镀碳纳米管铜岐片微通道冷却器散热性能实验研究

摘要：本文以空气为冷却介质,对镀碳纳米管铜岐片微通道冷却器进行了气冷散热性能实验研究。通过测量微冷却器出入口温度、底面温度与压降,研究了镀碳纳米管铜岐片微冷却器的散热性能。对镀碳纳米管的铜岐片和硅岐片微冷却器,通过实验比较得到,两种材料微冷却器的热阻在低热流密度时,温度变化梯度较大,随着热流密度的提高,热阻变化趋于稳定,并且镀碳纳米管的铜岐片微冷却器散热性优于硅岐片材料微冷却器。     

微通道换热器的数值模拟和结构优化

为提高微通道换热器的换热效率,利用COMSOL耦合求解流动和传热方程,对微通道换热器换热特征进行数值模拟.通过分析微通道换热器的温度、微通道的入口与出口的压差以及微通道换热器的总热阻等参数,对其换热性能进行评估.优化微换热器的几何结构可以有效提高换热性能.数值模拟结果表明：当微通道的高宽比为0.8、微通道与间隔的宽度比为0.6、微通道数为71时热阻最小,换热性能最佳.     

涡轮叶片凸包强化传热的数值仿真研究

为了提高发动机高温涡轮叶片的冷却效率,延长使用时间,通过增强换热技术,采用数值仿真计算方法,在Realizable k-ε湍流模型上对球形凸包壁面的光滑矩形通道进行了换热特性研究,分析了凸包区域流场特性以及导致凸包区域换热增强的机理.在Re=20000 ～60000的范围内比较了三种不同凸包深度的换热性能,研究了凸包深度对换热和流阻的影响,计算结果表明随着凸包深度增加,换热增强因子和流阻增大因子增加,平均综合换热性能也有所增强.计算数据显示Re数对凸包壁面的换热增强因子和阻力增大因子的影响相对较小,对平均综合传热性能的影响也相对较小.仿真结果验证-了仿真模型可为增强换热性能设计提供依据.     

模块液体冷却技术及其应用与分析

随着电子技术的迅速发展,电子元器件的总功率密度大幅度增长而物理尺寸却越来越小,而且高温的温度环境会影响电子元器件的性能.有效解决电子元器件的散热问题已成为当前电子元器件和电子设备制造的关键技术,液体冷却技术可在一定程度上适应高热流密度的散热要求.针对模块上电子元器件的液冷问题,该文综述液体冷却的特点,设计不同通道形式的冷板,并进行适当的应用分析.     

沸腾情形下开放式毛细微槽中的干涸特性实验研究

利用高速摄像仪、CCD以及宽视场体视显微技术对液体在微槽内的润湿、蒸发和沸腾现象进行了可视化观察和描述,对发生沸腾换热现象时的竖直矩形毛细微槽群热沉中的液体沿微槽槽道方向的干涸点高度(润湿高度)进行了测量,并对微槽几何尺寸、工质等因素对润湿高度的影响进行了实验研究.实验结果表明:微槽群的高强度的强化换热特性是由薄液膜蒸发和核态沸腾换热的共同作用造成的;发生沸腾换热现象时,微槽内的液体润湿高度随着输入加热功率的增加能得到有限度地升高;一定热负荷下,微槽较深、较宽以及微槽群密度较大时液体的润湿高度较高;在微槽内发生核态沸腾的情形下,甲醇的润湿高度要远大于乙醇和蒸馏水.     

出流比对带侧流梯形扰流柱通道换热的影响

为了解侧向出流比对扰流柱通道端壁换热的影响,对简化后的涡轮叶片尾缘扰流柱冷气通道进行了数值仿真研究.结果表明:出流比对端壁表面的换热有很大影响.出流比为0时,梯形通道端壁换热系数呈不对称分布,靠近梯形长边处较大,窄边处较小;出流比大于0时,端壁靠近梯形窄边通道弦向出流口区域的换热系数随着出流比的增大而增大,而靠近梯形长边区域换热系数则随着出流比的增大而降低;出流比对通道端壁表面换热的影响随着雷诺数的增大而增大.     

集成微流体测控芯片的研制

设计、研制了集成有微泵、微沟道、微流量传感器、温度传感器的微流体测控芯片.采用有限元软件ANSYS模拟分析了将其作为冷却芯片时微沟道的散热作用,分析确定了芯片上各元件的结构.该集成芯片为硅-玻璃结构,在硅片上,利用ICP法刻蚀无阀微泵泵体和微沟道;在7740玻璃片上,以溅射、剥离法制作微流量和温度传感器;图形精确对准后硅/玻璃以静电键合方法封接.无阀微泵采用压电元件驱动.测试结果表明:集成芯片具有冷却功能,循环水的流速最大可达25.4mm/s.     

不同错开位置锯齿翅片热力特性的三维仿真

对通道壁面沿流动方向周期性地错开而在横向上通道壁面有几组不同错开位置的强化换热翅片的层流流动和传热情况进行了三维仿真分析。这类翅片经常被应用在汽车和电子设备的冷却系统中。三维有限元方法用来模拟Re数在100-1500范围时翅片的速度场和温度场，考虑了通道壁面的不同错开位置(SSP)对翅片传热性能的影响。仿真结果与以前的试验数据也进行了比较研究。     

微传感器表面温度非接触测试及In2O3微传感器气敏特性的研究

基于“相同温度下同一物体所产生的辐射功率相同”这一原理,搭建了一套非接触式微小芯片表面工作温度的测试平台.利用该平台对汉威电子出品的一种平面陶瓷基微气体传感器衬底的表面工作温度进行了测试,明确了其表面温度与加热电流之间的关系及芯片表面工作温度分布图.在此基础上,确定了In2 O3纳米纤维的最佳工作温度,研究了最佳工作温...     

V型微通道热沉的加工与测试

基于MEMS技术的V型微通道冷却器具有低热阻、低流量,高效率以及体积小等特点,能够对激光二极管阵列和其他高功率密度器件进行快速、高效地散热,成为一种新型的散热方案.介绍了V型微通道热沉的加工工艺,并利用研制的V型微通道热沉样品,模拟热源加载,进行了测试热沉散热性能的试验.通过试验数据得到微通道热沉的面积热阻仅为0.0543 K·cm2/W.     

V型微通道热沉的 流体流动与传热问题研究

V型微通道热沉具有体积小、流速小、散热效率高等优点,是将多个DL线阵组装为面阵并实现高性能冷却封装的良好解决方案.本文采用计算流体力学软件Fluent建立了V型微通道的数值模型,研究了其中的流体流动与传热问题.仿真结果表明,设计的V型微通道可满足激光二极管线阵的散热要求.仿真分析结果与V型微通道热沉样品的模拟热源加载实验测试数据对比,吻合较好,证明了数值仿真的有效性.     

Interlayer cooling potential in vertically integrated packages

The heat-removal capability of area-interconnect-compatible interlayer cooling in vertically integrated, high-performance chip stacks was characterized with de-ionized water as coolant. Correlation-based predictions and computational fluid dynamic modeling of cross-flow heat-removal structures show that the coolant temperature increase due to sensible heat absorption limits the cooling performance at hydraulic diameters ≤200 μm. An experimental investigation with uniform and double-side heat flux at Reynolds numbers ≤1,000 and heat transfer areas of 1 cm² was carried out to identify the most efficient interlayer heat-removal structure. The following structures were tested: parallel plate, microchannel, pin fin, and their combinations with pins using in-line and staggered configurations with round and drop-like shapes at pitches ranging from 50 to 200 μm and fluid structure heights of 100–200 μm. A hydrodynamic flow regime transition responsible for a local junction temperature minimum was observed for pin fin in-line structures. The experimental data was extrapolated to predict maximal heat flux in chip stacks having a 4-cm² heat transfer area. The performance of interlayer cooling strongly depends on this parameter, and drops from >200 W/cm² at 1 cm² and >50 μm interconnect pitch to <100 W/cm² at 4 cm². From experimental data, friction factor and Nusselt number correlations were derived for pin fin in-line and staggered structures.     

Effect of wall roughness on performance of microchannel applied in microfluidic device

The influence of wall roughness on flow and heat transfer performance in microchannels at low Reynolds number is investigated in this paper. Two sizes of PMMA microchannels are fabricated by microinjection molding and the width is 20 μm and 800 μm respectively. The surface profile of bottom wall is described by the two-dimensional fractal geometry method and it is found there is error within 5% between surface roughness obtained by the fractal geometry method and actual roughness. Then, the effects of dimensionless relative roughness (5–7.5%), fractal dimension (1.5–1.8), aspect ratio (0.025–4) on the flow resistance and heat transfer performance are analyzed by numerical and experimental method respectively. Reynolds number considered here are 10–60. The results show that the better flow performance and heat transfer performance can be obtained with high aspect ratio of rectangular microchannel. However, increasing surface roughness not only increases the heat transfer performance, but also introduces a large flow resistance, which makes the friction coefficient rise sharply. As a result, surface roughness has great influence on the flow and heat transfer performance, and the most suitable surface morphology should be obtained according to the specific application.

     

A microchannel heat exchanger design for microelectronics cooling correlating the heat transfer rate in terms of Brinkman number

Microchannel heat exchangers are a well known device in the application of microelectronics cooling. In this paper, liquid microchannel heat exchangers were designed and investigated with varying channel width in order to find the maximum cooling efficiency when combined with pumping performance. A recently developed correlation of heat transfer rate in terms of Nusselt number and Brinkman number was adopted to predict cooling efficiency of the microchannel heat exchanger and was compared with the experimental results. Conventional heat transfer theories and numerical commercial code were also used to predict the cooling efficiency. The measured minimum thermal resistance of the microchannel heat exchanger showed a good agreement with the prediction from the new correlation, whereas calculation results from conventional theories and numerical code showed large divergence. It can be seen that the microchannel heat exchanger can be optimized when combined with pumping performance. In addition, the new correlation of heat transfer rate in terms of Brinkman number can be quite a useful tool in design of microchannel heat exchanger.     

MPTL板翅式换热器性能的数值分析

研究机械泵驱动的两相冷却回路(MPTL)换热器传热效能优化问题,由于换热器的应用环境极为复杂,目前的实验数据极度匮乏,而且结构特殊,现有的标准叉流板式换热器的设计方法并不适用。为了提出可行的设计优化方法,针对某典型MPTL板翅式换热器,建立一种简化的三维物理数学模型,采用有限体积法及流固耦合方法深入研究该换热器在典型结构及设计工况下的流场特性,随后研究其在不同翅高及进口雷诺数时的换热性能变化规律。数值仿真结果表明,换热器换热效率较高,压力损失较小,且随着翅高的降低、进口雷诺数的增加,换热性能逐渐提高。结果证明,可为换热器的进一步设计与优化提供有益的参考。     

Single-phase laminar and turbulent heat transfer in smooth and rough microtubes

An experimental campaign was carried out studying laminar and turbulent heat transfer in uniformly heated smooth glass and rough stainless steel microtubes from 0.5 mm down to 0.12 mm. Heat transfer in turbulent regime proved to be coherent—within experimental accuracy—with the classic Gnielinski correlation for the Nusselt number. For the laminar case, an anomalous drop in Nusselt number for decreasing Reynolds number was observed in the smooth glass tubes. As the stainless steel tubes manifested relatively normal diabatic behaviour in this regime (apart from the evident influence of the thermal development region that increases heat transfer above the thermally fully developed value), the explanation of this unexpected diminution of the Nusselt number must be sought in the dispersion of heat, put in externally through the thin film deposited on the glass tube outer surface, to peripheral attachments to the test section. This distorts the measured energy balance of the experiment, especially as the convective force of the fluid diminishes, resulting in lower Nusselt numbers at lower Reynolds numbers.     

Microelectronic chip cooling: an experimental assessment of a liquid-passing heat sink,a microchannel heat rejection module,and a microchannel-based recirculating-liquid cooling system

Results of heat transfer testing of heat absorption modules (HAM), heat rejection modules (HRM), and a recirculating-liquid cooling system are reported. Low-profile, Cu-based, microchannel heat exchangers (MHEs) were fabricated and used as the HAM as well as components for assembly of a microchannel HRM. Detailed experimental assessment of two different liquid-passing HRMs and a microchannel-based recirculating-liquid cooling system was carried out, and benchmarked against all-solid devices of the same geometric dimensions. Incorporating microchannel liquid flow through each fin, the device-level heat transfer performance of the microchannel HRM was improved by up to ~50%. Detailed testing of a microchannel-based recirculating-liquid cooling system indicate that low-profile Cu MHEs are highly effective in heat flux removal while having a small area/volume footprint, and that enhancing the HRM performance is critical to boosting the overall performance of such recirculating-liquid cooling systems.     

Numerical analysis of heat transfer in a manifold microchannel heat sink with high efficient copper heat spreader

A manifold microchannel heat sink integrated with a high efficient copper heat spreader is presented. A series analysis of three-dimensional fluid flow and heat transfer performance in this mirochannel heat sink and conventional structure are performed by CFX commercial software package. The temperature difference along the flow direction in the new microchannel heat sink is less than that of the conventional microchannel heat sink due to effect of the transverse channel arrays. The maximum heat flux input of the new microchannel heat sink increases 75% more than the conventional structure with the flow rate of 1 m/s. The new design has better heat transfer characteristics than conventional one for the full range of flow rates considered.     

基于传热理论的热电能量转换系统集成分析

热电能量转换系统可实现热能和电能的直接转换。在一个完整的热电系统中,热电器件与冷热端换热器组成热阻网络,该热阻网络与冷热源之间的换热对系统性能具有决定性影响。该文从网络节点间的耦合传热关系出发,分析了外部换热对系统内部温度分布的影响,得到了实际热环境中热电系统输出性能的近似理论表达式。在此基础上,该文建立了外部换热条件与系统峰值输出功率的直接关系,并提出一套热电能量转换系统设计策略,可用于热电发电系统的快速设计。     

Waterways structural optimum design of electric car radiator

Thermal resistance was composed by thermal resistance of Aluminum substrate,thermal resistance of convective heat transfer and the thermal resistance of the cooling liquid.The change rule was studied through the calculation on Aluminum plate thermal resistance,thermal resistance of convective heat transfer and the thermal resistance of the cooling liquid.Its change regularity was simulated by toolbox In the MATLAB,and it was found that thermal resistance of convective heat transfer effect on the efficiency was most obvious in a certain amount of the heat and flow for thermal resistance of the Pin-fin radiator under the premise.The structural parameters of radiator were related to the size of thermal resistance.