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Loreto Oyarte Gálvez, Nicolás Rivas, Devaraj van der Meer
The behavior of a vertically vibrated granular bed is reminiscent of a liquid in that it exhibits many phenomena such as convection and Faraday-like surface waves. However, when the lateral dimensions of the bed are confined such that a quasi-one-dimensional geometry is formed, the only phenomena that remain are bouncing bed and the granular Leidenfrost effect. This permits the observation of the granular Leidenfrost state for a wide range of energy injection parameters and more specifically allows for a thorough characterization of the low-frequency oscillation (LFO) that is present in this state...
April 2018: Physical Review. E
Roxana-Elena Avrămescu, Mihaela-Violeta Ghica, Cristina Dinu-Pîrvu, Denisa Ioana Udeanu, Lăcrămioara Popa
Liquid marbles are versatile structures demonstrating a pseudo-Leidenfrost wetting regime formed by encapsulating microscale volumes of liquid in a particle shell. The liquid core is completely separated from the exterior through air pockets. The external phase consists of hydrophobic particles, in most cases, or hydrophilic ones distributed as aggregates. Their interesting features arise from the double solid-fluid character. Thus, these interesting formations, also known as “dry waters”, have gained attention in surface science...
May 9, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
S Arora, J-M Fromental, S Mora, Ty Phou, L Ramos, C Ligoure
We investigate freely expanding sheets formed by ultrasoft gel beads, and liquid and viscoelastic drops, produced by the impact of the bead or drop on a silicon wafer covered with a thin layer of liquid nitrogen that suppresses viscous dissipation thanks to an inverse Leidenfrost effect. Our experiments show a unified behavior for the impact dynamics that holds for solids, liquids, and viscoelastic fluids and that we rationalize by properly taking into account elastocapillary effects. In this framework, the classical impact dynamics of solids and liquids, as far as viscous dissipation is negligible, appears as the asymptotic limits of a universal theoretical description...
April 6, 2018: Physical Review Letters
Divya Vinayachandran, Saravanakarthikeyan
Intraoral frostbite as such, is an unusual occurrence. Careful literature review revealed rare cases of intraoral frostbite, attributed to intentional inhalational abuse of fluorinated hydrocarbons, dry ice, liquid nitrogen etc,.1,2 Hypothermal injuries of the gastric mucosa caused by ingestion of liquid nitrogen have been reported but none of these patients suffered from any direct injury affecting the oral mucosa.3 Here, we report the first case of intraoral frostbite causing injury to the oral mucosal tissues due to the direct contact of liquid nitrogen, highlighting the mechanism of the injury...
April 21, 2018: Australian Dental Journal
Safouene Ouenzerfi, Souad Harmand, Jesse Schiffler
As discovered by Leidenfrost, liquids placed on very hot solids levitate on a cushion of their own vapour. This is called also calefaction phenomenon, a dynamical and transient effect, as vapour is injected below the liquid and pressed by the drop weigh. To account the film vapor, we consider the surface tension magnitude as well as the Marangoni effect (in particular the thermal one) which arise with imbalance of surface tension forces. For standard liquids, these forces contribute to amplify the thickness of film layer and the levitation of the droplet...
April 19, 2018: Journal of Physical Chemistry. B
Yangjie Li, Yong Liu, Hong Gao, Roy Helmy, W Peter Wuelfing, Christopher Welch, R Graham Cooks
Forced degradation is a method of studying the stability of pharmaceuticals in order to design stable formulations and predict drug product shelf life. Traditional methods of reaction and analysis usually take multiple days, and include LC-UV and LC-MS product analysis. In this study, the reaction/analysis sequence was accelerated to be completed within minutes using Leidenfrost droplets as reactors (acceleration factor: 23 - 188) and nanoelectrospray ionization MS analysis. The Leidenfrost droplets underwent the same reactions as seen in traditional bulk solution experiments for three chemical degradations studied...
April 13, 2018: Chemistry: a European Journal
Corey M Leidenfrost, Matthew D Scalco, Elizabeth Randall, Peter S Martin, Samuel J Sinclair, Travis J Stewart, Ronald Schoelerman, Daniel Antonius
Early identification of treatment needs in incarcerated individuals with serious mental illness has significant implications. Validated assessment instruments to guide treatment are lacking in correctional settings. Hierarchical linear modeling was used to examine the predictive validity of the Level of Care Index (LOCI) in 35 inmates admitted to a specialized treatment unit. The LOCI score was predictive of levels of depressogenic psychopathology and psychological well-being as well as changes in these constructs over time...
April 2018: Journal of Correctional Health Care
I I Katkov, V F Bolyukh, G T Sukhikh
Kinetic (dynamic) vitrification is a promising trend in cryopreservation of biological materials because it allows avoiding the formation of lethal intracellular ice and minimizes harmful effects of highly toxic penetrating cryoprotectants. A uniform cooling protocol and the same instruments can be used for practically all types of cells. In modern technologies, the rate of cooling is essentially limited by the Leidenfrost effect. We describe a novel platform for kinetic vitrification of biological materials KrioBlast TM that realizes hyper-fast cooling and allows overcoming the Leidenfrost effect...
March 2018: Bulletin of Experimental Biology and Medicine
Istafaul Haque Ansari, Nicolas Rivas, Meheboob Alam
We report patterns consisting of coexistence of synchronous and asynchronous states [for example, a granular gas co-existing with (i) bouncing bed, (ii) undulatory subharmonic waves, and (iii) Leidenfrost-like states] in experiments on vertically vibrated binary granular mixtures in a Hele-Shaw cell. Most experiments have been carried out with equimolar binary mixtures of glass and steel balls of same diameter by varying the total layer height (F) for a range of shaking acceleration (Γ). All patterns as well as the related phase diagram in the (Γ,F) plane have been reproduced via molecular dynamics simulations of the same system...
January 2018: Physical Review. E
Aditya Jetly, Ivan U Vakarelski, Sigurdur T Thoroddsen
We investigate the effect of thin air layers naturally sustained on superhydrophobic surfaces on the terminal velocity and drag force of metallic spheres free falling in water. The surface of 20 mm to 60 mm steel or tungsten-carbide spheres is rendered superhydrophobic by a simple coating process that uses a commercially available hydrophobic agent. By comparing the free fall of unmodified spheres and superhydrophobic spheres in a 2.5 meter tall water tank, it is demonstrated that even a very thin air layer (∼1-2 μm) that covers the freshly dipped superhydrophobic sphere can reduce the drag force on the spheres by up to 80%, at Reynolds numbers from 105 to 3 × 105 , owing to an early drag crisis transition...
February 28, 2018: Soft Matter
Mohammad Khavari, Tuan Tran
The Leidenfrost transition leads a boiling system to the boiling crisis, a state in which the liquid loses contact with the heated surface due to excessive vapor generation. Here, using experiments of liquid droplets boiling on a heated surface, we report a phenomenon, termed oscillating boiling, at the Leidenfrost transition. We show that oscillating boiling results from the competition between two effects: separation of liquid from the heated surface due to localized boiling and rewetting. We argue theoretically that the Leidenfrost transition can be predicted based on its link with the oscillating boiling phenomenon and verify the prediction experimentally for various liquids...
October 2017: Physical Review. E
Hua-Yi Hsu, Ming-Chieh Lin, Bridget Popovic, Chii-Ruey Lin, Neelesh A Patankar
Surface wettability is recognized as playing an important role in pool boiling and the corresponding heat transfer curve. In this work, a systematic study of pool boiling heat transfer on smooth surfaces of varying wettability (contact angle range of 5° - 180°) has been conducted and reported. Based on numerical simulations, boiling curves are calculated and boiling dynamics in each regime are studied using a volume-of-fluid method with contact angle model. The calculated trends in critical heat flux and Leidenfrost point as functions of surface wettability are obtained and compared with prior experimental and theoretical predictions, giving good agreement...
2017: PloS One
Sylwia Wciślik
In this paper, a review of the impact of most common nanoparticles on the Leidenfrost temperature T Leid in heat transfer applications is delivered. Moreover, a simple economic analysis of the nanoparticles use is proposed. When coolant is distilled water, T Leid can range 150-220 °C; occasionally, it can even amount to over 400 °C. When the base liquid is modified by additives, considerable changes in the character of heat transfer are observed. Out of five nanofluids under consideration in this study, the best thermal effect (up to 50%) is obtained when Al2 O3 nanofluid having particle sizes ~39 nm and volume concentration of 0...
2017: Chemické Zvesti
Arjang Shahriari, Onur Ozkan, Vaibhav Bahadur
An applied electric field can fundamentally eliminate the Leidenfrost effect (formation of a vapor layer at the solid-liquid interface at high temperatures). This study analyzes electrostatic suppression of the Leidenfrost state on liquid substrates. Electrostatic suppression on silicone oil and Wood's metal (liquid alloy) is studied via experimentation, high-speed imaging, and analyses. It is seen that the nature of electrostatic suppression can be drastically different from that on a solid substrate. First, the Leidenfrost droplet completely penetrates into the silicone oil substrate and converts to a thin film under an electric field...
November 8, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jonathan T Pham, Maxime Paven, Sanghyuk Wooh, Tadashi Kajiya, Hans-Jürgen Butt, Doris Vollmer
The contact between liquid drops and hot solid surfaces is of practical importance for industrial processes, such as thermal spraying and spray cooling. The contact and bouncing of solid spheres is also an important event encountered in ball milling, powder processing, and everyday activities, such as ball sports. Using high speed video microscopy, we demonstrate that hydrogel drops, initially at rest on a surface, spontaneously jump upon rapid heating and continue to bounce with increasing amplitudes. Jumping is governed by the surface wettability, surface temperature, hydrogel elasticity, and adhesion...
October 13, 2017: Nature Communications
Michiel A J van Limbeek, Paul B J Hoefnagels, Chao Sun, Detlef Lohse
In many applications, it is crucial to control the heat transfer rate of impacting drops on a heated plate. When the solid exceeds the so-called Leidenfrost temperature, an impacting drop is prevented from contacting the plate by its own evaporation. But the decrease in the resulting cooling efficiency of the impacting drop is yet not quantitatively understood. Here, we experimentally study the impact of such water drops on smooth heated surfaces of various substances. We demonstrate that, in contrast to previous results for other liquids, water exhibits spray in the vertical direction when impacting sapphire and silicon...
October 25, 2017: Soft Matter
Cheng Luo, Manjarik Mrinal, Xiang Wang
In this work, we explored self-propulsion of a Leidenfrost drop between non-parallel structures. A theoretical model was first developed to determine conditions for liquid drops to start moving away from the corner of two non-parallel plates. These conditions were then simplified for the case of a Leidenfrost drop. Furthermore, ejection speeds and travel distances of Leidenfrost drops were derived using a scaling law. Subsequently, the theoretical models were validated by experiments. Finally, three new devices have been developed to manipulate Leidenfrost drops in different ways...
September 20, 2017: Scientific Reports
Ivan U Vakarelski, Evert Klaseboer, Aditya Jetly, Mohammad M Mansoor, Andres A Aguirre-Pablo, Derek Y C Chan, Sigurdur T Thoroddsen
Minimizing the retarding force on a solid moving in liquid is the canonical problem in the quest for energy saving by friction and drag reduction. For an ideal object that cannot sustain any shear stress on its surface, theory predicts that drag force will fall to zero as its speed becomes large. However, experimental verification of this prediction has been challenging. We report the construction of a class of self-determined streamlined structures with this free-slip surface, made up of a teardrop-shaped giant gas cavity that completely encloses a metal sphere...
September 2017: Science Advances
Qibin Li, Yitian Xiao, Xiaoyang Shi, Shufeng Song
To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide...
September 7, 2017: Nanomaterials
Hong Hu, Cheng Xu, Yang Zhao, Kirk J Ziegler, J N Chung
All power production, refrigeration, and advanced electronic systems depend on efficient heat transfer mechanisms for achieving high power density and best system efficiency. Breakthrough advancement in boiling and quenching phase-change heat transfer processes by nanoscale surface texturing can lead to higher energy transfer efficiencies, substantial energy savings, and global reduction in greenhouse gas emissions. This paper reports breakthrough advancements on both fronts of boiling and quenching. The critical heat flux (CHF) in boiling and the Leidenfrost point temperature (LPT) in quenching are the bottlenecks to the heat transfer advancements...
July 21, 2017: Scientific Reports
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