Abstract:

In industrial and agricultural settings, obliquely impacting droplets on a liquid film is a common phenomenon with significant scientific and practical importance. However, due to limitations in experimental techniques, the heat transfer characteristics associated with this oblique impact have not been systematically explored. In this study, we address this gap by employing a super hydrophobic guide rail to stably generate droplets at controlled impact angles, enabling a detailed experimental investigation into the heat transfer behavior of oblique droplet impact on a liquid film. The cooling performance across the observed region is quantitatively evaluated using the peak value and standard deviation of the wall cooling coefficient. The study found that the wall cooling process can be divided into a rapid cooling stage and a recovery stage, and the time scale of the rapid cooling stage is much smaller than that of the recovery stage. Both the peak value and standard deviation of the wall cooling coefficient decrease with increasing Weber number and impact angle, while they increase with higher heating power. During the recovery phase, at any given time, both parameters continue to decrease with larger Weber numbers and impact angles, and their rate of change grows more pronounced with increasing heating power.

Key words: droplet, oblique impact, liquid film, flow, heat transfer, two-phase flow

摘要：

利用超疏水导轨稳定生成了具有特定撞击角度的液滴，实验研究了液滴倾斜撞击液膜过程中的传热特性，并利用壁面冷却系数最大值及其标准差来综合评估整个观测区域的冷却效果。研究发现，壁面冷却过程可以划分为快速冷却阶段和恢复阶段，快速冷却阶段的时间尺度远小于恢复阶段的时间尺度。壁面冷却系数最大值和标准差的峰值随Weber数和撞击角度的增加而减小，随加热功率的增加而增加。在恢复阶段，同一时间的壁面冷却系数最大值和标准差随Weber数和撞击角度的增加而减小，参数变化速率随加热功率增加而增加。

关键词: 液滴, 倾斜撞击, 液膜, 流动, 传热, 两相流