Performance Analysis of a Thermoelectric Solar Collector Integrated with a Heat Pump

A novel heat pump system is proposed. A thermoelectric solar collector was coupled to a solar-assisted heat pump (TESC-HP) to work as an evaporator. The cooling effect of the system’s refrigerant allowed the cold side of the system’s thermoelectric modules to work at lower temperature, improving the conversion efficiency. The TESC-HP system mainly consisted of transparent glass, an air gap, an absorber plate that acted as a direct expansion-type collector/evaporator, an R-134a piston-type hermetic compressor, a water-cooled plate-type condenser, thermoelectric modules, and a water storage tank. Test results indicated that the TESC-HP has better coefficient of performance (COP) and conversion efficiency than the separate units. For the meteorological conditions in Mahasarakham, the COP of the TESC-HP system can reach 5.48 when the average temperature of 100 L of water is increased from 28°C to 40°C in 60 min with average ambient temperature of 32.5°C and average solar intensity of 815 W/m², whereas the conversion efficiency of the TE power generator was around 2.03%.     

热回收在全新风除湿机中的节能研究

分析了GB/T20109-2006所述全新风除湿机节能的5个方面:1)冷凝热回收.2)室内回风热回收.3)冷凝水冷回收.4)处理后新风冷回收.5)新风热回收.通过对典型案例做深入探讨发现:采用板翅式热回收器或热管换热器对新风处理后新风进行冷回收预冷新风,能够降低制冷系统冷负荷20％～30％,显著提高全新风除湿机的单位输入功率除湿量.     

Performance Improvement of a Power Conversion Module by Liquid Micro-Jet Impingement Cooling

Liquid micro-jet array impingement cooling of a power conversion module with 12 power switching devices (six insulated gate bipolar transistors and six diodes) is investigated. The 1200-V/150-A module converts dc input power to variable frequency, variable voltage three-phase ac output to drive a 50HP three-phase induction motor. The silicon devices are attached to a packaging layer [direct bonded copper (DBC)], which in turn is soldered to a metal base plate. DI water micro-jet array impinges on the base plate of the module targeted at the footprint area of the devices. Although the high heat flux cooling capability of liquid impingement is a well-established finding, the impact of its practical implementation in power systems has never been addressed. This paper presents the first one-to-one comparison of liquid micro-jet array impingement cooling (JAIC) with the traditional methods, such as air-cooling over finned heat sink or liquid flow in multi-pass cold plate. Results show that compared to the conventional cooling methods, JAIC can significantly enhance the module output power. If the output power is maintained constant, the device temperature can be reduced drastically by JAIC. Furthermore, jet impingement provides uniform cooling for multiple devices placed over a large area, thereby reducing non-uniformity of temperature among the devices. The reduction in device temperature, both its absolute value and the non-uniformity, implies multi-fold increase in module reliability. The results thus illustrate the importance of efficient thermal management technique for compact and reliable power conversion application     

某组合式冷板的结构设计及制造工艺

针对某相控阵面天线单元间距小、TR组件与天线单元硬线连接、TR组件热流密度高的特点,提出了一种组合式冷板的解决方案.将两块冷板有机组合在一起,解决了上述结构特点引起的单块冷板壁厚薄、刚度差、水接头安装困难等问题;单块冷板内部采用小截面流道增加换热系数,解决了高热流密度TR组件散热问题.还就组合式冷板内部流道成型、外形加...     

A Four-Quadrant Operation Diagram for Thermoelectric Modules in Heating–Cooling Mode and Generating Mode

The operation of a thermoelectric module in heating–cooling mode, generating mode, and regenerating mode can be discussed in terms of power, cooling load, and current. A direct current machine in motoring mode and generating mode and an induction motor in motoring mode and regenerating mode are analogous to thermoelectric modules. Therefore, the first objective of this work is to present the four-quadrant (4-Q) operation diagram and the 4-Q equivalent circuits of thermoelectric modules in heating–cooling mode and generating mode. The second objective is to present the cooling and regenerating curves of a thermoelectric module in cooling mode and regenerating mode. The curves are composed from the cooling powers and the generating powers, the input and output current, the thermal resistance of the heat exchanger, and the different temperatures that exist between the hot and cold sides of the thermoelectric module. The methodology used to present the data involved drawing analogies between the mechanical system, the electrical system, and the thermal system; an experimental setup was also used. The experimental setup was built to test a thermoelectric module (TE₂) in cooling mode and regenerating mode under conditions in which it was necessary to control the different temperatures on the hot and cold sides of TE₂. Two thermoelectric modules were used to control the temperature. The cold side was controlled by a thermoelectric module labeled TE₁, whereas the hot side was controlled by a second thermoelectric module labeled TE₃. The results include the power, the cooling load, and the current of the thermoelectric module, which are analogous to the torque, the power, the speed, and the slip speed of a direct current machine and an induction motor. This 4-Q operation diagram, the 4-Q equivalent circuits, and the cooling and regenerating curves of the thermoelectric module can be used to analyze the bidirectional current and to select appropriate operating conditions in the cooling and regenerating modes.     

利用冷却塔供冷实践初探

介绍冷却塔进行节能供冷的工作过程,通过对工程实例中发现的一些问题进行分析,提出利用开式冷却塔加板式热交换器并联于制冷机的冬季供冷系统是较经济实用的形式,且必须同时注意冷却塔冬季的热工曲线、冷却塔供冷与制冷机供冷工况切换、冷水机组配置、冷却水系统水处理问题等。     

某办公楼中央空调节能措施的经济效益分析

通过对具体工程实例分析和论述,得出中央空调的节能可以通过提高制冷主机冷凝器的换热效率来提高主机在常年运行时高效节能,并利用冷凝热回收技术来回收原来冷却塔带走的热量,这样既可得到免费热水,又可以减少冷却塔的排放热量,利用新风全热换热器来回收排风中的冷量,并通过空调自动控制系统,在中央空调各种不同工况时,进行优化控制,实现整个系统的节能运行,从而达到降低整个中央空调系统能耗的目的。     

Experimental investigation of a Peltier cells cooling system for a Switch-Mode Power Supply

The results are presented of an experimental investigation in a liquid cooled Switch-Mode Power Supply (SMPS). The target is a quantitative analysis of the performance of a cooling system designed to dissipate the heat generated by the active and passive electronic components of this SMPS, in order to limit its maximum operational temperature. The active components are cooled with a liquid cold plate. The passive components are cooled with an air flow. The temperature of this airflow is controlled with Peltier cells exchanging heat with the cold plate. Measurements are made of temperature and of electric efficiency of the SMPS. The cooling system is placed in an experimental tool where it is possible to measure and control the cooling liquid flow. A detailed analysis of the thermal behaviour of this cooling system is given. Finally, the practical significance of the problem is discussed.     

Improvement of Cooling Performance of a Thermoelectric Air Cooling System Using a Vapor Chamber Heat Sink

Since vapor chambers exhibit excellent thermal performance, they are suited to use as the basis of a heat sink. This work presents the results of tests carried out to investigate the potential application of a vapor chamber heat sink for improving the cooling performance of a thermoelectric (TE) air cooling system. To this end, two sets of TE air coolers were constructed. The cold side of the TE module of both sets was fixed to a conventional plate-fin heat sink. The hot side of one set was fixed to a vapor chamber heat sink, whereas the other set was fixed to a conventional plate-fin heat sink. The effects of air flow rate and electric current supplied to the TE module on the cooling performance were considered. Experimental data were compared with corresponding data for a conventional plate-fin heat sink. It also has been experimentally proven that the use of a vapor chamber heat sink increases the coefficient of performance (COP) by up to 34.2%.     

Remote heat sink concept for high power heat rejection

This paper addresses heat rejection concepts intended to reject 100 W (or more) from the CPU of a desktop computer or server. A high-performance, air-cooled thermo-syphon heat rejection system is described that meets the goal. This concept is believed to represent the highest performance that has been reported for an air-cooled heat rejection system. A working fluid is boiled in a small chamber mounted on the CPU, and the vapor is condensed in the tubes of the remotely located air-cooled condenser. The air-cooled heat exchanger provides much higher performance than is obtainable with conventional "round-tube" technology. The boiling design is compared with other systems that have been proposed, e.g., liquid or two-phase cooling in micro-channels, and is shown to provide better performance. The heat exchange technology may also be applied to refrigerated cooling.     

固态T/ R组件冷板扩展热阻分析与优化准则

电子设备的功率器件和散热冷板之间由于存在面积差异,产生扩展热阻,在高热流密度条件下(>100 W/ cm2 )温升效应尤为明显。文中通过对固态T/ R组件冷板扩展热阻的简化近似解的分析计算,研究了冷板的导热系数、厚度、半径、对流换热系数等参数扩展热阻的影响规律,发现冷板存在厚度和半径的工程最优值使得扩展热阻或总热阻最小,建立了相应的尺寸优化准则,然后通过计算流体力学(computiatonal fluid dynamics,CFD)数值试验进行了计算验证,结果表明CFD解和简化解结果一致,研究结论可用于指导冷板或热扩展板的工程设计。     

Encapsulated Thermoelectric Modules for Advanced Thermoelectric Systems

An encapsulated thermoelectric (TE) module consists of a vacuum-tight stainless-steel container in which an SiGe or BiTe TE module is encapsulated. This construction enables maximum performance and durability because: the thermal expansion mismatch between the hot and cold sides of the container can be accommodated by a sliding sheet in the container; the TE module inside is always kept in a vacuum environment, therefore no oxidation can occur; and the pressure difference between the inside and outside of the container reduces thermal contact resistance inside the container. Our encapsulated SiGe module features higher operating temperature—up to 650°C for both hot and cold sides. Other high-temperature modules and conventional BiTe modules, including both-sides and one-side skeleton types, have been encapsulated. Several variants of the encapsulated module are available. Encapsulated thermoelectric modules with integrated coolers contain cooling panels through which water can pass. If the module hot side is heated by a radiating heat source (radiation coupling) or convection of a hot gas or fluid (convection coupling), no pressing force on the module is necessary. It therefore features minimum contact resistance with the cooling duct, because no pressure is applied, maximum TE power, and minimum installation cost. Another, larger, variant is a quadruple flexible container in which four modules (each of maximum size 40 mm × 40 mm) are encapsulated. These encapsulated modules were used in a powder metallurgy furnace and were in use for more than 3000 h. Application to cryogenic temperatures simulating the liquid nitrogen gas vaporizer has been also attempted.     

Reliability enhancement by integrated liquid cooling in power IGBT modules for hybrid and electric vehicles

Insulated Gate Bipolar Transistor (IGBT) modules in power train system of Hybrid and Electric Vehicles (HEV/EV) are working in harsh environment and high reliability and long lifetime are required. In this work, reliability enhancement by integrated liquid cooling structure in HEV/EV IGBT module is investigated. The thermal resistance of junction to heat sink can be reduced more than 50% by direct liquid cooling as eliminating thermal grease layer, so both active and passive temperature swings decrease significantly which will enhance module reliability and lifetime. The lifetime of modules with conventional and integrated liquid cooling structures are estimated under mission of standard driving cycles. We found that lifetime is prolonged obviously by direct cooling pin–fin base plate, and the compact module also makes the application power system simple and reliable.     

天线微小通道冷板金属3D打印成型工艺研究

微小通道液冷散热技术是近年来电子设备热设计研究的热点,已逐渐用于高热流密度电子设备的散热.然而真正实现工程应用仍存在诸多困难,主要原因是与之匹配的工艺技术尚不完善.研究了天线铝合金微小通道冷板的3D打印技术,介绍了工艺流程,加工了多个小尺寸芯片和大尺寸天线阵面的微小通道冷板.经分析,3 D打印基本能实现复杂拓扑结构微小通道冷板的成型,但仍存在通道堵塞、表面凹坑和翘曲等问题.     

Tm:YLF激光器温度场分布计算与实验

设计并研究了双晶四端泵浦的Tm:YLF激光器。利用Ansys软件中的稳态热分析模块计算了散热底板水通道在热交换系数分别为1000W/（m2℃）、4 000W/（m2℃）、8000W/（m2℃）和15000W/（m2℃）以及采用TEC制冷时对应的晶体夹具及散热底板的温度分布。根据计算结果,在采用水温16℃中等强制对流及以上时与TEC制冷控温18~20℃时对Tm:YLF晶体冷却效果近似,可近似等效于TEC制冷。根据模拟计算的结果,设计了可用光纤耦合半导体激光器泵浦的U型腔结构Tm:YLF激光器。在采用16℃冷却水直接冷却晶体夹具时,单晶双端泵浦和双晶四端泵浦的Tm:YLF输出功率分别达到了25。9W和46W的激光输出,对应的斜效率分别为40。7%和37。1%。在实验过程中,晶体夹具未出现温度过高。实验结果说明设计的直接传导冷却系统可有效地冷却泵浦功率在140W时的双晶四端泵浦结构Tm:YLF晶体。     

Thermal module design and analysis of a 230 W LED illumination lamp under three incline angles

This study investigates on the thermal performance of the 230 W LED projection lamp cooling module in the natural convection and modifies fin parameters including fin spacing, height and thickness and LED base plates materials to achieve optimal heat dissipation and performance through experimental and simulation analysis. Results show that the best values of cooling module are 1.1 mm aluminum fin thickness, 7.5 mm pitch, and 31 mm height and can effectively reduce the LED junction temperature under 75 °C at 90° incline angle. The impact of the incline angle of the LED vapor chamber-based plate to the thermal performance of the present cooling module should be assessed before such a structure of vapor chamber cooling system is used to cool high power LED system. And the experimental results are in good agreement with the theoretical results, whose calculating error is not more than ±10%. A novel comparative process of 230 W LED projection light is developed.     

Active control of boundary conditions for dynamic thermal characterization of electronic components

This paper presents a practical realization of the system for the active control of boundary conditions during the dynamic thermal characterization of electronic components. The control of boundary conditions is exercised by the dual cold plate cooling assembly equipped with Peltier thermo-electric modules and an appropriate control circuit. Additionally, a tensometer bridge is used to assure the parallel alignment of surfaces and to adjust the contact thermal resistance between particular layers. The operation of the entire control system is illustrated based on a practical example where Peltier module currents are adjusted in real time so as to impose isothermal or constant heat flux boundary conditions on a power diode package surface during measurements performed with time varying power dissipation in the device.     

Kälteerzeugung aus Niedertemperaturabwärme

The technical feasibility of utilising 70–90°C waste heat for the production of 0–4°C cold using ejector technology and water as sole refrigerant was successfully tested at a 10 kW pilot installation. Achieving high values for the condenser temperature is critical for process stability at increased ambient temperatures and depends on the specific consumption of motive steam. At the pilot plant the stability limit for 90°C of the motive steam temperature was found to be 29.5°C. Such high condenser temperature values open the possibility to reject condenser heat against air all through the year via a cooling tower. The coefficient of performance (COP) depends on the motive steam temperature and achieved values of 0.23 up to 0.42 at the test rig. Currently the economic competitiveness of the technology is investigated for application in case of milk production at large scale.     

Experimental study of microrectangular groove structure covered with multi mesh layers on performance of flat plate heat pipe for LED lighting module

The paper presents a novel concept for a coronary-stent-like model to solve the problem of compactness between wick and copper mesh, which can enhance the performance of the hybrid structure flat plate heat pipe (FPHP) of LED lighting modules. The various wick structures combine axial rectangular grooved structures, manufactured in aluminum extraction, and the concept of a coronary-stent-like model, which provides a supportive copper mesh and wick structure. In this study, the performance of FPHP was experimentally measured at different inclination angles and heating areas. The axial rectangular groove structure and copper mesh layer structures have different permeabilities and capillary pumping forces, and combining these two structures could be beneficial for pumping the required operational fluid across the axial groove structure and from the condenser to the evaporator under different inclinations of the flat plate heat pipe. The exterior wall temperature of the FPHP was measured to evaluate the thermal resistance and vapor heat transfer coefficient at the condenser and evaporator for 31 × 31 and 10 × 10 mm² heating areas. The experimental result showed that the FPHP has better performance in both the junction temperature of the LED light module and the uniformity of the substructure temperature. The highest FPHP temperature was decreased by 28%, as compared to a commercial substrate. In addition, a 200 W LED light module, running for 9 h with FPHP, maintained luminance at about 2080 lux due to its low thermal resistance and high capillary force.     

Thin Thermoelectric Generator System for Body Energy Harvesting

Wearable thermoelectric generators (TEGs) harvest thermal energy generated by the body to generate useful electricity. The performance of these systems is limited by (1) the small working temperature differential between the body and ambient, (2) the desire to use natural air convection cooling on the cold side of the generator, and (3) the requirement for thin, lightweight systems that are comfortable for long-term use. Our work has focused on the design of the heat transfer system as part of the overall thermoelectric (TE) system. In particular, the small heat transfer coefficient for natural air convection results in a module thermal impedance that is smaller than that of the heat sink. In this heat-sink-limited regime, the thermal resistance of the generator should be optimized to match that of the heat sink to achieve the best performance. In addition, we have designed flat (1?mm thickness) copper heat spreaders to realize performance surpassing splayed pin heat sinks. Two-dimensional (2-D) heat spreading exploits the large surface area available in a wristband and allows patterned copper to efficiently cool the TE. A direct current (DC)/DC converter is integrated on the wristband. The system generates up to 28.5???W/cm² before the converter and 8.6???W/cm² after the converter, with 30% efficiency. It generates output of 4.15?V with overall thickness under 5?mm.