Evaporation/boiling in thin capillary wicks (II) - Effects of volumetric porosity and mesh size
Evaporation/boiling in thin capillary wicks (II) - Effects of volumetric porosity and mesh size
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DOI：
10.1115/1.2349508
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发表时间：
2006-12-01
影响因子：
--
通讯作者：
Peterson, G. P.
中科院分区：
文献类型：
--
作者：
Li, Then;Peterson, G. P.
这里提出的是第二个两部分的调查，旨在系统地识别和调查的参数影响蒸发和沸腾内，薄毛细管芯吸结构的体积孔隙率和网孔尺寸的范围。实验研究在稳态条件下，在大气压下进行。研究的第一部分描述了芯吸制造工艺和实验测试设备，并重点关注毛细芯厚度的影响（ASME J. Heat Transfer，128，pp. 1312-1319）。在第二部分中，我们研究了体积孔隙率和网格尺寸变化的影响。实验结果表明，临界热流密度（CHF）强烈依赖于网格尺寸和体积孔隙率;而蒸发/沸腾传热系数受网格尺寸的影响显著，但对体积孔隙率的依赖性不强。实验结果进一步说明，在CHF时，热应力集中在垂直方向和水平方向上由金属丝和加热壁形成的角部以及金属丝之间。这三个压力的最小值决定了通过毛细芯产生的最大毛细压力。系统地介绍和分析了实验结果和观察结果，并从理论上研究了局部气泡和液-汽界面动力学。基于热通量和蒸发之间的相对关系，经典的核态沸腾理论，和相变现象的直观观察，以及通过结合这里得到的结果与第一部分的调查中得到的那些，这些毛细芯吸结构的蒸发/沸腾传热制度进行了识别和讨论。
Presented here is the second of a two-part investigation, designed to systematically identify and investigate the parameters affecting the evaporation from and boiling within, thin capillary wicking structures with a range of volumetric porosities and mesh sizes. The experimental studies were investigated under steady-state conditions at atmospheric pressure. Part I of the investigation described the wicking fabrication process and experi mental test facility, and focused on the effects of the capillary wick thickness (ASME J. Heat Transfer, 128, pp. 1312-1319). In Part II, we examine the effects of variations in the volumetric porosity and the mesh size. The experimental results presented here indicate that the critical heat flux (CHF) was strongly dependent on both the mesh size and the volumetric porosity; while the evaporation/boiling heat transfer coefficient was significantly affected by mesh size, but not strongly dependent on the volumetric porosity. The experimental results further illustrate that the menisci at the CHF are located in the corners, formed by the wire and the heated wall and between the wires in both the vertical and horizontal directions. The minimum value of these three menisci determined the maximum capillary pressure generated through the capillary wick. The experimental results and observations are systematically presented and analyzed, and the local bubble and liquid vapor interface dynamics are examined theoretically. Based on the relative relationship between the heat flux and superheat, classic nucleate boiling theory, and the visual observations of the phase-change phenomena, as well as by combining the results obtained here with those obtained in Part I of the investigation, the evaporation/boiling heat transfer regimes in these capillary wicking structures are identified and discussed.