2-DIMENSIONAL FREEZING OF WATER-FILLED BETWEEN VERTICAL CONCENTRIC TUBES INVOLVING DENSITY ANOMALY AND VOLUME EXPANSION

Freezing of an initially superheated water filled within an axisymmetric enclosure is studied numerically. Simulation is carried out using a computational method recently developed by the authors to treat moving boundary problems in axisymmetric geometries. Emphasized is the influence of both volume expansion and density anomaly upon freezing via natural convection. Two distinctive types of thermal boundary conditions are identified and utilized to guide our efforts to investigate the freezing process. Due to the density anomaly of pure water, fluid flow direction reverses depending on the initial superheat of water and thereby the interface slope exhibits an inversion behavior. By assuming that the water does not flood over the ice surface, the volume-change-induced rise of ice formed results in a substantially curved surface. Effects of several parameters characterizing phase-change process of interest are investigated. Numerical results clearly reveal that freezing undergoes multiple stages and proceeds in a complicated manner especially when the water is superheated over the density-extremum temperature.