Evaporation/boiling in thin capillary wicks (I) - Wick thickness effects
Evaporation/boiling in thin capillary wicks (I) - Wick thickness effects
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DOI：
10.1115/1.2349507
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发表时间：
2006-12-01
影响因子：
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通讯作者：
Wang, Yaxiong
中科院分区：
文献类型：
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作者：
Li, Chen;Peterson, G. P.;Wang, Yaxiong
这里介绍的是两部分研究中的第一部分，旨在系统地识别和研究影响薄毛细芯吸结构的蒸发/沸腾和临界热通量（CHF）的参数。的蒸发/沸腾传热系数，特性，和CHF进行了研究，在稳态条件下的各种毛细结构与范围内的芯厚度，体积孔隙率，和网格尺寸。在第一部分的调查中，我们描述了芯吸的制造过程和实验测试设备，并专注于毛细芯厚度的影响。在第二部分中，我们研究的体积孔隙率和网孔尺寸的变化的影响，以及薄的毛细芯吸结构的蒸发/沸腾现象的详细讨论。开发了一种最佳烧结工艺，并用于制造供试品，该供试品使用多层均匀的烧结各向同性铜网制造。该工艺最小化了加热壁和毛细芯之间的界面接触热阻，并且增强了铜网层之间的接触条件。由于有效地降低了壁与毛细芯之间的接触热阻，蒸发/沸腾传热系数和临界热通量（CHF）都表现出显著的改善，观察到传热系数高达245.5 kW/m（2）K，CHF值超过367.9 W/cm（2）。实验结果表明，而蒸发/沸腾传热系数，这增加了热通量，只涉及到暴露的表面积，并不受毛细芯厚度的影响，CHF的稳态操作是强烈依赖于毛细芯厚度和增加成比例地增加与芯厚度。除了这些观察结果，实验测试和随后的分析已经导致毛细芯吸结构的新的蒸发/沸腾曲线的发展，这提供了对这些毛细芯吸结构中的蒸发/沸腾过程的独特性质的新的物理见解。样品结构和制造工艺，以及测试程序进行了详细描述和系统的实验结果和意见进行了介绍和分析。
Presented here is the first of a two-part investigation designed to systematically identify and investigate the parameters affecting the evaporation/boiling and critical heat flux (CHF) from thin capillary wicking structures. The evaporation/boiling heat transfer coefficient, characteristics, and CHF were investigated under steady-state conditions for a variety of capillary structures with a range of wick thicknesses, volumetric porosities, and mesh sizes. In Part I of the investigation we describe the wicking fabrication process and experimental test facility and focus on the effects of the capillary wick thickness. In Part II we examine the effects of variations in the volumetric porosity and the mesh size as well as presenting detailed discussions of the evaporation/boiling phenomena from thin capillary wicking structures. An optimal sintering process was developed and employed to fabricate the test articles, which were fabricated using multiple, uniform layers of sintered isotropic copper mesh. This process minimized the interface thermal contact resistance between the heated wall and the capillary wick, as well as enhancing the contact conditions between the layers of copper mesh. Due to the effective reduction in the thermal contact resistance between the wall and capillary wick, both the evaporation/ boiling heat transfer coefficient and the critical heat flux (CHF) demonstrated dramatic improvements, with heat transfer coefficients up to 245.5 kW/m(2)K and CHF values in excess of 367.9 W/cm(2), observed. The experimental results indicate that while the evaporation/boiling heat transfer coefficient, which increases with increasing heat flux, is only related to the exposed surface area and is not affected by the capillary wick thickness, the CHF for steady-state operation is strongly dependent on the capillary wick thickness and increases proportionally with increase in the wick thickness. In addition to these observations, the experimental tests and subsequent analysis have resulted in the development of a new evaporation/boiling curve for capillary wicking structures, which provides new physical insights into the unique nature of the evaporation/boiling process in these capillary wicking structures. Sample structures and fabrication processes, as well as the test procedures are described in detail and the experimental results and observations are systematically presented and analyzed.