Comparing Internal Flow in Freezing and Evaporating Water Droplets Using PIV

Document identifier: oai:DiVA.org:ltu-77123
Access full text here:10.3390/w12051489
Keyword: Engineering and Technology, Mechanical Engineering, Fluid Mechanics and Acoustics, Teknik och teknologier, Maskinteknik, Strömningsmekanik och akustik, Evaporation, Freezing, Water droplet, Internal flow, Marangoni flow, Strömningslära, Fluid Mechanics
Publication year: 2020
Relevant Sustainable Development Goals (SDGs):
SDG 9 Industry, innovation and infrastructure
The SDG label(s) above have been assigned by OSDG.ai

Abstract:

The study of evaporation and freezing of droplets is important in, e.g., spray cooling, surface coating, ink-jet printing, and when dealing with icing on wind turbines, airplane wings, and roads. Due to the complex nature of the flow within droplets, a wide range of temperatures, from freezing temperatures to heating temperatures, have to be taken into account in order to increase the understanding of the flow behavior. This study aimed to reveal if natural convection and/or Marangoni convection influence the flow in freezing and evaporating droplets. Droplets were released on cold and warm surfaces using similar experimental techniques and setups, and the internal flow within freezing and evaporating water droplets were then investigated and compared to one another using Particle Image Velocimetry. It was shown that, for both freezing and evaporating droplets, a shift in flow direction occurs early in the processes. For the freezing droplets, this effect could be traced to the Marangoni convection, but this could not be concluded for the evaporating droplets. For both evaporating and freezing droplets, after the shift in flow direction, natural convection dominates the flow. In the end of the freezing process, conduction seems to be the only contributing factor for the flow.

Authors

Linn Karlsson

Luleå tekniska universitet; Strömningslära och experimentell mekanik
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Anna-Lena Ljung

Luleå tekniska universitet; Strömningslära och experimentell mekanik
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Staffan Lundström

Luleå tekniska universitet; Strömningslära och experimentell mekanik
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