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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

LEVITATION OF ORDERED ARRAYS OF LIQUID MICRODROPLETS OVER SOLID-GAS AND LIQUID-GAS INTERFACES

Dmitry V. Zaitsev
Kutateladze Institute of Thermophysics SB RAS, 1, Lavrentiev Ave, Novosibirsk, 630090, Russia; Novosibirsk State University, 2, Pirogova str., Novosibirsk, 630090, Russia

Dmitry P. Kirichenko
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, 630090, Russia; Novosibirsk State University, Novosibirsk, 630090, Russia

Vladimir V. Ajaev
Kutateladze Institute of Thermophysics SB RAS, 1, Lavrentiev Ave, Novosibirsk, 630090, Russia; Department of Mathematics, Southern Methodist University, Dallas TX 75275, USA

Oleg A. Kabov
Kutateladze Institute of Thermophysics of the Siberian Branch of the Russian Academy of Sciences, 1, Acad. Lavrentyev Ave., Novosibirsk, 630090, Russia; Institute of Power Engineering, National Tomsk Polytechnic Research University, 7, Usova Street, Tomsk, 634050, Russia; Novosibirsk State University, 2, Pirogova str., Novosibirsk, 630090, Russia

DOI: 10.1615/IHTC16.bae.024306
pages 1471-1478


KEY WORDS: Boiling and evaporation, Nano/Micro scale measurement and simulation, Levitation, liquid microdroplets, evaporation, structured arrays

Abstract

Levitating droplets of liquid condensate are known to organize themselves into ordered arrays over hot liquid-gas interfaces. The mechanism of levitation is the Stokes force acting onto a drop from the flow originated at the interface. We report experimental observation of levitation and self-organization of liquid microdroplets (with size on the order of 10 µm) over both hot liquid-gas interfaces and heated dry solid surfaces. In the experiment a copper block heated from below is used as the substrate. Degassed ultra-pure water is used as the working liquid. Optical recording is made using a high-speed camera equipped with a microscope objective of high resolving power. Working liquid is deposited with a syringe onto the substrate to form a horizontal liquid layer. The heater is then switched on, resulting in evaporation and formation of droplet array levitating over liquid surface. With a short pulse of air jet a dry spot is formed on the copper surface. When the array moves to the dry spot, the droplets continue to levitate over the solid dry surface. Even though the life-time of the array is shorter over the dry surface, its geometric characteristics are remarkably similar to the case of levitation over liquid-gas interface. Mathematical models are developed that explain droplet levitation for both configurations and lead to new power laws for the levitation height as a function of droplet size. The predictions of the models are in good quantitative agreement with the experimental data. Using the insights from the models and new experiments, we are able to resolve some long-standing controversies from previous studies of levitating liquid droplets.

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