On the enormous enhancement in water evaporation rates obtained by employing a different polar ambient

Abstract

Enhancing evaporation rates are of great practical interest in many technological applications, such as water desalination or drying in industry. Evaporation mass flux is a function of ambient temperature, relative humidity, and velocity of the air passing over it. Since the conventional methods of increasing evaporation, namely increasing temperature, surface area, and so on, may not be always practically feasible or economical, novel methods of evaporation enhancement are necessary. The current study proposes that the introduction of a polar gas ambient above an evaporating liquid can drastically enhance its evaporation rate when the dipole moments of the evaporating liquid and the ambient gas are comparable. Thus, we explore the possibility of evaporation enhancement of water by introducing a polar Tetrafluoroethane gas ambient. The weight loss of water due to evaporation as well as the ambient temperature and air circulation conditions were measured. For each case, a companion experiment was carried out simultaneously under the same ambient conditions but without the presence of polar gas ambient. Each experiment lasted for 4 h. The evaporation rate has been found to be crucially dependent upon the polar gas ambient, the temperature as well as circulation conditions. Depending upon the temperature and circulation conditions, an enhancement of 59%–373% in evaporation rate has been recorded by the introduction of tetrafluoroethane gas ambient over the water surface. Some insights into the underlying mechanisms have been suggested in light of the physics of the evaporation process. Finally, some comparisons in the measured enhancement in evaporation rates under different experimental conditions are observed to concur with the suggested physical mechanism.