照明用大功率LED射灯散热建模研究

散热问题是LED灯具成为新一代照明光源亟待解决的关键问题之一。提出一种LED灯具散热建模方法:选用LED射灯作为代表产品进行散热建模研究,采用三维造型软件建立LED灯具产品三维模型,然后导入有限元流体热分析软件(CFD)进行热仿真。研究散热仿真过程中的热阻设置、热量载荷计算和边界条件设定等关键问题,并求解LED射灯的工作温度分布情况;将仿真分析结果与实验室测试数据进行对比分析研究。研究结果表明,运用该方法可以对室内照明LED灯具进行较为准确的散热分析,仿真温度误差在4℃左右,仿真结果对灯具开发设计具有重要参考价值。     

LED灯具散热建模仿真关键问题研究

有限元流体热分析软件(CFD)常被用于对LED灯具散热进行建模仿真,与散热相关的参数分析、计算与设置等问题是影响仿真精度的关键因素。综合研究了边界条件设置、热阻计算、热量载荷分析和散热器等仿真建模的关键问题,并与实验室温度测量相结合来验证仿真方法的准确性。结果表明,该方法对室内照明LED灯具能进行较为准确的散热分析,仿真温度误差在4℃左右,仿真结果对LED灯具开发设计具有重要参考价值。     

Q波段行波管的螺旋线结构的热分析

通过ANSYS软件仿真模拟和理论计算相结合的方法对Q波段行波管的螺旋线结构的散热系统进行了热分析,建立了准确的ANSYS模型,仿真模拟结果和理论计算结果较为一致,从而得到了一些有设计参考价值的散热数据。并在该模型的基础上分析了接触热阻对螺旋线温升的影响,为进一步的优化设计提供了一个参考。     

FC-PBGA644封装的热仿真模拟

FC-PBGA(Filp Chip-PBGA)倒装球栅格阵列封装相比BGA封装易于实现高密度封装,具有更好的电性能和热性能。利用有限元分析软件对封装产品进行建模仿真计算,添加各自的材料热导热系数、边界条件等,在产品设计研发阶段获得温度分布云图。通过计算其热阻,同时对此封装产品散热性能进行优化改进,得出基板尺寸的最优参数设计,可以通过添加散热盖改善其散热性能,提高产品可靠性。     

LTCC封装散热通孔的仿真与优化设计

低温共烧陶瓷（LTCC）封装散热通孔设计是集成电路封装设计的重要内容之一。以某CLCC40型LTCC外壳为例,使用有限元仿真软件对几种不同的散热通孔设计进行3D建模和稳态热仿真。通过对比芯片结到外壳的热阻仿真结果,得到了散热通孔的优化设计方案。仿真结果表明,采用该设计的LTCC外壳的散热效果优于质量分数为92%的氧化铝陶瓷外壳,但略差于氮化铝陶瓷外壳。     

牵引变流系统热设计与温升仿真研究

牵引变流系统是决定机车(动车组)动力配置的重要组成部分。变流器功率密度是车载动力系统的重点追求目标值,冷却方式与散热能力在很大程度上影响着变流系统的容量配置。本文主要介绍了CRH3型高速列车牵引传动系统基本结构及冷却方式,辅以HXD2型机车辅助逆变器自然散热工作方式,运用二次线性化的方法对逆变器主功率器件损耗进行建模,依流程计算出具体损耗值。利用热仿真软件FloTHERM和ICEPAK对功率模块特定工作状态下的热分布情况进行仿真,并与试验数据比对,证明了建模及仿真分析的有效性,为变流器的损耗计算及散热设计提供了前期指导和后期验证。     

基于ANSYS Icepak的密闭机箱散热仿真分析

根据机箱热载荷等边界要求,对密闭机箱中的电子功能模块的热功耗和机箱热稳态下散热表面的热流密度进行了分析和计算。通过计算机箱与外部空气自然对流冷却下的热流密度值来分析机箱的整体散热性能,并将计算结果与空气自然对流散热的热流密度阈值进行比较;在此基础上使用建模软件UG NX7.5完成机箱的CAD数字样机建模;使用ANSYS Icepak有限元热仿真分析软件进行CFD(计算流体动力学分析)和热仿真分析,完成了机箱参数设定、网格划分,对机箱进行精确的热仿真计算,验证机箱热设计的可靠性,为其他同类电子设备热仿真分析与散热优化设计提供了参考。     

大功率LED太阳花散热器的结构优化

对一款大功率LED太阳花散热器(RHS)进行了热阻建模、工作温度测量和软件仿真。依据传热学基本原理建立热阻模型,采用数字温度表进行温度测量,借助专业电子产品热分析软件Icepak进行模拟仿真。在误差允许的范围内,散热器温度的实验值与理论值保持一致,证明了利用Icepak进行软件仿真的可行性与可靠性。在此基础上,运用控制变量法,以散热器最高工作温度为目标,利用Icepak软件对散热器的肋片数量、铝板直径和铝板厚度进行优化,为该散热器的结构优化提供了参考。     

陶瓷封装的等效热方法及其仿真验证

利用等效热模型理论,对陶瓷封装器件与测试印制电路板(Printed Circuit Board,PCB)的模型热阻进行了等效计算,并使用Icepak热分析软件进行热仿真模拟,计算得到芯片到环境的热阻值,最后通过使用T3Ster-热阻测试仪得到陶瓷器件表面温度分布情况并计算出实际热阻.研究表明,通过等效热模型仿真热阻与未...     

关于大数据时代数据中心散热技术的研究

本文简要介绍了数据中心产热的原因,分析了传统成熟的散热方式和新兴的散热方式。同时设计了一款集成脉动热管（PHP）辅助空调散热的机柜及相关散热系统,机柜的科学可行性采用数值计算与软件仿真结合的双重检验,系统的核心为脉动热管-精密空调双路径散热,接触热阻和传热热阻显著降低,预制化的机柜大幅减少机房建设周期。     

Analysis of Convective Thermal Resistance in Ducted Fan-Heat Sinks

The thermal performance of plate fin, round pin-fin, and offset strip-fin heat sinks with a duct-flow type fan arrangement was analytically evaluated. Heat sinks of 65mm$times hbox60, hboxmm hboxplan hboxareatimes hbox50 hboxmm hboxheight$with a 4300-RPM dc fan (60mm$times$15mm) were chosen for the performance comparison. A constant temperature, 6-mm thick heat sink base plate is assumed so that thermal spreading resistance is not involved. The operating point on the fan curve is based on the flow pressure drop impedance curve through a heat sink using the friction factor correlation for the chosen heat sink. The loss coefficients at both the entrance and the exit of the heat sink are included in the flow impedance curve. The operating point is defined by the balance point of the flow impedance curve and the fan performance curve. After determining the operating air velocity, the convective thermal resistance of heat sinks is evaluated from the Nusselt number correlation for the chosen heat sink. Results obtained show that optimized round pin-fin heat sinks provide 32.8%–46.4% higher convective thermal resistance compared to an optimized plate-fin heat sink. The optimized offset strip-fin heat sink shows a slightly lower convective thermal resistance than the plate-fin heat sink. As the offset strip length decreases, however, thermal performance seriously deteriorates.     

Characterization of compact heat sink models in natural convection

In this study, an approximate analytical-numerical procedure is used to model natural convection cooling of heat sinks using electronics cooling software. The analysis evolves in two stages: a numerical simulation of the detailed heat sink, and a simulation of a compact model that exhibits similar thermal and flow resistance characteristics to those of the actual heat sink. From the analysis, the thermal resistance of the heat sink is evaluated. Subsequently, the effective thermal conductivity that must be assigned to the compact heat sink is determined using the Nusselt number correlation for free convection over a vertical plate. Due to the algebraic form of the Nusselt number correlation, the effective thermal conductivity is determined in an iterative fashion. The purpose of a compact heat sink is to reduce computational effort while retaining a desired level of accuracy. In this article, the compact modeling scheme is first applied to either an extruded or a pin-fin heat sink in order to validate the procedure under laminar conditions. Subsequently, the same approach is applied to a multichip system consisting of a set of pin-fin heat sinks placed in series. At both individual and system-level models, it is found that the compact approach results in substantial savings in mesh size and computing time. These savings are accompanied by a small acceptable error that is less than 10% relative to the detailed model predictions     

半导体激光抽运源大通道水冷热沉的接口设计

针对普通大功率半导体激光抽运源用大通道水冷热沉热阻高、工作时热沉表面在大通道水流方向存在明显温升进而导致加载其上的激光bar寿命不一致以及抽运源整体光谱宽度难以控制的问题,利用商用有限元软件ANSYS仿真获得抽运源工作时不同冷却水流量条件下热沉内部温度场分布,分析该结构热沉热阻系统的构成及整体热阻瓶颈所在。实际中通过改变冷却水接口结构,获得“入口效应”,提高了大通道热沉整体换热性能,进一步减小热沉表面温度梯度。利用所设计的新接口大通道水冷热沉获得3 bar线阵120 W连续(CW)输出半导体激光器抽运源,输出中心波长为807.7 nm,光谱宽度(FWHM)为2.8 nm。     

Forced Air Cooling of CPUs With Heat Sinks: A Numerical Study

A common ATX form factor personal computer system is modeled in detail. The flow and temperature fields inside the chassis are numerically investigated as a conjugate heat transfer problem. The computational effort is concentrated on the forced air cooling of the CPU using a heat sink. Three different commercial heat sink designs are analyzed by using commercial computational fluid dynamics software packages Icepak and Fluent. The grid independent, well converged, and well posed simulations are performed, and the results are compared with the experimental data. It is observed that flow obstructions in the chassis and the resulting air recirculation affect the heat sink temperature distribution. The specific thermal resistance values for the heat sinks are compared. It is observed that although they have different geometries, all of the three heat sinks have similar specific thermal resistances. The best heat sink is selected and modified in order to have a lower maximum temperature distribution in the heat sink by changing the geometry and the material. Especially, replacing aluminum with copper as the heat sink material improved the performance. The importance of modeling the entire chassis is demonstrated by comparing the simulation results with the results from a model of only the CPU-heat-sink-fan assembly.      

Performance Analysis of Pin-Fin Heat Sinks With Confined Impingement Cooling

This work assesses the performance of pin-fin heat sinks with confined impingement cooling using numerical simulation. The extent to which the Reynolds number, the height and the width of the fins, the nozzle-to-heat sink distance, the thermal conductivity, the upper confining plate and the fin number affect the thermal resistance are considered. The work shows that increasing the Reynolds number reduces the thermal resistance, but the effect decreases slowly as the Reynolds number increases. Although increasing the fin height can reduce the thermal resistance, reduction decreases. The fin width that is associated with the minimum thermal resistance increases with the Reynolds number. The optimal nozzle-to-heat sink distance increases with the Reynolds number. The thermal resistance decreases with an increasing thermal conductivity; however, the drop in the thermal resistance becomes smaller. The presence of the upper confining plate increases the thermal resistance. Additionally, the thermal resistance initially decreases and then increases slowly as the fin number increases.     

Design and Simulation of the CPU Fan and Heat Sinks

Traditional design methods to achieve improvement in heat sink performance are not suitable for meeting new thermal challenges. Revolutionary rather than evolutionary concepts are required for removing heat from the electronic components. We have recently developed an emerging novel approach, the integration design of the forced convection air cooling system. The aerodynamic design for the miniature axial-flow fan is conducted and a CPU fan is designed to be integrated with the radial fins in order to form a complete fan-heat sink assembly. The 3-D data of the fan generated by FORTRAN program are imported into Pro/E to create its 3-D model. The performance curve of the fan prototype fabricated by the computer numerically controlled machine is tested in a standard wind tunnel. To reduce the economic cost and prompt the design efficiency, the computational fluid dynamics is adopted to estimate the initial fan's performance. A series of radial heat sinks is designed in accordance with the outflow angle of airflow discharged from the fan. The inlet angle of the fin is arranged so that the incoming flow from the upstream impeller matches the fin's angle of heat sinks. Using the multi-block hexahedral grid technique, the numerical simulation of the system, including the fan and heat sinks, is performed by means of Multiple Reference Frame (MRF) and RNG k-$varepsilon$ Model. Our results indicate that the thermal resistance of the streamlined heat sink is decreased by 15.9% compared to the traditional heat sink and the entropy generation rate of the streamlined heat sink is lower. The experiments support our simulation results. The series of heat sinks is able to achieve the productive thermal performance when the integration design concept is utilized.      

自然空气冷却情况下功率器件散热器的优化设计

介绍了功率器件散热器的散热原理，提出散热器的优化问题。叙述了功率器件在自然空气冷却状态下如何初选散热器，并采用散热器优化软件对散热器进行优化设计。讨论了散热器的理论优化和工程优化的不同，在工程实际情况下功率器件如何与散热器达到最优匹配；还分析了不同工作状态下界面热阻、功耗和热辐射等因素对散热效果的影响。     

电子芯片冷却用微管道散热器的换热性能分析

在对电子芯片内部冷却用的微管道散热器进行传热性能分析时,现有分析方法大都仅能在假设微管道下壁上的热载荷处于均匀分布时适用.当微管道下壁上的热载荷处于任意分布情况时,利用文中设计的有限元分析法可对微管道散热器的传热性能进行分析.在微管道下壁上的热载荷处于不同的分布情况下,利用伽辽金有限元公式计算了微管道散热器中的微管道表面温度分布、流体温度分布及散热器总热阻等;通过与现有的分析方法所得结果进行对比:在对热载荷均匀分布状态下的微管道散热器进行传热性能分析时,有限元方法完全可作为CFD(Calculated Fluid Dynamics)法的一种替代,且使用有限元方法对微管道散热器进行传热分析时的运算更为快捷.当微管道下壁上的热载荷处于任意非均匀分布状态时,利用文中设计的有限元分析法仍可有效地对微管道散热器的传热性能进行分析;因此有限元分析法也可用于研究微管道散热器的几何参数对散热器传热性能的影响.     

半导体激光器封装中热应力和变形的分析

为了解决半导体激光器封装的热应力和变形问题,利用有限元软件ANSYS对SnPb、In、AuSn三种焊料焊接激光器管芯的情况分别进行了模拟,得到了相应的热应力大小和变形情况,分析了焊料和热沉对激光器热应力和变形的影响.对比了这几种不同封装方法的激光器发光区图像的弯曲程度,验证了模拟结果.由模拟和实验结果可见,采用In焊料是减小激光器热应力和变形的最佳选择.另外,适当增加热沉厚度,选择热匹配的材料,焊接时进行预热,可减小激光器的热应力和变形.通过模拟和实验分析,提出了减小热应力和变形的方法,为优化激光器的封装设计提供了参考依据.     

Thermal compact modeling of parallel plate heat sinks

Growing complexity of electronic systems has resulted in an increased computational effort in CFD modeling of electronic systems. To reduce the computational effort, one or several heat sinks can be represented by a compact "porous block" model, with an effective thermal conductivity and pressure loss coefficient. In this study of parallel plate heat sinks in laminar forced convection, a methodology is developed to rigorously determine the thermal properties of compact heat sink models that provide a high level of accuracy. The results of an extensive set of CFD simulations for a three heat sink channel covering two distinct heat sink geometries, air velocities from 0.25 m/s to 2 m/s and various spacings between the heat sinks, were used to create and evaluate the fidelity of compact models. The results of this study establish the validity and value in using the porous block compact model representation for noncritical heat sinks in an electronic assembly. The results also reveal that a location-independent porous-block representation can yield excellent agreement in the prediction of the thermal characteristics of state-of-the-art heat sinks.