Evaporation-induced flow around a droplet in different gases
TL;DR: In this article, the influence of the ambient gas on the evaporation induced flow around a droplet at atmospheric conditions was investigated, and it was shown that the evapse-induced flow in these gases for different liquids was measured using particle image velocimetry.
Abstract: It is known from recent studies that evaporation induces flow around a droplet at atmospheric conditions. This flow is visible even for slowly evaporating liquids like water. In the present study, we investigate the influence of the ambient gas on the evaporating droplet. We observe from the experiments that the rate of evaporation at atmospheric temperature and pressure decreases in a heavier ambient gas. The evaporation-induced flow in these gases for different liquids is measured using particle image velocimetry and found to be very different from each other. However, the width of the disturbed zone around the droplet is seen to be independent of the evaporating liquid and the size of the needle (for the range of needle diameters studied), and only depends on the ambient gas used.It is known from recent studies that evaporation induces flow around a droplet at atmospheric conditions. This flow is visible even for slowly evaporating liquids like water. In the present study, we investigate the influence of the ambient gas on the evaporating droplet. We observe from the experiments that the rate of evaporation at atmospheric temperature and pressure decreases in a heavier ambient gas. The evaporation-induced flow in these gases for different liquids is measured using particle image velocimetry and found to be very different from each other. However, the width of the disturbed zone around the droplet is seen to be independent of the evaporating liquid and the size of the needle (for the range of needle diameters studied), and only depends on the ambient gas used.
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TL;DR: In this paper, a nanocapillary membrane containing both nanopores and nanochannels based on an assembly of holey graphene oxide (HGO) nanosheets was constructed to enable water molecules to permeate and simultaneously evaporate from the nanostructure.
23 citations
TL;DR: In this article , a nanocapillary membrane containing both nanopores and nanochannels based on an assembly of holey graphene oxide (HGO) nanosheets was proposed to enable water molecules to permeate and simultaneously evaporate from the nanostructure.
19 citations
TL;DR: In this article , a highly flexible and efficient evaporation-induced electricity generator (EIEG) that dexterously exploits the directional water capillary flow inside the silicon nanowires (SiNWs) mesh nanopores is developed.
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22 Dec 1991
TL;DR: In this paper, the evaporation rate from single drops as well as collections of drops on a solid substrate, both experimentally and theoretically, is studied. But the authors focus on the single drop and do not consider the effect of diffusion of water through the air.
Abstract: We study the evaporation rate from single drops as well as collections of drops on a solid substrate, both experimentally and theoretically. For a single isolated drop of water, in general the evaporative flux is limited by diffusion of water through the air, leading to an evaporation rate that is proportional to the linear dimension of the drop. Here, we test the limitations of this scaling law for several small drops and for very large drops. We find that both for simple arrangements of drops, as well as for complex drop size distributions found in sprays, cooperative effects between drops are significant. For large drops, we find that the onset of convection introduces a length scale of approximately 20 mm in radius, below which linear scaling is found. Above this length scale, the evaporation rate is proportional to the surface area.
152 citations
TL;DR: In this paper, an experimental and theoretical study of the effect of the atmosphere on the evaporation of pinned sessile droplets of water is described, and a mathematical model that takes into account both the atmospheric pressure and the nature of the ambient gas on the diffusion of water vapor in the atmosphere and the thermal conductivity of the substrate is developed.
Abstract: An experimental and theoretical study of the effect of the atmosphere on the evaporation of pinned sessile droplets of water is described. The experimental work investigated the evaporation rates of sessile droplets in atmospheres of three different ambient gases (namely, helium, nitrogen, and carbon dioxide) at reduced pressure (from 40 to 1000 mbars) using four different substrates (namely, aluminum, titanium, Macor, and polytetrafluoroethylene) with a wide range of thermal conductivities. Reducing the atmospheric pressure increases the diffusion coefficient of water vapor in the atmosphere and hence increases the evaporation rate. Changing the ambient gas also alters the diffusion coefficient and hence also affects the evaporation rate. A mathematical model that takes into account the effect of the atmospheric pressure and the nature of the ambient gas on the diffusion of water vapor in the atmosphere and the thermal conductivity of the substrate is developed, and its predictions are found to be in encouraging agreement with the experimental results.
147 citations
TL;DR: In this paper, the authors used the Rayleigh number to analyse the contribution of natural convection and an empirical model was developed combining diffusive and convective transport for each type of fluid.
107 citations
TL;DR: The results show that when a droplet evaporates sufficiently fast it exhibits a vigorous interior flow that is driven by surface tension gradients.
Abstract: Although droplet evaporation is widely assumed to be a diffusion process, our results show that when a droplet evaporates sufficiently fast it exhibits a vigorous interior flow. This flow is driven by surface tension gradients. The typical interior flow field behavior is shown as well as measurements of the droplet surface area and volume as it evaporates. We also discuss the droplet lifetime and how the system tends toward a state of marginal stability. \textcopyright{} 1996 The American Physical Society.
106 citations
TL;DR: In this paper, the authors investigated the contribution of the natural convective transport in the vapor phase on the evaporation rate of an evaporating sessile droplet, and they presented experimental results obtained with two gravity levels: 1 g and μg.
Abstract: We investigate the contribution of the natural convective transport in the vapor phase on the evaporation rate of an evaporating sessile droplet. When comparing the experimental data with the quasi-steady diffusion-controlled evaporation model, an increasing deviation with substrate temperature that was attributed to the effect of the natural convection on the vapor field has been recently highlighted. To validate this analysis, we present experimental results obtained with two gravity levels: 1 g and μg. The contribution of the natural convection is analyzed with the Grashof number, and an empirical model is developed combining diffusive and convective transport.
99 citations