VOID FORMATION IN UNIDIRECTIONAL FREEZING FROM ABOVE

Experiments were conducted to observe the solidification sequence and final shrinkage void distribution for liquids solidified from above in a rigid, constom-volume container. The overall void distribution appears to depend strongly on the initial liquid temperature and to a lesser extent on the cooling rate. A thermodynamic model has been developed that follows the liquid, vapor, and solid phases throughout the cooling process. Several void-formation phenomena are then examined qualitatively with reference to the thermodynamic model. We feel that these results will lead eventually to better void management in phase-change materials for storing thermal energy.