冻结过程中非常规热行为的机理
On the mechanism responsible for unconventional thermal behaviour during freezing
摘要：
在这项研究中，进行了相同的实验底部冷却凝固流体混合物，表现出小平面和树枝状微观结构。成分对流的强度与凝固的微观结构形态，在糊状和散装流体区的单独的瑞利数的帮助下。虽然树枝状凝固经历了单调下降的散装流体温度，凝固的小面的情况下，揭示了一个非常规的，异常的温度上升，在共晶相的起始在散装液体。基于散装液体的温度分布，三个不同的制度的传热在液体中观察到的凝固过程中，即对流为主，过渡，传导为主。在不同的初始组成以及在冷冻时形成多面形态的其他混合物的帮助下，分析和验证了观察结果。通过在固液界面之前的指示性控制体积中执行能量平衡，进一步确定观察到的温度升高。在冷冻过程中的液体的温度增益背后的合理机制进一步推广的帮助下，一个简化的一维数值模型，并扩展到金属是低普朗特数的混合物。这项研究揭示了新的见解的作用，微观结构形态在管理的运输现象中的散装液体。
英文摘要：
In this study, identical experiments of bottom-cooled solidification fluidic mixtures that exhibit faceted and dendritic microstructures were performed. The strength of compositional convection was correlated with the solidifying microstructure morphology, with the help of separate Rayleigh numbers in the mushy and bulk-fluid zones. While the dendritic solidification experienced a monotonic decrease in the bulk fluid temperature, solidification of the faceted case revealed an unconventional, anomalous temperature rise in the bulk liquid, at the initiation of the eutectic phase. Based on the bulk-liquid temperature profile, three distinct regimes of heat transfer were observed in the liquid over the course of solidification, namely - convection-dominated, transition, and conduction-dominated. The observations were analyzed and verified with the help of different initial compositions, as well as other mixtures that form faceted morphology upon freezing. The observed temperature rise was further ascertained by performing an energy balance in an indicative control volume ahead of the solid-liquid interface. The plausible mechanism behind the gain in temperature of the liquid during freezing was further generalized with the help of a simplified one-dimensional numerical model, and was extended to metals which are low Prandtl number mixtures. The study sheds new insights into the role of microstrostructural morphology in governing the transport phenomena in the bulk liquid.
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