Experimental study of evaporation of sessile droplets of the water-ethanol solution with different concentrations

Abstract

The dynamics of the geometric parameters of droplets of a water-ethanol solution lying on a Teflon plate was investigated using high-speed microphotography. It was found that the evaporation of water droplets occurred with a constant contact line, and the evaporation of droplets of a water-ethanol solution was accompanied by its movement. At the initial stage of evaporation, the higher the concentration of ethanol in the drop was, the greater was the change in the contact spot diameter, corresponding to the change in the diameter of the spot of ethanol. Using the method of infrared thermography, three stages of temperature change of evaporating droplets were found. The first stage corresponds to the initial sharp decrease in temperature. The second stage is a process at a constant temperature. And finally, the third stage is the stage of its smooth growth to the ambient air temperature. A similar pattern with some features was observed for droplets with different concentrations of ethanol. At the initial stage of evaporation, the droplet temperature changed like the temperature of ethanol droplet, and then its behavior was similar to the temperature change of water droplets. The higher the ethanol concentration in the droplet was, the larger the change in temperature was, similar to the change in the temperature of the ethanol droplet.