Evaporation of a liquid sessile droplet subjected to forced convection
https://doi.org/10.32362/2500-316X-2021-9-5-57-66
Abstract
Experiments on measuring the rate of evaporation of liquid sessile droplets into air show that the rate of evaporation increases in the presence of forced convection flows. However, data on the effect of convection on evaporation are often contradictory and should be clarified. The paper presents a numerical analysis of evaporation from the surface of a water droplet subjected to forced convection in the gas phase. The drop is located on a smooth horizontal isothermal substrate; the mode with constant contact angle is considered. The shape of the drop has axial symmetry, the same for the velocities and pressure. Forced convection compatible with the symmetry conditions are represented by flows directed downward along the axis of the system and diverging along the sides near the drop and the substrate. The mathematical model is constructed for evaporation controlled by diffusion in the gas phase and takes into account surface tension, gravity, and viscosity in both media, buoyancy and Marangoni convection. The results indicate the existence of the mutual influence of liquid and gaseous media. Thus, a drop vibrates under the influence of movements in the atmosphere, which generates a density wave in the gas: the drop «sounds». The magnitude of the velocity in a liquid is 50 times less than the characteristic velocity in air. It is found that the evaporation rate does not change in the presence of forced convection flows, which contradicts most of the experimental works. The reason for the discrepancies is supposed to be the appearance of nonequilibrium conditions at the boundary of the condensed phase: under these conditions, the evaporation regime ceases to be diffusional.
About the Authors
A. Е. Korenchenko
MIREA – Russian Technological University
Russian Federation
Russian Federation
Anna E. Korenchenko, Dr. Sci. (Phys.-Math.), Professor, Department of High Mathematics, Institute of Integrated Safety and Special Instrument Engineering
78, Vernadskogo pr., Moscow, 119454
Scopus Author ID 10043443100
A. A. Zhukova
Sechenov First Moscow State Medical University
Russian Federation
Russian Federation
Anna A. Zhukova, Cand. Sci. (Chem.), Associate Professor
21, 5 Parkovaya ul., Moscow, 105043
Scopus Author ID 12757009400
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The paper presents a numerical analysis of evaporation from the surface of a water droplet subjected to forced convection in the gas phase. Forced convection compatible with the symmetry conditions are represented by flows directed downward along the axis of the system and diverging along the sides near the drop and the substrate. It is found that the evaporation rate does not change in the presence of forced convection flows, which contradicts most of the experimental works. The reason for the discrepancies is supposed to be the appearance of nonequilibrium conditions at the boundary of the condensed phase: under these conditions, the evaporation regime ceases to be diffusional.
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For citations:
Korenchenko A.Е., Zhukova A.A. Evaporation of a liquid sessile droplet subjected to forced convection. Russian Technological Journal. 2021;9(5):57-66. https://doi.org/10.32362/2500-316X-2021-9-5-57-66
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