Optimization of thermoelectric cooling regimes for heat-loaded elements taking into account the thermal resistance of the heat-spreading system

A mathematical model has been proposed for analyzing and optimizing thermoelectric cooling regimes for heat-loaded elements of engineering and electronic devices. The model based on analytic relations employs the working characteristics of thermoelectric modules as the initial data and makes it possible to determine the temperature regime and the optimal values of the feed current for the modules taking into account the thermal resistance of the heat-spreading system.     

Calculation of the Thermal Resistance of a Heat Distributer in the Cooling System of a Heat-Loaded Element

Numerical simulation is performed for heat transfer in a heat distributer of a thermoelectric cooling system, which is located between the heat-loaded element and the thermoelectric module, for matching their sizes and for heat flux equalization. The dependences of the characteristic values of temperature and thermal resistance of the copper and aluminum heat distributer on its thickness and on the size of the heatloaded element. Comparative analysis is carried out for determining the effect of the thermal conductivity of the material and geometrical parameters on the heat resistance. The optimal thickness of the heat distributer depending on the size of the heat-loaded element is determined.     

热电制冷LED自然对流散热的设计与优化

为提升高热流密度下LED灯具的自然对流散热性能,以一款基于热电制冷（TEC）的单颗LED小型灯具模组为研究对象,在采用实验测量和回归拟合准确获得TEC性能参数的基础上,建立了有无TEC参与散热的等效热路模型,并选择合理的数学公式对其进行性能描述,进而遵循本文设计的计算流程快速得到各种散热性能数据。LED模组的散热分析表明：在恒定的LED热功率下,施加最佳的TEC电流可获得最高的散热性能;LED热功率越低,安装TEC的散热性能越比常规方法优异。经遗传算法优化前后的性能对比分析表明：优化后结构中TEC的合理工作区明显增大,能满足LED更高功率的散热需求;当LED为0.493 W时,优化后结构的最佳结温仅为15.66℃,远低于30℃的环境温度。基于TEC实验数据建立的等效热路模型,能为装配TEC的LED模组提供快速完整的散热设计分析与结构优化的合理方案。     

Thermoelectric power generation in a thermoacoustic refrigerator

Commercially available solid-state thermoelectric devices may be used for their electrical power generation capabilities when coupled to a thermoacoustic refrigerator or heat pump. General performance characteristics as well as bulk thermal conductivity for a selection of thermoelectric elements was first found by using a two-plate apparatus to maintain a constant temperature difference across the element. Further studies of an element’s performance when placed in series with the thermoacoustic refrigerator’s heat exchangers will be presented. Design considerations for using thermoelectric elements in a no-moving parts electrical power generation scheme will be discussed.     

Thermoelectric power of vacuum evaporated PbTe films

Variation of thermoelectric power with thickness of the vacuum evaporated PbTe films has been investigated. The films were deposited on mica, glass, quartz and LiF substrates, under identical conditions. Attempts have been made to derive a relation which represents the variation of thermoelectric power with thickness of the film. The temperature variation of thermoelectric power has also bsen studied.     

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。     

基于热阻网络的大功率LED热管散热研究

LED结温高一直是大功率LED发展的技术瓶颈,随着单位热流密度的不断攀升,在自然冷却条件下,单纯的直肋热沉散热方式已不能满足散热要求。应用热管技术设计了热管散热系统,对该系统的传热机理和传热路线进行分析,建立该系统对应的热网络模型,对各部分热阻进行分析与计算,求得总的理论总热阻,计算得出理论结温;同时应用有限元方法对该系统进行仿真分析,对LED模块（0.025 m0.025 m0.005 m）输入30 W 电功率,得出其仿真结温稳定在58.19℃,满足结温小于65℃的要求,说明应用热管的散热系统满足设计要求。由热阻网络模型计算得出的理论结温为57.43℃,与仿真结果相差0.76℃,其误差仅为1.31％,验证了理论分析计算的正确性,对实际工程中热设计具有指导意义。     

Evaluating the efficiency of thermo-electric conversion of heat from gas combustion in a small-scale system with counterflow heat exchange

The efficiency of thermoelectric conversion of heat from gas combustion was evaluated in a small-scale system consisting of two channels with opposing gas flows and thermocouples located in the separating wall. Combustion occurred in the chamber fed with fresh mixture heated by combustion products through heat-conducting walls of the channel. In the channel walls, there were thermoelectric converters. It has been shown that in this system, the maximum conversion efficiency of heat from gas combustion may be close to the maximum efficiency of thermoelectric conversion calculated by the maximum acceptable working temperature of the hot side of the converter. This conclusion is valid in the case when the adiabatic combustion temperature of the gas mixture is below the maximum allowable operating temperature of the hot side of the thermoelectric converter. The considered system is promising for the burning of low-calorific gas mixtures and does not require additional energy for cooling the cold side of the thermoelectric converter.     

Highly flexible and excellent performance continuous carbon nanotube fibrous thermoelectric modules for diversified applications

A highly flexible and continuous fibrous thermoelectric (TE) module with high-performance has been fabricated based on an ultra-long single-walled carbon nanotube fiber, which effectively avoids the drawbacks of traditional inorganic TE based modules. The maximum output power density of a 1-cm long fibrous TE module with 8 p-n pairs can reach to 3436 μW·cm^-2, the power per unit weight to 2034 μW·g^-1, at a steady-state temperature difference of 50 K. The continuous fibrous TE module is used to detect temperature change of a single point, which exhibits a good responsiveness and excellent stability. Because of its adjustability in length, the flexible fibrous TE module can satisfy the transformation of the temperature difference between two distant heat sources into electrical energy. Based on the signal of the as-fabricated TE module, a multi-region recognizer has been designed and demonstrated. The highly flexible and continuous fibrous TE module with excellent performance shows a great potential in diversified applications of TE generation, temperature detection, and position identification.     

高功率二极管激光器相变冷却技术

根据高功率二极管激光器的散热需求,设计了一种储能式相变冷却实验系统,并开展了喷雾相变冷却器和微通道相变冷却器的设计。采用多孔微结构的换热表面,用氨做制冷剂,实现了喷雾相变冷却器表面温度37 ℃时,散热功率密度达到了511 W/cm2。采用节流汽化原理,分别设计了背冷式相变微通道冷却器和薄片型的模块式相变微通道冷却器,背冷式相变微通道冷却器采用氨做制冷剂, 散热功率密度达到了550 W/cm2,采用R124做制冷剂,散热功率密度约270 W/cm2。采用R124做制冷剂,实现了脉冲激光功率3 kW和连续激光功率100 W的相变冷却二极管激光器模块封装。     

计算机CPU芯片散热技术

随着计算机CPU芯片朝高集成化、小型化和高频化趋势发展,为CPU提供高效的散热方案成为全球关注的研究热点。阐述了高温对CPU性能影响的机理,综述了常用的CPU散热技术如风冷、水冷散热、热电制冷及热管散热和微槽道散热技术的原理,研究进展及优缺点,并对这一领域的发展前景进行了展望。     

Electronic transport and specific heat of 1T-V Se2

The low-temperature thermoelectric power and the specific heat of 1T-V Se₂ (vanadium diselenide) have been reported along with the electrical resistivity and Hall coefficient of the compound. The charge density wave (CDW) transition is observed near 110 K in all these properties. The thermoelectric power has been measured from 15 K to 300 K, spanning the incommensurate and commensurate CDW regions. We observed a weak anomaly at the CDW transition for the first time in the specific heat of V Se₂. The linear temperature dependence of the resistivity and thermoelectric power at higher temperatures suggests a normal metallic behavior and electron–phonon scattering above the CDW transition. The positive thermoelectric power and negative Hall coefficient along with strongly temperature-dependent behavior in the CDW phase suggest a mixed conduction related to the strongly hybridized s–p–d bands in this compound.     

Optimized Peltier cooling via an array of quantum dots with stair-like ground-state energy configuration

With the advancement in fabrication and scaling technology, the rising temperature in nano devices has attracted special attention towards thermoelectric or Peltier cooling. In this paper, I propose optimum Peltier cooling by employing an array of connected quantum dots with stair-like ground-state eigen energy configuration. The difference in ground state eigen energy between two adjacent quantum dots in the stair-like configuration is chosen to be identical with the optical phonon energy for efficient absorption of lattice heat. I show that in the proposed configuration, for a given optical phonon energy, one can optimize the cooling power by tuning the number of stages in the array of quantum dots. A further analysis demonstrates that the maximum cooling power at a given potential bias under optimal conditions does not depend strongly on the optical phonon energy or the number of stages at which the maximum cooling power is achieved, provided that the optical phonon energy is less than kT. The proposed concept can also be applied to $2?D$ or bulk resonant tunnel and superlattice structures with stair-like resonant energy configuration.     

Large Seebeck coefficients in iron‐oxypnictides: a new route towards n‐type thermoelectric materials

The iron‐oxypnictide compounds, recently reported as a new class of superconductors when appropriately doped, exhibit large Seebeck coefficients, of the order of –100 µV/K, while keeping good electrical conductivity. Their power factor shows a peak at low temperatures, suggesting possible applications of these materials in thermoelectric cooling modules in the liquid nitrogen temperature range. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

准一维有机超导体(TMTSF)2ClO4的高精度温差电动势研究

测量了准一维有机超导体(TMTSF)2ClO4单晶a方向不同降温速率下的高精度温差电动势(6—280K).高温下的温差电动势表现出线性行为，不能被正常的一维电子能带理论所解释.在240K左右观察到温差电动势斜率发生反常突变.在140K左右温差电动势向下逐渐偏离线性行为，这与1D—2D的维度渡越相关.对阴离子有序—无序相变温度Ta（Ta=24K）附近的温差电动势结果与比热和电阻率的数据进行了比较.对于极慢速降温的温差电动势，求导后可以看到相变的痕迹.随着通过Ta降温速率的增大，在Ta之下的温差电动势数值出现了一个逐渐增大的整体抬高.对此进行了讨论. 关键词： 低维体系 输运性质 温差电动势     

Enhanced thermoelectric power in dual-gated bilayer graphene

The thermoelectric power of a material, typically governed by its band structure and carrier density, can be varied by chemical doping that is often restricted by solubility of the dopant. Materials showing large thermoelectric power are useful for many industrial applications, such as the heat-to-electricity conversion and the thermoelectric cooling device. Here we show a full electric-field tuning of thermoelectric power in a dual-gated bilayer graphene device resulting from the opening of a band gap by applying a perpendicular electric field on bilayer graphene. We uncover a large enhancement in thermoelectric power at a low temperature, which may open up a new possibility in low temperature thermoelectric application using graphene-based device.     

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利用ANSYS CFX有限元程序建立了HL-2M欧姆测试线圈和冷却水模型,应用热传导和对流换热方程建立了流固边界层,对线圈的温升和冷却进行了流固耦合计算。计算结果表明,线圈由焦耳热引起的最高温升与电流密度、等效放电运行时间有关,而冷却水流量对最高温升影响较小,冷却水流量主要决定线圈的冷却时间间隔的长度,欧姆测试线圈的最长冷却时间间隔为5min。     

Magnetocaloritronic nanomachines

We introduce and study a magnetocaloritronic circuit element based on a domain wall that can move under applied voltage, magnetic field and temperature gradient. We draw analogies between Carnot machines and possible devices employing such a circuit element. We propose a realization of magnetocaloritronic cooling and point out the parallels between the operational principles of magnetocaloritronic and thermoelectric cooling and power generation. Following this analogy, we introduce a magnetocaloritronic figure of merit that encodes information about the maximum efficiency of such devices. Even though the magnetocaloritronic figure of merit turns out to be very small for transition-metal based magnets, we speculate that larger numbers may be expected in ferromagnetic insulators.     

喷流冷却复合陶瓷薄片激光器的热特性仿真分析及实验研究

为分析喷流冷却复合陶瓷薄片激光器的热特性,设计用于冷却复合陶瓷薄片的喷流冷却系统.利用湍流换热理论和计算流体动力学仿真方法建立喷流冷却复合陶瓷薄片激光器的流固耦合热仿真模型,定义评价其冷却能力和冷却均匀性的定量参数.根据该仿真模型得到喷流冷却系统的最优设计参数,并进行实验验证.使用163孔喷板,流量为0.2kg/s,入口温度为20℃,在1200 W泵浦时获得359 W激光输出功率,并测得复合陶瓷薄片上表面的最高温度为92℃.激光输出功率与复合陶瓷薄片上表面温度均与泵浦功率呈近似正线性关系,且温度的实验值与仿真值相符度较高.     

Mechanism of heat transfer in heterogeneous droplets of water under intense radiant heating

Thermocouple measurements of temperature have been performed at three main points of heterogeneous water droplet–high-temperature gases system: on the surface and in the depth of a solid inclusion, as well as on the free surface of the water droplet. Investigations have been carried out for water droplets of an initial volume of 5–15 μl with single inclusions of cubic graphite particles of a typical size of 1 mm. The gas temperature varied from 700 K to 1200 K, which corresponds to the main practical applications: thermal purification of water from solid and liquid impurities, fire extinguishing, treatment of heat-loaded surfaces of power equipment, etc. A hypothesis about the dominant role of radiant heat transfer in vaporization within heterogeneous water droplets has been grounded. It has been shown that in a short period (a few seconds), the surface temperature of an opaque solid inclusion within a droplet can reach the boiling point of water. A significant change in the optical properties of water with increasing temperature has been revealed, i.e., water became partially transparent to the infrared radiation. Presence of an opaque heterogeneous inclusion enhances this effect due to intensification of the heating of the water film. The heat and mass transfer characteristics obtained in the experiments were used for designing a model that takes into account the radiative properties of water film and adequately reproduces the results of thermocouplemeasurements. Based on the findings of the investigations, a conclusion has been formulated that models of high-temperature evaporation of water droplets should be developed with due account of changes in the optical properties of water and formation of a vapor buffer layer around inclusions.