【作者】 崔珍珍；

【导师】 夏国栋；

【作者基本信息】 北京工业大学 ， 热能工程， 2013， 博士

【摘要】 随着微电子技术的迅速发展，先进设备与器件的热负荷不断提高，传统冷却器的设计与制作已经无法满足现代技术飞速发展的要求。伴随着微加工技术的日臻完善，使更为复杂的微通道热沉进入国际传热学界的研究视野。同时微尺度流动测试技术也成为国内外研究的焦点。本文研究内容主要包括两大部分：不同结构微针肋热沉流动与传热特性；微尺度单相及两相流场测试技术。第一部分内容，本文主要提出了长菱形微针肋热沉及组合式微针肋热沉。在研究过程中，加工了硅基长菱形微针肋热沉，并对其流动与换热性能进行了实验研究和数值模拟。结果显示：在实验Re数范围内，长菱形针肋的换热系数随Re的增大而增大。相同Re数下，热流密度对换热系数的影响较小。热阻随泵功的增加不断降低；在泵功较小时，热阻降低的速度较快；当泵功增大到一定值时，热阻的变化趋势趋于平缓。在一定的泵功下不同热流密度之间的总热阻值并没有太大的区别，Nu随着Re增大均增大。与同样尺寸圆形、菱形针肋相比，45o长菱形针肋具有较好的的换热性能，可以避免针肋尾部涡脱落造成的阻力损耗，同时长菱形针肋尾部延伸拓展了换热面积并扩大固体导热区，从而提高换热效果。对于组合式微针肋热沉，采用数值模拟进行强化传热研究。流场中加入以一定冲角布置的三角小肋可以有效强化换热，且不同的冲角所产生的强化换热效果不同。结果表明：所设计的4种布置方式的微针肋，在相同Re，冲角越大，压降也越大，平均Nu也越大，因此存在一个最优化角度布置即冲角为30°时，可使强化换热效果达到最佳。组合式微针肋主要通过三角小肋的存在破坏边界层的发展，在圆肋尾部形成纵向涡，减小尾部回流，增强流场的扰动性和混和性，提高流场和温度场的协同性，使整体和局部的换热都得到极好强化第二部分内容，本文主要基于Micro-PIV流场可视化实验台，进行了单相流体横掠顺排圆形微针肋的流场测试及Y型进口微通道内液液两相混合流场测试。在研究过程中，加工制作了PDMS材质顺排圆形微针肋，并在小雷诺数下对其内部流场特性进行测试。结果表明：顺排圆形微针肋沿第1-2排针肋之间主通道方向流速呈周期性变化；在较小雷诺数下，涡量分布区域面积较小，涡量主要集中分布于沿着流向微针肋的左右两侧，且涡量强度大小相近；较小雷诺数下的涡量在与流动垂直方向的扩散能力大于较大雷诺数的涡量。对PDMS材质Y型进口微通道内液液两相流场进行可视化研究。结果表明：Y型通道中生成的液弹，形状规则，大小均一。液弹的形成经历了生长，冲刷，拉伸，脱落的过程。在恒定流量比下，Y形通道内液弹的轴向长度随连续相Ca数增大而减小；在恒定连续相Ca数下，Y形通道内液弹的轴向长度随流量比增大而增大。更多还原

【Abstract】 With the development of technology, the higher integration degree of electronicdevices results in more heat flux. The traditional cooler design and production hasbeen unable to meet the rapid development of modern technology. As themicro-processing technology is getting more sophisticated, more complex,micro-channel heat sink has become goes into the international heat transfer academicresearch. The microscale flow test technology has become the focus of research athome and abroad.The content of this paper includes two parts: the flow and heat transfer of two kindmicro pin fin heat sink; microscale single-phase and two-phase flow testingtechniques.For the first part of the contents, we propose long-diamond shaped micro pin finheat sink and a combined micro pin fin heat sink.During the study, the silicon long-diamond shaped micro pin fin was processed.Experimental research and numerical simulation about the flow and heat transfer oflong-diamond shaped micro pin fin were performed. The results showed that: withinthe range of the number of experiments Re, the heat transfer coefficient of thelong-diamond shaped micro pin fin increases with Re. with same Reynolds number,the heat flux has no effect on heat transfer coefficient. Thermal resistance decreasedwith the increased pump power. The thermal resistance decreased faster when pumppower is small. And the thermal resistance becomes a certain value when the pumppower increases to a point. There is no total thermal resistance difference for differentheat fluxes. Nu increases with the increase of Re. Compared with the same sizecircular, and diamond micro pin fin,45o long-diamond micro pin fin has the bestrheat transfer performance. The long-diamond design avoids the vortex sheddingwhich will cause the resistance loss. Also, the long-diamond design extends the heattransfer area and conductivity of solid. Thereby it enhanced the heat transfer effect.A numerical simulation about the heat transfer characteristic for combined micropin fin has been done. The heat transfer effect of the combined micro-pin fin withdifferent angles decreased as the Re increasing among the present Re range. Therefore,this new structure was more appropriate for the condition of low Re. The combinedmicro-pin fin could damage the development of boundary layer by the little triangularmicro-pin fins, it could form longitudinal vortexs in the tail of circular micro-pin finand decrease backflow, enhance the effect of disturbance and mixing. The combinedmicro-pin fin improved the synergy of flow field and tempreture field; the heattransfer effect could be enhanced greatly for both the whole and the local. Thecombined micro-pin fin improved the synergy of flow field and tempreture field; theheat transfer effect could be enhanced greatly for both the whole and the local. The second part of this paper is mainly based on Micro-PIV flow visualizationexperimental system. Two parts of flow field testing were performed: the ingle-phasefluid flow field measurement of in-lined circular micro pin fin and liquid-liquidtwo-phase mixture flow field measurement of Y-import microchannel.In the course of the study, device of in-lined circular micro pin fin was processedusing PDMS material. And its internal flow field testing was performed. The resultsshow that: the velocity along the direction of the main channel at thefirst to secondrow of in-lined circular micro pin fin changes periodically. At lower Reynoldsnumbers, the vorticity distribution area is small. Vorticity mainly distributes at thearea along the flow of the left and right sides of the micropin fin, and the vorticitystrength is almost the same. At low Reynolds numbers, the vorticity diffusioncapacityin the direction perpendicular to the flow is greater than that at large Reynoldsnumber.A liquid-liquid phase flow field visualization test was performed in PDMS materialY imported micro channel. The results show that the slug flow in Y imported microchanne is regular shape, uniform size. The formation of the liquid projectile hasexperienced growth, scouring, and stretching, shedding process. With the constantflow rate ratio, the axial length of slug decreased with the increased continuous phaseCa; with the constant continuous phase Ca, the axial length of slug increase with theincreased flow ratio.更多还原