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.     

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.     

The influence of the Thomson effect on the performance of a thermoelectric cooler

The temperature distribution of a thermoelectric cooler under the influence of the Thomson effect, the Joule heating, the Fourier’s heat conduction, and the radiation and convection heat transfer is derived. The influence of the Thomson effect on the temperature profiles, on the fraction of the Joule’s heat that flows back to the low-temperature side, and consequently on the maximum attainable temperature difference and the maximum allowable heat load are emphasized and explored. The results suggest that the cooling efficiency of a thermoelectric cooler can be improved not only by increasing the figure-of-merit of the thermoelectric materials but also by taking advantage of the Thomson effect. A possible development direction for the thermoelectric materials is thus given.     

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.     

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.     

Characterization of a thermoelectric cooler based thermal management system under different operating conditions

The performance of a thermoelectric cooler (TEC) based thermal management system for an electronic packaging design that operates under a range of ambient conditions and system loads is examined using a standard model for the TEC and a thermal resistance network for the other components. Experiments were performed and it was found that the model predictions were in good agreement with the experimental results. An operating envelope is developed to characterize the TEC based thermal management system for peak and off peak operating conditions. Parametric studies were performed to analyze the effect of the number of TEC module(s) in the system, geometric factor of the thermo-elements and the cold to hot side thermal resistances on the system performance. The results showed that there is a tradeoff between the extent of off peak heat fluxes and ambient temperatures when the system can be operated at a low power penalty region and the maximum capacity of the system.     

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.     

Thermodynamic modelling of a solid state thermoelectric cooling device: Temperature–entropy analysis

This article presents the temperature–entropy analysis, where the Thomson effect bridges the Joule heat and the Fourier heat across the thermoelectric elements of a thermoelectric cooling cycle to describe the principal energy flows and performance bottlenecks or dissipations. Starting from the principles of thermodynamics of thermoelectricity, differential governing equations describing the energy and entropy flows of the thermoelectric element are discussed. The temperature–entropy (T–S) profile in a single Peltier element is pictured for temperature dependent Seebeck coefficient and illustrated with data from commercial available thermoelectric cooler.     

包覆吸水膜的管式蒸发散热器性能的实验研究

应用间接蒸发散热的原理,在空调冷凝器表面包覆吸水膜,利用水蒸发带走热量.这样蒸发面积达到了最大值,并且能够通过毛细力自动补充蒸发的水分.空调冷凝器中热工质的温度和热容比间接散热器中的一次空气大,能够提高蒸发表面温度,提高蒸发量,进而提高散热效率.通过对通有热水的表面覆盖吸水纸膜的单铜管的实验研究,得出了该方式的传热系数以及水膜的,导热系数,证明了该散热方式较空调冷凝器空气强制对流和其它蒸发散热方式的优势.     

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.     

包覆吸水膜的管式蒸发散热器性能的实验研究

应用间接蒸发散热的原理,在空调冷凝器表面包覆吸水膜,利用水蒸发带走热量.这样蒸发面积达到了最大值,并且能够通过毛细力自动补充蒸发的水分.空调冷凝器中热工质的温度和热容比间接散热器中的一次空气大,能够提高蒸发表面温度,提高蒸发量,进而提高散热效率.通过对通有热水的表面覆盖吸水纸膜的单铜管的实验研究,得出了该方式的传热系数以及水膜的导热系数,证明了该散热方式较空调冷凝器空气强制对流和其它蒸发散热方式的优势.     

Heat transfer performance of thermoelectric cooling integrated with wavy channel heat sink with different magnetic distances

Thermoelectric cooling (TEC) reverses the electrical energy to temperature caused by the Peltier effect, where a temperature difference occurs between two conductors, that is, hot and cold junctions. This article presents the enhanced heat transfer of a TEC module using a TEC1-12710 model integrated with a wavy channel heat sink using ferrofluid as a coolant under continuous and pulsating flows, where the differences in the distance of the magnetic field are considered. Square permanent magnets measuring 30 mm × 20 mm × 4 mm (width × length × height) are used to transmit a magnetic field to the heat sink and then tested under a magnetic distance of 10–30 mm. The test is performed at a water flow rate from 0.0083 to 0.028 kg/s and supplied with a constant TEC voltage of 12 V. By applying a magnetic field to the TEC module with a magnetic distance of 20 mm and a ferrofluid concentration ratio of 0.015%, the cooling efficiency increases by approximately 18.64%. Hence, using pulsating flow may improve thermal efficiency by approximately 23%. The results show an exponential increase in the cooling efficiency when both passive and active cooling techniques are used.     

On the ‘reaction in chain’ in the thermoelectric conversion of energy through thermocouples: Theoretical implications of the phenomenon

It is shown, experimentally, that in certain initial conditions of temperature, and for certain parameters, a ‘reaction in chain’ may start in a thermocouple, and produce a ‘permanent regime’, through which heat from a single course is converted into electrical energy. It is shown, theoretically, that the phenomenon occurs when compensation of heat losses due to thermal conduction, through Peltier and Thomson heat is realized, so that the efficiency is affected only by the Joule effect, and may attain much higher values than through conventional operation of these thermoelectric devices, conventional peration requiring two heat sources, a hot and a cold one.     

A novel hybrid photovoltaics/thermoelectric cooler distillation system

In this paper, a novel hybrid photovoltaics/thermoelectric cooler (PV/TEC) distillation system has been introduced. The limitation for distillation system working under hot arid climate is the heat removal required for the condensation process. The novelty of the proposed system is that it utilizes TEC to improve the condensation process. The proposed system composed of two porous layers separated by an air gap. The upper porous layer is installed at the back of a PV module; the lower porous layer is installed at the top of a TEC modules layer. This system can provide the demand of electricity and potable water for those people who live in rural areas (using one unit or more). The proposed system prevents PV module from overheating and actively enhancing the condensation process of the evaporated water. A steady‐state mathematical model has been proposed. This model was solved and simulated by equation solver software. Wind speed, solar radiation, and ambient temperature effect on the system performance were simulated and discussed. Results showed that the maximum productivity of the system reached an ambient temperature of 298 K, solar radiation of 1000 W/m² and wind speed of 5.5 m/s. The maximum yield of the system was 4.2 kg of distilled water per day with a net electrical output power of 73 W with an overall efficiency of 57.9% and PV cell efficiency of 12.32%.     

NONEQUILIBRIUM ELECTRONS AND PHONONS IN THIN FILM THERMIONIC COOLERS

The effect of hot carriers on the cooling performance of single barrier heterostructure thermionic coolers is studied theoretically. By studying nonequilibrium characteristics of electrons and phonons in the device, fundamental limitation in the cooler performance is analyzed. In particular, we investigated the effect of various boundary conditions at heterojunctions on the electron and phonon temperature distributions. These boundary conditions have a strong impact on the device operation. Thin film devices under high voltage or in high current density are examples of situations where electrons and phonons are not in equilibrium and a coupled transport equation should be solved for an accurate analysis. In a thermoelectric/thermionic device one measures the lattice temperature while cooling occurs in the electron gas. Although at low currents electrons and phonons have the same equilibrium temperature, by increasing the current they may have different temperatures, which can lead to a reduction in cooling power density. We will show that in materials with faster electron energy relaxation, that is, higher electron-phonon coupling, thermionic cooling performance is less affected by high current injection and that recently demonstrated SiGe thin film coolers are not limited by hot carrier effects.     

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.     

Development of an energy-saving module via combination of solar cells and thermoelectric coolers for green building applications

A solar-driven thermoelectric cooling module with a waste heat regeneration unit designed for green building applications is investigated in this paper. The waste heat regeneration unit consisting of two parallel copper plates and a water channel with staggered fins is installed between the solar cells and the thermoelectric cooler. The useless solar energy from the solar cells and the heat dissipated from the thermoelectric cooler can both be removed by the cooling water such that the performance of the cooling module is elevated. Moreover, it makes engineering sense to take advantage of the hot water produced by the waste heat regeneration unit during the daytime. Experiments are conducted to investigate the cooling efficiency of the module. Results show that the performance of the combined module is increased by increasing the flow rate of the cooling water flowing into the heat regeneration water channel due to the reductions of the solar cell temperature and the hot side temperature of the thermoelectric coolers. The combined module is tested in the applications in a model house. It is found that the present approach is able to produce a 16.2 °C temperature difference between the ambient temperature and the air temperature in the model house.     

A solar cavity-receiver packed with an array of thermoelectric converter modules

We report on the design of a solar cavity-receiver packed with an array of thermoelectric converter (TEC) modules, which enables efficient capture of concentrated solar radiation entering through a small aperture. A 1 kW demonstrator (proof-of-concept) containing 18 TEC modules, each consisting of Al₂O₃ absorber/cooler plates, and p-type La_1.98Sr_0.02CuO₄ and n-type CaMn_0.98Nb_0.02O₃ thermoelements, was subjected to peak solar concentration ratios exceeding 600 suns over its aperture. The TEC modules were operated at 900 K on the hot side and 300 K on the cold side. The measured solar-to-electrical energy conversion efficiency was twice that of a directly irradiated TEC module. A heat transfer model was formulated to simulate the solar cavity-receiver system and experimentally validated in terms of open-circuit voltages measured as a function of the mean solar concentration ratio. Vis-à-vis a directly irradiated TEC module, the cavity configuration enabled a reduction of the re-radiation losses from 60% to 4% of the solar radiative power input. Theoretical considerations for TEC with figure-of-merit higher than 1 indicate the potential of reaching solar-to-electrical energy conversion efficiencies exceeding 11%.     

Numerical study on convective flow in a three-dimensional enclosure with hot solid body and discrete cooling

The aim of the present numerical study is to analyze the effect of cooler location and aspect ratio and position of the hot solid body inside the enclosure on three-dimensional natural convection flow in a cubical enclosure. The cooler and heater positions and aspect ratio of the heater in a cavity are examined under different combinations of partially cooling vertical sidewalls and, hot solid body in the cubical cavity. That is, (i) different cooler locations with a fixed size of the hot solid body, and, (ii) centrally located hot solid body with different aspect ratio. The three-dimensional convective flow and thermal arrangements in the enclosure are analyzed using the distribution of streamlines, isosurfaces, and Nusselt number. It is found that the cooler location and aspect ratio of hot solid body play a key role on convective cooling and energy transport inside the enclosure. The unit aspect ratio of hot solid body provides higher energy transport inside the enclosure for all cooler positions.