Experimental Visualization and Numerical Analysis of Cooling and Freezing Processes of Water around Two Horizontal Tubes Placed in Vertical Arrangement

This paper aims to clarify the cooling and freezing processes of water around two horizontal tubes placed in vertical arrangement, as the basic research for an ice-on-coil type of ice thermal storage system. When water is cooled and frozen in this system, natural convection occurs by the difference of local density. This natural convection governs the heat transfer characteristics and much influences the cooling and freezing processes. Especially, the flow pattern of this convection drastically changes on the way of cooling, because water has a maximum density at 4°C. This complex flow pattern was experimentally visualized by the laser measurement techniques, and calculated by the finite difference method with body fitted coordinate system. These experimental flow visualization and calculation were performed with varying the cooling rate. We could acquire some interesting relations among the flow pattern, the heat transfer characteristics, the release of supercooling and the growth of ice.