Internal circulation in a single droplet evaporating in a closed chamber

Mandal, Deepak Kumar; Bakshi, Shamit

doi:10.1016/j.ijmultiphaseflow.2012.01.008

Cited by 62 publications

(92 citation statements)

References 26 publications

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“…As strong evaporation occurred near the contact line during this stage, the ethanol concentration near the contact line will be low compared to the droplet's centre, which led to large surface tension gradient and resulted in Marangoni convection flowing from the centre of the droplet to the contact line, forming downward vortices. These symmetric and significant vortices were also reported in droplets of pure alcohols like methanol and ethanol by [8], which confirmed that the solutal effect of ethanol was mainly driving the evaporation in this stage and generated internal flow patterns of symmetric downward vortices.…”

Section: Resultssupporting

confidence: 75%

“…The average internal flow rates calculated from raw images were 0.13 mm/s, 0.44 mm/s and 0.77 mm/s for input power of 0.5W, 1W and 2W respectively. Evaporation rate was also enhanced with the increased input power because shear stress produced by internal flow constantly entrains surrounding gas into the region near the interface and this motion constantly removes evaporated vapour from the interface and brings in fresh air to the droplet surface, increasing the heat convection [8]. It is worth mentioning that only internal flow patterns of upward vortices appeared.…”

Section: Resultsmentioning

confidence: 99%

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Internal flow patterns of an evaporating multicomponent droplet on a flat surface

Qiu

2016

International Journal of Thermal Sciences

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Evaporation processes of droplets with different ethanol/water volume ratios (0% ethanol/100% water, 5% ethanol/95% water and 10% ethanol/90% water, respectively) on a hydrophobic silicon dioxide surface covered by a layer of FAS were investigated by PIV method. It was found that the evaporation process of heated two-component droplets can be divided into three stages, downward vortex stage, transition stage and upward vortex stage sequentially, while for a pure water droplet only the upward vortex stage exists. The mechanism of those three stages was analysed in detail, combining previous theories of Marangoni effects, buoyancy effect and experiment results. Besides, it was also found that initial composition and input power affected the duration of the three stages, especially the downward vortices and transition stage which are related to ethanol evaporation: In low input power, the transition stage of the high ethanol fraction droplet occurred earlier and lasted a shorter time than the low ethanol fraction droplet, while, in high input power, the transition stage of the low ethanol fraction droplet occurred earlier and lasted a shorter time than the high ethanol fraction droplet. That phenomenon was also analysed with ethanol evaporation in different thermal and solutal conditions. INTRODUCTIONThe evaporation of droplets is important in many applications such as coatings (automobile exteriors and photoresist deposition), droplet-based microfluidics [10], inkjet printing [9], film formation [2] and even spotting DNA microarray data [1]. Evaporation of monocomponent droplets has been studied for decades [11][12][13][14][15]. Recently, experimental and numerical investigations have been focused on multicomponent evaporation because it has more applications and its mechanism is more complicated than monocomponent droplets [2][3][4][5][6][7][16][17][18]. Among the first researchers to study multicomponent droplets, Newbold and Amundson [16] derived an accurate model to describe the evaporation of a

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Section: Resultssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Internal flow patterns of an evaporating multicomponent droplet on a flat surface

Qiu

2016

International Journal of Thermal Sciences

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“…Further, it also needs to be revealed whether the magnetic field enhances evaporation by modulating the thermal convection or the solutal convection or both. Accordingly, an analysis has been proposed to deduce the dominant mechanism involved in the field influenced Furthermore, uneven cooling of the pendent shape leads to surface convection or thermo-Marangoni convection along the droplet surface [33,34]. The present approach theorizes that the magnetic field induces enhanced evaporation, thereby leading to augmented thermo-convection, which aids in further hastened evaporation.…”

Section: Scaling Analysis Of Field-induced Magneto-thermal Advectionmentioning

confidence: 96%

“…It is evident from the visualization studies (Figure 7) that the effective magnitude of the circulation velocity 22 enhances with magnetic field strength. This internal circulation has been established to be caused by thermo-solutal advection [33,34] in case of solute based droplets or multi-component droplets, and the major discussion is present in these reports in the literature [34,35]. In brief, the thermosolutal gradients generated within the droplet leads to advection currents, which manifests as internal circulation.…”

Section: Role Of Enhanced Internal Advectionmentioning

confidence: 99%

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Magnetohydrodynamics- and magnetosolutal-transport-mediated evaporation dynamics in paramagnetic pendant droplets under field stimulus

et al. 2018

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Evaporation kinetics of pendant droplets is an area of immense importance in several applications, in addition to possessing rich fluid dynamics and thermal transport physics. This article experimentally and analytically sheds insight into the augmented evaporation dynamics of paramagnetic pendant droplets in the presence of a magnetic field stimulus. The literature provides information that solutal advection and the solutal Marangoni effect lead to enhanced evaporation in droplets with solvated ions. The main focus of this article is to modulate the thermosolutal advection with the aid of an external magnetic field and comprehend the dynamics of the evaporation process under such complex multiphysics interactions. Experimental observations reveal that the evaporation rate enhances as a direct function of the magnetic moment of the solvated magnetic element ions, thereby pointing at the magnetophoretic and magnetosolutal advection. Additionally, flow visualization by particle image velocimetry illustrates that the internal advection currents within the droplet increase in magnitude and are distorted in orientation by the magnetic field. A mathematical formalism based on magnetothermal and magnetosolutal advection has been proposed via scaling analysis of the species and energy conservation equations. The formalism takes into account all major governing factors, viz., the magnetothermal and magnetosolutal Marangoni numbers, magneto-Prandtl and magneto-Schmidt numbers, and the Hartmann number. The modeling establishes the magnetosolutal advection to be the dominant factor behind the augmented evaporation dynamics. Accurate validation of the experimental internal circulation velocity is obtained from the proposed model. This study reveals rich insight into the magnetothermosolutal hydrodynamics in paramagnetic droplets.

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Heating and Evaporation of Monocomponent Droplets

Sazhin

2014

Droplets and Sprays

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Internal circulation in a single droplet evaporating in a closed chamber

Cited by 62 publications

References 26 publications

Internal flow patterns of an evaporating multicomponent droplet on a flat surface

Internal flow patterns of an evaporating multicomponent droplet on a flat surface

Magnetohydrodynamics- and magnetosolutal-transport-mediated evaporation dynamics in paramagnetic pendant droplets under field stimulus

Heating and Evaporation of Monocomponent Droplets

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