CAREER: Enhanced Two-phase Thermal Management Using Self-sustained Flow Oscillations at the Microscale

职业：利用微尺度自持流动振荡增强两相热管理

• 批准号: 0748249
• 负责人: Vinod Narayanan
• 金额: $ 40万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-15 至 2014-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0748249&HistoricalAwards=false
• 关键词: CAREER; Enhanced; Two; phase; Thermal

0748249NarayananThe broad goal of this CAREER project is to establish an integrated research and educational framework in the field of thermal management. Dissipation of heat loads at levels of ~ 102 to 103 W/cm2 is of great interest in the cooling of high-power electronics. Current predominant cooling methods include spray and liquid jet impingement evaporation, and flow boiling in microchannel heat sinks. Although these methods have demonstrated capability of removing high heat fluxes, significant challenges still exist in improving cooling efficiencies. The primary intent of the proposed research is to demonstrate, by the use of inherent flow oscillations, enhancement in heat transfer rate per unit coolant mass flux beyond that currently achieved using evaporative liquid jet and spray impingement, with no additional pumping power penalty. An organ pipe resonance mechanism will be used to create a self-sustained, self-excited oscillatory jet (SOJ). The hypotheses to be considered include the following: (1) Flow oscillations enhance heat transfer rates through both periodic renewal of the hydrodynamic and thermal boundary layers and the increased convective heat transport by bubble oscillations at the surface, (2) Critical heat flux (CHF) can be increased (beyond that attained by free-surface liquid jets and sprays) due to the effective rewetting of the surface by transverse flow oscillations, and (3) Use of flow oscillations mitigates surface deposition and aggregation of nanoparticles when using nanofluids.To test the above hypotheses, a predominantly experimental approach is proposed to document the heat transfer rate and CHF onset. Key momentum and thermal transport mechanisms will be identified by quantitative imaging of fluid temperature using laser induced fluorescence, jet flow field using particle image velocimetry, bubble dynamics using high-speed imaging, and surface temperature using IR thermography. The effect of flow oscillations on surface microstructures and nanofluids will also be studied.Several aspects of the research will be integrated into the University Honors College (UHC) curriculum through (a) an undergraduate Heat Transfer course, (b) a proposed Honors colloquium, and (c) UHC theses. At the graduate level, research outcomes will be disseminated through two existing classes as well as through a new special topics class based on the research area. Each summer, motivated high-school students will participate in research activities through the Apprenticeship in Science and Engineering program (www.saturdayacademy.org). The intellectual merit pertains to the following novel aspects: (a) study of the jet flow oscillation phenomenon under phase change conditions, (b) coupling of jet flow oscillations with existing enhancement mechanisms such as microstructured surfaces and nanofluids, and (c) performing detailed imaging to delineate the physical mechanisms of convective heat transport. Broader Impacts include education of three PhD, one MS, and several undergraduate and high-school students in the field of thermal management. Enhancement of heat transfer rates and developing methods to delay the onset of CHF in two-phase thermal management are of critical importance to the performance of high-power electronics and avionics, as well as for computer chip cooling. Utilization of passive enhancement methods to achieve enhancement in thermal and fluid transport fosters reductions in energy use by effective use of available resources.

0748249 Narayanan这个CAREER项目的广泛目标是在热管理领域建立一个综合的研究和教育框架。在~ 102至103 W/cm 2的水平下的热负荷的耗散在高功率电子设备的冷却中具有极大的兴趣。目前主要的冷却方法包括喷雾和液体射流冲击蒸发，以及微通道热沉中的流动沸腾。尽管这些方法已经证明了去除高热通量的能力，但在提高冷却效率方面仍然存在重大挑战。所提出的研究的主要目的是证明，通过使用固有的流量振荡，在每单位冷却剂质量流量的传热速率的增强超过目前使用蒸发液体射流和喷雾冲击，没有额外的泵送功率的惩罚。风琴管共振机制将被用来创建一个自我维持，自激振荡射流（SOJ）。需要考虑的假设包括：（1）流动振荡通过流体动力边界层和热边界层的周期性更新以及通过表面处的气泡振荡增加的对流热传输来增强热传递速率，（2）临界热通量（CHF）可以增加（超出自由表面液体射流和喷雾所获得的）由于横向流动振荡对表面的有效再润湿，（3）流动振荡的使用减轻了纳米流体的表面沉积和纳米颗粒的聚集。为了验证上述假设，提出了一种主要的实验方法来记录传热速率和CHF开始。 关键的动量和热传输机制将被确定的定量成像的流体温度，使用激光诱导荧光，射流场使用粒子图像测速，气泡动力学使用高速成像，和表面温度使用红外热成像。流动振荡对表面微观结构和纳米流体的影响也将研究。研究的几个方面将通过（a）本科生传热课程，（B）拟议的荣誉座谈会和（c）UHC论文整合到大学荣誉学院（UHC）课程中。在研究生一级，研究成果将通过两个现有的类以及通过一个新的专题类的基础上的研究领域传播。每年夏天，积极的高中生将通过科学和工程学徒计划（www.saturdayacademy.org）参加研究活动。智力上的优点属于以下新的方面：（a）在相变条件下的射流振荡现象的研究，（B）耦合射流振荡与现有的增强机制，如微结构表面和纳米流体，和（c）进行详细的成像描绘对流热传输的物理机制。更广泛的影响包括在热管理领域的三个博士，一个MS，和几个本科生和高中生的教育。在两相热管理中，提高传热速率和开发延迟CHF发生的方法对于大功率电子设备和航空电子设备的性能以及计算机芯片冷却至关重要。利用被动增强方法来实现热和流体传输的增强，通过有效利用可用资源来促进能量使用的减少。