Evaporation of charged alcohol droplets suspended by electrodynamic balance

Abstract

The evaporation dynamics of charged, sub-millimeter droplets of short-chain alcohols, suspended in the air by means of an electrodynamic balance are investigated in this study. Condensation of water from the ambient air onto the evaporating droplet results from evaporative cooling, and droplet evaporation is that of a multi-component system. The non-ideal mixing of condensed water and alcohol leads self-aggregation of the alcohol, which can occur in two distinct modes: enclosed-phase and Janus. The evaporative behavior of each mode is analyzed over a broad range of ambient relative humidity for five alcohols. The charges on the droplets can induce Coulombic fissions, which were observed in the two modes of phase separation. The charges act on the gas phase water dipoles, leading to an increase in vapor concentration in the surroundings of the droplet and an eventual cease of evaporation. These results were consistent in the five types of alcohol (methanol, ethanol, isopropanol, 1-propanol, and 1-butanol) at all values of relative humidity investigated (15% - 51%).