Ice-dependent liquid-phase convective cells during the melting of frozen sessile droplets containing water and multiwall carbon nanotubes

Ivall, Jason; Renault-Crispo, Jean-Sébastien; Coulombe, Sylvain; Servio, Phillip

doi:10.1016/j.ijheatmasstransfer.2016.05.053

Cited by 11 publications

(8 citation statements)

References 50 publications

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“…This behaviour is well-documented and common not only in levitated systems but in systems with melting at a gas-liquid interface generally. 14,50 In brief, when the buoyant force brings the remaining solid phase to the top of the droplet, this creates a vertical thermal gradient where, in this case, the top is cooled by the THF hydrate, and the bottom is warmed by the gaseous interface. In turn, a sufficiently great surface tension gradient develops at the air-liquid interface such that convective currents, which originated at the droplet center and moved towards the bottom of the droplet, became convective cells that spun about the horizontal axis.…”

Section: Melting Of Levitated Thf Hydratesmentioning

confidence: 99%

“…In turn, a sufficiently great surface tension gradient develops at the air-liquid interface such that convective currents, which originated at the droplet center and moved towards the bottom of the droplet, became convective cells that spun about the horizontal axis. 50 This form of surface tension-driven flow due to a thermal gradient is known as Bénard-Marangoni convection, and systems exhibiting this behaviour tend towards larger Marangoni numbers (Ma). Calculating this value as in previous pure water studies results in a Ma value of 6.9 x 10 3 , which is considered large enough to indicate that the convection cells result from the thermal gradient.…”

Section: Melting Of Levitated Thf Hydratesmentioning

confidence: 99%

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Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

et al. 2023

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Recent strategies developed to examine the nucleation of crystal structures like tetrahydrofuran (THF) hydrates without the effects of a solid interface have included acoustic levitation, where only a liquid−gas interface initially exists. However, the ability now exists to levitate and freeze multiple droplets simultaneously, which could reveal interdroplet effects and provide further insight into interfacial nucleation phenomena. In this study, using direct digital and infrared imaging techniques, the freezing of up to three simultaneous THF hydrate droplets was investigated for the first time. Nucleation was initiated at the aqueous solution−air interface. Two pseudo-heterogeneous mechanisms created additional nucleation interfaces: one from cavitation effects entraining microbubbles and another from subvisible ice particles, also called hydrate-nucleating particles (HNPs), impacting the droplet surface. For systems containing droplets in both the second and third positions, nucleation was statistically simultaneous between all droplets. This effect may have been caused by the high liquid−solid interfacial pressures that developed at nucleation, causing some cracking in the initial hydrate shell around the droplet and releasing additional HNPs (now of hydrate) into the air. During crystallization, the THF hydrate droplets developed a completely white opacity, termed optical clarity loss (OCL). It was suggested that high hydrate growth rates within the droplet resulted in the capture of tiny air bubbles within the solid phase. In turn, light refraction through many smaller bubbles resulted in the OCL. These bubbles created structural inhomogeneities, which may explain how the volumetric expansion of the droplets upon complete solidification was 23.6% compared with 7.4% in pure, stationary THF hydrate systems. Finally, the thermal gradient that developed between the top and bottom of the droplet during melting resulted in a surface tension gradient along the air−liquid interface. In turn, convective cells developed within the droplet, causing it to spin rapidly about the horizontal axis.

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Section: Melting Of Levitated Thf Hydratesmentioning

confidence: 99%

Section: Melting Of Levitated Thf Hydratesmentioning

confidence: 99%

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

et al. 2023

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“…Multiwalled carbon nanotubes (MWCNT) can also be applied for de-icing purposes [ 85 , 102 , 103 , 104 , 105 , 106 ]. In [ 107 ], the creation of a system consisting of a carbon nanofiber polymer (CNFP, 10–200 nm) as a heat source, an AlN-ceramic based insulating layer (0.5 mm), a MWCN/cement thermal conductive layer and a thermally insulated substrate is presented.…”

Section: Electrothermal Composite Materials For De-icing Applicationsmentioning

confidence: 99%

A Mini-Review on Recent Developments in Anti-Icing Methods

et al. 2021

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An aggressive impact of the formed ice on the surface of man-made objects can ultimately lead to serious consequences in their work. When icing occurs, the quality and characteristics of equipment, instruments, and building structures deteriorate, which affects the durability of their use. Delays in the adoption of measures against icing endanger the safety of air travel and road traffic. Various methods have been developed to combat de-icing, such as mechanical de-icing, the use of salts, the application of a hydrophobic coating to the surfaces, ultrasonic treatment and electric heating. In this review, we summarize the recent advances in the field of anti-icing and analyze the role of various additives and their operating mechanisms.

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“…Via adding multiwall carbon nanotubes as trace particles, experiments by Ivall et al also proved the thermocapillary convection inside a melting droplet. 30 Then, at appropriate time (28 s in Fig. 2), the surface temperature is reduced and the droplet is re-cooled.…”

Section: Main Textmentioning

confidence: 99%

Droplet re-icing characteristics on a superhydrophobic surface

Chu

Gao

Zhang

et al. 2019

Applied Physics Letters

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Water icing is a natural phase change phenomenon which happens frequently in nature and industry and has negative effects on a variety of applications. Deicing is essential for iced surfaces, but even for a nanoengineered superhydrophobic surface, deicing may be incomplete with many adherent unmelted ice droplets which have potential of re-icing. Here, we focused on the droplet re-icing characteristics on a solid superhydrophobic surface, which has lacked attention in previous studies. Our results show that, the nucleation and ice crystal growth characteristics of a re-icing droplet are quite different with those of a first-time icing droplet. During re-icing, secondary nucleation due to fluid shear always first occurs on the edges of unmelted ice, accompanied by fast-growing ice crystals that can trigger heterogeneous nucleation when in contact with the solid surface. The re-icing takes place under very small supercooling (less than 0.5 o C) and the superhydrophobic surface does not play a key role, meaning that any current icephobic surfaces lose their features, which poses great challenges for anti-icing. In addition, because of the small supercooling, no recalescence phenomenon appears during re-icing and the droplet keeps transparent instead of clouding. Owing to the unmelted ice floating on the top of the droplet, the droplet shape after re-icing is also distinguishing from that after normal icing but the pointy tip formation during re-icing and normal icing shows a uniformity. These results shall deepen the understanding on the anti-icing and deicing physics.

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Ice-dependent liquid-phase convective cells during the melting of frozen sessile droplets containing water and multiwall carbon nanotubes

Cited by 11 publications

References 50 publications

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

A Mini-Review on Recent Developments in Anti-Icing Methods

Droplet re-icing characteristics on a superhydrophobic surface

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