Experimental and Numerical Investigations of Natural Convection in Freezing Water

Thermal convection in a lid cooled cavity with phase change was studied experimentally and numerically. The ow and ice front structures, and their dependence on the ow parameters (Rayleigh number) were investigated. In the experiment, the onset of convection in an initially isothermal uid (water) in a 383838mm plexiglas box, which is instantaneously cooled from isothermal top wall to a temperature of ?10 o C, has been investigated. The other ve walls of the cavity are non-adiabatic, allowing the entry of heat from the external uid surrounding the cavity. The external temperature was varied from 5 o C to 20 o C. The temperature and velocity elds in the cavity were measured by means of liquid crystals suspended as small tracer particles in the liquid. After the convection starts a complicated ow pattern was observed, which also became visible in the structure of the ice surface. The symmetry of the ow was usually disturbed by existing small imperfection of the cavity and uctuations of initial eld conditions. It was found that the growing ice has a stabilising eeect on the ow. The experiments were compared with the 3D numerical simulation using nite-diierences code ICE3D.