数据中心服务器水冷散热器的数值模拟及实验验证

水冷散热器在数据中心服务器CPU芯片冷却技术中发挥着重要的作用.如何获得高性能的散热效率成为了该领域关注的重点.针对一种翅柱式水冷散热器,用数值模拟的方法,通过改变翅柱的结构参数来优化散热器的散热性能以及流动特性.在相同的翅柱间距下,改变翅柱的直径和高度,在不同的入口流量下,研究其温度、努塞尔数、压降、摩擦系数,分析比...     

针肋散热器针径和间距对性能影响分析

利用数值模拟方法分析了高度、直径和间距分别为15.0mm、0.1mm和0.5mm的型号1纯铜丝针肋散热器的散热和流动阻力特性,并与相同材料、相同高度,直径和间距分别为1.0mm和5.0mm的型号2在相同边界条件下进行对比。结果表明,前者散热性能高6%,但是后者通过增加丝径和扩大间距进行结构优化,针体总质量没有发生改变,而阻力损失从624.06Pa大幅降低到33.74Pa,并且在工艺上也容易实现。另外,由于两种针肋的针体在13.0~15.0mm高度上温度分布基本没有变化,可以适当降低高度,节省材料。     

逆变器水冷单元柜的不同通风散热结构和性能比较

讨论了用于逆变器冷却的水冷单元柜,针对柜内几种散热器和柜内通风结构方案进行了对比分析,探讨了影响水冷单元柜散热性能的因素,总结了提高水冷单元柜散热性能的措施。     

不同结构的CPU水冷散热器的性能分析

水冷散热器具有较高的冷却效率,广泛应用在CPU冷却技术中。建立了空腔式、翅柱式、隔板翅柱混合式三种不同结构的散热器模型,使用商用计算流体动力学软件ANSYS FLUENT进行流场数值模拟。在进口流量相同的情况下,通过对三种结构的散热器内的流动特征及温度分布的比较分析,发现翅柱式结构散热器内部流场湍动剧烈,可以显著提高CPU的冷却效果。在进口管道增加隔板后,散热器内的涡强度进一步增强,冷却效果略有提高,CPU表面上的冷却均匀性进一步提高。     

翅片式热管散热器自然对流换热特性分析与多目标结构优化

采用数值计算方法对一种应用于半导体制冷片热端散热的翅片式热管散热器进行模拟,探究自然对流条件下不同翅片参数对散热器换热特性的影响。结合多目标遗传算法(NSGA-Ⅱ),以影响散热器散热的两个主要参数——翅片表面传热系数和肋面效率为优化目标,对散热器整体做出综合优化,并对优化结果进行K均值聚类分析,提出了翅片端优化原则。结果表明,肋面效率对散热器性能的影响有限,提高表面传热系数可显著降低散热器总热阻;与未优化方案相比,所选优化方案可使基板热端面温度下降3.5K,散热器热阻降低18.22%。     

大功率集成LED热管散热器的传热性能

针对大功率集成LED单位热流密度高的特点,提出一种新型的翅片式重力热管散热器,并对其传热性能进行了实验研究,讨论了加热功率和充液率对散热器传热性能的影响。实验结果表明:在加热功率为150W、散热热流密度为37.5W/cm2时,翅片式重力热管散热器的系统热阻在0.08～0.33K/W,此时加热表面温度低于80℃,冷凝段管壁温度相差不超过3℃。该散热器不仅具有良好的均温性,且在工况变化时能快速重新达到稳定,满足大功率LED的散热需求。     

高性能商用车用散热器轻量化设计

为提高商用车冷却模块散热性能,实现冷却模块轻量化,采用计算流体动力学方法分析散热器的散热带高度、波峰距、开窗角度对散热性能的影响,得到最佳冷却模块性能参数;对散热器结构进行优化,并对优化后的散热器进行风洞试验和整车热平衡试验。结果表明：优化后的散热器质量减轻17.9%,散热性能提升1%～8%;通过优化散热带高度、波峰距以及开窗角度,可以提高冷却模块散热性能,实现轻量化,降低生产成本。     

竖直热沉自然对流散热的两种强化措施研究

为了对高效大功率远端射频模块(RRU)的散热器设计提供依据,本文提出了两种强化直翅式竖直热沉自然对流散热的有效措施:对完整热沉在中间位置开缝同时在开缝处添加挡片,以及对开缝热沉存在的局部传热不利区域开孔来强化散热。本文采用了实验手段结合数值模拟的方法,研究了两种逐次递进的改进措施对给定几何结构参数的直翅式竖直热沉散热性能的影响。研究结果表明:当开缝宽度为10 mm时,中间开缝并添加挡片之后,竖直热沉散热性能显著提升;开缝从中间位置分别向上或向下平移时,散热性能均逐渐减弱。添加挡片后的中间开缝热沉肋间流场存在传热死区,通过对该区域内的翅片开孔能够有效减少传热死区的面积;开孔不仅改变了肋间空气的流向,而且形成了漩涡现象和扰流运动,从而进一步强化了热沉整体的散热性能。     

大功率晶闸管风冷重力热管散热器的新结构与传热试验

本文介绍了蒸发段内壁采用轴向槽道加抑泡孔管的风冷重力热管散热器。性能试验表明:这种热管散热器的热阻低达0.0129℃/W,主要性能指标优于国内外同类热管散热器,风冷散热能力达到水冷散热器水平。     

风扇罩及串并联影响散热模块换热的试验研究

为解决车辆冷却系统中散热器模块常出现的散热能力不足的问题,对某型车辆的散热模块在风洞测试平台上进行试验研究;试验散热器模块为水散油散匹配不同直径的风扇罩,水散油散变换串并联方式,分别进行风洞试验,试验结果表明,风扇罩直径和串并联方式显著影响散热模块的散热和阻力性能,可以通过调整散热器匹配的风扇罩直径和变换串并联方式来提...     

Influence of fan setting height on the cooling performance of a plate‐fin‐type heat sink with microprocessor

The cooling performance of a plate‐fin‐type heat sink equipped with a cooling fan was investigated experimentally. The heat sink was 80 mm long, 43 mm wide, and 24 mm in height (including the 4‐mm‐thick base). The cooling fan was 40 × 40 × 15 mm and was set to direct the air flow vertically in the downstream half of the heat sink. We focused on the influence of the height (which varied from 5 to 20 mm) that the fan was set at, on the heat transfer coefficient of the heat sink. The maximum value of the heat transfer coefficient was achieved at a setting height of 5 mm. At this height, the volumetric heat transfer coefficient was 1.8 times as high as that in a parallel flow under the same fan power. This result indicates that the cooling performance of heat sinks with a cooling fan can be improved by using this kind of compact structure. © 2001 Scripta Technica, Heat Trans Asian Res, 30(6): 512–520, 2001     

Heat transfer and pressure loss characteristics of very compact heat sinks with plate fins cooled by jets

High-performance and very compact heat sinks have been developed for effective cooling of VLSIs with high heat-generation densities. Their heat transfer and pressure loss characteristics in air-jet cooling have been experimentally studied. The highly compact heat sinks were plate-fin arrays with a very small fin pitch of 0.4–2.0 mm. The rectangular jet nozzle width that gave the highest cooling performance was 30 to 40% of the streamwise length of the heat sinks. The influence of fin height on heat transfer became weak when the ratio of the height to the thickness of the fin exceeded approximately 35. When the air flow rate was constant, the thermal conductance increased as the fin pitch decreased. For a constant fin pitch, heat sinks with smaller fin thickness showed larger thermal conductance at a given blower power consumption. In our experimental range, the heat dissipation rate per unit heat sink volume increased as the base plate area of the heat sink became small. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(6): 399–414, 1998     

Measurement of performance of plate-fin heat sinks with cross flow cooling

This work assesses the performance of plate-fin heat sinks in a cross flow. The effects of the Reynolds number of the cooling air, the fin height and the fin width on the thermal resistance and the pressure drop of heat sinks are considered. Experimental results indicate that increasing the Reynolds number can reduce the thermal resistance of the heat sink. However, the reduction of the thermal resistance tends to become smaller as the Reynolds number increases. Additionally, enhancement of heat transfer by the heat sink is limited when the Reynolds number reaches a particular value. Therefore, a preferred Reynolds number can be chosen to reduce the pumping power. For a given fin width, the thermal performance of the heat sink with the highest fins exceeds that of the others, because the former has the largest heat transfer area. For a given fin height, the optimal fin width in terms of thermal performance increases with Reynolds number. As the fins become wider, the flow passages in the heat sink become constricted. As the fins become narrower, the heat transfer area of the heat sink declines. Both conditions reduce the heat transfer of the heat sink. Furthermore, different fin widths are required at different Reynolds numbers to minimize the thermal resistance.     

Multiwalled Carbon Nanotube Nanofluid for Thermal Management of High Heat Generating Computer Processor

Minichannel heat sink geometries with varying fin spacing were tested with de‐ionized water and MWCNT (1 wt %) nanofluid to evaluate their performance with flow components of a liquid cooling kit. Four heat sinks with fin spacing of 0.2 mm, 0.5 mm, 1.0 mm, and 1.5 mm were used in this investigation. Heat sink base temperature was analogous to processor operating temperature which was the prime parameter of interest in this investigation. The base temperature decreased by reducing the fin spacing and using multiwalled carbon nanotube (MWCNT) nanofluid. The lowest value of heat sink base temperature recorded was 49.7 ^°C at a heater power of 255 W by using a heat sink of 0.2 mm fin spacing and MWCNT nanofluid as a coolant. Moreover, as a result of reduced fin spacing and using MWCNT nanofluid as a coolant the value of overall heat transfer coefficient increased from 1200 W/m²K to 1498 W/m²K, translating to about a 15% increase. The value of thermal resistance also dropped by reducing the fin spacing and using MWCNT nanofluid. The most important aspect of the study is that the heat sinks and MWCNT nanofluid proved to be compatible with the pump and radiator of the commercial CPU liquid cooling kit. The pump was capable to handle the pressure drop which resulted by reducing the heat sink fin spacing and by using MWCNT nanofluid. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(7): 653–666, 2014; Published online 11 November 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21107     

新型多孔铜微通道热沉散热性能实验研究

新型多孔铜微通道散热技术采用多孔铜微通道结构,增加热沉与冷却工质的接触面积,提高热沉的散热性能。利用单室金属-气体共晶定向凝固工艺,通过控制冷却速度、过热度、气压等工艺参数,从而制备优质的多孔铜材料。根据多孔铜微通道热沉散热原理,搭建散热性能测试平台,研究冷却工质流量、多孔铜材料的孔径和孔隙率、入口截面斜率角对多孔铜微通道热沉散热性能的影响规律。结果表明:增加冷却工质流量有利于提高多孔铜微通道热沉的散热性能;在恒定体积流量下,减小孔径有利于提高多孔铜微通道热沉的散热性能;当多孔铜孔隙率为30.8%时,多孔铜微通道热沉散热性能最佳;入口截面斜率角对多孔铜微通道热沉散热性能的影响较小。     

Liquid cooling in the mini-rectangular fin heat sink with and without thermoelectric for CPU

In the present study, the liquid cooling in the mini-rectangular fin heat sink with and without thermoelectric for CPU is studied. Six mini-rectangular fin heat sinks with two different material types and three different channel widths are fabricated from the copper or aluminum with the length, the width and the base thickness of 37, 37, 5 mm, respectively. The de-ionized water is used as coolant. Effects of channel width, coolant flow rate, material type of heat sink and run condition of PC on the CPU temperature are considered. The liquid cooling in mini-rectangular fin heat sink with thermoelectric is compared with the other cooling techniques. The thermoelectric has a significant effect on the CPU cooling of PC. However, energy consumption is also increased. The results of this study are expected to lead to guidelines that will allow the design of the cooling system with improved heat transfer performance of the electronic equipments.     

Modeling and optimization of designing parameters for a parallel-plain fin heat sink with confined impinging jet using the response surface methodology

The parallel-plain fin (PPF) array structure is widely applied in convective heat sinks in order to create extended surface for the enhancement of heat transfer. In the present study, for investigating the influences of designing parameters of PPF heat sink with an axial-flow cooling fan on the thermal performance, a systematic experimental design based on the response surface methodology (RSM) is used. The thermal resistance and pressure drop are adopted as the thermal performance characteristics. Various designing parameters, such as height and thickness of fin, width of passage between fins, and distance between the cooling fan and the tip of fins, are explored by experiment. Those parameters affect the structure arrangement, geometry of fins and the status of impinging jet from an axial-flow cooling fan installed over the heat sink. A standard RSM design called a central composite design is selected as experimental plan for the four parameters mentioned above. An effective procedure of response surface methodology (RSM) has been proposed for modeling and optimizing the thermal performance characteristics of PPF heat sink with the design constrains. The most significant influential factors for minimizing thermal resistance and pressure drop have been identified from the analysis of variance. The confirmation experimental results indicate that the proposed model is reasonably accurate and can be used for describing the thermal resistance and pressure drop with the limits of the factors studied. The optimum designing parameters of PPF heat sink with an axial-flow cooling fan under constrains of mass and space limitation, which are based on the quadratic model of RSM and the sequential approximation optimization method, are found to be fin height of 60 mm, fin thickness of 1.07 mm, passage width between fins of 3.32 mm, and distance between the cooling fan and the tip of fins of 2.03 mm.     

Effects of shield on thermal-fluid performance of vapor chamber heat sink

This work investigates the effects of a shield on the thermal and hydraulic characteristics of plate-fin vapor chamber heat sinks under cross flow cooling. The surface temperature distributions of the vapor chamber heat sinks are measured using infrared thermography. The thermal-fluid performance of vapor chamber heat sinks with a shield is determined by varying the fin width, the fin height, the fin number and the Reynolds number. The experimental data thus obtained are compared with those without a shield.Experimental results indicate that the maximum surface temperature of the vapor chamber heat sink is effectively reduced by adding the shield, which forces more cooling fluid into the inter-fin channel to exchange heat with the heat sink. However, using the shield increases the pressure drop across the heat sink. The experimental data also show that the enhancement of the heat transfer increases with the Reynolds number, but the improvement declines as the Reynolds number increases. When the pumping power and heat transfer are simultaneously considered, vapor chamber heat sinks with thinner, higher or more fins exhibit better thermal-hydraulic performance.     

Thermal investigation of the conjugate heat transfer problem in multi-row circular minichannels

A numerical three-dimensional flow and conjugate heat transfer in circular minichannel-based multi-row heat sink is presented in this article. Effects of geometrical parameters including channel dimensions, channel arrangements (inline or staggered), and the number of channel rows with a single-pass flow on the thermal performance of the heat sink are presented. The determination of the bottom surface temperature, average heat transfer coefficient, thermal resistance as well as the pressure drop was reported. The number of rows and the diameter of the circular channel for a constant Reynolds number were found to have a remarkable cooling effect on the heat sink. It was found out that in the case of using four channel rows with the channel diameter of 1?mm, the cooling capacity is 88.5?W/cm² compared to 28?W/cm² for a single row 1?mm diameter.     

Optimum Thermal Analysis of a Heat Sink with Various Fin Cross-Sections by Adjusting Fin Length and Cross-Section

A theoretical analysis of a heat sink is presented in this study to pursue the purpose of maximum thermal dissipation and the least material cost. Due to the general derivation, the longitudinal fin arrays on a heat sink can have either square, rectangular, equilaterally triangular, or cylindrical cross-section. By input of the Biot number, Bi, heat transfer coefficient ratio, H, and the shape parameter, γ, the heat transfer equation, which is expressed in implicit form, can be solved by iterative method to calculate the optimum fin length and fin thickness. Meanwhile, the thermal resistance of a heat sink can be obtained to illustrate the cooling performance under various design conditions.