33 results on '"Jizhou He"'
Search Results
2. A three-terminal quantum dot heat engine based on ideal resonant tunneling
- Author
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JiaWei Wang, JiZhou He, Hao Su, and QinYun Zhao
- Subjects
Physics ,Heat current ,Maximum power principle ,Computer Networks and Communications ,Energy conversion efficiency ,Thermodynamics ,Mechanics ,Coefficient of performance ,symbols.namesake ,Solar cell efficiency ,Control and Systems Engineering ,Mechanical efficiency ,symbols ,Carnot cycle ,Heat engine - Abstract
In this paper, the model of a three-terminal quantum dot heat engine consists of two quantum dots with a single energy level, a cavity and two electron reservoirs is established. According to Landauer formula the expressions for the heat current, the output power and the efficiency are derived analytically. The performance characteristic curves of the output power versus the efficiency are plotted by numerical calculation. Moreover, the optimal performance parameters are determined. Then we optimize the output power and the efficiency respectively, the influence of the width of energy level and the heat leak on performance of the three-terminal thermoelectric heat engine is discussed. Lastly, the variation of the corresponding efficiency at the maximum power output with the Carnot efficiency between two reservoirs is discussed and the corresponding efficiency is compared with Carnot efficiency and CA efficiency. It is shown that this three-terminal heat engine is irreversible due to the existence of the width of energy level and the heat leak. Thus the curve of the power output versus the efficiency is a loop-shaped one. And due to the heat leak, the characteristics of the efficiency and the width of energy level is a non-monotone curve. The efficiency at the maximum power will be greater than the CA efficiency when the heat leak and the width of energy level are not taken into account.
- Published
- 2016
3. Finite-power performance of quantum heat engines in linear response
- Author
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Jizhou He, Yong-li Ma, Qin Liu, and Jianhui Wang
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Physics ,Maximum power principle ,Entropy production ,Mechanics ,01 natural sciences ,Brayton cycle ,010305 fluids & plasmas ,symbols.namesake ,0103 physical sciences ,Heat transfer ,symbols ,Otto cycle ,010306 general physics ,Carnot cycle ,Adiabatic process ,Heat engine - Abstract
We investigate the finite-power performance of quantum heat engines working in the linear response regime where the temperature gradient is small. The engine cycles with working substances of ideal harmonic systems consist of two heat transfer and two adiabatic processes, such as the Carnot cycle, Otto cycle, and Brayton cycle. By analyzing the optimal protocol under maximum power we derive the explicitly analytic expression for the irreversible entropy production, which becomes the low dissipation form in the long duration limit. Assuming the engine to be endoreversible, we derive the universal expression for the efficiency at maximum power, which agrees well with that obtained from the phenomenological heat transfer laws holding in the classical thermodynamics. Through appropriate identification of the thermodynamic fluxes and forces that a linear relation connects, we find that the quantum engines under consideration are tightly coupled, and the universality of efficiency at maximum power is confirmed at the linear order in the temperature gradient.
- Published
- 2019
4. Optimal performance of three-terminal nanowire heat engine based on one-dimensional ballistic conductors
- Author
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Yunyun Yang, Jizhou He, Shuai Xu, and Wei Li
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Materials science ,Nanostructure ,Terminal (electronics) ,business.industry ,Nanowire ,Optoelectronics ,Condensed Matter Physics ,business ,Electrical conductor ,Mathematical Physics ,Atomic and Molecular Physics, and Optics ,Energy (signal processing) ,Heat engine - Published
- 2020
5. Efficiency and power of minimally nonlinear irreversible heat engines with broken time-reversal symmetry
- Author
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Min Zhang, Jianhui Wang, Qin Liu, Wei Li, and Jizhou He
- Subjects
Maximum power principle ,05.70.Ln ,General Physics and Astronomy ,FOS: Physical sciences ,lcsh:Astrophysics ,01 natural sciences ,Article ,010305 fluids & plasmas ,symbols.namesake ,lcsh:QB460-466 ,0103 physical sciences ,Limit (mathematics) ,lcsh:Science ,010306 general physics ,nonlinear irreversible ,Condensed Matter - Statistical Mechanics ,Heat engine ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,heat engine ,Mechanics ,lcsh:QC1-999 ,Symmetry (physics) ,Power (physics) ,Nonlinear system ,T-symmetry ,symbols ,broken time-reversal symmetry ,lcsh:Q ,Carnot cycle ,lcsh:Physics ,efficiency at maximum power - Abstract
We study the minimally nonlinear irreversible heat engines in which the time-reversal symmetry for the systems may be broken. The expressions for the power and the efficiency are derived, in which the effects of the nonlinear terms due to dissipations are included. We show that, as within the linear responses, the minimally nonlinear irreversible heat engines can enable attainment of Carnot efficiency at positive power. We also find that the Curzon-Ahlborn limit imposed on the efficiency at maximum power can be overcome if the time-reversal symmetry is broken.
- Published
- 2018
6. Universality of maximum-work efficiency of a cyclic heat engine based on a finite system of ultracold atoms
- Author
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Yingying Hu, Jizhou He, Jianhui Wang, and Zhuolin Ye
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Physics ,Multidisciplinary ,Work output ,Particle number ,Science ,Thermodynamics ,01 natural sciences ,Heat capacity ,Article ,010305 fluids & plasmas ,Universality (dynamical systems) ,symbols.namesake ,Ultracold atom ,0103 physical sciences ,symbols ,Medicine ,010306 general physics ,Carnot cycle ,Finite set ,Heat engine - Abstract
We study the performance of a cyclic heat engine which uses a small system with a finite number of ultracold atoms as its working substance and works between two heat reservoirs at constant temperatures T h and T c (
- Published
- 2017
7. Endoreversible quantum heat engines in the linear response regime
- Author
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Honghui Wang, Jianhui Wang, and Jizhou He
- Subjects
Physics ,Thermal reservoir ,Entropy production ,Thermodynamics ,Mechanics ,Thermal conduction ,01 natural sciences ,010305 fluids & plasmas ,Quantum master equation ,0103 physical sciences ,Heat transfer ,010306 general physics ,Adiabatic process ,Thermodynamic process ,Heat engine - Abstract
We analyze general models of quantum heat engines operating a cycle of two adiabatic and two isothermal processes. We use the quantum master equation for a system to describe heat transfer current during a thermodynamic process in contact with a heat reservoir, with no use of phenomenological thermal conduction. We apply the endoreversibility description to such engine models working in the linear response regime and derive expressions of the efficiency and the power. By analyzing the entropy production rate along a single cycle, we identify the thermodynamic flux and force that a linear relation connects. From maximizing the power output, we find that such heat engines satisfy the tight-coupling condition and the efficiency at maximum power agrees with the Curzon-Ahlborn efficiency known as the upper bound in the linear response regime.
- Published
- 2017
8. Performance analysis of a tunneling thermoelectric heat engine with nano-scaled quantum well
- Author
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Nian Liu, Teng Qiu, Jizhou He, and Xiaoguang Luo
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Materials science ,business.industry ,Biasing ,General Chemistry ,Electron ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Thermal radiation ,Thermoelectric effect ,Optoelectronics ,General Materials Science ,business ,Quantum tunnelling ,Quantum well ,Leakage (electronics) ,Heat engine - Abstract
A numerical model of a nano-scaled thermoelectric heat engine with InP/InAs/InP trilayer quantum well (QW) is investigated. The expressions of those performance parameters, such as current, power output, and efficiency are expressed. By numerical calculation, the resonant tunneling behavior of electrons in the QW is described, which seems like a very good energy selective electron mechanism for the heat engine. After considering the radiation heat leakage, for fixed layer thicknesses of the QW, the optimum working regions of the heat engine with respect to the chemical potentials and the bias voltage are obtained numerically under the economic criterion. From these results, the power output can be increased by narrowing down the layer thicknesses. In addition, owing to the radiant heat leakage, the efficiency initially increases in the working regions and then decreases when the layer thicknesses increase gradually, from which one can obtain a maximum efficiency by optimizing layer thicknesses of QW. These results calculated here may provide a guide for the optimum designs of tunneling thermoelectric devices.
- Published
- 2014
9. The impact of energy spectrum width in the energy selective electron low-temperature thermionic heat engine at maximum power
- Author
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Teng Qiu, Jizhou He, Nian Liu, Ruiwen Li, Cong Li, and Xiaoguang Luo
- Subjects
Physics ,Maximum power principle ,Computer simulation ,General Physics and Astronomy ,Thermionic emission ,Electron ,Atomic physics ,Constant (mathematics) ,Upper and lower bounds ,Energy (signal processing) ,Heat engine - Abstract
A model of thermionic heat engine with the energy selective electron mechanism is studied. Analytical expressions of the power output and efficiency of this device are derived at low temperature, where the chemical potentials of the reservoirs are assumed to be constant. After discussing the impact of the energy spectrum width of the energy selective electron mechanism, we find two bounds ( η ± ) of efficiency at maximum power exist naturally. When the energy spectrum width increases gradually from zero and then to the semi-infinite case with the infinite upper limit, the efficiency at maximum power decreases monotonously from the upper bound η + to the lower bound η − at a given temperature ratio of the cold and hot reservoirs. The two bound are given by numerical simulation and by an analytical expression respectively. These results may provide some guidance for the application of the practical energy selective electron heat engines.
- Published
- 2013
10. Thermal entangled quantum heat engine
- Author
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Xian He, Jie Zheng, and Jizhou He
- Subjects
Statistics and Probability ,Thermal equilibrium ,Physics ,Work (thermodynamics) ,Quantum mechanics ,Otto cycle ,Quantum entanglement ,Condensed Matter Physics ,Adiabatic process ,Classical XY model ,Quantum ,Heat engine - Abstract
Based on a two-qubit Heisenberg XY model, we construct a four-level entangled quantum heat engine (QHE). It is an interesting quantum Otto cycle where the exchange constant is fixed and only the magnetic field is varied during the adiabatic steps. The expressions for several thermodynamic quantities such as the heat transferred, the work and the efficiency are derived. Moreover, the influence of the entanglement on the thermodynamic quantities is investigated numerically. Several interesting features of the variation of the heat transferred, the work and the efficiency with the concurrences of the thermal entanglement of different thermal equilibrium states are obtained. Finally, we discussed the maximum efficiency of the QHE.
- Published
- 2012
11. Thermal entangled four-level quantum Otto heat engine
- Author
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JiZhou He and Xian He
- Subjects
Thermal equilibrium ,Physics ,Work (thermodynamics) ,Quantum mechanics ,Isotropy ,Thermal ,General Physics and Astronomy ,Quantum Physics ,Quantum entanglement ,Quantum ,Heat engine ,Magnetic field - Abstract
Based on a two-qubit isotropic Heisenberg XXX model with a constant external magnetic field, we construct a four-level entangled quantum heat engine (QHE). The expressions for several thermodynamic quantities such as the heat transferred, the work and efficiency are derived. Moreover, the influence of the entanglement on the thermodynamic quantities is investigated analytically and numerically. Several interesting features of the variation of the heat transferred, the work and the efficiency with the concurrences of the thermal entanglement of different thermal equilibrium states are obtained.
- Published
- 2012
12. Performance analysis and parametric optimum criteria of a quantum Otto heat engine with heat transfer effects
- Author
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Hao Wang, Jizhou He, and Sanqiu Liu
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Engineering ,Maximum power principle ,business.industry ,Isochoric process ,Energy Engineering and Power Technology ,Mechanical engineering ,Mechanics ,Industrial and Manufacturing Engineering ,law.invention ,Otto engine ,law ,Compression ratio ,Heat transfer ,Otto cycle ,business ,Heat engine ,Parametric statistics - Abstract
The influence of both the quantum degeneracy and the finite rate heat transfer between the working substance and the cylinder wall on the optimal performance of an Otto engine cycle is investigated. Expressions for several important parameters such as the power output and efficiency are derived. By using numerical solutions, the curves of the power output and efficiency varying with the compression ratio of two isochoric processes are presented. It is found that there are optimal values of the compression ratio at which the power output and efficiency attain their maximum. In particular, the optimal performance of the cycle in strong and weak gas degeneracy and the high temperature limit are discussed in detail. The distinctions and connections between the quantum Otto engine and the classical are revealed. Moreover, the maximum power output and efficiency and the corresponding relevant parameters are calculated, and consequently, the optimization criteria of some important parameters such as the power output, efficiency and compression ratio of the working substance are obtained.
- Published
- 2009
13. Local stability analysis of an irreversible Carnot heat engine
- Author
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Jizhou He, Wenjie Nie, and Xinfa Deng
- Subjects
Thermal efficiency ,Materials science ,General Engineering ,Thermodynamics ,Heat transfer coefficient ,Condensed Matter Physics ,Heat capacity rate ,symbols.namesake ,Heat flux ,Heat transfer ,symbols ,Carnot heat engine ,Carnot cycle ,Heat engine - Abstract
The local stability of an irreversible Carnot heat engine has been studied based on the linearization technique for dynamical systems and local stability analysis. At two steady-states of the maximum power output and the maximum efficiency the expressions of the relaxation time of an irreversible Carnot heat engine are derived. It is found that the relaxation time is a function of the heat-transfer coefficient α and β, heat capacity C, temperatures of the heat reservoirs TH and TL, the degree of internal irreversibility ϕ and the internal heat conductance k. The influence of heat resistance, internal irreversibility and heat leak on the relaxation time is discussed. Phase portraits for the trajectories are presented in some representative cases. The results obtained here are more general and useful for the realistic irreversible heat engine than endoreversible heat engine.
- Published
- 2008
14. Performance analysis of a thermosize micro/nano heat engine
- Author
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Jizhou He and Wenjie Nie
- Subjects
Physics ,Thermoelectric generator ,Thermodynamic cycle ,Thermoelectric effect ,Heat exchanger ,General Physics and Astronomy ,Isobaric process ,Thermodynamics ,Ideal gas ,Isothermal process ,Heat engine - Abstract
In a recent paper [A. Sisman, I. Muller, Phys. Lett. A 320 (2004) 360] the thermodynamic properties of ideal gases confined in a narrow box were examined theoretically. The so-called “thermosize effects” similar to thermoelectric effects, such as Seebeck-like thermosize effect, Peltier-like thermosize effect and Thomson-like thermosize effect, were analyzed. Like the thermoelectric generator, based on the thermosize effects we have established a model of micro/nano scaled ideal gas heat engine cycle which includes two isothermal and two isobaric processes. The expressions of power output and efficiency of this cycle in the two cases of reversible and irreversible heat exchange are derived and the optimal performance characteristics of the heat engine is discussed by some numerical example. The results obtained here will provide theoretical guidance for the design of micro/nano scaled device.
- Published
- 2008
15. Performance of a quantum heat engine cycle working with harmonic oscillator systems
- Author
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ZhiYuan Mao, JianHui Wang, and JiZhou He
- Subjects
Physics ,Work (thermodynamics) ,Classical mechanics ,Maximum power principle ,Entropy production ,Control theory ,Thermodynamic cycle ,Harmonic ,Harmonic oscillator ,First law of thermodynamics ,Heat engine - Abstract
A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law of thermodynamics for a harmonic system and the time evolution of the system are obtained. The general expressions for several important parameters, such as the work, efficiency, power output, and rate of entropy production are derived. By means of numerical analysis, the optimally operating regions and the optimal values of performance parameters of the cycle are determined under the condition of maximum power output. At last, some special cases, such as high temperature limit and frictionless case, are discussed in brief.
- Published
- 2007
16. Performance analysis of a spin quantum heat engine cycle with internal friction
- Author
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Yong Xin, Jianhui Wang, and Jizhou He
- Subjects
Physics ,Maximum power principle ,Field (physics) ,Entropy production ,Thermodynamics ,Mechanics ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Entropy (classical thermodynamics) ,Thermodynamic cycle ,Quantum master equation ,Adiabatic process ,Mathematical Physics ,Heat engine - Abstract
An irreversible cycle model of a quantum heat engine with internal friction is established, which is composed of two adiabatic and two isomagnetic field processes. The working substance of the cycle consists of an ensemble of many non-interacting spin-1/2 systems. Based on a quantum master equation and semi-group approach, the general performance characteristics of the heat engine are investigated. The general expressions for several important parameters, such as the efficiency, power output, and rate of the entropy production, are derived. The performance of the cycle is optimized with respect to the temperatures of the working substance. By numerical solutions, the maximum power output and the corresponding parameters are calculated. The optimal regions of efficiency, temperatures of the working substance, and cycle period are determined. Moreover, the performance of the heat engine in the frictionless case is obtained, which is different from that in the friction case. Finally, the results obtained are generalized to the performance optimization of the heat engine working with spin-J systems.
- Published
- 2007
17. Efficiency at maximum power of a quantum heat engine based on two coupled oscillators
- Author
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Jianhui Wang, Zhuolin Ye, Wei-Sheng Li, Yiming Lai, and Jizhou He
- Subjects
Physics ,Mesoscopic physics ,Hot Temperature ,Maximum power principle ,Isochoric process ,Thermodynamics ,Models, Theoretical ,symbols.namesake ,Harmonic ,symbols ,Quantum Theory ,Carnot cycle ,Adiabatic process ,Harmonic oscillator ,Heat engine - Abstract
We propose and theoretically investigate a system of two coupled harmonic oscillators as a heat engine. We show how these two coupled oscillators within undamped regime can be controlled to realize an Otto cycle that consists of two adiabatic and two isochoric processes. During the two isochores the harmonic system is embedded in two heat reservoirs at constant temperatures T(h) and T(c)(
- Published
- 2015
18. Optimal Performance Analysis of Feynman’s Microscopic Heat Engine
- Author
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Yuling Xiao, Haitao Cheng, and Jizhou He
- Subjects
Physics ,symbols.namesake ,Classical mechanics ,symbols ,Feynman diagram ,Heat leak ,Statistical physics ,Stochastic motion ,Heat engine - Published
- 2015
19. Efficiency at maximum power for an Otto engine with ideal feedback
- Author
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Jizhou He, Zhaoqi Wu, Jianhui Wang, and Honghui Wang
- Subjects
Thermal efficiency ,Ideal (set theory) ,Maximum power principle ,General Physics and Astronomy ,Thermodynamics ,01 natural sciences ,Expression (mathematics) ,010305 fluids & plasmas ,law.invention ,symbols.namesake ,Otto engine ,law ,Control theory ,0103 physical sciences ,symbols ,Otto cycle ,010306 general physics ,Carnot cycle ,Heat engine - Abstract
We propose an Otto heat engine that undergoes processes involving a special class of feedback and analyze theoretically its response. We use stochastic thermodynamics to determine the performance characteristics of the heat engine and indicate the possibility that its maximum efficiency can surpass the Carnot value. The analytical expression for efficiency at maximum power, including the effects resulting from feedback, reduces to that previously derived based on an engine without feedback.
- Published
- 2016
20. A theoretical study on the performances of thermoelectric heat engine and refrigerator with two-dimensional electron reservoirs
- Author
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Jun Wang, Teng Qiu, Xiaoguang Luo, Kailin Long, Jizhou He, and Nian Liu
- Subjects
Condensed Matter - Materials Science ,Materials science ,Maximum power principle ,Statistical Mechanics (cond-mat.stat-mech) ,Refrigerator car ,General Physics and Astronomy ,Resonance ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Electron ,Coefficient of performance ,Computational physics ,Thermoelectric effect ,Energy transformation ,Condensed Matter - Statistical Mechanics ,Heat engine - Abstract
Theoretical thermoelectric nanophysics models of low-dimensional electronic heat engine and refrigerator devices, comprising two-dimensional hot and cold reservoirs and an interconnecting filtered electron transport mechanism have been established. The models were used to numerically simulate and evaluate the thermoelectric performance and energy conversion efficiencies of these low-dimensional devices, based on three different types of electron transport momentum-dependent filters, referred to herein as: kx, ky and kr filters. Assuming the Fermi-Dirac distribution of electrons, expressions for key thermoelectric performance parameters were derived for the resonant transport processes, in which the transmission of electrons has been approximated as a Lorentzian resonance function. Optimizations were carried out and the corresponding optimized design parameters have been determined, including but not limited to the universal theoretical upper bound of the efficiency at maximum power for heat engines, and the maximum coefficient of performance for refrigerators. From the results, it was determined that kr filter delivers the best thermoelectric performance, followed by the kx filter, and then the ky filter. For refrigerators with any one of three filters, an optimum range for the full width at half maximum of the transport resonance was found to be, no layout, 20 pages, 8 figures, 2 tables
- Published
- 2013
21. Efficiency at maximum power of a heat engine working with a two-level atomic system
- Author
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Yong-li Ma, Rui Wang, Jianhui Wang, and Jizhou He
- Subjects
Physics ,Mesoscopic physics ,Thermal efficiency ,Stirling engine ,Maximum power principle ,Isochoric process ,Thermodynamics ,law.invention ,symbols.namesake ,law ,symbols ,Adiabatic process ,Carnot cycle ,Heat engine - Abstract
We consider the finite-time operation of a quantum heat engine whose working substance is composed of a two-level atomic system. The engine cycle, consisting of two quantum adiabatic and two quantum isochoric (constant-frequency) processes and working between two heat reservoirs at temperatures T(h) and T(c)(
- Published
- 2013
22. Performance of a multilevel quantum heat engine of an ideal N-particle Fermi system
- Author
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Jianhui Wang, Rui Wang, Yong-li Ma, and Jizhou He
- Subjects
Physics ,symbols.namesake ,Particle number ,Maximum power principle ,symbols ,Thermodynamics ,Adiabatic process ,Fermi gas ,Carnot cycle ,Constant (mathematics) ,Quantum ,Heat engine - Abstract
We generalize the quantum heat engine (QHE) model which was first proposed by Bender et al. [J. Phys. A 33, 4427 (2000)] to the case in which an ideal Fermi gas with an arbitrary number N of particles in a box trap is used as the working substance. Besides two quantum adiabatic processes, the engine model contains two isoenergetic processes, during which the particles are coupled to energy baths at a high constant energy E(h) and a low constant energy E(c), respectively. Directly employing the finite-time thermodynamics, we find that the power output is enhanced by increasing particle number N (or decreasing minimum trap size L(A)) for given L(A) (or N), without reduction in the efficiency. By use of global optimization, the efficiency at possible maximum power output (EPMP) is found to be universal and independent of any parameter contained in the engine model. For an engine model with any particle-number N, the efficiency at maximum power output (EMP) can be determined under the condition that it should be closest to the EPMP. Moreover, we extend the heat engine to a more general multilevel engine model with an arbitrary 1D power-law potential. Comparison between our engine model and the Carnot cycle shows that, under the same conditions, the efficiency η = 1 - E(c)/E(h) of the engine cycle is bounded from above the Carnot value η(c) =1 - T(c)/T(h).
- Published
- 2012
23. Efficiency at maximum power output of quantum heat engines under finite-time operation
- Author
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Jianhui Wang, Jizhou He, and Zhaoqi Wu
- Subjects
Hot Temperature ,Statistical Mechanics (cond-mat.stat-mech) ,Maximum power principle ,FOS: Physical sciences ,Thermodynamics ,Models, Theoretical ,Dissipation ,symbols.namesake ,Energy Transfer ,symbols ,Quantum Theory ,Computer Simulation ,Finite time ,Carnot heat engine ,Carnot cycle ,Quantum statistical mechanics ,Quantum ,Condensed Matter - Statistical Mechanics ,Mathematics ,Heat engine - Abstract
We study the efficiency at maximum power, $\eta_m$, of irreversible quantum Carnot engines (QCEs) that perform finite-time cycles between a hot and a cold reservoir at temperatures $T_h$ and $T_c$, respectively. For QCEs in the reversible limit (long cycle period, zero dissipation), $\eta_m$ becomes identical to Carnot efficiency $\eta_{_C}=1-\frac{T_c}{T_h}$. For QCE cycles in which nonadiabatic dissipation and time spent on two adiabats are included, the efficiency $\eta_m$ at maximum power output is bounded from above by $\frac{\eta_{_C}}{2-\eta_{_C}}$ and from below by $\frac{\eta_{_C}}2$. In the case of symmetric dissipation, the Curzon-Ahlborn efficiency $\eta_{_{CA}}=1-\sqrt{\frac{T_c}{T_h}}$ is recovered under the condition that the time allocation between the adiabats and the contact time with the reservoir satisfy a certain relation., Comment: to be published in Phys. Rev. E (2012)
- Published
- 2011
24. Quantum Otto engine of a two-level atom with single-mode fields
- Author
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Jianhui Wang, Jizhou He, and Zhaoqi Wu
- Subjects
Physics ,Maximum power principle ,Isochoric process ,Atom (order theory) ,law.invention ,Otto engine ,Energy Transfer ,Models, Chemical ,law ,Quantum mechanics ,Exponent ,Quantum Theory ,Thermodynamics ,Computer Simulation ,Atomic physics ,Adiabatic process ,Quantum ,Heat engine - Abstract
We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent $\ensuremath{\theta}$ but is independent of the energy spectrum index $\ensuremath{\sigma}$.
- Published
- 2011
25. Ecological performance optimization analysis of a new irreversible quantum harmonic heat engine
- Author
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Jizhou He, Xian He, and Yuling Xiao
- Subjects
Classical mechanics ,Quantum master equation ,Numerical analysis ,Harmonic ,Applied mathematics ,Adiabatic process ,Quantum ,Isothermal process ,Harmonic oscillator ,Mathematics ,Heat engine - Abstract
A new cycle model of an irreversible quantum harmonic heat engine is established in this paper, which is composed of two isothermal processes, an adiabatic process and a constant frequency process. Based on the quantum master equation and semi-group approach, the general optimal performance characteristics of the cycle are investigated. Expressions for several important performance parameters such as the efficiency, the power output and the ecological function are derived analytically in high temperature limit. By numerical calculation, a set of performance characteristic curves is plotted, such as the optimal curves between the power output and efficiency, the ecological function and efficiency. A comparison of the corresponding efficiencies at the maximum ecological function and power output is also presented.
- Published
- 2011
26. Performance analysis of a two-state quantum heat engine working with a single-mode radiation field in a cavity
- Author
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Xian He, Jianhui Wang, and Jizhou He
- Subjects
Physics ,symbols.namesake ,Quantum dynamics ,Single-mode optical fiber ,symbols ,Thermodynamics ,Expectation value ,Adiabatic process ,Hamiltonian (quantum mechanics) ,Quantum ,Isothermal process ,Heat engine - Abstract
We present a performance analysis of a two-state heat engine model working with a single-mode radiation field in a cavity. The heat engine cycle consists of two adiabatic and two isoenergetic processes. Assuming the wall of the potential moves at a very slow speed, we determine the optimization region and the positive work condition of the heat engine model. Furthermore, we generalize the results to the performance optimization for a two-state heat engine with a one-dimensional power-law potential. Based on the generalized model with an arbitrary one-dimensional potential, we obtain the expression of efficiency as $\ensuremath{\eta}=1\ensuremath{-}\frac{{E}_{C}}{{E}_{H}}$, with ${E}_{H}$ (${E}_{C}$) denoting the expectation value of the system Hamiltonian along the isoenergetic process at high (low) energy. This expression is an analog of the classical thermodynamical result of Carnot, ${\ensuremath{\eta}}_{c}=1\ensuremath{-}\frac{{T}_{C}}{{T}_{H}}$, with ${T}_{H}$ (${T}_{C}$) being the temperature along the isothermal process at high (low) temperature. We prove that under the same conditions, the efficiency $\ensuremath{\eta}=1\ensuremath{-}\frac{{E}_{C}}{{E}_{H}}$ is bounded from above the Carnot efficiency, ${\ensuremath{\eta}}_{c}=1\ensuremath{-}\frac{{T}_{C}}{{T}_{H}}$, and even quantum dynamics is reversible.
- Published
- 2011
27. Power, Efficiency and Ecological Optimization for an Irreversible Braysson Heat Engine
- Author
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Xian He, Jizhou He, and Bei Yang
- Subjects
Thermal efficiency ,Materials science ,NTU method ,Ecology ,Thermodynamic cycle ,Heat transfer ,Heat sink ,Coefficient of performance ,Heat engine ,Heat capacity rate - Abstract
An irreversible Braysson heat engine cycle model, in which the heat transfer obeys a linear heat transfer law between the working fluid and the external heat reservoirs, with heat resistance, heat leak and internal irreversibility is established in this paper. The analytical expressions of power output, efficiency and ecological objective function are derived. These performance parameters are maximized with respect to the cycle temperatures along with the isobaric temperature ratio. The performance characteristic curves are obtained by numerical calculation. The optimal operating regions of the important parameters are determined.
- Published
- 2011
28. Effect of Multi-Irreversibilities on the Performance Characteristics of an Irreversible Air-Standard Diesel Heat Engine
- Author
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Junbin Li and Jizhou He
- Subjects
Optimal design ,Materials science ,Mechanical engineering ,Diesel cycle ,Mechanics ,complex mixtures ,Friction loss ,Cylinder (engine) ,law.invention ,Diesel fuel ,law ,Heat transfer ,Working fluid ,Heat engine - Abstract
An irreversible model of the air-standard Diesel heat engine cycle is established, in which the primary irreversibilities, such as the heat leak loss through the cylinder wall, friction loss, internal irreversibility and temperature-variable heat capacities, are considered. The analytic expressions of the power output and efficiency are derived. The relations between the power output and the ratio of the highest to the lowest pressure of the working fluid, between the efficiency and the ratio of the highest to the lowest pressure of the working fluid, as well as the optimal relation between the power output and the efficiency of the Diesel cycle are shown by numerical example. Moreover, the influence of these primary irreversible factors on the performance parameters of the Diesel heat engine is discussed. The results obtained here may provide some significant guidelines for the optimal design and operation of the practical Diesel heat engines.
- Published
- 2010
29. Quantum-mechanical engines working with an ideal gas with a finite number of particles confined in a power-law trap
- Author
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Jianhui Wang, Jizhou He, and Yong-li Ma
- Subjects
Physics ,symbols.namesake ,Quantum mechanics ,Exponent ,symbols ,General Physics and Astronomy ,Adiabatic process ,Carnot cycle ,Quantum ,Brayton cycle ,Ideal gas ,Heat engine ,Thermodynamic process - Abstract
Based on quantum thermodynamic processes, we make a quantum-mechanical (QM) extension of the typical heat engine cycles, such as the Carnot, Brayton, Otto, Diesel cycles, etc., with no introduction of the concept of temperature. When these QM engine cycles are implemented by an ideal gas confined in an arbitrary power-law trap, a relation between the quantum adiabatic exponent and trap exponent is found. The differences and similarities between the efficiency of a given QM engine cycle and its classical counterpart are revealed and discussed.
- Published
- 2015
30. A NANOTHERMOELECTRIC HEAT ENGINE WORKING WITH TWO-LEVEL QUANTUM SYSTEM
- Author
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Yuling Xiao, Yan-Chao Zhang, Hong-Ni Liang, and Jizhou He
- Subjects
Physics ,Master equation ,Quantum system ,Thermodynamics ,Statistical and Nonlinear Physics ,Power output ,Mechanics ,Condensed Matter Physics ,Energy (signal processing) ,Heat engine - Abstract
In this paper, we establish a nanothermoelectric engine consisting of two discrete energy levels embedded between two reservoirs at different temperatures and chemical potentials. Based on master equation, the expressions for the power output and efficiency of the nanothermoelectric engine are derived. The characteristic curves between the power output and the efficiency are plotted. Moreover, the optimal performance parameters are obtained by the numerical calculation. The influence of the strength of variations in electron–electron interactions on the optimal performance parameters is analyzed in detail.
- Published
- 2014
31. Optimization on a three-level heat engine working with two noninteracting fermions in a one-dimensional box trap
- Author
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Jizhou He and Jianhui Wang
- Subjects
Physics ,Thermal efficiency ,General Physics and Astronomy ,Thermodynamics ,Mechanics ,Fermion ,symbols.namesake ,Thermodynamic cycle ,symbols ,Adiabatic process ,Carnot cycle ,Quantum statistical mechanics ,Constant (mathematics) ,Heat engine - Abstract
We setup a three-level heat engine model that works with two noninteracting fermions in a one-dimensional box trap. Besides two quantum adiabatic processes, the quantum heat engine cycle consists of two isoenergetic processes, along which the particles are coupled to energy baths at a high constant energy EH and a low constant energy EC, respectively. Based on the assumption that the potential wall moves at a very slow speed and there exists a heat leakage between two energy baths, we derive the expressions of the power output and the efficiency, and then obtain the optimization region for the heat engine cycle. Finally, we present a brief performance analysis of a Carnot engine between a hot and a cold bath at temperatures TH and TC, respectively. We demonstrate that under the same conditions, the efficiency η=1-(EC/EH) of the engine cycle is bounded from above the Carnot efficiency ηc=1-(TC/TH).
- Published
- 2012
32. Performance analysis and parametric optimum criteria of an irreversible Bose–Otto engine
- Author
-
Sanqiu Liu, Hao Wang, and Jizhou He
- Subjects
Chemistry ,Isochoric process ,General Physics and Astronomy ,Thermodynamics ,Mechanics ,Thermodynamic system ,law.invention ,Otto engine ,law ,Thermodynamic cycle ,Compression ratio ,Otto cycle ,Heat engine ,Thermodynamic process - Abstract
An irreversible cycle model of a Bose–Otto engine is established, in which finite time thermodynamic processes and the irreversibility result from the nonisentropic compression and expansion processes are taken into account. Based on the model, expressions for the power output and efficiency of the Bose–Otto engine are derived. On the basis of the thermodynamic properties of ideal Bose gas, the effects of the irreversibility and the compression ratio of the two isochoric processes on the performance of the Bose–Otto engine are revealed and some important performance parameters are optimized. Furthermore, some optimal operating regions including those for the power output, efficiency, and the temperatures of the cyclic working substance at two important state points are determined and evaluated. Finally, several special cases are discussed in detail.
- Published
- 2009
33. Quantum boundary effect on the work output of a micro-/nanoscaled Carnot cycle
- Author
-
Jizhou He and Wenjie Nie
- Subjects
Physics ,symbols.namesake ,Work output ,Surface-area-to-volume ratio ,Isentropic process ,Isochoric process ,symbols ,General Physics and Astronomy ,Thermodynamics ,Boundary (topology) ,Function (mathematics) ,Carnot cycle ,Heat engine - Abstract
In this paper, the work output (W) and efficiency (η) of a Carnot cycle in micro-/nanoscale are calculated, in which the quantum boundary effect of gas particles as a working substance of cycle is considered. It is found that under the quantum boundary effect conditions, the work output of cycle depends sensitively on the surface area of the system (boundary of cycle) and cannot be predicted by the classical approximate result (WC), while the efficiency of cycle is independent of the surface area of the system and equals the Carnot efficiency (ηC). Further, the difference of work output of the micro-/nanoscaled Carnot cycle to that of the classical one, ΔW=W−WC, is introduced and can be expressed as the function of the temperature ratio τ=TL/TH of the two heat reservoirs, the volume ratio rV=V3/V1, and the surface area ratio rA=A3/A1 of the two isochoric processes. Variations of difference of work output, ΔW, with the temperature ratio τ and volume ratio rV for the different surface ratio rA are examined,...
- Published
- 2009
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