance. In the case of the second working medium (one-dimensional infinite potential well), the efficiency shows a constant result in the non-commutative space structure.

Performance Improvement of a Thermoacoustic Stirling Engine With In-Line Phase-Adjuster

Abstract This study examined the influence of an in-line phase-adjuster on the energy conversion efficiency of a thermoacoustic Stirling heat engine (TASHE). The numerical and experimental investigations were performed. An acoustic field in the system can be adjusted using the phase-adjuster. Therefore, the thermoacoustic engine could maintain high-level performance at all operating conditions. The engine is composed of a torus section where core components were located, and a long resonator pipe. The phase-adjuster or the telescopic in-line piston was set up at the tail of the resonance tube. The TASHE was modeled by employing DeltaEC to search the optimal configurations of the prototype. Due to the variations of acoustic loads or operating conditions from the design criteria, the engine absolutely cannot maintain maximum efficiency. The proposed phase-adjuster could bring back its maximum efficiency by re-matching the acoustic impedance in the regenerator. The TASHE was designed to operate with compressed air at 9 bar. In the experiments, the self-excited temperature of the engine was around 480 °C, and the steady-state temperature was about 397 °C. The TASHE can provide an acoustic power of up to 40 W. The thermo-to-acoustic efficiency of 12.03% related to 22.56% of the theoretical Carnot efficiency was achieved. There was a reasonably good agreement between the measured and DeltaEC simulation results. This can reflect on the preciseness of the proposed model. Furthermore, the function of the phase-adjuster in tuning the acoustic impedance was also demonstrated experimentally. In case of the TASHE being operated under the off-design conditions, i.e., due to pressure leak or heat losses, these scenarios would drop the efficiency of the system. The research presented in this study can confirm that the phase-adjuster is the component applied to tune the acoustic field in the regenerator accurately with minimum changes in the system. It could help to improve the efficiency of such consequences.

Parametric study for optimal performance of Coulomb-coupled quantum dots

We study the optimal output power and efficiency of the three-terminal quantum heat engine with Coulomb-coupled quantum-dots (CCQD). It has been well known that in the weak coupling regime, two kinds of dominant transport mechanisms are sequential tunneling and cotunneling processes in CCQD. What process becomes dominant, which can be controlled by several parameters such as temperature difference, bias voltage, Coulomb interaction and tunneling parameters, is one of the key problems to determine the performance of the heat engine. We show the parametric dependence of the output power and coefficient and find the optimal performance of this CCQD heat engine through genetic algorithm.