Comparison of nongradient methods with hybrid Taguchi-based epsilon constraint method for multiobjective optimization of cylindrical fin heat sink

The primary aim of the paper is to compare the different nongradient methods of multiobjective optimization for optimizing the geometry parameters of a cylindrical fin heat sink. The methods studied for comparison are Taguchi-based grey relational analysis, ε (epsilon) constraint method and genetic algorithm. The various responses that have been studied are electromagnetic emitted radiations, thermal resistance and mass of the heat sink. Since the responses are obtained using complex simulation softwares (HFSS—Ansoft for emitted radiations and CFD—Flotherm for thermal resistance), there is no way of calculating the derivates of the objective functions. Hence, the Taguchi design of experiments design is used to derive the linear regression equations for the responses studied, which are then taken as the objective functions to be optimized. A new hybrid method known as Taguchi-based epsilon constraint method has been proposed in this paper for obtaining nondominated Pareto solution set. The results obtained using the proposed method show that the Pareto optimal set is competitive in terms of diversity of the solutions obtained. It is not likely that there exists a solution, which simultaneously minimizes all the objectives using any of the multiobjective techniques implemented. The value path analysis has been done to compare the trade-off among the design alternatives for the chosen multiple objective parameter optimization problem.     

Experimental and CFD analysis of heat sinks with base plate for CPU cooling

Experimental and theoretical investigations of the thermal performance of a variety of heat sinks have been made. The heat sinks investigated were: straight finned, elliptical finned, small pin finned, circular disc finned, elliptical disc finned, frustum finned and double base straight finned. Realistic, manufacturable geometries are considered for minimizing thermal resistance at low velocity. The experimental results of several of the simple geometry heat sinks have been compared to those predicted by a commercially available computational fluid dynamics code fluent. The parameters such as fin geometry, fin pitch and fin height are optimized primarily in this paper and a second task is carried out to optimize base plate thicknesses, base plate materials and modify design of heat sink for improving the thermal performance in the next generation. Although the performance of heat sink is good, the temperature of heat sink at center is high. In this research work, the best heat sink geometry is selected and modified in order to reduce maximum temperature distribution and hot spots of heat sink at center by changing the geometry design and adding one more base. It is observed that flow obstructions in the chassis and the resulting air recirculation affect the heat sink temperature distribution.     

Modeling and simulation of a parallel plate heat sink using computational fluid dynamics

Desktop computers have changed to accommodate increasing power, approaching 100 W. Heat dissipation becomes a significant issue in efficiency promotion and stable operation of air-cooled microelectronics and power electronics components and assemblies. Finned heat sinks are commonly used devices for enhancing heat transfer from air-cooled microelectronics and power electronics components and assemblies. The use of finned heat sinks increases the effective surface area for convective heat transfer, reducing the thermal resistance and operating temperatures in air-cooled electronics. The task of selecting the best heat sink for a particular application from the hundreds of configurations available from the various manufacturers can be a formidable task for an engineer. In a typical heat sink design, the objective is to achieve target heat dissipation, while restricting the consumption of valuable resources such as mass, fan power, pressure drop, and space claim. In this research work, preliminary studies have been carried out for the performance improvement of a parallel-plate heat sink considering the various geometric parameters, such as number of fins, fin length, fin height, and base height. The modeling and simulation of the heat sink is carried out with the computational fluid dynamics package. The results are analyzed using analysis of variance and response graphs.     

Shape Optimization of a plate-fin type heat sink with triangular-shaped vortex generator

In this study the optimization of plate-fin type heat sink with vortex generator for the thermal stability is performed numerically. The optimum solutions in the heat sink are obtained when the temperature rise and the pressure drop are minimized simultaneously. Thermal performance of heat sink is influenced by the heat sink shape such as the base-part fin width, lower-part fin width, and basement thickness. To acquire the optimal design variables automatically, CFD and mathematical optimization are integrated. The flow and thermal fields are predicted using the finite volume method. The optimization is carried out by means of the sequential quadratic programming (SQP) method which is widely used for the constrained nonlinear optimization problem. The results show that the optimal design variables are as follows ; B₁=2.584 mm, B₂=1.741 mm, and t=7.914 mm when the temperature rise is less than 40 K. Comparing with the initial design, the temperature rise is reduced by 4.2 K, while the pressure drop is increased by 9.43 Pa. The relationship between the pressure drop and the temperature rise is also presented to select the heat sink shape for the designers.     

矩形肋片散热器几何参数对散热的影响分析

为考察矩形肋片散热器几何参数对散热效果的影响规律,文中应用热仿真分析软件Flotherm对矩形肋片散热器在不同结构参数下的模型进行了自然对流散热计算,通过对比分析不同模型的温度和热阻计算结果,探讨了散热器基板参数和肋片参数对其散热性能的影响。分析表明,改变散热器肋片的高度、长度和间距可有效降低散热器的热阻。这些几何参数可以作为散热器热设计变量,以进一步对散热器进行优化设计。     

基于ICEPAK仿真的散热器结构热设计研究

文中利用ICEPAK软件对多密度高功率芯片散热器结构进行了热设计研究。研究确立了影响翅片散热器散热性能的关键尺寸设计参数,如基板厚度、翅片高度、翅片厚度和翅片间距等,并得出了各尺寸设计参数对其散热效果的影响趋势,确定了散热器结构的最佳布局方案。此外,研究还建立了最佳布局的散热器结构实物并进行了高低温试验以模拟其高温散热情况。通过实验数据对比发现,仿真计算结果与实际较为吻合,进而验证了ICEPAK软件在电子设备散热设计方面的准确性与可靠性。     

Forced air cooling by using manifold microchannel heat sinks

A study of manifold microchannel (MMC) heat sinks for forced air cooling was performed experimentally. The manifold microchannel heat sink differs from a traditional microchannel (TMC) heat sink in that the flow length is greatly reduced to a small fraction of the total length of the heat sink. In other words, the MMC heat sink features many inlet and outlet channels, alternating at a periodic distance along the length of the microchannels while the TMC heat sink features one inlet and one outlet channels. The present study primarily focused to investigate the effects of geometrical parameters on the thermal performance of the manifold microchannel heat sinks for optimal design. Also, the thermal resistances of the MMC heat sinks were compared with those of the TMC heat sinks. Experimental results showed the thermal resistances of MMC heat sinks were affected strongly by the pumping power, the microchannel width and the manifold inlet/outlet channel width, but weakly by the microchannel thickness-width ratio and the microchannel depth coorporated with the manifold inlet/outlet channel width. However, it was found that there existed the optimum values of the latter parameters. Under the optimum condition of geometrical parameters in the present study, the thermal resistance of the MMC heat sink was approximately 35% lower than that of a TMC heat sink, which clearly demonstrated the effectiveness of using a manifold.     

大容量电力电子装置中板式水冷散热器的优化设计

为提高水冷散热器的散热能力、控制其温度均匀性,在散热器外形尺寸及流量一定的条件下,从理论上对层流范围内平板式水冷散热器的三个通道参数(通道数、散热片高度、散热片占空比)与散热器量纲一散热热阻的变化关系进行了推导。提出可根据这些变化关系来对任意尺寸平板式水冷散热器的各通道参数进行优化选择,在工程设计上具有很好的指导意义,仿真和试验结果证明了方法的有效性并表明:小通道尺寸的平板式水冷散热器对于解决大热流密度器件的散热更为有效,散热效率更高;在同样的参数情况下,流量增大则散热器效率降低,应综合考虑散热器流阻和流体平均温升的控制要求来选择流量。     

Constructal design of finned tubes used in air-cooled heat exchangers

The present study documents the constructal design and optimization of finned tubes used in air-cooled heat exchangers. The considered tubes are equipped with annular fins. The aim is to minimize the overall thermal resistance by morphing the geometry. The geometrical and thermo-physical parameters considered are the number of fins, ratio of fin height to tube diameter, Stanton number, ratio of fin conductivity to air conductivity, ratio of in-tube fluid conductivity to air conductivity and dimensionless pressure drop. Two constraints are applied in the optimization process: fixed overall volume of heat exchanger and fixed volume fraction of fin material. It is found that there exist optimal values for the number and the height of fins. Moreover, the optimal heat transfer has an extremum in a special volume fraction of fin material.     

CPU散热器结构设计与热分析

CPU散热器是将CPU核心热量迅速导出的关键,已成为获得新一代电子芯片的主要问题之一。采用数值模拟方法对放射状太阳花CPU散热器进行三维流场及温度场分析,探讨放射状散热器在不同的肋片形状、肋片数N和肋片厚度等各种不同的参数作用下,对于整体散热器散热和流动性能的变化与影响,同时分析了太阳花散热器自然对流和瞬时动态特性。     

层次脉状结构液冷均温板优化设计研究

由于耐热型植物具有良好的传热传质能力,结合流道拓扑优化设计和耐热型植物高级脉序的叶脉结构特征,提出一种层次脉状结构液冷均温板的设计方法。以热交换最大和流阻最小为目标开展主流道拓扑优化设计,提取胡杨叶高级脉序的结构特征,形成液冷均温板的次流道。定义结构像素密度作为描述次流道中孔的密度参数,分析其对层次脉状结构液冷均温板的传热传质性能的影响。研究结果表明,层次脉状结构的液冷流道具有较小的流阻和良好的均温性,同时主、次流道尺寸存在最优匹配。进一步研究胡杨叶脉的分布规律,发现液冷板主、次流道尺寸最优匹配规律与胡杨叶低、高级脉序尺寸匹配规律相近。研究结果不仅为液冷均温板的设计提供新思路,而且验证了耐热植物叶脉结构特征对其传热传质性能产生的正面影响。最后加工液冷板,通过试验验证了设计方法的有效性及数值模拟的准确性。     

基于ANSYS Icepak的热管模块设计与仿真分析

NVIDIA JETSON TX2高功率系统芯片的散热功率一般在25 W左右,一般的风扇与肋片式散热器组合的散热方式存在体积大、高度高、不方便整合在小型系统中等问题,而热管、风扇、铜鳍片散热器组合的散热方式具有高度低、体积小、传热效率高等优点。文中首先对热管模块进行结构设计;然后对热管模块设计的合理性进行计算验证,并利用ANSYS Icepak对热管模块进行热稳态仿真,发现主要芯片的温度都在要求范围内,表明设计合理;最后将热管模块装入系统进行温度测试。结果表明,主要芯片的计算、仿真与实验的温度基本一致。     

用于大功率激光二极管列阵的硅基微通道热沉研制

将田口稳健设计方法用于面向大功率激光二极管列阵的硅基屋脊式微通道热沉的优化设计,利用正交试验和信噪比分析实现了参数的稳健优化。采用激光二极管条对样品进行了封装和测试。利用砷化镓激光波长的温度漂移系数估算出了中间的激光二极管条的有源区温升。测试结果表明,该微通道热沉的单位面积热阻约为0.070 K•cm2/W,与有限元分析结果基本一致。     

基于遗传算法的散热器翅片优化设计

为了设计工程约束下的高性能散热器,基于散热器热阻网络模型,建立了散热器优化目标函数,利用遗传算法对目标函数进行优化,获取了工程条件约束下散热性能最优的散热器几何参数。计算结果与商用软件仿真结果符合较好,表明文中所建模型的准确性和有效性。文中的研究为提高高性能散热器的设计能力及新产品的研发效率提供了有益参考。     

型材散热器的优化设计

本文针对散热器在强迫风冷条件下的散热性能优化问题进行了分析研究.对于所采用的优化方案的热分析模型作了描述.分析了绕流对散热器性能的影响,并根据一种较为简便的数学模型,用迭代的方法确定出肋片上的实际流速.最后给出了采用这些模型计算出的在不同工作环境下型材散热器的优化尺寸.     

Effect of channel and plenum aspect ratios on the performance of microchannel heat sink under different flow arrangements

Microchannels based heat sinks are considered as potential thermal management solution for electronic devices. The overall thermal performance of a microchannel heat sink depends on the flow characteristics within microchannels as well as within the inlet and outlet plenum and these flow phenomena are influenced by channel aspect ratio, plenum aspect ratio and flow arrangements at the inlet and outlet plenums. In the present research work an experimental investigation has been carried out to understand how the heat transfer and pressure drop attributes vary with different plenum aspect ratio and channel aspect ratio under different flow arrangements. For this purpose microchannel test pieces with two channel aspect ratios, 4.72 and 7.57 and three plenum aspect ratios, 2.5, 3.0 and 3.75 have been tested under three flow arrangements, namely U-, S- and P-types. Test runs were performed by maintaining three constant heat inputs, 125 W, 225 W and 375 W in the range 224.3 ?? R_e ?? 1121.7. Reduction in channel width (increase in aspect ratio, defined as depth to width of channel) in the present case has shown about 126 to 165% increase in Nusselt number, whereas increase in plenum length (reduction in plenum aspect ratio defined as width to length of plenum) has resulted in 18 to 26% increase in Nusselt number.     

A numerica1 study of fluid flow and heat transfer in different microchannel heat sinks for electronic chip cooling

Four different microchannel heat sinks are designed to study the effects of structures in microchannel heat sinks for electronic chips cooling. Based on the theoretic analysis and numerical computation of flow and heat exchange characteristics, the electronic chip’s temperature and flow rate distributions are obtained. The correspondence between flow pressure drop and chip’s temperature in the four microchannel heat sinks is also studied and analyzed. Numerically analyzed results indicate that the topological structure in microchannel heat sink has a significant influence on electronic chips cooling. This study shows various thermal properties in the four microchannel heat sinks.     

铜铝微通道热沉的三维数值结构优化

在恒定泵功0.05 W条件下,对水冷铜基和铝基微通道热沉对流换热进行详细数值模拟和结构优化。通过将数值预测结果与前人已发表的试验结果进行对比,验证所使用的数值模型的正确性。同时讨论在恒定泵功下微通道几何结构对微通道热沉中温度分布的影响。模拟结果显示水冷铜基微通道热沉最优的几何结构参数为通道深为580μm,通道宽为90μm,通道密度为100个/cm;铝基微通道热沉最优的几何结构参数为通道深为620μm,通道宽为80μm,通道密度为100个/cm。     

平直翅片热管散热器的正交数值模拟优化

文中以平直翅片热管散热器为研究对象,研究了翅片厚度、翅片间距、翅片高度、翅片宽度和热管直径 5 个结构参数对翅片换热性能和阻力特性的影响,采用正交实验设计的方法设计了上述结构参数的 15 个组合方案,利用 CFD 数值模拟的方法对每个组合方案下翅片的流动换热性能进行了模拟。以努塞尔数 Nu 、阻力系数f、传热性能综合评价指标(Performance Evaluation Criteria, PEC)作为评价指标,在每个评价指标下利用极差分析挑选出性能最优的组合方案。 该方法能快速获得散热器结构的优化方案,并分析出主要影响因素,对工程应用有一定的指导意义。 结果表明:影响 Nu 和 f 的最主要因素是热管直径,影响 PEC 的最主要因素是翅片厚度。 对于本文研究的散热器,其最优参数组合方案为:翅片厚度为 0. 6 mm,翅片间距为 2. 2 mm,热管直径为 6 mm,翅片高度为 65 mm,翅片宽度为 28 mm。     

某固态功放设备的强迫风冷散热设计

通过对某发射机用固态功放的热设计,阐述了在设备强迫风冷热设计中的设计思路,介绍了结合式鳍片散热器在设备热设计中的应用,以及独立式风道的结构形式,并通过热测试验证了设计的合理性。