Thermographic Observation of High-Frequency Ethanol Droplet Train Impingement on Heated Aluminum and Glass Surfaces

Abstract

The present study considers the impingement of a train of ethanol droplets on heated aluminum and glass surfaces. The surface temperature is allowed to vary in the interval 140°C–240°C. Impingement is considered with an inclination of 63 degrees. The droplet diameter is 0.2 mm in both aluminum and glass surface experiments. Thermal gradients are observed with a thermographic camera. It is found that in comparison to glass, the aluminum surface displays very small liquid accumulations and better evaporation performance due to its higher thermal conductivity. The relatively low thermal conductivity of glass results in higher thermal gradients on the surface. The droplet impact area on the aluminum surface is smaller than the corresponding area for the glass surface. Interestingly, the liquid accumulation area is not symmetrical. Moreover, the extension of the droplet train impact region decreases on increasing the surface temperature because higher temperature values allow greater surface energy levels that enhance significantly the evaporation rate.