LED灯具石墨散热器结构优化设计

以朗硕LS-QL0X灯具散热器结构为参考模型,研究了石墨散热器替代铝散热器后灯具的散热状况,讨论了石墨散热器翅片长度、翅片角度、翅片厚度及散热器导热系数对LED灯具散热状况的影响,并在此基础上对散热器结构进行了正交优化分析。仿真结果表明,灯具散热影响因素大小的顺序为散热器导热系数>翅片角度>翅片长度>翅片厚度,最优仿真结果是散热器导热系数为50W/(m·℃)、翅片角度为7°、翅片长度为19mm、翅片厚度为0.7mm,优化后芯片最高温度为37.52℃,比优化前温度下降了20.6%。优化后的LED石墨散热器灯具的最高温度比铝散热器灯具芯片仅高出2.23℃,质量却比铝散热器减少了25.9%。研究表明优化后的石墨散热器可以满足LED灯具的散热要求,且能有效减轻灯具的整体质量。     

出水方式对水冷芯片散热器换热性能影响

本文采用数值模拟的方法研究了4种不同出流方式的散热器在不同冷却水流量下的换热效果,散热器冷却水进口均为中间喷射式。A、B型散热器均设置一个出口,分别位于散热器的一角及一边的中心;C、D型散热器均设置4个出口,分别位于散热器的四角及四边的中心。对比验证数值模拟结果与实验结果,得到数值模拟相对误差不高于7%。分析散热器的传热系数、速度分布、压力损失、综合系数,结果表明:4出口散热器传热系数不及单出口换热器,但流动阻力较小,散热器综合系数较高,C、D型散热器综合系数较A、B型散热器提高了50%以上,且具有更好的均温性,因此喷射流4出口散热器具有较好的换热和流动效果。     

某电源模块自然冷却散热器的优化设计

以某功率为70W的电源模块散热器为例,用传统的热设计理论及经验公式进行散热设计,初步确定散热器结构要素。应用热分析软件Icepak对散热器各参数进行了优化设计,并且分析数据,得出自然冷却散热器设计的一些规律。     

多芯片平板热管散热器性能的实验研究

设计了一种新型多芯片平板热管散热器,通过测试模拟芯片的表面温度,对散热器在不同空气流速、芯片数目及位置和加热功率下的散热性能进行了实验研究。测试结果表明:在环境温度为20℃、芯片表面温度控制在80℃的条件下,散热器水平使用时,单芯片、双芯片和三芯片的最大散热能力分别为310W,390W和500W;散热器竖直使用时,其最大散热能力分别为275W,408W,500W。由此得出,多芯片平板热管散热器的散热性能较单芯片散热器具有更大优势。实验结论与平板热管的热扩散效果吻合良好,而且符合现代电子器件散热的要求。     

数据中心服务器CPU水冷散热器的优化设计

如何强化水冷散热器的散热性能以维持计算机芯片的正常工作温度,成为数据中心服务器冷却问题研究的焦点。本文以水冷散热装置的综合系数F和芯片温度为目标参数,采用正交试验法对散热器的基板厚度、槽道(位于基板)位置、槽道数量和槽道宽度进行了优化设计,针对不同的需求得到最佳的组合为F指数和T指数散热器。结果表明:当冷却水体积流量为0.4 L/min,进口温度为20℃时,T指数和F指数散热器的散热极限热流密度分别为78 W/cm~2,65 W/cm~2。并从散热器底板的温度分布和总热阻两个方面分析其散热性能,T指数散热器的底板温度梯度和总热阻均低于F指数散热器,表明T指数散热器优于F指数散热器;但是在不同的体积流量下,F指数散热器的压降要低于T指数散热器。芯片在热流密度为65 W/cm~2以下时,F指数散热器槽道内流体的流动效果较好而且可满足数据中心服务器的散热要求,而更高的热流密度应选用T指数散热器进行冷却。     

公交客车空调铜、铝翅片散热器抑菌性能对比研究

通过公交客车空调铜、铝翅片散热器抑菌性能的比对、分析,比较车载空调铜制散热器与传统铝制散热器翅片表面的微生物水平及通过空调系统送风对车厢内空气质量的影响。在公交客车空调未投入使用期及投入使用末期对公交客车送风口、呼吸带空气及空调散热器翅片进行微生物采样检验,以公交客车停车场大气作为对照。与铝相比,铜作为表面材料能显著降低翅片表面细菌总数和真菌总数。空调采用铜翅片散热器可降低呼吸带空气中细菌总数的水平,具有显著的抑菌性能。     

成组散热器噪声控制

结合工程实例,分析了某冷藏设备室外成组散热器噪声超标及散热不畅所引起的工作不正常原因.结合成组散热器的特点及现场施工条件设计了散热器的消声结构,通过在出风口加消声管道和在进风口加装隔声和消声结构的方式,获得8～12dB的降噪量.既保证了噪声的达标排放,同时解决了散热器的散热不良问题.     

用于地铁变流器的平板微热管散热器数值模拟与实验研究

本文将平板微热管应用于地铁变流器IGBT散热器中,设计了一种新型平板微热管散热器,通过对物理模型的合理简化,建立数学模型,利用ICEPAK软件对传统翅片散热器和平板微热管散热器进行数值模拟对比,并通过实验验证计算的正确性。研究结果表明:平板微热管散热器极大提升了散热器散热效率;在极限功率工作条件下,平板微热管散热器的最高温度为70. 27℃,比传统翅片散热器降低了25. 79℃;理论计算得到IGBT结温为110. 23℃,满足IGBT工作要求;数值模拟结果与实验结果基本吻合,最大温度误差为7. 07%。     

民用建筑热水采暖系统运行中常见问题分析

目前民用建筑采暖方式多为散热器系统,且层数较多,因此在使用过程中经常出现个别楼层散热器不热现象,现对散热器不热问题进行原因分析如下。     

液冷散热器性能测试系统的研制

热阻和流阻是评价液冷散热器性能的主要参数。该文研制一套高精度的液冷散热器性能测试系统,由液冷散热器的进口流体温度控制单元、进口流量控制单元、模拟热源控制单元及测量单元组成。在台面温度测量方面,由于现有标准(GB/T 8446.2—2004)规定的温度测点位置不适应液冷散热器热阻测量,提出改进方法。开发相应的测试软件,具有系统控制、数据实时采集、测试报告输出等功能。并对某型号液冷散热器进行实验研究,通过实验数据对系统的测量不确定度进行分析,流阻测试的不确定度为0.48%,热阻测试的不确定度为2.4%。验证系统用于散热器流阻热阻测试的可靠性。     

姿控飞轮电控系统共模辐射分析与抑制

 为降低飞轮电控系统对其他星载电子设备的电磁干扰,以PWM全桥电路共模辐射源为研究对象,重点分析由开关管和散热片协同导致的共模辐射．建立铝制带鳍散热片计算模型,应用有限元数值计算法分析散热器能量耦合及辐射发射机理,以屏蔽作为主要抑制手段,研究屏蔽板尺寸、放置位置及通风孔对共模辐射抑制效应,并进一步提出屏蔽板改进结构．计算结果表明：使用2块屏蔽板在正确放置时就可有效抑制辐射,且屏蔽板越长,对共模辐射抑制效果越好;屏蔽板上有孔缝存在,对应的辐射就要比无孔时高,开孔个数本身对辐射的影响并不大．改进后的结构对共模辐射抑制效果更优于原结构,尤其体现在3.9 GHz窄频带范围内．     

烧结式微热管的工质灌注、抽真空与封接

目前微电子与光电子芯片对散热要求日益增高,烧结式微热管已经成为其理想的散热元件,对微热管进行快速抽真空,使微热管中的工质量与真空度符合要求,是决定其制造质量与成本的重要因素。通过对微热管的工作原理及其抽真空-工质灌注-冷焊的制造方法进行分析,提出一种分别采用工质冻结-抽真空-冷焊法与二次除气-冷焊法对烧结式微热管进行抽真空的方法。大量的实验表明,采用所提出的制造方法不仅可以保证微热管中工质量与真空度达到要求,而且抽真空的时间大约比原有方法节省了2/3,具有很好的传热性能。     

Development of a switchless sorption compressor for the cryogenic refrigeration within the METIS instrument: Part II. Experimental demonstration

Due to its vibration-free feature, sorption-based refrigeration technology has been proposed for the cryogenic cooling of the Mid-infrared E-ELT Imager and Spectrograph (METIS) instrument in the European Extremely Large Telescope. Sorption compressor is the most critical component in the METIS sorption refrigerator. A switchless sorption compressor has been designed for replacing the conventional gas-gap heat switch design. In this paper, the METIS switchless sorption compressor is validated in an experimental setup with a down-scaled version. The detailed design of the sorption compressor is introduced and the experimental setup is described. Then, the experimental procedures and results are discussed, including single-cell operation, multi-cell operation, and verification of the effects of the aluminum-foil inserts, the cycle time and the heat-sink temperature on the compressor performance. Finally, the experimental result showed good agreement with the simulations, and the deviation from the simulation to the measurement is caused by the model input inaccuracy.     

Strain Field Analysis in Electronic Components by ESPI: Bad Thermal Contact and Damage Evaluation

Designing electronic components and devices is a complex task that must include also considerations about thermo-mechanical behavior of the component itself. This aspect, in fact, can affect the reliability of the device as a consequence of the thermal stresses that are introduced in the component while it is working. Stress concentration can arise, in fact, due to different thermal expansion coefficients of the materials involved. Determining the thermo-mechanical response by numerically methods is not simple and not always possible so that experimental methods are preferable. In this paper, specifically, the electronic speckle pattern interferometry technique was adopted to measure full-field strain of the component during exercise. By using an optical technique it is possible to get information about the behavior of the component without being in contact with the component itself so that the dissipation coefficient is not altered. The system was able to detect gradients of deformation in the component itself connected to the different distribution of internal current in the component. Moreover, it was observed, that the presence of bad thermal contact between the package and the heat sink can be revealed because it results in a different thermos-mechanical behavior of the component. Finally, a critical defect was introduced in the component and it was observed the way the presence of damage affects the in-plane displacement of the component. Very huge differences were observed leading to the consideration that this kind of approach could be conveniently adopted also as a damage detection tool.     

Numerical investigation of influence of treatment of the coke component on hydrodynamic and catalytic cracking reactions in an industrial riser

A three dimensional gas-solid reactive flow model based on the Eulerian-Eulerian approach was used to simulate the hydrodynamic, heat transfer and catalytic cracking reaction within in a conventional Fluid Catalytic cracking (FCC) riser. A 12-lump kinetic model was used to represent the catalytic cracking reaction network. It was proposed a catalyst deactivation model as a function of the weight percentage of coke amount on the catalyst to replace the deactivation model dependent of the residence time. It was compared the effects of novel treatment for coke component (coke produced in the solid phase) with common treatment (coke produced in the gas phase) on the fluid dynamic and catalytic cracking. The results showed that the treatment for coke component affects radial distribution of coke mass flow. It also showed that the treatment for coke plays an important role in simulation with catalyst deactivation as a function of coke amount on catalyst.     

TMA4000在电子工业领域中使用标准测试方法的应用

电子线路板的主要破坏原因之一是由热膨胀引起的问题。要防止这种情况发生,电子工程师采用热导体来发散热量,用低膨胀性材料来配合低膨胀率的硅片和陶瓷绝缘体的使用。热机械分析（TMA）长期以来应用于测量线路板、电子元件和组成材料（CTE）。针对玻璃化转变温度、热膨胀系数变化的点、样品软化和应力释放效应的发生,已经建立起成熟可靠的标准测试方法。对于层状复合产品,TMA相应的测试方法可以确定在评估升温过程中材料的分层所需时阃。TMA4000的设计大大简化了上述测试过程,非常适用于测量低膨胀率的小器件的膨胀。本应用文章提供了这些标准方法的一些案例。     

Numerical study on effect of CuO-water nanofluid on cooling performance of two different cross-sectional heat sinks

In this paper, effect of CuO nanoparticles in distilled water on heat dissipation from electronic components is investigated numerically. Computational Fluid Dynamics (CFD) simulations are carried out to study the rectangular and circular cross-sectional shaped heat sinks, and influence of their sectional geometry on the flow and heat transfer characteristics. The three-dimensional governing equations for fluid flow and heat transfer are solved using finite volume method. The two-phase and single-phase models are used to simulate the nanofluid flow. Comparisons of the numerical results with corresponding experimental data show that the two-phase model is more accurate than the single-phase model. Also, effect of various nanoparticle volume fraction on thermal and hydrodynamic characteristics of the heat sink are discussed in details for two different geometry of channel. The results show that the heat sink with nanofluid has better heat transfer rate in comparison with the water-cooled heat sink. A comparison between rectangular and circular channels at the same Reynolds number and cross section area shows that the heat sink with rectangular channels has lower thermal resistance.     

冷凝器翅片表面流体流动及换热过程的三维数值模拟

本文应用CFD软件FLUENT对冷凝器常用的平翅片和波纹翅片表面的流体流动及换热过程进行了数值模拟,获得了翅片表面流体的流场图、温度场图、压力场图以及翅片换热量、平均表面换热系数等重要数据,并通过这些图形、数据对两种翅片的流体流动特性和传热性能进行了比较.     

Improved heat-sink structure providing single-crystal soi films prepared by lamp zone melting

In order to localize the remaining defects encountered in lamp zone melting recrystallization of silicon on insulator (SOI) films, we have used an improved heat-sink technique. It consists of a periodic surface relief etched down into the underlying SiO₂ and extending along 4″ wafers. The resulting film contains SOI stripes separated by narrow lines where the defects are localized. This technique also avoids the de-wetting of the liquid silicon within the large molten zone used. By using a combination of seeding with the heat-sink structure, we obtain a quasi-single-crystal film on 4″ wafers.     

Cooling system for the soft X-ray spectrometer onboard Astro-H

The Soft X-ray Spectrometer (SXS) is a cryogenic high resolution X-ray spectrometer onboard the X-ray astronomy satellite Astro-H which will be launched in 2014. The detector array is cooled down to 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from the room temperature to the ADR heat-sink is composed of superfluid liquid He, a Joule-Thomson cryocooler, and double-stage Stirling cryocoolers. It is designed to keep 30 l of liquid He for more than 5 years in the normal case, and longer than 3 years even if one of the cryocoolers fails. Cryogen-free operation is also possible in the normal case. It is fully redundant from the room temperature to the ADR heat-sink.