用NH4Cl-H2O溶液共晶凝固实验模拟Bridgman法晶体生长过程

利用NH4Cl-H2O溶液的共晶凝固模拟Bridgman法晶体生长过程,通过粒子图像测速系统测量了矩形腔和圆柱腔内NH4Cl-H2O溶液共晶凝固过程中的流场,结合温度变化得到了凝固过程中流动和温度的耦合规律.实验结果表明:在侧壁和底部冷却条件下,两种腔室内溶液共晶凝固过程中流场的变化基本相似,形成竖壁面附近溶液向下流动、中心区域溶液向上流动的对流涡;凝固开始后,热交换和潜热的释放使液相区内温度下降趋于平缓;圆柱腔内出现了角区绕流和二次对流涡现象.实验得到的流动和温度变化规律为理论建模及数值计算提供了有用的实验数据.

Experimental Investigation of NH4Cl-H2O Eutectic Solution Solidification for Simulating Crystal Growth with Bridgman Method

The crystal growth process with Bridgman method was simulated via NH4Cl-H2O solution eutectic solidification.The flow fields of NH4Cl-H2O solution during solidification in both rectangular cavity and cylindrical cavity were measured with particle image velocimetry(PIV).With the temperature varying,the coupling rules of fluid flow and temperature during eutectic solidification process were observed.Cooling both at sidewall and bottom,the evolution of flow field was about the same in the two kinds of cavities during the solidification process.Convection vortex occurred in the liquid region flowing downward along the vertical sidewalls,and upward in the center region.Heat transfer and latent heat release made the temperature decrease slowly.The rule between flow field and temperature during the eutectic solidification approached the crystal growth process of Bridgman method,and offered valuable data for theoretical modeling and numerical calculation.