机车散热器空气流动的数值模拟分析

以DF4B型机车散热器为例,应用Pro／E造型软件对散热器零件进行了三维建模,应用GAMBIT软件进行了计算网格划分,应用Fluent软件建立了散热器仿真模型和数值模拟,并应用计算流体力学（CFD）和数值传热学方法计算了散热器内的温度场和速度场,分析了散热器内部的介质流动状态和热力分布情况。计算分析结果与试验数据有较好的吻合,验证了仿真模型的准确性和可行性。模拟结果表明,翅片形状对流场分布和强化换热的影响较大,为散热器的优化设计提供了理论依据。     

浅析海上风电机组的散热布置

海上风电发展前景广阔,开发大容量海上风电机组所面临的主要问题包括如何有效地冷却发电机、齿轮箱及变频器等核心部件。通过分析某MW级海上风电机组冷却系统的散热器空间布置形式、散热通道结构设计以及散热器所配风扇性能,利用CFD软件对散热通道内流场进行了三维数值模拟,结果表明,散热器的布置形式直接影响散热通道的系统阻力,进而影响散热器所配风扇与系统的特性匹配。     

热光伏散热器形状设计与分析

热光伏发电是通过光伏电池直接将辐射热能转换为电能的一种技术,而其中的散热器的设置是为了保证热光伏电池乃至整个系统正常运行的重要前提。采用强迫风冷发射状肋片散热器作为系统的散热装置;利用Fluent软件对五种肋片形状的散热器进行稳态温度场和流场数值模拟,总结出肋片式散热器的肋片数与热阻、压降特性曲线,并根据场协同原理,由温度场和压力场计算出协同角大小,确定了热光伏系统的最优散热器结构为交叉肋片。     

管翅式散热器顺排结构与错排结构的CFD模拟

应用CFD技术对管翅式散热器顺排结构与错排结构的流体流动及换热过程进行了数值模拟,获得了两种结构流体的速度场图、温度场图、压力场图以及出口温度分布和出口压力分布等重要数据,并通过这些图形、数据对两种结构的流体流动特性和传热性能进行了比较。研究结果可以用于管翅式散热器结构的优化,为换热器设计提供指导。     

SCAL型间接空冷塔内外空气流动和传热性能数值研究

利用计算流体力学软件CFD,对自然通风状态下,某电厂2×300 MW机组两机一塔的SCAL型间接空冷散热器空冷塔内外空气的流动和传热性能进行数值模拟、分析和研究。确定考核工况基准下,不同环境风速对空冷塔通风量和间接空冷散热器散热量以及机组背压的影响。模拟结果显示,随着环境风速的增加,空冷塔内外流场发生复杂变化,空冷塔通风量和散热器散热量降低,机组背压升高,将引起很大的经济损失。这为间接空冷系统空冷散热器的优化设计提供了参考。     

计算流体力学在水散热器芯部外形尺寸设计中的应用

为了将计算流体力学(CFD)方法方便地用于散热器芯部外形尺寸设计中,提出了试验设计、CFD计算、近似公式与序列二次规划法相结合的优化设计算法,避免了在优化设计过程中CFD计算时间过长的问题。对管片式水散热器芯部的空气流场进行了CFD数值计算,并通过与试验数据的对比验证了空气流动阻力的计算精度。在此基础上,对一种管带式水散热器进行了优化设计。结果显示:在保持散热器传热量和水侧流动阻力基本不变的情况下,优化设计后的空气侧流动阻力下降了23%。     

间接空冷机组空冷塔塔群内空气流动及传热性能研究

由于具有巨大的节水优势,间接空冷机组在我国富煤少水区域得到广泛应用。研究环境风对间接空冷系统的影响机理对指导电厂运行具有重要意义。以某电厂间接空冷机组为基础,构建水平布置散热器的空冷塔群物理和数学模型,通过数值模拟方法分析环境风对塔内空气流场及空冷散热器换热性能的影响。结果表明:环境风对空冷系统塔内空气流场影响较大,进而影响空冷散热器的散热性能。随着风速的增加,空冷塔的换热性能不断恶化。在临界风速时额定负荷下,下游空冷塔换热量比上游空冷塔减少2.5%。     

典型低温散热器性能实验和案例分析

为提高供暖系统能效和节约能源,采用低温供暖系统扩大新能源和可再生能源供热比例是目前重要的发展方向。首先通过散热器标准实验对铜铝复合低温散热器、铝制低温散热器和铜管强制低温散热器这3种低温散热器的散热性能进行了分析,结果表明:3种散热器低温工况拟合曲线与高温工况拟合曲线具有共线性,可以使用高温工况拟合曲线进行低温工况散热量计算。以北京某办公楼为建筑原型,进行低温散热器选型分析,结果表明低温工况下,强制对流散热器散热性能最好,且占地面积与铜铝复合散热器、铝制散热器在高温工况下的占地面积相近,适宜于在示例建筑中应用。所得研究结果为低温供散热器的实际应用提供了理论基础和实验数据。     

薄壁式散热器扁管的应用

为了达到整车轻量化的目的,采用了薄壁式散热器扁管。但扁管减薄后,散热器疲劳强度也随之减弱,无法通过整车耐久试验。针对散热器的失效模式,对散热器扁管进行了局部加强,并通过CAE分析及台架试验,对加强前后的散热器进行了对比,最后通过韦伯分析得出,加强后的散热器可以满足整车耐久性试验要求的结论。     

基于传热理论的散热器故障检测

采用热电偶测温技术对正常工况运行下的的普通散热器进行温度检测,通过传热理论研究散热器温度分布规律,对该散热器各个部位温度分布进行了动态分析。检测出散热器易出故障的部位、总结散热器故障原因主要来自于散热器构造、内部结构及金属腐蚀等方面。     

车用散热器结构强度静力学分析

建立了车用管带式散热器的有限元模型,并对其强度进行了计算分析,得出了散热器各部件应力分布及其危险位置,分析比对了改变主片约束,减震垫厚度,护板结构及整体约束时,芯体应力场分布及危险位置的变化情况,计算结果与散热器实际失效情况相符,对散热器结构设计有一定参考价值。     

基于ANSYS技术的CPU热管式散热器换热规律实验研究与数值模拟

CPU的工作温度是判断CPU性能的一项重要参数,为克服解析计算求取CPU温度精确值的困难,利用ANSYS有限元软件对热管式散热器与普通翅片散热器进行了热特性分析,模拟计算出稳态温度场分布,以及不同功率下CPU中心点的换热特性。研究结果表明,在稳定状态时,热管式散热器较普通翅片散热器具有极强的热传导性能;在CPU高功率工作时,普通翅片散热器CPU温度超过85℃无法满足换热要求,而热管式散热器CPU温度低于75℃,完全达到换热效果;模拟计算值与实验值最大相差4．1℃,应用数值模拟的方法研究CPU热管式散热器换热特性是可行。     

微槽群平板热管散热器传热性能的研究

分别选择不同的翅片间距和高度,对一种新型微槽群平板热管散热器的翅片结构进行优化,得到了热管散热器的最佳整体结构。结果表明:翅片的间距为14mm、高度为60mm时,平板热管散热器的传热性能最好。将热管、管脚以及翅片的温度与实验结果进行对比,结果吻合良好。     

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。     

基于CFD分析的散热器结构优化

利用STAR—CCM＋软件对某款设计中的散热器进行了流动与传热性能的分析,分析结果显示,按空气来流方向为散热器芯体前端,空气侧的对流换热系数远远高于其后端。这表明散热器芯体前端的利用率较高。将散热器芯体变薄之后,分别计算空气来流速度为5m／s、10m／s和15m／s三工况下其单芯体散热量。在来流速度为15m／s的工况下修改后散热器的散热量为原散热器的75％左右,并且随着来流速度的降低,该数值逐渐的增大。这样在相同的散热需求时,新的结构可以较大的节约材料。     

Exergy and energy analysis of a wavy fin radiator with variously shaped nanofluids as coolants

The present study deals with the energy and exergy analysis of a wavy fin radiator deploying various shapes of Al₂O ₃‐water as nanocoolant. The effects of radiator effectiveness, pumping power, heat transfer rate, and performance index with variously shaped nanoparticles, mainly spherical, brick, and platelet, on coolant flow rates and air velocities have been investigated. Also, the impacts of entropy, second law efficiency, entropy generation number, and irreversibility on radiator performance analysis have been considered with steady‐state assumptions. Theoretical analysis revealed that the spherical particle–based nanocoolant showed 21.9%, and 18.2% higher effectiveness than platelet and brick nanocoolants. However, minimization in the entropy generation is observed in the platelet shape of the nanoparticle. The second law efficiency is 13% higher for the spherical nanocoolant compared with the brick nanocoolant. An optimum entropy generation number is found at a coolant flow rate of 13 l/min and then gradually decreases with an increase in the coolant flow rate. For all the considered operating parameters, the spherical nanoparticle showed a better performance than brick and platelet nanofluids as a radiator coolant. Due to the enhanced overall performance for the spherical nanofluid, it may be considered as a potential candidate for a radiator coolant.     

Analysis and experimental verification of an improved cooling radiator

Roof ponds cooled by nocturnal long wave radiation have often been proposed as a cheap and effective means of providing thermal comfort in buildings in hot-arid locations. Many of the schemes incorporate flat-plate radiators through which the water is circulated at night to be cooled. This paper analyzes the parameters affecting the performance of such a radiator, specifically designed for nocturnal radiative cooling. A cheap, simple and flexible design for a cooling radiator was suggested as a result of the analysis, and tested at the experimental facilities of the Center for Desert Architecture at Sede-Boqer, Israel. The mean nightly cooling output of the radiator - due to the combined effect of radiation and convection - was over 90 watts/m² under typical desert meteorological conditions. The analytical model adapted for this application allows accurate calculation of the fluid temperature at the outlet of the radiator, as a function of the properties of the radiator, the meteorological conditions and the operating parameters of the cooling system.     

PERFORMANCE OF A HEAT PIPE THERMOSYPHON RADIATOR

A heat pipe thermosyphon radiator for use in domestic and industrial heating applications is presented. A test cell for the radiator is described and various experimental tests have been performed to determine the feasibility and performance of a heat pipe thermosyphon radiator. The thermosyphon radiator has been tested with freon 11, acetone, methanol and water as working fluids, and was compared with a conventional radiator. Best performance was obtained using methanol and acetone, and compares well with the conventional radiator. In addition, with these working fluids the thermosyphon radiator, by design, has desirable isothermal surfaces. The worst performance was with water, where local hot and cold spots formed on the radiator surface and the performance was poor. A natural convection/radiation model is presented for the thermosyphon radiator, and good agreement between measured and calculated heat transfer is obtained. The model reveals that typically 60% of the heat is transferred by natural convection and the remaining 40% by radiation. Advantages and further development of the thermosyphon radiator are discussed. © 1997 by John Wiley & Sons, Ltd.     

Thermal/structural analysis of radiators for heavy-duty trucks

A thermal/structural coupling approach is applied to analyze thermal performance and predict the thermal stress of a radiator for heavy-duty transportation cooling systems. Bench test and field test data show that non-uniform temperature gradient and dynamic pressure loads may induce large thermal stress on the radiator. A finite element analysis (FEA) tool is used to predict the strains and displacement of radiator based on the solid wall temperature, wall-based fluid film heat transfer coefficient and pressure drop. These are obtained from a computational fluid dynamics (CFD) simulation. A 3D simulation of turbulent flow and coupled heat transfer between the working fluids poses a major difficulty because the range of length scales involved in heavy-duty radiators varies from few millimeters of the fin pitch and/or tube cross-section to several meters for the overall size of the radiator. It is very computational expensive, if not impossible, to directly simulate the turbulent heat transfer between fins and the thermal boundary layer in each tube. In order to overcome the computational difficulties, a dual porous zone (DPZ) method is applied, in which fins in the air side and turbulators in the water side are treated as porous region. The parameters involved in the DPZ method are tuned based on experimental data in prior. A distinguished advantage of the porous medium method is its effectiveness of modeling wide-range characteristic scale problems. A parametric study of the impact of flow rate on the heat transfer coefficient is presented. The FEA results predict the maximum value of stress/strain and target locations for possible structural failure and the results obtained are consistent with experimental observations. The results demonstrate that the coupling thermal/structural analysis is a powerful tool applied to heavy-duty cooling product design to improve the radiator thermal performance, durability and reliability under rigid working environment.