Study of the phenomenon of the interaction between sessile drops during evaporation

Abstract

This research work represents an experimental study of the interaction between water drops deposited on a substrate at ambient temperature. To examine this phenomenon, the evaporation of a single drop deposited on a substrate was first investigated. Then, several drops were deposited alongside on the same substrate under the same conditions. The central drop dynamic behavior was also examined and compared with that of a single drop. This comparison shows the effect of the interaction between the neighboring drops, which delayed the evaporation of these drops and particularly the central droplet, on evaporation. In fact, three configurations were studied by changing the initial distance, d, between the drops (d = 0.2 mm, d = 7 mm, and d = 15 mm). The obtained results reveal that the interaction phenomenon becomes less important by increasing the distance between the drops. This is important for optimizing many industrial applications, such as spray drying, fuel injection in combustion engines, and other applications.

Competitive evaporation of multiple sessile droplets

“…To this end, we compare the theoretical predictions of the present model with the recent experimental results of Khilifi et al (2019) for seven relatively closely spaced droplets. Khilifi et al (2019) studied the evaporation of sessile droplets of water at an initial temperature of 20 • C on a sapphire substrate into an enclosed chamber with 50 % humidity at an ambient temperature of 21 • C. Initial experiments using an isolated droplet revealed that the droplets evaporate in an SS mode with an initial contact angle ofθ 80 • and a receding contact angle of θ 36 • . To investigate the interactions between the droplets, they then studied a (slightly imperfect) 'I'-shaped configuration of seven nearly identical droplets with approximate radius 7.5 × 10 −4 m and volume 7 × 10 −10 m 3 a distance 2 × 10 −4 m apart (their 'Configuration (b)').…”

“…Previous studies of the evaporation of multiple sessile droplets have used a variety of experimental, numerical and analytical approaches (Lacasta et al 1998;Schäfle et al 1999;Kokalj et al 2010;Sokuler et al 2010;Carrier et al 2016;Castanet et al 2016;Shaikeea et al 2016;Shaikeea & Basu 2016a,b;Hatte et al 2019;Khilifi et al 2019;Schofield et al 2020). The critical difference in comparison with what is observed with a single droplet is the occurrence of 'shielding', in which the presence of other droplets causes a droplet to evaporate more slowly than it would in isolation.…”

The shielding effect extends the lifetimes of two-dimensional sessile droplets

“…Our reference point is the lifetime of a single droplet with initial semi-widthR 0 , which from (1), (37) and (38) is given bŷ…”

“…In practice, droplets rarely occur in isolation, and so it is important to understand how droplets evaporate in the presence of other evaporating droplets. Previous studies of the evaporation of multiple sessile droplets have employed a variety of experimental, numerical and analytical approaches [27][28][29][30][31][32][33][34][35][36][37][38]. The critical difference between the evaporation of single and of multiple droplets is the occurrence of the shielding effect, namely that the presence of other evaporating droplets increases the local vapour concentration, and so each droplet evaporates more slowly than it would in isolation.…”

Study of transient condensation occurring during the starting of the evaporation of a droplet deposited on a heated substrate

“…In fact, the flow evaporated at the liquid-gas interface has been the subject of several works. For example, Dorra Khilifi et al [5] studied experimentally the neighborhood effect on the evaporation of a water drop. By carrying this study, they proved that the total evaporation of drops, which were close to each other, was noticeable minimized, compared to that of a single drop.…”