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首页> 外文期刊>International Journal of Heat and Mass Transfer >Film boiling of subcooled liquids. Part Ⅰ: Leidenfrost phenomenon and experimental results for subcooled water
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Film boiling of subcooled liquids. Part Ⅰ: Leidenfrost phenomenon and experimental results for subcooled water

机译：过冷液体的薄膜沸腾。第一部分：过冷水的莱顿弗罗斯特现象和实验结果

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Film boiling of subcooled liquids is important, at least, for two applications: for systems of post-accident cooling in nuclear power plants and for quenching technology. An analysis of the previous results shows that at high water subcooling film boiling presents a particular mode of boiling heat transfer, dissimilar greatly to saturated film boiling mainly by high intensity of heat transfer; this statement appears to be true, even though the researchers themselves do not recognize it. As at the temperature much higher than that of homogeneous nucieation, liquid-vapor phase transition occurs practically instantly, an actual temperature at the liquid/solid interface cannot be higher than the attainable limiting temperature of liquid. The possible mechanisms of high intensity heat transfer between the surface and subcooled liquid at the absence of liquid/solid contact and the conditions of this regime incipience require experimental and theoretical investigations. The present paper describes the method and the results of experimental study of heat transfer during cooling the spherical patterns from nickel, stainless steel, and copper with initial temperature above 700 ℃ in water at subcoolings up to 70 K. In distinction to all the previous studies temperature was measured in several points of the spheres that gives new information on the cooling process. It is revealed that at high cooling rates the temperature field can lose its spherical symmetry, high temperature gradients are observed not only in the radial direction, but also along the surface. At high subcoolings the heat transfer regime of high intensity arises at the surface temperature 600-700 ℃ that excludes a possibility of liquid/solid direct contact; heat flux density can be as high as 5-7 MW/m~2.
机译：至少对于两个应用而言，过冷液体的薄膜沸腾非常重要：对于核电厂的事后冷却系统和淬火技术。对先前结果的分析表明，在高水位过冷状态下，薄膜的沸腾呈现出一种特殊的沸腾传热模式，与饱和薄膜的沸腾有很大不同，主要是由于高传热强度。即使研究人员本身并不认可这一说法，这似乎也是正确的。由于在比均相成核的温度高得多的温度下，实际上几乎立即发生了液-汽相变，因此液/固界面处的实际温度不能高于液体可达到的极限温度。在没有液/固接触的情况下，表面和过冷液体之间的高强度传热的可能机理以及这种状态的开始条件需要进行实验和理论研究。本文介绍了在初始温度700℃以上的水中将镍，不锈钢和铜的球形图案冷却到70 K时在水中冷却时的传热方法和实验研究结果。在球的几个点上测量了温度，从而提供了有关冷却过程的新信息。结果表明，在高冷却速率下，温度场可能会失去其球形对称性，不仅在径向方向而且沿表面都观察到高温梯度。在较高的过冷度下，在表面温度600-700℃时会出现高强度的传热状态，这排除了液体/固体直接接触的可能性；热通量密度可高达5-7 MW / m〜2。

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