Formation and Deformation of Liquid Drops in Microchannels
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ion and Deformation of Liquid Drops in Microchannels F. V. Ronshina*, Yu. A. Dementyeva, and E. A. Chinnova a
Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected] Received April 21, 2020; revised April 21, 2020; accepted April 23, 2020
Abstract—The laws of drop formation are experimentally studied in narrow horizontal microchannels with rectangular section with heights from 50 to 150 μm. It is shown that there exists a new flow regime when the drops in the form of vertical liquid bridges move along the microchannel. Three mechanisms of formation of such drops are distinguished: formation directly near the liquid nozzle, departure of drops from liquid moving at the lateral sides of channel, and drop formation due to destruction of severely deformed drops and horizontal liquid bridges. It is established that the deformation of drops increases with increasing Weber number. It is demonstrated that the drops begin to deform when the first critical value of the Weber number is achieved and begin to be destroyed when the second one is achieved. Keywords: microchannel, two-phase flow, drops, flow regimes DOI: 10.1134/S1063785020080131
The studies of drop flows under different conditions are widely presented in many publications. For instance, in works [1, 2], the interaction and destruction of drops in a free flow are investigated, which is important for developing firefighting technologies. The spray, drop, and jet cooling are intensely used in such branches of industry as metallurgy, power engineering, the chemical and food industry, and aerospace industry [3]. The capillary hydrodynamics and heat exchange in microsystems are attracting everincreasing attention, which is related to development of electronics and medicine and to the general tendency of device miniaturization, in particular, in aerospace, transport, and power engineering. The studies of two-phase flows in microchannels of different geometry were considered in reviews [4, 5]. The formation of liquid drops was observed at transition from the annular to drop-annular mode at high velocities of gas (above 10–20 m/s). In particular, this phenomenon was investigated in horizontal rectangular channels with a thickness of 1 mm [6] and in vertical tubes with a diameter larger than 1 mm [7]. In narrower horizontal microchannels the small drops at the channel lower wall were revealed at small superficial velocities of liquid in the slug, intermittent, and jet flow regimes [8]. A similar phenomenon was observed in the case of the slug regime in work [9] for a vertical rectangular channel with a thickness of 0.3 mm. As the height of the microchannel decreases, the liquid drops begin to form in the two-phase flow,
with these drops being represented by vertical liquid bridges between the upper and lower walls of the microchannel and by the sessile drops at the walls of the microchannel. Investigation of two-phase flow regimes and drop formation in horizontal narrow rectangular chann
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