The impingement of liquid boiling droplet onto a molten phase change material as a direct-contact solidification method

Abstract

The boiling of a fluid dripping on the surface of molten phase-change materials provides an efficient means for heat exchange or cooling of the melt. For the first time, in this study, the impact of acetone drops onto molten paraffin as a direct-contact solidification method is experimentally investigated to get a better insight into the interaction between the drop boiling and the heat extraction process from the phase change materials during impact. As the acetone drop impacts the molten paraffin surface, acetone starts to boil, and a portion of molten paraffin is solidified. Four impact Weber numbers (corresponding to heights of 10, 20, 30, and 40 cm) for the acetone drop and six surface temperatures for the molten paraffin (66, 68, 70, 75, 80, and 90 °C) are considered. Given the range of these two parameters, four distinct regimes of impact were observed using a high-speed camera and categorized, including the formation of the crater, crown, returned liquid paraffin column (jet), and the drop pinching off from the jet tip. Moreover, as We increased or the paraffin surface temperature decreased, the solidified paraffin’s on the molten surface grew. A correlation was obtained based on the impact Weber number and surface temperature of molten paraffin to determine the spread of solidified paraffin area on the melt free surface after drop impact. Results also showed that both the maximum crater depth and width increase with the increment of both the molten paraffin temperature and the impact Weber number.