Performance characteristics and optimal analysis of a nonlinear diode refrigerator

This paper establishes a model of a nonlinear diode refrigerator consisting of two diodes switched in the opposite directions and located in two heat reservoirs with different temperatures.Based on the theory of thermal fluctuations,the expressions of the heat flux absorbed from the heat reservoirs are derived.After the heat leak between the two reservoirs is considered,the cooling rate and the coefficient of performance are obtained analytically.The influence of the heat leak and the temperature ratio on the performance characteristics of the refrigerator is analysed in detail.     

考虑透射概率的能量选择性电子热泵

研究了具有不同温度和不同化学势的两个热库中的电子通过一个能量透射谱进行传输的问题,得到电子通过能量透射谱传输所产生的热流.进一步考虑了两个热库之间的辐射热漏流,数值计算出电子热泵的性能参数,绘出了热泵的性能特征曲线.分析了热漏、共振中心能级位置和能级宽度等参数对热泵工作性能的影响.当共振能级宽度无限小时,热泵系数可以达到Carnot值.     

考虑透射概率的能量选择性电子热泵

研究了具有不同温度和不同化学势的两个热库中的电子通过一个能量透射谱进行传输的问题,得到电子通过能量透射谱传输所产生的热流.进一步考虑了两个热库之间的辐射热漏流,数值计算出电子热泵的性能参数,绘出了热泵的性能特征曲线.分析了热漏、共振中心能级位置和能级宽度等参数对热泵工作性能的影响.当共振能级宽度无限小时,热泵系数可以达到Carnot值. 关键词： 透射谱 态密度 辐射热漏 电子热泵     

周期激励下Chen系统的簇发现象分析

对于周期激励下的Chen系统,当激励项的频率和原系统的固有频率存在量级上的差异时,系统表现出两个时间尺度下的动力学行为.首先,将激励项作为一个变量对系统进行了分岔分析.然后应用快慢分析法探讨了在不同的参数条件下,激励项周期变化时产生的对称式折叠簇发、对称式亚临界Hopf簇发、对称式Hopf-同宿簇发现象及其产生机制.同时还讨论了激励幅值和频率对系统不同簇发的影响.     

双势垒InAs/InP纳米线异质结热电子制冷机

研究了具有不同温度和不同化学势的两个热库中电子通过一个双势垒InAs/InP纳米线异质结进行的传输.利用传输矩阵法得到了电子的传输概率,进而计算得到电子传输所产生的热流.通过数值计算给出了热电子制冷机的性能特征曲线.进一步分析了势垒宽度和势阱宽度对制冷机工作性能的影响.研究发现,当势阱宽度一定时,随着势垒宽度变大共振中心能级的位置变大,共振能级宽度变小,同一偏压对应的制冷率变小,相对制冷系数变大.当势垒宽度一定时,随着势阱宽度变大,同一偏压对应的相对制冷系数变小.当势垒和势阱宽度同时变化时,得到的曲线与势垒宽度一定势阱宽度变化时得到的曲线基本相似.这表明制冷率和相对制冷系数主要受势阱宽度变化的影响.     

Theory of inert gas-condensing vapor thermoacoustics: transport equations

The preceding paper [J. Acoust. Soc. Am. 112, 1414-1422 (2002)] derives the propagation equation for sound in an inert gas-condensing vapor mixture in a wet-walled pore with an imposed temperature gradient. In this paper the mass, enthalpy, heat, and work transport equations necessary to describe the steady-state operation of a wet-walled thermoacoustic refrigerator are derived and presented in a form suitable for numerical evaluation. The requirement that the refrigerator operate in the steady state imposes zero mass flux for each species through a cross section. This in turn leads to the evaluation of the mass flux of vapor in the system. The vapor transport and heat transport are shown to work in parallel to produce additional cooling power in the wet refrigerator. An idealized calculation of the coefficient of performance (COP) of a wet-walled thermoacoustic refrigerator is derived and evaluated for a refrigeration system. The results of this calculation indicate that the wet-walled system can improve the performance of thermoacoustic refrigerators. Several experimental and practical questions and problems that must be addressed before a practical device can be designed and tested are described.     

实际回热式布雷顿制冷机的性能优化

用有限时间热力学方法分析实际回热式布雷顿制冷机的性能特性,以制冷率和制冷系数为优化目标,优化了高低、温侧换热器和回热器的热导率分配以及工质和热源间的热容率匹配,并采用数值计算分析了各参数值对最优性能的影响特点.所得结果对工程制冷系统设计有一定的指导意义。     

纳米线异质结构对电子制冷机性能的影响

研究了在具有不同温度和不同化学势的两个热库中电子通过一个三势垒纳米线异质结构进行传输的问题,利用传输矩阵法得到了电子的传输概率,进而算出了电子传输所产生的热流.通过数值计算绘出了电子制冷机的性能特征曲线.分析了偏压和异质结结构对制冷机性能的影响,重点讨论了中间势垒高度和宽度对电子传输概率、制冷率和制冷系数的影响. 关键词： 电子制冷机 三势垒纳米线 性能参数 传输矩阵法     

Flux-dependent anti-crossing of resonances in parallel non-coupled double quantum dots

We present novel resonant phenomena through parallel non-coupled double quantum dots (QDs) embedded in each arm of an Aharonov-Bohm (AB) ring with magnetic flux passing through its center. The electron transmission through this AB ring with each QD formed by two short-range potential barriers is calculated using a scattering matrix at each junction and a transfer matrix in each arm. We show that as the magnetic flux modulates, a distortion of the grid-like square transmission occurs and an anti-crossing of the resonances appears. Hence, the modulation of magnetic flux in this system can have an equivalent effect to the control of inter-dot coupling between the two QDs.     

Reprint of : Three-terminal heat engine and refrigerator based on superlattices

We propose a three-terminal heat engine based on semiconductor superlattices for energy harvesting. The periodicity of the superlattice structure creates an energy miniband, giving an energy window for allowed electron transport. We find that this device delivers a large power, nearly twice than the heat engine based on quantum wells, with a small reduction of efficiency. This engine also works as a refrigerator in a different regime of the system's parameters. The thermoelectric performance of the refrigerator is analyzed, including the cooling power and coefficient of performance in the optimized condition. We also calculate phonon heat current through the system and explore the reduction of phonon heat current compared to the bulk material. The direct phonon heat current is negligible at low temperatures, but dominates over the electronic at room temperature and we discuss ways to reduce it.     

Spectrum of the H− Ion in the s-Wave Model

 The H⁻ ion in the s-wave model has one bound state and a Rydberg series of resonances, one associated with each inelastic threshold of the electron hydrogen system. We calculate the energy of the bound state and the energies of the resonances as well as their total widths up to N = 9 and partial widths up to N = 7. Received July 5, 1999; revised February 18, 2000; accepted for publication February 22, 2000     

Performance optimization analysis of a thermoelectric refrigerator with two resonances

Based on electron transport theory,the performance of k x and k r filtered thermoelectric refrigerators with two resonances are studied in this paper.The performance characteristic curves between the cooling rate and the coefficient of performance are plotted by numerical calculation.It is shown that the maximum cooling rate of the thermoelectric refrigerator with two resonances increases but the maximum coefficient of performance decreases compared with those with one resonance.No matter which resonance mechanism is used(k x or k r filtered),the cooling rate and the performance coefficient of the k r filtered refrigerator are much better than those of the k x filtered one.     

Heat transistor: demonstration of gate-controlled electronic refrigeration

We present experiments on a superconductor-normal-metal electron refrigerator in a regime where single-electron charging effects are significant. The system functions as a heat transistor; i.e., the heat flux out from the normal-metal island can be controlled with a gate voltage. A theoretical model developed within the framework of single-electron tunneling provides a full quantitative agreement with the experiment. This work serves as the first experimental observation of Coulombic control of heat transfer and, in particular, of refrigeration in a mesoscopic system.     

Crossings and Anticrossings of Unbound States

We investigate the characteristic crossings and anticrossings of energies and widths of a doublet of resonances, observed in the vicinity of, and at a degeneracy of unbound states, when the control parameters of the system are varied. This characteristic behavior is explained in terms of the local, topological structure of the surfaces that represent the complex energy eigenvalues in parameter space in the vicinity of a degeneracy point. In the simple but illustrative case of the scattering of a beam of particles by a double barrier potential well with two regions of trapping, we solved numerically the implicit, transcendental equation that defines the eigenwave numbers of a degenerate isolated doublet of resonances as functions of the real, control parameters of the system. We found that, at a degeneracy of unbound states, the surface representing the resonance eigenwave numbers as functions of the control parameters has an algebraic branch point of rank one. Unfolding the degeneracy point, crossings and anticrossings of energies and widths are obtained as projections of sections of the eigenwave number surfaces.     

半导体冰箱冷热端散热条件实验研究

半导体制冷器件是一种高热流密度元件,在红外测量、低温超导、生物医学、空间技术等领域有重要的应用,还可开发成专用制冷装置,适用于野外施工、勘探,考古以及郊游等户外活动食品饮料的保鲜,也可用于食品、饮料及医用疫苗等的冷藏。在给定工况下,通过改善半导体器件的冷热端散热条件,可使系统制冷量和制冷性能系数大幅提高。本文设计了实验装置,特别设计了8种实验工况对采用强迫对流换热和热端采用热管换热器散热的实际半导体制冷装置进行了实验分析,提出了改善半导体制冷元件散热条件的具体措施。     

两级烟气废热溴化锂制冷机热能利用经济性分析

废热溴化锂制冷机可以直接利用烟气废热或化学反应热来驱动进行制冷,因此废热回收的综合利用率比较高。论文对烟气废热驱动废热溴化锂制冷机的热能利用的经济性进行了分析,在烟气废热驱动溴化锂制冷机中,溴化锂制冷机的COP仅仅反映的是溴化锂制冷机本身的性能,不能作为衡量废热溴化锂制冷机废热制冷的效率高低和性能好坏的标准,因此本文采用废热利用率和废热制冷率对烟气废热溴化锂制冷机的废热制冷性能指标,废热制冷率与炯效率分析结果相一致,通过比较发现,二级烟气双效废热驱动废热溴化锂制冷机的废热制冷率最高,炯效率也最高。     

非线性二极管系统构成的不可逆热机性能特征分析

研究了一个非线性二极管系统构成的不可逆热机的性能,它是由分别处于两个温度不同的热库中,完全相同的两个非线性二极管反向连接后并联上一个电容器组成的.运用非线性系统涨落理论计算出从两个热库中吸收的热流,考虑热漏损失后得出热机的功率和效率.通过数值模拟可以绘出热机的性能特征曲线以及优化性能参数随两热库温度比等主要参量的特征曲线.分析了二极管的非线性强度、热漏损失和温度比对热机性能特性的影响.最后,讨论了理想二极管热机的性能特征.     

Muonic atoms in the neighbourhood of lead

In a previous paper the electroexcitation of various giant multipole resonances in heavy nuclei has been discussed in Born approximation. This has given only the qualitative features of the cross section, since the electron wave functions in heavy nuclei are considerably distorted by the nuclear charge. Therefore we derive in this paper the corresponding cross sections using a phase shift analysis for the electron wave functions. Moreover, the coupling between giant resonances and surface oscillations has been taken into account. This leads to transitions not only to the several giant resonances itself but also to their “satellites” (i.e. giant resonance plus surface oscillations). Since the giant resonances have rather large widths, the calculated differential cross sections have been folded using a Lorentz shape and plotted against excitation energy. It is shown that the quadrupole giant resonance levels should be observed very clearly at scattering angles of the electron of about 40° (primary energy of the electrons about 200 MeV). It seems, however, unlikely to observe the monopole giant resonance as a distinct peak of the electron cross section because of the relatively large damping to be expected.     

热电制冷机性能分析与实验验证

1引言用有限时间热力学1‘－‘］分析热电制冷单元的最优性能已取得了一些成果［3－‘l。实际的热电制冷机往往由很多个制冷单元组成,是多热电堆制冷机。本文分析由任意个热电单元组成的制冷机性能,导出考虑传热不可逆性、焦耳效应、内部导热效应时的制冷率、制冷系数与...     

Experimental investigation of a thermoacoustic-Stirling refrigerator driven by a thermoacoustic-Stirling heat engine

In this paper, a thermally-driven thermoacoustic refrigerator system without any moving part is reported. This refrigeration system consists of a thermoacoustic-Stirling heat engine and a thermoacoustic-Stirling refrigerator; that is, the former is the driving source for the latter. Both the subsystems are designed to operate on traveling-wave mode. In the experiment, it was found that the DC-flows had significant negative effect on the heat engine and the refrigerator. To suppress these DC-flows, two flexible membranes were inserted into the two subsystems and worked very well. Then extensive experiments were made to test the influence of different parameters on refrigeration performance of the whole system. The system has so far achieved a no-load temperature of -65 degrees C, a cooling capacity of about 270 W at -20 degrees C and 405 W at 0 degrees C; in fact, the result showed a good prospect of the refrigeration system in room-temperature cooling such as food refrigeration and air-conditioning.