关键词: 凝结, 水溶液, 粗糙度, 接触角, 临界成核能

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