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...     

沟槽式散热器水冷服务器基板流动与散热性能的研究

如何在较低功耗下,使服务器基板CPU低于规定温度已成为数据中心冷却问题的关键。研究了沟槽式水冷散热器对服务器基板芯片的散热。首先,通过开展沟槽式散热器冷却一个模拟CPU服务器基板的实验,对散热器水冷却过程的流动特性和传热特性做了研究,并分别获得"压降-流量"和"进口水温-流量"的性能拟合公式。其次,开展采用集成式沟槽散热器冷却含多CPU服务器基板的实验研究,通过实验测试,改变冷却水的流量和入口温度,以期获取芯片温度为70和80℃时所提供的最小能耗。实验结果表明:进口温度为25℃时,芯片温度维持在80℃以下的最佳流量为0.8 L/min;使芯片温度稳定在70℃以下的最佳流量为1.0 L/min。     

平直型散热器的正交设计和数值模拟

以芯片最高温度为试验指标,翅片高度、翅片厚度和翅片数目为影响因素,对平直型散热器进行正交设计和数值模拟,求出在影响因素的范围内平直型散热器的最佳结构参数。通过对正交试验结果的极差分析,找出散热器影响因素的主次顺序。并通过对优选出的散热器结构和原来的一款散热器进行流场和温度场的对比分析。     

管带式水散热器冷却空气侧阻力性能数值模拟

传统的散热器流动阻力性能分析是依靠大量的试验来完成,而通过计算流体力学(CFD)模拟计算可以在获得直观结果的同时大幅度地减少试验工作量。建立了管带式水散热器冷却空气侧波纹翅片通道的稳态湍流数学模型,对车用管带式水散热器冷却空气侧阻力性能进行数值分析,计算结果与试验数据基本吻合。通过分析得到阻力系数与平均流速拟合函数,经过修正可以用于不同环境温度下阻力性能分析预测。     

新型矿用车管芯式散热器阻力性能的数值模拟

利用ANSYS Flotran模块对不同速度下的管芯式散热器的空气流动速度和压降进行数值模拟,模拟值与试验值吻合,表明利用ANSYS对管芯式散热器阻力性能进行模拟的方法是可行的。     

间接空冷系统空冷散热器运行特性的数值模拟

以某6×1000 MW间接空冷电厂主要建筑物和空冷塔平面布局为例,通过CFD模拟,得到了冷却空气流场、温度场,分析了机组热负荷、环境气温、风速、风向对空冷散热器进口空气流速的影响.结果表明:处于环境风上游的空冷散热器单元,其迎面风速最大,空气温度最低,冷却效果最好;而处于侧面的空冷散热器单元,迎面风速最小,空气温度最高,冷却效果最差.随机组热负荷增加,空冷散热器冷却空气流量增加,随环境气温、风速增加,空冷散热器冷却空气流量减小.风向的改变也会影响散热器的运行特性.     

电力电子器件IGBT用水冷板式散热器热力性能的数值模拟

设计了一种新型流道的电子器件IGBT用水冷板式散热器,利用Fluent软件对其在不同进口流速的工况下进行了数值模拟计算,对结果进行了对比分析,最后确定了最优进口流速。利用相似原理对散热器Nu数和Re数的关联式进行了确定,为以后水冷板式散热器的优化设计提供了依据。     

两种电子设备散热器的对比数值模拟研究

本文用Icepak软件分别对有热管和无热管散热器进行了数值模拟对比研究,对数值模拟的过程和结果进行分析比较,结果表明有热管散热器的效果明显强于无热管散热器,同时显示了Icepak在电子设备散热研发过程中的重要作用.     

机车散热器空气侧CFD数值模拟与仿真研究

为了研究内燃机车散热器的传热与流动特性,采用了CFD仿真计算与试验相结合的方法,两者之间散热器传热系数的最大相对误差为7．9％。通过分析得到空气吸热量与空气质量流速的拟合函数,可用于散热器散热量的预测。讨论了CFD计算所得散热器流场云图及空气质量流速与散热量和流动阻力关系曲线,得出只有当空气流速大于某一数值时散热片上开小孔才能有利于增强换热,但空气流速在增大散热器散热量的同时增加了空气的流动阻力。     

散热器回流高度变化对变压器温度的数值模拟

建立了片式散热器的模型,通过模拟分析得到了散热器内部各点的温度场、速度场、压力场分布状况,分析了散热器回流口高度变化对散热效率的影响,并给出了计算分析。     

Numerical investigation on the heat transfer and flow in the mini-fin heat sink for CPU

Fluid flow and heat transfer in the mini-rectangular fin heat sink for CPU of PC using de-ionized water as working fluid are numerically investigated. Based on the real PC operating conditions, the three-dimensional governing equations for fluid flow and heat transfer characteristics are solved using finite volume scheme. The standard k–ε turbulent model is employed to describe the flow structure and behavior. The predicted results obtained from the model are verified by the measured data. There is a reasonable agreement between the predicted results and experiments. The results of this study are expected to lead to guidelines that will allow the design of the cooling system with improved cooling performance of the electronic equipments increasing reliable operation of these devices.     

Numerical simulation of heat transfer enhancement in wavy microchannel heat sink

In this paper, heat transfer and water flow characteristics in wavy microchannel heat sink (WMCHS) with rectangular cross-section with various wavy amplitudes ranged from 125 to 500 μm is numerically investigated. This investigation covers Reynolds number in the range of 100 to 1000. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using the finite-volume method (FVM). The water flow field and heat transfer phenomena inside the heated wavy microchannels is simulated and the results are compared with the straight microchannels. The effect of using a wavy flow channel on the MCHS thermal performance, the pressure drop, the friction factor, and wall shear stress is reported in this article. It is found that the heat transfer performance of the wavy microchannels is much better than the straight microchannels with the same cross-section. The pressure drop penalty of the wavy microchannels is much smaller than the heat transfer enhancement achievement. Both friction factor and wall shear stress are increased proportionally as the amplitude of wavy microchannels increased.     

Numerical study on natural convection heat dissipation of flared fin heat sink for high concentrating photovoltaic module cooling

High operating temperature of solar cell in high concentrating photovoltaic system reduces its electrical power efficiency and lifetime. Therefore, it is urgent to find an efficient cooling method to manage the temperature of solar cells. In this paper, we presented a structure and established a three-dimensional numerical model of flared heat sink to investigate the performance with different structural parameters. The simulation results reveal that the thermal resistance gradually decreases and tends to be constant as the increase in non-dimensional fin length. In addition, the thermal resistance of flared fin heat sink decreases with the increase in fin number to a certain value and then increases. The value of thermal resistance is minimum when the fin number of flared fin heat sink reaches to 13.     

Numerical simulation of stacked microchannel heat sink with mixing-enhanced passive structure

The paper is focused on the investigation of numerical simulation of stacked two-layer microchannel heat sink with enhanced mixing passive microstructure. In contrast to the smooth microchannel studies in the literature, the microchannel with embedded passive microstructure is chosen. The computational fluid dynamics (CFD) will be used to simulate the flow and heat transfer in a stacked two-layer microchannels with multiple MEMS easy-processing passive microstructures. To simulate the conjugated heat transfer among the heatsink and fluid, the three-dimensional conjugated model is used to solve this problem. The important parameters (e.g. the ratio of embedded structure height to microchannel height and fluid property) are investigated. The ratio of embedded structure height to microchannel height is changed from 0.13 to 0.26. The microchannel Reynolds number is fixed at 14.8. The stacked microchannel with passive structures has better performance than the smooth microchannels.     

Numerical simulation of fluid flow and heat transfer in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall

The paper is focused on the investigation of fluid flow and heat transfer characteristics in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall. In contrast to the new microchannel heat sink, the corresponding conventional rectangular microchannel heat sink is chosen. The computational fluid dynamics is used to simulate the flow and heat transfer in the heat sinks. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. The SIMPLEX method is used for the computations. The effects of flow rate and heat flux on pressure drop and heat transfer are presented. The results indicate that the microchannel heat sink with offset fan-shaped reentrant cavities in sidewall improved heat transfer performance with an acceptable pressure drop. The fluid flow and heat transfer mechanism of the new microchannel heat sink can attribute to the interaction of the increased heat transfer surface area, the redeveloping of the hydraulic and thermal boundary layers, the jet and throttling effects and the slipping over the reentrant cavities. The increased heat transfer surface area and the periodic thermal developing flow are responsible for the significant heat transfer enhancement. The jet and throttling effects enhance heat transfer, simultaneously increasing pressure drop. The slipping over the reentrant cavities reduces pressure drop, but drastically decreases heat transfer.     

Thermal intensification of heat transfer characteristics on the plate‐fin heat sink with piezoelectric fan

This study applied the computational fluid dynamic (CFD) code, ANSYS Fluent for simulating the effect a piezoelectric fan installed inside the rectangular channel by numerical simulation method for transient flow field and investigating the influence of each parameter. To remove the disorganized form of energy from the electronic components, the reversible piezoelectric effect is employed to energize the piezoelectric fan. To observe the variation of fan characteristics and to predict the convective heat transfer coefficient, CFD code ANSYS Fluent 15.0 is used. The numerical simulation parameters included are Nusselt number, number of fins (n = 12 and 14), and counter‐shift (inward and outward‐phase), and distance between the upper portion of the fan tip to the front part of the low thermal reservoir. Numerical analysis was carried out to evaluate the effect of thermal flow fields on the heat sink and piezoelectric fan employed in a flow domain. the results showed that by varying the height from channel bottom to the center of piezoelectric fan improves the performance of the piezoelectric fan, piezoelectric fan swinging in a transient phenomena and also simultaneously influences fluid flow behavior on the heat source surface, the fan vibration at counter‐phase has a better rate of heat transfer than vibration in in‐phase.     

Investigating the effect of various fin geometries on the thermal performance of a heat sink under natural convection

Experimentally investigates heat dissipation by different longitudinal fins fitted to a cylindrical heat sink under natural convection conditions. Five aluminum fin configurations at base temperatures (70°C, 85°C, 100°C, and 115°C) were studied. The first fin was plain (fin1), while second fin had a triangular edge (fin2). The rest fins have the same triangular edge but with six 1cm circular perforations near the edge (fin3). While the perforations in fin4 were in the middle longitudinal fin length. The last fin (fin5) had twelve 0.5 cm circular perforations distributed into two columns. The measurements were validated with theoretical correlation with an acceptable deviation. The results showed that fin2, fin3, fin4, and fin5 dissipate more heat by 2.4%, 8.7%, 11.4%, and 5% than the flat fin with 9.8%, 11.85%, 11.85%, and 10.82% weight reduction, respectively. The heat transfer coefficient enhanced by 7.98%, 16.81%, 12.35%, and 5.44% for fin5, fin4, fin3, and fin2, respectively. Large circular perforation was more effective to dissipate heat especially when located near the heat source as in fin4 which gives the best heat dissipation with more weight reduction. The proposed fins efficiency were greater than 92%.     

Study of heat transfer enhancement in a nanofluid-cooled miniature heat sink

This paper reports numerical solution for thermally developing temperature profile and analytical solution for fully developed velocity profile in a miniature plate fin heat sink with SiO₂–water nanofluid as coolant. The flow regime is laminar and Reynolds number varies between 0 and 800. The heat sink is modeled using porous medium approach. Modified Darcy equation for fluid flow and the two-equation model for heat transfer between the solid and fluid phases are employed to predict the local heat transfer coefficient in heat sink. Results show that the nanofluid-cooled heat sink outperforms the water-cooled one, having a considerable higher heat transfer coefficient. The effects of channel aspect ratio and porosity on heat transfer coefficient of the heat sink are studied in detail. Based on the results of our analysis, it is found that an increase in the aspect ratio or the porosity of the plate fin heat sink enhances the heat transfer coefficient.     

An experimental investigation of heat transfer in pin fin array

Detailed heat transfer measurements were performed by using 178 thermocouples in a channel with pin fin array. Local heat transfer coefficients and local heat transfer enhancement coefficients were obtained for eight Reynolds numbers ranging from 2000 to 100,000 on the endwall of the channel. The endwall boundary conditions for heat transfer investigation are heating the bottom endwall and heating symmetrically the bottom and top endwalls with constant heat flux. The mechanism of heat transfer enhancement with pin fin array has been discussed. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 533–541, 2001     

Numerical simulation on flow and heat transfer performances of serrated and wavy fins in plate-fin heat exchanger for hydrogen liquefaction

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