USSR Cooperative Research on Heat and Mass Transfer During Directional Solidification in a Centrifuge

这是克拉克森大学和苏联科学院空间研究所（IKI）空间材料科学实验室的联合研究项目，旨在阐明大型离心机定向凝固过程中发生的传输现象。克拉克森大学和空间研究所（IKI）为实现这一目标而进行了独特的配置。先前对大型离心机中输运现象的研究显示出意想不到的结果，这些结果尚未得到充分解释。例如，发现温度振荡开始的临界旋转速率，温度波动停止的临界旋转速率更高。几个定向凝固实验显示了一个“神奇的g”，在这个“神奇的g”下，杂质偏析和微观结构变成了凝固过程中熔体完全缺乏对流所期望的样子。克拉克森大学将开发理论模型来预测熔体中的对流和传质，固体中的温度分布，固液界面形状以及离心机凝固过程中的冻结速率。这些模型的预测将与在苏联机器上进行的实验进行比较。克拉克森和IKI的科学家将共同改进苏联的仪器，以便在凝固过程中测量材料内部的温度，并确定材料和钢筒之间的传热系数。我们将添加当前界面划分或振动界面划分，以允许我们确定界面形状和冻结速率随时间的变化。我们还将合作开发和执行离心机的流动可视化实验。

This is a joint research project between Clarkson University and the Laboratory of Materials Science in Space at the Space Research Institute (IKI) of the USSR Academy of Sciences to elucidate the transport phenomena that occur during directional solidification in a large centrifuge. Clarkson University and the Space Research Institute (IKI) are uniquely configured to accomplish this goal. Prior research on transport phenomena in large centrifuges has shown unexpected results that have not yet been fully explained. For example, a critical rotation rate was found for the onset of temperature oscillations, with a higher critical rotation rate for cessation of temperature fluctuations. Several directional solidification experiments exhibited a "magic g" at which impurity segregation and microstructure became what one would expect from a complete lack of convection in the melt during solidification. Theoretical models will be developed at Clarkson University to predict convection and mass transfer in the melt, temperature distribution in the solid, solid-liquid interface shape, and freezing rate during solidification in the centrifuge. Predictions of these models will be compared with experiments carried out on the Soviet apparatus. Clarkson and IKI scientists will work together to modify the Soviet apparatus to permit temperatures to be measured inside the material during solidification, and to determine the heat transfer coefficient between the material and the steel cartridge. We will add either current interface demarcation or vibration interface demarcation to allow us to determine the interface shape and freezing rate versus time. We will also cooperate in development and execution of flow visualization experiments in the centrifuge.