The Effect of Baffle Structure and Rotational Speed on the Flow Field in the Silicon Purification Process via the Rotational Segregation Method: A Water Model Study on Tracer Transport and Concentration Variation

This study experimentally investigated, using a water-model hydrodynamic analogue, the effects of crystallizer rotational speed and baffle configuration on the flow-field structure, mass transfer, and mixing behavior inside the crucible of a rotational segregation model system relevant to silicon processing. Three configurations were examined: no baffle, straight baffles, and inclined baffles. Flow visualization and stimulus–response tracer experiments were conducted at 200 and 300 rpm to compare their effects on the main flow pattern and mixing characteristics. The results showed that, without baffles, a complete annular main flow formed, and the fluid moved downward spirally along the crystallizer wall. Mixing was relatively fast, indicating limited potential for local tracer retention. With straight baffles, the main flow was strongly obstructed and redistributed, and the mixing time in local bottom regions, especially in front of the 90° baffle, was markedly prolonged. This behavior suggested a more favorable hydrodynamic environment for local retention and accumulation in the model system, and the effect was most evident at 200 rpm. With inclined baffles, transport in the upper region was enhanced, whereas bottom flow was weakened. Although the tracer could move downward along the baffle surface, it was rapidly swept away after reaching the bottom, indicating reduced stability of local accumulation. Increasing the rotational speed from 200 to 300 rpm strengthened the overall flow and shortened the mixing time under all conditions. Overall, straight baffles, particularly at 200 rpm, produced the strongest tendency for local retention in the present model system. These results provide preliminary hydrodynamic insight into flow regulation and transport behavior in rotational segregation systems.