Abstract: The influence of coagulation agent,roughness and contact angle on the solidification of droplet on a cooled surface were experimentally studied. A semiconductor chilling plate make the surface keep cold. A thermocouple measures the temperature of droplet center,and a camera records solidification process. The cooled surface is divided into hydrophilic and hydrophobic,one is copper surface and another is sprayed nano-film. Coagulation agents are sodium chloride,potassium chloride and sodium bicarbonate, respectively. From the image recorded by camera,a protuberance form at the top of the completely froze droplet,and the contact area between the droplet and the hydrophilic surface is larger than that on hydrophobic surface,so solidification time of droplet on hydrophilic surface is less. By data analysis,the critical nucleation energy decreases with the roughness of hydrophilic surface,but hydrophobic surfaces is opposite. The increase of coagulation agent concentration can increase the surface energy and the critical nucleation energy, but reduce the phase equilibrium temperature. The critical nucleation energy of sodium chloride solution is minimum and potassium chloride solution is maximum.

Key words: condensation, aqueous solution, roughness, contact angle, critical nucleation energy

摘要： 用实验方法研究了添加剂种类、浓度、粗糙度和表面接触角对液滴在冷表面凝结过程的影响。用半导体制冷片对冷表面进行降温，用K型热电偶测量液滴中心的温度，用相机记录整个凝结过程。冷表面分为以铜为基体的亲水表面和喷涂了纳米膜的疏水表面2种，添加剂为氯化钠、氯化钾、碳酸氢钠3种。相机记录的图像可以看出，水滴完全凝固时会在顶部形成突起，相同体积的液滴与亲水表面的接触面积比疏水表面大，故在亲水表面凝固所用的时间少。通过数据分析得到，亲水表面液滴的临界成核能随粗糙度的增加而降低，但疏水表面相反；添加剂浓度增大会增加表面能，降低溶液平衡温度，增加临界成核能；临界成核能大小排序为氯化钠溶液 < 碳酸氢钠溶液 < 氯化钾溶液。

关键词: 凝结, 水溶液, 粗糙度, 接触角, 临界成核能