Evaporation of water drops in the presence of satellite drops

Common evaporation conditions include open and closed systems, and, more commonly, semi-closed environment in which evaporation is enabled but suppressed so that the environment's humidity is influenced by the system. We study the evaporation of a water droplet placed on a silanized silicon surface in a semi-closed environment and its evaporation suppression when it is surrounded by other drops, hereon "satellite" drops. The evaporation rate of water drops in a semi-closed environment or chamber is shown to be a function of the relative humidity inside the chamber; however, the evaporation suppression is a function of total liquid-vapor surface area of the drops. A group of semi-closed systems consisting of central drops surrounded by satellite drops and covered under a glass dome are used in this thesis. During the first few minutes of evaporation when the total surface area, total volume and total heights of the satellite drops are nearly kept constant, the evaporation rate of the central drops is found to be decreasing with the increase in surface area and then remains constant for all the configurations of satellite drops. With time the rate further increases if all the satellite drops evaporate. The evaporation flux for these central drops at first decreases and then becomes constant since their total surface area doesn't experience a major change. But eventually the flux rapidly increases and the time it takes to increase is longer for the central drops with satellite drops that have a bigger total surface area throughout. Additionally, the relative humidity of the drops is found using Rowan equation and Shanahan-Bourges equation and the one in open air is found to accede with the measured relative humidity thus holding the equations to be true for the 90° +/- 6° contact angle range for the former and less than 90° contact angles for later equation. All the drops in the experiments conducted went through constant contact radius followed by constant contact angle and then mixed mode. Furthermore, it was found that the central drop evaporation rate is independent of the distance of satellite drops from the central drop. Finally, there is no thin precursor film found to be formed in between two drops when they are placed next to each other on the same solid surface or on two different solid surfaces of which one is small and the other is big.