TITLE:
Visualization of Double-Diffusive Convection and Unsteady Solidification on a Vertical Circular Cylinder
AUTHORS:
Kazuki Ohnishi, Shigeo Kimura, Takahiro Kiwata, Nobuyoshi Komatsu, Takaaki Kono
KEYWORDS:
Solidification, Flow Visualization, Double-Diffusive Convection, Vertical Cylinder, Heat Transfer
JOURNAL NAME:
Journal of Flow Control, Measurement & Visualization,
Vol.3 No.4,
October
21,
2015
ABSTRACT: This paper describes experimental results on the solidification process over the vertically positioned circular cylinder, placed in an aqueous solution of sodium nitrate, where the aqueous solution in the vessel is heated from the bottom. After the initiation of solidification by cooling the cylinder below the liquidus temperature, the pure ice formation on the cylinder causes the rejection of solute into the surrounding aqueous solution. The solute enriched vertical fluid layer over the ice then falls on the bottom of the vessel due to its higher density, and accumulates there. This process results in the formation of solute rich and hot horizontal layer (heavy layer), underlying the relatively cold but less concentrated fluid layer (light layer). As this process advances, however, because of the continuing influx of solute rich fluid, the lower heavy layer occupies more space, and the interface of the two layers rises slowly. The pH indicator method has been successfully employed in order to visualize the flows during this process. In this report, we document the evolution of both temperature and flow fields in the aqueous solution quantitatively, as the solidification progresses and the density discontinuity of the two layers rises.