Natural Convection Characteristics of Pool Penetration Into a Melting Miscible Substrate

Experiments were performed to gain an understanding of the convective heat transfer process occurring in a warm liquid pool as it penetrates into an underlying meltable solid of less dense material, for the case where the molten phase of the solid and pool liquid are mutually miscible. Previous experimental work on downward melting penetration made use of warm aqueous salt solution pools overlying solid polyethylene glycol (PEG) or ice, or pools of heated organic liquids with benzene as the frozen substrate. Owing to the complexity of the melting trends observed in these studies, particularly with PEG substrates, a sufficiently definitive theory of the phenomenon has not yet emerged. As part of the present study, an attempt was made to reproduce the previous experimental results for salt-solution-pool penetration into PEG. An unexpected strong effect of initial solid PEG temperature on melting rate was uncovered for this polymer material. It was found that the unconventional melting trends reported previously at high pool-to-substrate density ratios could be eliminated if careful control of the initial PEG temperature is maintained. These new experimental data indicate that the melting of PEG by an overlying pool of heavier salt solution has much in common with classical, turbulent, thermal convection above a horizontal surface. Additional experiments were conducted which seem to support this conclusion for other pool–substrate material pairs as well.