影响热电制冷性能的关键因素及其分析

在忽略汤姆逊效应的情形下,推导出热电制冷臂的传热微分方程,利用数值模拟的方法,分析了在不同工作电流下各种热电效应的影响,及工作电流和冷、热端换热系数3种因素对热电制冷性能的综合影响。分析了3种因素对热电制冷性能的影响程度与顺序,发现电流是最关键的影响因素,且需要较低制冷温度时可提高冷端换热系数,需要较大制冷量或制冷系数时可适当提高热端换热系数,但冷、热端换热系数对制冷性能的影响存在一个最优值。提出了热电制冷器件的设计和应用的优化工况及方案,在提高制冷性能的同时节约了成本。     

太阳能半导体空调制冷装置模块化实验研究

建立了以水为热交换媒介的太阳能热电模块制冷实验系统.系统配置了双位能量存储装置,用以储存昼夜温差能和太阳光电转换电能,以备无日照或日照不足时系统能够连续工作.热电制冷装置模块化,用以适应制冷功率变化较大的空间制冷,并在制冷启动与温度维持不同阶段实现较大功率的切入或撤出.制冷模块以半导体热电元件为核心,冷热端均以导热性能良好的紫铜作为热交换材料,以热容量较大的水作为冷却液和散热循环液.热交换装置采取集合散热冷却分流的集散一体化热交换系统.对制冷模块制冷性能进行了实验分析,并对制冷效果进行了模拟实验,实验结果基本达到了设计的预期.     

热电制冷模块热物性参数理论获取方法及精度分析

获取精确的热电模块的热物性参数值是热电制冷系统性能分析的关键。制冷量是衡量热电制冷性能的参数,根据厂商数据单以及半导体材料与温度相关的热物性经验公式,绘制了采用常物性参数法、变物性参数法分析制冷量的性能曲线图,并提出通过热电臂内热平衡的微分表达式获得不同工况下制冷量的准确值及标准性能曲线图;通过数值对比分析发现,常物性参数法在计算热电制冷量时有最大约6 W的绝对误差,但可以通过改善常物性参数获取精度减小计算误差;而变物性参数法最大绝对误差仅为1.5 W,该热物性参数获取方法精度较高,适用于分析热电制冷性能。     

热电制冷器制冷工作电流特性分析

随着高性能制冷CCD成像系统已经成为航天成像式探测的一个重要发展方向,热电制冷作为一种有效的电子设备冷却方法广泛用于重要部件的主动热控.为了实现热电制冷器工作电流的合理选择,在分析热电制冷机理的基础上,首先介绍了热电模块的3种工作模式(制冷、加热和热电发电),同时研究了热电偶内温度分布的一般形式,最后,在第一类边界条件...     

基于热电制冷的大功率LED散热性能分析

提出了一种新型的基于热电制冷的大功率LED热管理方法。这种大功率LED阵列模块采用板上封装技术制造。为了解决散热问题,采用了热电制冷器将LED芯片产生的热量转移到周围的环境中。利用热电偶测量了大功率LED阵列模块在不同工作条件下的温度分布,LED的光学性能则通过光强分布测试仪来测试。结果表明,这种采用热电制冷的大功率LED阵列封装模块能够显著降低器件的工作温度,与不采用热电制冷器相比,基板温度能够降低36％以上,光学性能测量表明LED阵列模块的发光效率达到30．18lm／W。     

无量纲优值对热电制冷系统性能影响分析

建立了无量纲稳态系统热力学模型。并用该模型分析了优值系数对系统性能的影响,优值系数是热电制冷器性能的内在制约,散热和温度条件则是热电制冷性能的外在制约,无量纲优值体现了二者对系统的影响。热电制冷系统的特殊优势再度受到人们关注,但在热电材料优值系数受到限制的现实条件下,热电制冷系统在能效上是难以与压缩式制冷空调系统比较的。     

电子器件热电制冷温度条件的优化

基于热电制冷热力学循环分析了热电制冷器正常工作的温度条件,以及两种极限工况性能受工作温度条件的制约关系。优值系数是热电制冷器性能的内在制约,散热和温度条件则是热电制冷性能的外在制约,热电制冷元件工作的温度特性与电子元件工作的理想温度条件是非常适应的。基于热电制冷的主动冷却技术对高热流密度电子集成部件的封装散热具有重大意义。     

CCD芯片热电制冷系统的非稳态性能分析

随着电子设备不断向小型化、集成化发展,热电制冷技术作为一种有效的主动冷却方法被广泛用于重要部件的温度控制。为了获得最佳的制冷效果,文中针对散热受限条件下的CCD芯片热电制冷系统非稳态过程,建立了一个数值分析模型。分析结果表明:在散热受限时,热电制冷系统的传热过程长时间处于非稳态过程;在不超过最大制冷电流的条件下,增大制冷电流可以提高制冷效果,但是大的制冷电流可能出现温度回升的现象;虽然热端散热能力的提高可以改善制冷效果,但是存在一个极限值,这与热电制冷器(TEC)的优值系数有关;当系统载荷发生变化时,合理改变制冷电流和热端散热能力可以提高系统的温度稳定性,其中制冷电流对系统温度稳定性的影响更大。     

一种测试半导体制冷器的瞬态方法

ZT值、最大制冷温差和响应时间是表征半导体制冷器性能的重要参数.文中介绍了一种能同时测量这三个参数的瞬态方法,并讨论了热沉对测试结果的影响.利用一个由恒流脉冲发生器和数据采集卡组成的简单测试系统测得制冷器在小电流下的电阻电压和塞贝克电压,通过这两个电压推导出ZT值、最大制冷温差.这种瞬态方法是非接触式测量,准确度高,可用于薄膜热电器件测试;另外瞬态方法耗时短,可大大缩短半导体制冷器可靠性测试的周期.采用这种方法对4mm×4mm×2.4mm的热电制冷器进行实验,环境温度300K时,测得ZT值为0.39,最大温差58.5K,响应时间20s.     

电子元器件热电冷却技术研究进展

在深刻分析热电制冷机理的基础上,结合国内外学者对热电制冷技术用于电子元器件热管理的理论分析,从芯片整体表面散热和局部热点消除两方面,详细介绍了集成电路芯片热电冷却实验的国内外研究进展;对芯片热电冷却技术的数值模拟与热电制冷器(TEC)的选型优化进行了详细报道;指出国内缺乏芯片热电冷却的应用研究,在芯片散热的整体研究水平上与国外仍有差距.芯片热电冷却及其表面的热管理将是今后提高电子元器件散热性能的一个重要研究方向.     

New Physical Model for Thermoelectric Generators

In this paper we describe a new analytical physical model for thermoelectric generators (TEGs). The model includes the Thomson effect, the Peltier heat, a parameterization of the Joule heat, as well as all thermal and electrical resistances. Geometry optimization and investigations of the influence of Peltier heat and the heat source, as well as heat sink conditions and the load resistance, which affect the output power, are presented. The results are compared with measurements of commercially available thermoelectric generators and the fundamental thermodynamic limit. A comparison between the generators is performed.     

微电子芯片热电冷却系统的传热特性

针对微电子芯片热管理技术的现状和传统冷却技术的不足,建立微电子芯片热电冷却装置及其性能测试系统,采用热阻分析模型对传热过程进行研究.结果表明:在热电冷却过程中,帕尔帖效应占主导作用,TEC(热电冷却系统)自身热阻θ2随工作电流I的增大而降低.当芯片功率为20 W时,芯片与TEC冷面的界面热阻θ1在I为2.1 A时取得最...     

Simulation of the <Emphasis Type="Italic">Q</Emphasis><Subscript>max</Subscript> mode of a thermoelectric cooler taking into account thermal resistances at the cool and hot sides

It is necessary to take into account the thermal resistances of structural components located between a material and a heat emitting medium (on the cold side) and between a material and a heat absorbing medium (on the hot side) when simulating thermoelectric cooling devices. A dimensionless mathematical model taking into account the mentioned thermal resistances and describing the cooling and heating capacity, voltage, and coefficient of performance of the devices, depending on current, is proposed in this study. Using this model, the optimal values of the current and thermal resistances on the hot and cold side of the devices can be found for implementation of the maximum cooling capacity mode and other operating conditions.     

Special Important Aspects of the Thomson Effect

A comprehensive study of the mechanisms of heating and cooling originating from an electrical current in semiconductor devices is reported. The variation in temperature associated with the Peltier effect is not related to the presence of heat sources and sinks if the heat flux is correctly determined. The Thomson effect is commonly regarded as a heat source/sink proportional to the Thomson coefficient, which is added to the Joule heating. In the present work, we will show that this formulation of the Thomson effect is not sufficiently clear. When the heat flux is correctly defined, the Thomson heat source/sink is proportional to the Seebeck coefficient. In the conditions in which the Peltier effect takes place, the temperature gradient is created, and, consequently, the Thomson effect will occur naturally.     

Two-dimensional simulation of thermal runaway in a nonplanarGTO-thyristor

The problem of electrothermal stability due to different cooling conditions has been investigated by computing the thermal transients in a nonplanar GTO-thyristor. In the first simulation, a steady state occurs with a heat sink removing all the dissipated power. In the second simulation severe thermal runaway is induced due to bad cooling conditions, allowing the analysis of destructive electrothermal interaction. The simulations are based on an advanced model for self-heating effects in silicon devices derived from first principles of irreversible thermodynamics. Self-consistently incorporating a phenomenological model of band gap narrowing in order to take account of heavy doping effects. The system of governing equations is valid in both the steady state and the transient regimes. Four characteristic effects contributing to the heat generation can be identified: Joule heating, recombination heating, Thomson heating, and carrier source heating. Thermal runaway is significantly accelerated in the simulations based on the thermodynamic model of thermoelectric transport compared to a conventional heuristic theory of thermoelectricity. The importance of the entropy balance equation is emphasized in order to derive the mathematical form of the heat flux and the current relations for electrons and holes. Limitations of underlying assumptions are discussed. It is shown that the heat generation implies the Thomson relations     

Advanced Thermoelectric Materials for Flexible Cooling Application

Flexible cooling devices, which aim to fulfill the essential requirement of complex working environments and enable local heat dissipation, have become the cutting-edge area of refrigeration technology. Thermoelectric (TE) material represents a promising candidate for various flexible cooling applications, including wearable personal thermoregulation devices. With the increasing interest in the Peltier effect of conductive polymers and inorganic films on flexible substrates, flexible cooling devices have undergone rapid development. Herein, the fundamental mechanisms, basic parameters, and temperature measurement techniques for evaluating the cooling performance are summarized. Moreover, recent progress on TE materials, such as flexible inorganic and organic materials for Peltier cooling studies, is reviewed. More importantly, insights are provided into the key strategies for high-performance Peltier devices. The final part details the existing challenges and perspectives on flexible TE cooling to inspire additional research interests toward the advancement of refrigeration technology.     

Detailed Modeling and Irreversible Transfer Process Analysis of a Multi-Element Thermoelectric Generator System

Thermoelectric (TE) power generation technology, due to its several advantages, is becoming a noteworthy research direction. Many researchers conduct their performance analysis and optimization of TE devices and related applications based on the generalized thermoelectric energy balance equations. These generalized TE equations involve the internal irreversibility of Joule heating inside the thermoelectric device and heat leakage through the thermoelectric couple leg. However, it is assumed that the thermoelectric generator (TEG) is thermally isolated from the surroundings except for the heat flows at the cold and hot junctions. Since the thermoelectric generator is a multi-element device in practice, being composed of many fundamental TE couple legs, the effect of heat transfer between the TE couple leg and the ambient environment is not negligible. In this paper, based on basic theories of thermoelectric power generation and thermal science, detailed modeling of a thermoelectric generator taking account of the phenomenon of energy loss from the TE couple leg is reported. The revised generalized thermoelectric energy balance equations considering the effect of heat transfer between the TE couple leg and the ambient environment have been derived. Furthermore, characteristics of a multi-element thermoelectric generator with irreversibility have been investigated on the basis of the new derived TE equations. In the present investigation, second-law-based thermodynamic analysis (exergy analysis) has been applied to the irreversible heat transfer process in particular. It is found that the existence of the irreversible heat convection process causes a large loss of heat exergy in the TEG system, and using thermoelectric generators for low-grade waste heat recovery has promising potential. The results of irreversibility analysis, especially irreversible effects on generator system performance, based on the system model established in detail have guiding significance for the development and application of thermoelectric generators, particularly for the design and optimization of TE modules.