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首页> 外文期刊>International Journal of Heat and Mass Transfer >Effects of surface wettability on pool boiling process: Dynamic and thermal behaviors of dry spots and relevant critical heat flux triggering mechanism
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Effects of surface wettability on pool boiling process: Dynamic and thermal behaviors of dry spots and relevant critical heat flux triggering mechanism

机译：表面润湿性对池沸腾过程的影响：干斑的动态和热行为及相关临界热通量触发机构

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In this paper, we investigate experimentally and numerically the influences of surface wettability on the boiling process from nucleate boiling to critical heat flux (CHF). The boiling surfaces with four different wettabilities (apparent contact angles) are examined. Using a simple optic setup, sequential phase distribution images on the boiling surfaces were acquired, and we analyzed the dynamics of microlayer, bulk liquid region, and dry spots with the processed images. The variation of surface wettability significantly affected the liquid and vapor phase behaviors on the boiling surface, such as the growth and shrinkage of the microlayer and dry spot, wetting velocity and area portion of the dry spot. As a result, the CHF increased with the surface wettability, and we found the CHF is triggered from a local dry spot where the liquid wets the spot no longer and is violently scattered by strong evaporation at the triple contact line. Our numerical simulation results, in which the three-dimensional transient heat diffusion equation was solved for the boiling substrate using the phase distribution images as boundary conditions, indicated that certain dry spots (critical dry spot) can be highly overheated under high heat flux condition, and they lead significant heat transfer degradation and, eventually, the CHF. With the numerical results and observation of the phase distribution images at the CHF conditions, we postulated the allowable wetting temperature and formulated it as a function of surface wettability through considering the balance between vapor recoil and surface tension forces. The wetting temperature increased with surface wettability, and it was confirmed by the numerical results. Finally, we proposed a qualitative relation to elucidate the influence of surface wettability on the CHF based on the heat conduction via the vapor on a critical dry spot and heat flux partitioning concept.
机译：在本文中，我们在实验和数值上进行调查，在数值上对核心沸腾到临界热通量（CHF）的核解过程对沸腾过程的影响。检查具有四种不同的湿润的沸点（表观接触角）。使用简单的光学设置，获取沸点上的顺序相位分布图像，并通过处理图像分析了微层，散装液区域和干斑的动态。表面润湿性的变化显着影响沸腾表面上的液体和气相行为，例如微层和干燥点的生长和收缩，干燥点的干燥点，润湿速度和面积部分。结果，CHF随着表面润湿性而增加，我们发现CHF从局部干燥点触发，其中液体润湿的液体不再是通过三重接触线的强烈蒸发剧烈散射。我们使用相位分布图像作为边界条件为沸基板解决了三维瞬态热扩散方程的数值模拟结果，表明某些干斑（临界干燥点）在高热通量条件下可以高热，并且它们导致显着的传递降解，最终，CHF。利用CHF条件下的相位分布图像的数值结果和观察，我们通过考虑蒸汽反冲和表面张力之间的平衡，将允许的润湿温度发出来并将其作为表面润湿性的函数。润湿温度随表面润湿性而增加，并通过数值结果证实。最后，我们提出了一种定性关系，以阐明基于通过蒸汽的热传导在临界干燥点和热通量分配概念上的热传导来阐明表面润湿性对CHF的影响。

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