Characterization of Convection Patterns During the Solidification Process Using Particle Image Velocimetry

This experimental study focused mainly on the solidification of a binary mixture of ammonium chloride and water (NH₄Cl-H₂O) in a differentially heated cavity. One vertical wall is cooled at temperature T_C, and the opposite vertical wall is kept at constant temperature T_H = +20°C. The effect on the solidification process of the initial concentration of ammonium chloride and cooling conditions is examined. Particle image velocimetry (PIV) is used for the visualization of the dynamic field during the solidification process. The temperature distribution at discrete locations in the solution and on the vertical cooling wall was monitored using thermocouples. The convection flow patterns, the ice thickness, and the temperature distribution were obtained for various initial concentrations of ammonium chloride ranging from 0wt% to 20wt% (sub-eutectic and near-eutectic growth). The convection patterns obtained for different initial concentrations showed significant differences. The results showed that the process of solidification is slower with an increase in the initial concentration levels of the binary solution. The ice growth rate was almost double at the bottom of the cavity.