VOID FORMATION IN RADIAL SOLIDIFICATION OF CYLINDERS

Experiments were carried out to observe the solidification sequence and void distribution for two different experimental liquids (cyclohexane and butanediol) enclosed in Pyrex tubes. Both liquids exhibited about ten percent volumetric shrinkage during the phase transition from liquid to solid. To evaluate the possibility of regulating void formation by soluble gases, tests were conducted both in the presence and absence of dissolved air. A physical model has been developed which predicts the essential features of the solidification pattern under earth's gravity field of 1-g for cylindrical geometries and allows extrapolation of the results to outer space conditions of 0-g. Finally, an attempt was made to determine analytically the final void shape which would result from each nucleated bubble in 0-g. Understanding these aspects of the solidification process is vital to development of better thermal energy storage systems for space power applications.