A numerical study on the performance of miniature thermoelectric cooler affected by Thomson effect

Miniature thermoelectric cooler (TEC) has been considered as a promising device to achieve effective cooling in microprocessors and other small-scale equipments. To understand the performances of miniature thermoelectric coolers, three different thermoelectric cooling modules are analyzed through a three-dimensional numerical simulation. Particular attention is paid to the influence of scaling effect and Thomson effect on the cooling performance. Two different temperature differences of 0 and 10 K between the top and the bottom copper interconnectors are taken into account. In addition, three different modules of TEC, consisting of 8, 20 and 40 pairs of TEC, are investigated where a single TEC length decreases from 500 to 100 μm with the condition of fixed ratio of cross-sectional area to length. It is observed that when the number of pairs of TEC in a module is increased from 8 to 40, the cooling power of the module grows drastically, revealing that the miniature TEC is a desirable route to achieve thermoelectric cooling with high performance. The obtained results also suggest that the cooling power of a thermoelectric cooling module with Thomson effect can be improved by a factor of 5-7%, and the higher the number of pairs of TEC, the better the improvement of the Thomson effect on the cooling power.     

Measurements of thermoelectric properties of a thermoelectric cooler

The effective thermoelectric parameters of a single stage cooler were measured as a function of temperature and compared with those of the n and p type materials from which the thermoelements were prepared. The performance of the cooler was calculated by a computerized iterative process using measured parameters and compared with experimentally determined characteristics. The influence of electrical contact resistance on the performance of the cooler is not negligible.     

汤姆逊效应对热电发电机驱动热电制冷机装置性能的影响

建立了包含汤姆逊效应的热电发电机驱动热电制冷机(TEG-TEC)装置热力学模型,运用非平衡热力学理论和数值计算方法进行了性能分析,对比考虑和不考虑汤姆逊效应2种情况,分析了汤姆逊效应对装置性能的影响。结果表明,汤姆逊效应使TEG-TEC装置性能降低,且降低幅度随热电发电机高温热源温度或制冷空间温度升高而减小。当热电发电机热节点温度和热电制冷机冷节点温度分别取450K和285K,热电单元比取0.5时,汤姆逊效应使制冷率降低29.98%,使制冷系数降低23.02%,使极限制冷温差降低11.35%。考虑到汤姆逊效应的影响,应当将有限数量的热电单元适当多地分配到热电发电机中。文中结论为实际TEG-TEC装置的设计和运行提供了理论指导。     

Energetic and exergetic analyses of a combined system consisting of a high-temperature polymer electrolyte membrane fuel cell and a thermoelectric generator with Thomson effect

A combined system model consisting of a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC), a regenerator and a thermoelectric generator (TEG) is proposed, where the TEG is applied to harness the generated waste heat in the HT-PEMFC for extra electricity production. The TEG considers not only the Seebeck effect and Peltier effect but also the Thomson effect. The mathematical expressions of power output, energy efficiency, exergy destruction rate and exergy efficiency for the proposed system are derived. The energetic and exergetic performance characteristics for the whole system are revealed. The optimum operating ranges for some key performance parameters of the combined system are determined using the maximum power density as the objective function. The combined system maximum power density and its corresponding energy efficiency and exergy efficiency allow 19.1%, 12.4% and 12.6% higher than that of a stand-alone HT-PEMFC, while the exergy destruction rate density is only increased by 8.6%. The system performances are compared between the TEG with and without the Thomson effect. Moreover, the impacts of comprehensive parameters on the system performance characteristics are discussed. The obtained results are helpful in developing and designing such an actual combined system for efficient and clean power production.     

Integrating high-temperature proton exchange membrane fuel cell with duplex thermoelectric cooler for electricity and cooling cogeneration

To harvest the waste heat from exothermic reaction processes, a novel hybrid system model mainly incorporating a high-temperature proton exchange membrane fuel cell (HT-PEMFC) and a duplex thermoelectric cooler is conceptualized to theoretically predict the potential performance limit. The duplex thermoelectric cooler is composed of a thermoelectric generator (TEG) and a thermoelectric cooler (TEC), where the TEG harvests the waste heat to generate electricity and the TEC utilizes the generated electricity for cooling production. A mathematical model is established to estimate the proposed system performance from both exergetic and energetic perspectives considering various irreversible effects, from which effectiveness and practicality of the proposed system can be examined. The hybrid system maximal output power density allows 14.1% greater than that of the basic HT-PEMFC, whereas the according destruction rate density of exergy is decreased by 7.7%. The feasibility and effectiveness of the proposed system configuration are verified. Moreover, substantial parametric analyses indicate that the proposed system performance can be improved by elevating the HT-PEMFC operating temperature, inlet relative humidity and doping level while worsened by enhancing the leak current density, electrolyte thickness and Thomson coefficient. The results acquired may be helpful in designing and optimizing such an actual hybrid system.     

Performance of a modulated solar thermoelectric cooler

The performance of a solar thermoelectric cooler subjected to a modulated heat input is studied analytically. Numerical results show that modulation has no effect on the mean value of performance parameters but does significantly affect performance fluctuations about the mean value. High frequency modulation at low N_g/N_r ratio is found to be best suited for maximum oscillation of the coefficient of performance while low frequency modulation with high N_g/N_r ratio is best suited for maximum cold space temperature oscillation.     

Performance evaluation of the recuperative heat exchanger in a miniature Joule–Thomson cooler

To develop effective heat exchangers for miniature and micro-Joule–Thomson (J–T) cooling system, the performance of the recuperative heat exchanger in a miniature J–T cooler is analyzed and evaluated. The evaluation is based on a theoretical model of the Hampson-type counter-flow heat exchanger. The effect of the pressure and temperature-dependent properties and longitudinal heat conduction are considered. The results of the numerical simulation are validated with the corresponding experimental measurements. The performance of the heat exchanger on effectiveness, flow and various heat conduction losses as well as liquefied yield fraction are analyzed and discussed. The simulation model provides a useful tool for miniature J–T cooler design.     

Methodology on sizing and selecting thermoelectric cooler from different TEC manufacturers in cooling system design

The search and selection for a suitable thermoelectric cooler (TEC) to optimize a cooling system design can be a tedious task as there are many product ranges from several TEC manufacturers. Although the manufacturers do provide proprietary manuals or electronic search facilities for their products, the process is still cumbersome as these facilities are incompatible. The electronic facilities often have different user interfaces and functionalities, while the manual facilities have different presentations of the performance characteristics. This paper presents a methodology to assist the designer to size and select the TECs from different manufacturers. The approach will allow designers to find quickly and to evaluate the devices from different TEC manufacturers. Based on the approach, the article introduces a new operational framework for an Internet based thermoelectric cooling system design process that would promote the interaction and collaboration between the designers and TEC manufacturers. It is hoped that this work would be useful for the advancement of future tools to assist designers to develop, analyze and optimize thermoelectric cooling system design in minimal time using the latest TECs available on the market.     

Exergy analysis of single‐stage and multi stage thermoelectric cooler

Thermoelectric devices are solid‐state devices. Semiconductor thermoelectric cooling, based on the Peltier effect, has interesting capabilities compared to conventional cooling systems. In this work second law analysis of thermoelectric coolers has been done with the help of exergy destruction. In the first part, performance of single‐stage thermoelectric coolers and multi stage thermoelectric coolers has been compared for same number of thermoelectric elements i.e. 50. The performance parameters considered to compare their performance are rate of refrigeration, coefficient of performance, second law efficiency and exergy destruction. In second part, multi stage thermoelectric coolers have been analyzed for three different combinations of number of elements in two stages of thermoelectric coolers. The result of the analysis shows that the performance of a multi stage thermoelectric cooler which has total 50 elements gives best performance when it has 30 elements in hotter side and 20 elements in colder side out of the three cases considered. The comparison of single‐stage thermoelectric cooler and multistage thermoelectric cooler shows that for same number of elements rate of refrigeration (ROR) of single‐stage thermoelectric cooler is much higher than that of multi stage thermoelectric cooler. The COP remains same for both of them but the peak value of cop is obtained at much lower value of current supplied in multi stage thermoelectric cooler. Exergy destruction has constant values in single stage as well as multi stage thermoelectric cooler when the two stages have equal number of elements but it decreases with increase in x. The result of comparison of multistage thermoelectric cooler for three values of x i.e. 0.5, 1, 1.5 shows that the COP, ROR and second law efficiency improve and exergy destruction degrades with increase in x and the best performance has been obtained for x = 1.5 out of the three values considered. Copyright © 2013 John Wiley & Sons, Ltd.     

Numerical analysis on the cooling of a laser diode package with a thermoelectric cooler

An LD (laser diode), an essential unit of an LD package, has higher output power and faster working speed than an LED (light‐emitting diode) but it is more expensive. The thermal characteristic of an LD should be estimated as the working performance as it is closely related to its temperature. The thermal expansion causes changes in its shape and position, which lead to a crucial problem regarding light transmission. An LD is located on the submount for insulation and cooling and all of them work in a closed package filled with an inert gas. A TEC (thermoelectric cooler) is used in order to control the temperature of the package, especially the LD. © 2001 Scripta Technica, Heat Trans Asian Res, 30(5): 357‐370, 2001     

Effect of Mach number on thermoelectric performance of SiC ceramics nose-tip for supersonic vehicles

This paper focus on the effects of Mach number on thermoelectric energy conversion for the limitation of aero-heating and the feasibility of energy harvesting on supersonic vehicles. A model of nose-tip structure constructed with SiC ceramics is developed to numerically study the thermoelectric performance in a supersonic flow field by employing the computational fluid dynamics and the thermal conduction theory. Results are given in the cases of different Mach numbers. Moreover, the thermoelectric performance in each case is predicted with and without Thomson heat, respectively. Due to the increase of Mach number, both the temperature difference and the conductive heat flux between the hot side and the cold side of nose tip are increased. This results in the growth of the thermoelectric power generated and the energy conversion efficiency. With respect to the Thomson effect, over 50% of total power generated converts to Thomson heat, which greatly reduces the thermoelectric power and efficiency. However, whether the Thomson effect is considered or not, with the Mach number increasing from 2.5 to 4.5, the thermoelectric performance can be effectively improved.     

Experimental and analytical study on thermoelectric self cooling of devices

This paper presents and studies the novel concept of thermoelectric self cooling, which can be introduced as the cooling and temperature control of a device using thermoelectric technology without electricity consumption.For this study, it is designed a device endowed with an internal heat source. Subsequently, a commonly used cooling system is attached to the device and the thermal performance is statistically assessed. Afterwards, it is developed and studied a thermoelectric self cooling system appropriate for the device.Experimental and analytical results show that the thermal resistance between the heat source and the environment reduced by 25-30% when the thermoelectric self cooling system is installed, and indicates the promising applicability of this technology to devices that generate large amounts of heat, such as electrical power converters, transformers and control systems. Likewise, it was statistically proved that the thermoelectric self cooling system leads to significant reductions in the temperature difference between the heat source and the environment, and, what is more, this reduction increases as the heat flow generated by the heat source increases, which makes evident the fact that thermoelectric self cooling systems work as temperature controllers.     

Effect of irreversibilities on the performance of a thermoelectric generator

Using an externally and internally irreversible heat engine model, the maximum power and thermal efficiency at maximum power output have been determined for a thermoelectric generator. The irreversibilities can be characterized by a single parameter named the device-design parameter. The efficiency and power decrease with an increase of the device-design parameter which appears in the equations for maximum power and efficiency.     

Experimental study of a domestic thermoelectric cogeneration system

Thermoelectric application for power generation does not appear to be appealing due to the low conversion efficiency given by the current commercially available thermoelectric module. This drawback inhibits its wide application because of the overall low thermal efficiency delivered by typical thermoelectric applications. This paper presents an innovative domestic thermoelectric cogeneration system (TCS) which overcomes this barrier by using available heat sources in domestic environment to generate electricity and produce preheated water for home use. This system design integrates the thermoelectric cogeneration to the existing domestic boiler using a thermal cycle and enables the system to utilise the unconverted heat, which represents over 95% of the total absorbed heat, to preheat feed water for domestic boiler. The experimental study, based on a model scale prototype which consists of oriented designs of heat exchangers and system construction configurations. An introduction to the design and performance of heat exchangers has been given. A theoretical modelling for analysing the system performance has been established for a good understanding of the system performance at both the practical and theoretical level. Insight has also been shed onto the measurements of the parameters that characterise the system performance under steady heat input. Finally, the system performance including electric performance, thermal energy performance, hydraulic performance and dynamic thermal response are introduced.     

Geometric optimization of thermoelectric coolers in a confined volume using genetic algorithms

The demand for thermoelectric coolers (TEC) has grown significantly because of the need for a steady, low-temperature operating environment for various electronic devices such as laser diodes, semiconductor equipment, infrared detectors and others. The cooling capacity and its coefficient of performance (COP) are both extremely important in considering applications. Optimizing the dimensions of the TEC legs provides the advantage of increasing the cooling capacity, while simultaneously considering its minimum COP. This study proposed a method of optimizing the dimensions of the TEC legs using genetic algorithms (GAs), to maximize the cooling capacity. A confined volume in which the TEC can be placed and the technological limitation in manufacturing a TEC leg were considered, and three parameters––leg length, leg area and the number of legs––were taken as the variables to be optimized. The constraints of minimum COP and maximum cost of the material were set, and a genetic search was performed to determine the optimal dimensions of the TEC legs. This work reveals that optimizing the dimensions of the TEC can increase its cooling capacity. The results also show that GAs can determine the optimal dimensions according to various input currents and various cold-side operating temperatures.     

Performance of solar cells using thermoelectric module in hot sites

The ambient temperature at Madinah site is between 40 °C and 50 °C during the summer months and sometimes is over 50 °C. The cell temperature reaches the value of 83 °C. This affects the behaviors of solar cells (SC) and decreases their efficiency. The performance of solar cells is presented in this work using thermoelectric module (TEM) as cooling system. In fact, we have found experimentally that the efficiency of solar cells decreases with increase in its temperature. The efficiency of solar cells drops by 0.5% per °C rise in temperature. So, it's necessary to operate them at lower temperature in order to increase their efficiency. Cooling the solar cells would enhance its performance. The hybrid PV/TEM system is proposed for PV applications in hot sites.     

热电发电器的研究进展

简要介绍了热电发电器的原理、特点、基本结构及其改进措施,总结了近年来国内外在热电发电器件研究方面的现状,最后展望了热电发电器的前景。     

半导体制冷电极工作性能的数值模拟

通过对稳定情况下半导体制冷器P型元件的工作模型分析,给出了其工作性能的分析解和数值解.结果显示对于单级制冷器,其制冷元件工作在较大温差下时,考虑温度对材料性能的影响是必要的.     

An effective Seebeck coefficient obtained by experimental results of a thermoelectric generator module

This article proposes a concept of “effective Seebeck coefficient”, which discusses the inconsistency between the theoretical Seebeck coefficient and the measured one. The inconsistency can be explained via contact effect and thermal resistor network. Two different clamping forces are applied to the TEG module to observe the contact effect. Throughout the experiments, the electric resistance seems insensitive to the clamping force; somehow the thermal contact effect dominates the TEG module performance. In addition, a thermal resistor network, which is used to calculate the exact temperature difference traverse the TE ingot, has been constructed. After applying a suitable clamping pressure and modifying the actual ΔT with thermal resistor network, the “effective Seebeck coefficient” has been proposed. Notably, this proposed value is very helpful for better understanding characteristics of the behavior of the TEG module operating in the actual conditions we provided, and it can be used to predict the performance of the TEG module under any other condition.     

Parametrical analysis of the design and performance of a solar heat pipe thermoelectric generator unit

This paper describes a solar heat pipe thermoelectric generator (SHP-TEG) unit comprising an evacuated double-skin glass tube, a finned heat pipe and a TEG module. The system takes the advantage of heat pipe to convert the absorbed solar irradiation to a high heat flux to meet the TEG operating requirement. An analytical model of the SHP-TEG unit is presented for the condition of constant solar irradiation, which may lead to different performance characteristics and optimal design parameters compared with the condition of constant temperature difference usually dealt with in other studies. The analytical model presents the complex influence of basic parameters such as solar irradiation, cooling water temperature, thermoelement length and cross-section area and number of thermoelements, etc. on the maximum power output and conversion efficiency of the SHP-TEG. Simulation based on the analytical model has been carried out to study the performance and design optimization of the SHP-TEG.