Evgeniya Orlova

Evaporation of liquid droplets from a surface of anodized aluminum

The results of study of evaporation of water droplets and NaCl salt solution from a solid substrate made of anodized aluminum are presented in this paper. The experiment provides the parameters describing the droplet profile: contact spot diameter, contact angle, and droplet height. The specific rate of evaporation was calculated from the experimental data. The water droplets or brine droplets with concentration up to 9.1 % demonstrate evaporation with the pinning mode for the contact line. When the salt concentration in the brine is taken up to 16.7 %, the droplet spreading mode was observed. Two stages of droplet evaporation are distinguished as a function of phase transition rate.

The influence of the drop formation rate at spreading over a microstructured surface on the contact angle

The article presents the experimental dependences of a macro-contact angle and the diameter of a distilled water drop spreading over solid microstructured surface on surface average roughness (Ra) and fluid flow rate (G). It has been found that at changing G from 0.005 to 0.02 ml/s, the contact angle decreases, and at a liquid flow rate over 0.02 ml/s, it increases. With small values of G (0.005−0.01 ml/s), the drop diameter grows throughout the spreading process. In the range of G from 0.02 to 0.16 ml/s at the final stage of spreading, the contact line pinning, i.e., the diam-eter constancy, has been detected. The hypothesis about the mechanism of the pinning process has been formulated: it is due to the zero sum of all forces acting on the drop (inertia, viscosity, friction, gravity, and surface tension).