Influence of the suspender in evaporating pendant droplets

The influence of the suspender on the evaporation of droplets under quiescent atmospheric conditions was studied experimentally using pendant droplets of ethanol (volatile) and water (non-volatile). Conducting and non-conducting suspenders of different materials and configurations (a steel needle, glass needle, steel rod, and glass rod) were evaluated. For both liquids, it is observed that the rate of evaporation is higher with steel suspenders. More importantly, for ethanol droplets, there is a difference in the evaporation rates between the needle and rod configurations of the same material. Thus, it is shown for the ethanol droplet that the configuration (needle versus solid rod) also plays a role in the evaporation process, apart from the material. The water droplet does not show this dependence. Visualization of internal flow and heat transfer calculations explain this observation. The results will be useful in choosing an appropriate suspender while using the pendant droplet method for studying complex interactions in an evaporating droplet.