Convective Flows in Evaporating Sessile Droplets

Barmi, M. Rezaei; Meinhart, Carl

doi:10.1021/jp408241f

Cited by 65 publications

(38 citation statements)

References 37 publications

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“…12. This indicates a rather constant evaporation rate throughout drying which is in correspondence with observations by Ruiz and Black [6] and Barmi and Meinhart [12]. The increased heat and mass transfer rates obtained at smaller contact angles might thus be balanced out by decreased surface area and internal conduction.…”

Section: Coupling Of Internal and External Flowsupporting

confidence: 88%

Heat and mass transfer boundary conditions at the surface of a heated sessile droplet

Ljung

Lundström

2017

Heat Mass Transfer

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This work numerically investigates how the boundary conditions of a heated sessile water droplet should be defined in order to include effects of both ambient and internal flow. Significance of water vapor, Marangoni convection, separate simulations of the external and internal flow, and influence of contact angle throughout drying is studied. The quasisteady simulations are carried out with Computational Fluid Dynamics and conduction, natural convection and Marangoni convection are accounted for inside the droplet. For the studied conditions, a noticeable effect of buoyancy due to evaporation is observed. Hence, the inclusion of moisture increases the maximum velocities in the external flow. Marangoni convection will, in its turn, increase the velocity within the droplet with up to three orders of magnitude. Results furthermore show that the internal and ambient flow can be simulated separately for the conditions studied, and the accuracy is improved if the internal temperature gradient is low, e.g. if Marangoni convection is present. Simultaneous simulations of the domains are however preferred at high plate temperatures if both internal and external flows are dominated by buoyancy and natural convection. The importance of a spatially resolved heat and mass transfer boundary condition is, in its turn, increased if the internal velocity is small or if there is a large variation of the transfer coefficients at the surface. Finally, the results indicate that when the internal convective heat transport is small, a rather constant evaporation rate may be obtained throughout the drying at certain conditions.

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Section: Coupling Of Internal and External Flowsupporting

confidence: 88%

Heat and mass transfer boundary conditions at the surface of a heated sessile droplet

Ljung

Lundström

2017

Heat Mass Transfer

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“…Numerical simulations have confirmed high evaporative flux at the contact line of the thin-film region (Barmi and Meinhart, 2014;Deegan et al, 1997Deegan et al, , 2000Yunker et al, 2011). Because of this, salt supersaturation increases close to the corners creating a chemical potential difference inside the trapped brine.…”

Section: Microscopic Viewmentioning

confidence: 81%

Salt precipitation during CO 2 storage—A review

Miri

Hellevang

2016

International Journal of Greenhouse Gas Control

169

127

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“…They used spatial profile of evaporation mass flux described by Hu and Larson [2] in their model and showed that the spatial profile of temperature at the liquid-gas interface depends on the ratio of thermal conductivity of the substrate to that of the droplet. Simulations by Barmi and Meinhart [10] quantified the internal convection against Marangoni number and they found that the Marangoni convection becomes negligible as the droplet volume decreases during the evaporation.…”

Section: Introductionmentioning

confidence: 99%

A combined computational and experimental investigation on evaporation of a sessile water droplet on a heated hydrophilic substrate

Kumar

Bhardwaj

2018

International Journal of Heat and Mass Transfer

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We numerically and experimentally investigate evaporation of a sessile droplet on a heated substrate. We develop a finite element (FE) model in two-dimensional axisymmetric coordinates to solve coupled transport of heat in the droplet and substrate, and of the mass of liquid vapor in surrounding ambient while assuming diffusion-limited, quasi-steady evaporation of the droplet.The two-way coupling is implemented using an iterative scheme and under-relaxation is used to ensure numerical stability. The FE model is validated against the published spatial profile of the evaporation mass flux and temperature of the liquid-gas interface. We discuss cases in which the two-way coupling is significantly accurate than the one-way coupling. In experiments, we visualized side view of an evaporating microliter water droplet using a high-speed camera at different substrate temperatures and recorded temperature of the liquid-gas interface from the top using an infrared camera. We examine the dependency of inversion of the temperature profile across the liquid-gas interface on the ratio of the substrate thickness to the wetted radius, the ratio of the thermal conductivity of the substrate to that of the droplet and contact angle. A regime map is plotted to demarcate the inversion of the temperature profile for a wide range of these variables.A comparison of measured evaporation mass rate with the computed values at different substrate temperature show that the evaporation mass rate increases non-linearly with respect to the substrate temperature, and FE model predicts these values close to the experimental data. Comparisons of time-averaged evaporation mass rate obtained by the previous and present models against the measurements suggest that the evaporative cooling at the interface and variation of diffusion coefficient with temperature should be taken into account in the model in order to accurately capture the measurements. We compare the measurements of time-varying droplet dimensions and of temperature profile across the liquid-gas interface with the numerical results and found good agreements. We quantify increase in the evaporation mass flux and evaporation mas rate by the substrate heating and present the combined effect of substrate heating, the ratio of the substrate thickness to the wetted radius, substrate-droplet thermal conductivity ratio and the contact angle on the evaporation mass rate.

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Convective Flows in Evaporating Sessile Droplets

Cited by 65 publications

References 37 publications

Heat and mass transfer boundary conditions at the surface of a heated sessile droplet

Heat and mass transfer boundary conditions at the surface of a heated sessile droplet

Salt precipitation during CO 2 storage—A review

A combined computational and experimental investigation on evaporation of a sessile water droplet on a heated hydrophilic substrate

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