基于余热回收的半导体温差发电模型及数值模拟

本文提出一种改进的半导体温差发电模型,在温差发电器热端加上矩形格栅,并将这种格栅近似看作黑体,同时进一步运用FLUENT软件对该半导体温差发电系统的流场、温度场进行了数值仿真计算,并对仿真结果进行分析。结果表明该模型确实能够提高温差发电器的热端温度、冷端与热端的温差,使大量余热得到有效的利用;冷热端的温差比无格栅时提高了49.33%。模拟结果还表明格栅的几何尺寸选取对温差发电器热端的温度及冷热端温差有一定的影响。     

Mini-Contact Enhanced Thermoelectric Coolers for On-Chip Hot Spot Cooling

Shrinking feature size and increasing transistor density, combined with the high performance demanded from next-generation microprocessors, have led to on-chip high heat flux “hot spots,” which have emerged as the primary driver for thermal management of today's integrated circuit (IC) technology. This article describes the use of a mini-contact to enhance the cooling flux of a miniaturized thermoelectric cooler (TEC) for on-chip hot-spot remediation. A package-level numerical simulation is developed to predict the on-chip hot spot cooling capability achievable with such a mini-contact enhanced TEC. Attention is focused on the hot-spot temperature reduction associated with variations in mini-contact size and thermoelectric element height, as well as the parasitic effect from the thermal contact resistance introduced by the mini-contact. A preliminary experiment has been conducted to verify the numeric model and to demonstrate the effects of the mini-contact on hot-spot cooling.     

Experimental investigation and numerical analysis for one-stage thermoelectric cooler considering Thomson effect

This study conducts experimental investigation and numerical analysis for one-stage thermoelectric cooler (TEC) considering Thomson effect. Three Seebeck coefficient models are applied to numerically and experimentally study the Thomson effect on TEC. Results show that higher current, higher hot side temperature, or lower heat load can increase the temperature difference between the cold and hot sides. Opposite trends are found for COP. Specific current should be chosen as the upper threshold in thermoelectric cooler design. The cooling performance can improve when the Thomson heat maintains positive.     

Experimental study and analysis on novel thermo-electric cooler driven by solar photovoltaic system

Experimental study and analysis on thermoelectric cooler driven by solar photovoltaic system has been carried out. Here the research attention is on testing of system performance under solar insolation. Experimental results revealed that unit could maintain the temperature in the cooler at 10–15°C and have a coefficient of performance (COP) of about 0.34. Analysis of thermoelectric cooling system has been conducted on the basis of COP, cooling capacity and environmental issues. Further investigations verified that the performance of the system is a function of solar insolation rate and temperature difference of hot and cold sides of thermoelectric module etc. There subsist most favorable solar insolation rate which allows COP and cooling production to be maximum value respectively. It is anticipated that the cooler would have prospective for cold storage of vaccine, food and drink in remote and rural areas or outdoor conditions where electricity is not available.     

高温温差发电装置集热器结构数值仿真研究

设计了一种针对高温烟气的圆筒式温差发电装置,在装置中设置分流桶增强烟气侧的换热效果。利用Ansys Fluent软件对装置的温度场、速度场及排气压降进行仿真模拟,分析了不同分流桶的桶直径、端盖孔直径和分流孔直径对热电模块冷热端温度分布的影响。仿真结果表明：温差发电系统集热器通道中设置分流桶可以实现高效温差发电,分流桶端盖未开孔时装置的换热效果优于端盖开孔结构;适当减小分流孔直径或增大分流桶直径会提升热电模块的冷热端温差,分流孔直径为2 mm时的换热效果最优,分流桶直径过大会使热电模块温度分布及温差的均匀性降低;系统烟气压降会随着分流孔直径的增大或分流桶直径的减小而降低。     

基于改进贪心算法的温差电器件电-热耦合效应研究

温差电器件实际工作时由于内电阻的存在不可避免地会产生焦耳热,传统的温差电研究中虽注意到温差发电过程中的焦耳热现象,但只是在等效计算热功率时消去焦耳热部分,而忽略了焦耳热对温差电器件热、冷端温度分布的影响。针对传统研究的不足,考虑实际应用中的电-热耦合效应,运用理论推导的方法建立了第三类边界条件下的温差发电负载模型,并利用改进贪心算法迭代求解,最后以SP1848-21745型温差发电片为例,通过试验验证了模型与算法的正确性。模型的数值求解与发电片实测结果对比表明,考虑了电-热耦合效应的温差发电负载模型的热电输出值更接近实测值。     

Power generation characteristics of a sandwich‐type self‐heating thermoelectric generator with spatially varying embedded heat source

Power generation characteristics of a sandwich‐type thermoelectric generator in which the heat source is embedded into thermoelectric elements are investigated. Our previous work on a similar concept only considered a uniform heat source distribution inside thermoelectric elements. In this work, the effect of the spatial distribution of a heat source is examined. In particular, the effect of the concentration of heat source near the one end, that is, the hot end, is intensively studied as a potential means of improving the efficiency of the device. Although the effects of heat source concentration in impractical cases without heat transfer limitations on the cold side remain ambiguous, it become clear that heat source concentration indeed has positive effects in more realistic cases with finite heat transfer coefficients imposed on the cold side. Because of the relatively low efficiency of typical thermoelectric generation, a significant amount of heat must be dissipated from the cold end of the thermoelectric element. Greater heat source concentration near the hot end leads to more effective utilization of available heat source, reduces the amount of heat rejected at the cold end, and lowers the hot end temperature of the thermoelectric element. Overall, it is suggested that heat source concentration can be used as a method to achieve more efficient operation and better structural integrity of the system. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

冷、热端温度对半导体热电堆发电性能影响的初步研究

对半导体热电堆的发电性能进行了实验研究,得出这种半导体热电堆在冷端温度不变的情况下,其发电性能与热端温度的关系,以及半导体热电堆在热端温度的情况下,冷端温度对其发电性能的影响,发现半导体热电堆作为电源时,其内阻对它的性能指标有很大的影响,而且内阻随着温度的升高而增大,采用间化的方法从理论上计算了热电堆的特性,得到了计算与实验结果基本吻合。     

A computational model for two-stage 4K-pulse tube cooler: Part II. Predicted results

The internal physical processes and performance of a two-stage pulse tube cooler operating at 4 K-temperature region are numerically analyzed by a new mixed Eulerian-Lagrangian computational model. The detailed time-variations of gas temperature, pressure, mass flow rate, enthalpy flow in a cycle, in the first and the second-stage regenerators are presented in the paper. The behavior of the various gas elements, which enter the pulse tube from its cold end has been revealed and discussed. More attention is paid to the effects of different regenerative materials on the performance of the 4 K two-stage pulse tube cooler.     

A Computational Model for Two-Stage 4K-Pulse Tube Cooler: Part Ⅱ. Predicted Results

IntroductionDue to several advances in pulse tube cooler, 4 K-pulse tube coolers have developed rapidly in recent years.In contrast to the GM coolers, pulse tube coolers operaewithout mechanical moving pats in the low temperatllreregion, thereby elindnating the potential problems(mechanical vibration, lifetime, reliability) inherent tothe GM coolers.It was of special imPoftance that Matsubara and Gaoin l994['], first made the liquid-helium temPerature rangeaccessible reaching 3.6 K with a …     

Transient cooling of thermoelectric coolers and its applications for microdevices

If a current pulse with a magnitude several times higher than the steady state optimum current is applied to a thermoelectric cooler, an instantaneously lower temperature than that reachable at the steady state can be obtained. Most previous studies of this transient cooling effect focus on the minimum temperature achievable for free standing thermoelectric (TE) elements. In this work, we systematically study the transient response of thermoelectric coolers with and without mass loads through examination of both the minimum temperature reached and the time constants involved in the cooling and the recovering stages. For integrated thermoelectric cooler-passive mass load systems, two distinguishable cooling regimes, uniform cooling and interfacial cooling, are identified, and the criterion for utilization of the transient cooling effect is established based on the time constants. Although the results of this work are generally applicable, the discussions are geared towards cooling of microdevices that are of current interests.     

Numerical simulation of nanostructured thermoelectric generator considering surface to surrounding convection

Thermoelectric systems (TE) can directly convert heat to electricity and vice-versa by using semiconductor materials. Therefore, coupling between heat transfer and electric field potential is important to predict the performance of thermoelectric generator (TEG) systems. This paper develops a general two-dimensional numerical model of a TEG system using nanostructured thermoelectric semiconductor materials. A TEG with p-type nanostructured material of Bismuth Antimony Telluride (BiSbTe) and n-type Bismuth Telluride (Bi₂Te₃) with 0.1 vol.% Silicon Carbide (SiC) nanoparticles is considered for performance evaluations. Coupled TE equations with temperature dependant transport properties are used after incorporating Fourier heat conduction, Joule heating, Seebeck effect, Peltier effect, and Thomson effect. The effects of temperature difference between the hot and cold junctions and surface to surrounding convective on different output parameters (e.g., thermal and electric fields, power generation, thermal efficiency, and current) are studied. Selected results obtained from current numerical analysis are compared with the results obtained from analytical model available in the literature. There is a good agreement between the numerical and analytical results. The numerical results show that as temperature difference increases output power and amount of current generated increase. Moreover, it is quite apparent that convective boundary condition deteriorates the performance of TEG.     

Examination of the Cooling Performance of a Two-Stage Thermoelectric Cooler Considering the Thomson Effect

The cooling performance of two-stage thermoelectric coolers test modules for different types (serial, parallel, and separate) are examined in this study. Thomson heat is taken into account in order to discuss its effect on temperature prediction and the internal heat transfer mechanism. Three different Seebeck coefficient models (constant Seebeck model, quadratic polynomial Seebeck model, and log-linear Seebeck model) are examined through experimental investigation and numerical simulation for suitability and accuracy. Results show that the best Seebeck coefficient model is the quadratic polynomial Seebeck model (PSM). Thomson heat can enhance the cooling performance of thermoelectric cooler under specific conditions.     

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.     

CFD simulation of a Gifford–McMahon type pulse tube refrigerator

Pulse tube refrigerator has the advantages of long life and low vibration over the conventional cryocoolers, such as Gifford–McMahon (GM) and Stirling coolers because of the absence of moving parts in low temperature. This paper performs a two-dimensional computational fluid dynamic (CFD) simulation of a Gifford–McMahon type double inlet pulse tube refrigerator (DIPTR), operating under a variety of thermal boundary conditions. A commercial Computational Fluid Dynamics (CFD) software package Fluent 6.1 is used to model the oscillating flow inside a pulse tube refrigerator. Helium is used as working fluid for the entire simulation. The simulated DIPTR consists of a transfer line, an after cooler, a regenerator, a pulse tube, a pair of heat exchangers for cold and hot end, an orifice valve with connecting pipe, a double inlet valve with connecting pipe and a reservoir. The simulation represents fully coupled systems operating in steady-periodic mode. The externally imposed boundary condition is sinusoidal pressure inlet by user defined function at one end of the tube and constant temperature or heat flux boundaries at the external walls of the hot end and cold-end heat exchangers. The general results, such as the cool down behaviors of the system, phase relation between mass flow rate and pressure at pulse tube section and the temperature profile along the wall of the cooler are presented.The simulation shows the minimum decrease in temperature at cold-end heat exchanger for a particular combination of cryocooler assembly. The CFD simulation results are compared with available experimental data. Comparisons show that there is a reasonable agreement between CFD simulation and experimental results.     

Development of cold‐hot water dispenser with thermoelectric module systems

In the present study, the results of a cold‐hot water dispenser with a thermoelectric module system (TMS) are presented. The cold‐hot water dispenser with thermoelectric module system consists of a cold water loop, a hot water loop, a coolant loop, and a thermoelectric module. The thermoelectric cooling and heating modules consist of four and two water blocks, nine and three thermoelectric plates, respectively. The cooling and heating capacities obtained from the cold‐hot water dispenser with TMS are compared with those from a conventional cold‐hot water dispenser with a compression refrigeration system (CRS). As compared with the conventional cold‐hot water dispenser with CRS, the cold‐hot water dispenser with TMS can be operated at the minimum cold water temperature of 10 to 13°C and the maximum hot water temperature of 65°C. The obtained results are expected provide guidelines to design cold‐hot water dispensers with TMS.     

低温下半导体热电材料发电性能的初步研究

为了对液化天然气(LNG)的冷能回收利用，对半导体热电材料在低温下的发电性能进行了实验研究，得到了这种热电材料的发电性能随冷端温度变化的关系，并发现在热端温度不变的情况下，冷端温度在特定温度下热电堆的输出电动势达到最大值。运用数值方法理论计算了该热电堆在实验所处条件下的输出电动势。并将计算值与实验值进行了对比。     

An Investigation of the Thermal Stresses Induced in a Thin-Film Thermoelectric Cooler

This work aims at investigating the thermal stresses induced within a four-layered thin-film thermoelectric cooler. The one-dimensional (1D) temperature and thermal-stress distributions are firstly analyzed under the consideration of Joule heating, the conduction heat transfer as well as Thomson heating. Followed are two-dimensional (2D) calculations of the thermal stresses with the commercial software ANSYS. The validity of the 1D analytical model is then examined by a comparison of its predicted thermal stresses with the numerical ones obtained from the 2D model. In the 2D model, the thermoelectric element becomes curved due to the shrinkage and the fixed boundary conditions. The latter also causes huge values and rapid changes of thermal stresses near the ends. In the middle portion of the thermoelectric element where the thermal effect dominates, the thermal stresses predicted by the 1D model are not much different from those computed from the 2D model. Quantitative differences arise from the fact that the 1D model does not count the stresses induced by the non-zero Poisson's ratios. In addition, the normal-stress distributions are pretty uniform across the layer thickness (the variation is less than 1MPa within each layer in the worst case). These results verify the possibility of using the 1D model for a preliminary estimate of the thermal stresses induced within the layered thin-film thermoelectric element. The 1D model nonetheless fails to capture the behaviors near the ends of the thermoelectric element.