水平矩形翅片椭圆管束的自然对流放热实验研究

本文对狭窄矩形槽道内水平矩形翅片管束的自然对流放热进行了实验研究，揭示了矩形翅片和张力绕片椭圆管束 的放热强度与板间距ｄ、管间距Ｓ１、Ｓ２及空气流通截面     

散热片基板开孔对自然对流换热的影响

为研究自然对流情况下矩形散热片基板开孔对换热的影响,采用数值模拟方法对基板开孔的散热片的传热性能进行了分析,讨论了开孔后换热强化的物理机制。结果表明:开孔后发热元件的温度降低;通孔破坏了散热片基板上速度边界层的形成,从而强化了局部表面处的对流换热。     

水平放置离散矩形直翅片强制对流的传热研究

实验了不同空气流速时水平放置离散矩形直翅片组的稳态传热着重探讨了翅片列间距对翅片组散热性能和阻力损失的影响,用离散翅片的长度作为定性尺寸,得到了计算直线排列的离散翅片组平均对流传热系数的无量纲传热准数关系式     

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%。     

散热带翅片参数对车用水箱散热器流动传热性能的影响

采用数值仿真结合正交设计方法对工程车用散热器的主要几何参数进行了计算和分析.通过极差和方差分析,获得了各参数对散热器的散热和流动性能影响的敏感次序以及显著性水平,并拟合出参数-性能关联式.同时,进行了风洞试验验证上述数值仿真方法.结果表明:仿真结果与试验测试数据趋势吻合良好,该仿真方法可以有效地进行翅片参数对散热器流动传热性能的影响研究,有利于缩短设计周期和减少设计成本.     

高速燃气喷射管道表面自然对流散热分析

将热阻比拟为等效电阻,采用有限体积元法对超音速燃气喷射管道传热及表面自然对流散热进行数值计算,得到喷射管壁温度分布和表面不同自然对流散热及参数变化对壁温的影响.由于管两端自然对流散热作用,管中部温度高于两端;随着表面自然对流换热增强管壁温度逐渐降低;选用不同材质时,随材质导热系数增大管内外壁温差线性增大.     

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。     

竖壁自然对流换热系数计算研究

本文对竖壁自然对流求解提出了新的条件假设，给出了其合理的控制方程，通过计算，得出了自然对流计算的新准则关系式，拓展准则的适用范围，可以为工程精计算采用。     

自然对流温度场节能改造

本文通过热流理论分析和传热计算,指出了某一运行多年的自然对流温度场的不足,为了节能增效,采取了快捷的改造措施。工程竣工后试运转表明节能率可达50%,对所有自然对流温度场的改造具有普遍指导意义和重要参考借鉴作用。     

A novel heat dissipation fin design applicable for natural convection augmentation

In this study, a comparative study of heat sink having various fin assembly under natural convection is investigated. The fin pattern includes a rectangular, a trapezoidal and an inverted trapezoidal configuration. Tests were performed in a well controlled environmental chamber having a heat load ranging from 3 to 20 W. From the test results, the heat transfer coefficient of the conventional rectangular fins is higher than that of the trapezoidal fins while the heat transfer coefficient of the inverted trapezoidal fins is higher than the trapezoidal one by approximately 25%, and it exceeds that of convectional rectangular fin by about 10%. The heat transfer improvements of the inverted trapezoidal fin are mainly associated with a larger temperature difference and inducing more air flow into the heat sink.     

Thermal optimization of plate-fin heat sinks with fins of variable thickness under natural convection

In this study, thermal performance of a vertical plate-fin heat sink under natural convection was optimized for the case in which the fin thickness varied in the direction normal to the fluid flow. For this optimization, the averaging approach presented in an earlier paper for the case of the heat sinks under forced convection was extended to study the performance of heat sinks under natural convection. In the case of an air-cooled heat sink, the thermal resistance decreases by up to 10% when the fin thickness is allowed to increase in the direction normal to the fluid flow. However, the difference between the thermal resistances of heat sinks with uniform thickness and the heat sinks with variable thickness decreases as the height decreases and as the heat flux decreases.     

Enhancement of natural convection heat transfer from a vertical heated plate using inclined fins

An enhancement technique is developed for natural convection heat transfer from a vertical heated plate with inclined fins, attached on the vertical heated plate to isolate a hot air flow from a cold air flow. Experiments are performed in air for inclination angles of the inclined fins in the range of 30° to 90° as measured from a horizontal plane, with a height of 25 to 50 mm, and a fin pitch of 20 to 60 mm. The convective heat transfer rate for the vertical heated plate with inclined fins at an inclination angle of 60° is found to be 19% higher than that for a vertical heated plate with vertical fins. A dimensionless equation on the natural convection heat transfer of a vertical heated plate with inclined fins is presented. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(6): 334–344, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20168     

Active control of natural convection in a fluid layer with volume heat dissipation

A fluid layer subjected to an internal heating source and cooled from above and below is studied. Using linear stability analysis and numerical simulation it is shown that the critical Rayleigh number related to the bifurcation from the motionless conductive state to a convective state can be increased by controlling the heating power. A feedback-control strategy using the deviation of the real fluid temperature from that of the associated conductive state is applied for this purpose.     

Correlations for heat dissipation and natural convection heat-transfer from horizontally-based,vertically-finned arrays

Experimental data for heat dissipation from five duralumin vertical rectangular fin-arrays with the base horizontally oriented were measured. These measurements were to extend data obtained earlier from aluminum fin-arrays using the same experimental system and method. Data collated from earlier and present work covered the range of inter-fin separation distances from 6.25 to 7.95 mm. The range of the fin base excess temperature above the ambient air temperature, however, was quite extensive, from 19.0±0.1°C to 125.0±0.1°C. The fin length range was from 127 to 254 mm, the height from 6.35 to 38.10 mm, the thickness from 1.02 to 3.10 mm and the number of fins per array from 10 to 33. Relevant non-dimensional parameters formulated by earlier similarity analyses were used to generalize the data. Two types of correlations, one which used the inter-fin separation distance as the prime geometric parameter, and the other, which used half of the fin length, were presented and deviations discussed.     

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.     

Enhancement of natural convection fins by high-frequency forced oscillations

This paper conveys a numerical simulation of an active enhancement device for natural convection in the interfin spaces of a fin array. A baseline solution for the non-enhanced situation revealed that the confinement created by the walls of adjacent fins and the base surface gave rise to a drastic reduction of the heat transfer coefficient values compared with those for the standard vertical plate. This outcome demonstrated the necessity for enhancement. The enhancement device investigated here communicated with the interfin space via an opening in the base surface. Enhancement was achieved by alternately introducing and extracting air into and from the space. The frequency of the introduction/extraction cycle was varied over values of 0, 10, 50, and 100 Hz. For each of these cases, spatially local, cycle-averaged heat transfer coefficients were determined on the bounding surfaces of the interfin space and on the outboard surface of a fin that faced a large ambient space. Results were also obtained for the cycle- and spatially averaged coefficients. Even at a low oscillation frequency of 10 Hz, the interfin heat transfer coefficients were significantly enhanced but not sufficiently to overcome the confinement effect. At 100 Hz, the enhancement gave rise to coefficient values that are about 64 times greater than the unenhanced values.     

Effect of fins on forced convection heat transfer around a tube

Effect of fins on heat transfer around a tube was investigated experimentally. A test tube of 30 mm diameter was installed in a test section of an open‐type wind tunnel as a single tube, or as a center tube in a single tube row and in a tube bundle of staggered layout. Fins made of paper were put on the test tube having certain fin spacing. It was clarified from the experiment that the local heat transfer coefficient around the tube degrades with decreasing fin spacing, especially on the downstream side of the tube, and the minimum fin spacing where the effect of the fin begins to appear is the largest for the single tube and the smallest for the tube bundle. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(5): 445–454, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10098