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https://www.readbyqxmd.com/read/28936527/origin-of-spray-formation-during-impact-on-heated-surfaces
#1
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...
September 22, 2017: Soft Matter
https://www.readbyqxmd.com/read/28931942/self-propulsion-of-leidenfrost-drops-between-non-parallel-structures
#2
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
https://www.readbyqxmd.com/read/28913434/self-determined-shapes-and-velocities-of-giant-near-zero-drag-gas-cavities
#3
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
https://www.readbyqxmd.com/read/28880207/rapid-evaporation-of-water-on-graphene-graphene-oxide-a-molecular-dynamics-study
#4
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
https://www.readbyqxmd.com/read/28733647/boiling-and-quenching-heat-transfer-advancement-by-nanoscale-surface-modification
#5
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
https://www.readbyqxmd.com/read/28655427/the-development-and-efficacy-of-a-group-intervention-program-for-individuals-with-serious-mental-illness-in-jail
#6
Corey M Leidenfrost, Ronald M Schoelerman, Michael Maher, Daniel Antonius
Providing cost-effective means to treat the influx of individuals with serious mental illness entering the correctional system is a major challenge. Failure to provide appropriate mental health treatment may lead to poor outcomes, including recidivism and suicide. Group intervention is an effective and cost efficient way to provide mental health treatment. However, it has been understudied in jail settings. To meet the needs of jail-inmates with serious mental illness, an eight-week group-based module curriculum was developed and studied through analyses of perceived usefulness, retention of key material, and associations with cognitive ability, improvement in psychiatric symptoms, and level of motivation...
June 24, 2017: International Journal of Law and Psychiatry
https://www.readbyqxmd.com/read/28644495/non-wetting-drops-at-liquid-interfaces-from-liquid-marbles-to-leidenfrost-drops
#7
Clint Y H Wong, Mokhtar Adda-Bedia, Dominic Vella
We consider the flotation of deformable, non-wetting drops on a liquid interface. We consider the deflection of both the liquid interface and the droplet itself in response to the buoyancy forces, density difference and the various surface tensions within the system. Our results suggest new insight into a range of phenomena in which such drops occur, including Leidenfrost droplets and floating liquid marbles. In particular, we show that the floating state of liquid marbles is very sensitive to the tension of the particle-covered interface and suggest that this sensitivity may make such experiments a useful assay of the properties of these complex interfaces...
August 9, 2017: Soft Matter
https://www.readbyqxmd.com/read/28582621/self-rotation-induced-propulsion-of-a-leidenfrost-drop-on-a-ratchet
#8
Manjarik Mrinal, Xiang Wang, Cheng Luo
A Leidenfrost drop is capable of self-propelling on a ratchet, which consists of asymmetric teeth. In this work, the corresponding movements were first experimentally investigated. Because the detected motion could not be interpreted using existing propulsive mechanisms, a new propulsive mechanism was then developed, followed by force analysis using a scaling law.
June 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28497789/underwater-leidenfrost-nanochemistry-for-creation-of-size-tailored-zinc-peroxide-cancer-nanotherapeutics
#9
Mady Elbahri, Ramzy Abdelaziz, Duygu Disci-Zayed, Shahin Homaeigohar, Justyna Sosna, Dieter Adam, Lorenz Kienle, Torben Dankwort, Moheb Abdelaziz
The dynamic underwater chemistry seen in nature is inspiring for the next generation of eco-friendly nanochemistry. In this context, green synthesis of size-tailored nanoparticles in a facile and scalable manner via a dynamic process is an interesting challenge. Simulating the volcano-induced dynamic chemistry of the deep ocean, here we demonstrate the Leidenfrost dynamic chemistry occurring in an underwater overheated confined zone as a new tool for customized creation of nanoclusters of zinc peroxide. The hydrodynamic nature of the phenomenon ensures eruption of the nanoclusters towards a much colder region, giving rise to growth of monodisperse, size-tailored nanoclusters...
May 12, 2017: Nature Communications
https://www.readbyqxmd.com/read/28470271/effect-of-surface-topography-and-wettability-on-the-leidenfrost-effect
#10
REVIEW
Lieshuang Zhong, Zhiguang Guo
When deposited on a superheated surface, a droplet can be levitated by its own vapour layer, a phenomenon that is referred to as the Leidenfrost effect. This dynamic effect has attracted interest for many potential applications, such as cooling, drag reduction and drop transport. A lot of effort has been paid to this mechanism over the past two and half centuries. Herein, we not only review the classical theories but also present the most recent theoretical advances in understanding the Leidenfrost effect. We first review the basic theories of the Leidenfrost effect, which mainly focuses on the relationship between the drop shape, vapour layer and lifetime...
May 18, 2017: Nanoscale
https://www.readbyqxmd.com/read/28337398/desorption-in-mass-spectrometry
#11
Dilshadbek Tursunbayevich Usmanov, Satoshi Ninomiya, Lee Chuin Chen, Subhrakanti Saha, Mridul Kanti Mandal, Yuji Sakai, Rio Takaishi, Ahsan Habib, Kenzo Hiraoka, Kentaro Yoshimura, Sen Takeda, Hiroshi Wada, Hiroshi Nonami
In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e., ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described...
2017: Mass Spectrometry
https://www.readbyqxmd.com/read/28221808/decoupled-hierarchical-structures-for-suppression-of-leidenfrost-phenomenon
#12
Nazanin Farokhnia, Seyed Mohammad Sajadi, Peyman Irajizad, Hadi Ghasemi
Thermal management of high temperature systems through cooling droplets is limited by the existence of the Leidenfrost point (LFP), at which the formation of a continuous vapor film between a hot solid and a cooling droplet diminishes the heat transfer rate. This limit results in a bottleneck for the advancement of the wide spectrum of systems including high-temperature power generation, electronics/photonics, reactors, and spacecraft. Despite a long time effort on development of surfaces for suppression of this phenomenon, this limit has only shifted to higher temperatures, but still exists...
March 14, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28002051/macrotextured-spoked-surfaces-reduce-the-residence-time-of-a-bouncing-leidenfrost-drop
#13
Colin J Patterson, Samira Shiri, James C Bird
Liquid drops can bounce when they impact non-wetting surfaces. Recently, studies have demonstrated that the time that the bouncing drop contacts a superhydrophobic surface can be reduced by incorporating ridged macrotextures on the surface. Yet the existing models aimed at explaining this phenomenon offer incompatible predictions of the contact time when a drop impacts multiple intersecting macrotextures, or spokes. Furthermore, it is unclear whether the effects of the macrotexture on the drop hydrodynamics extend to non-wetting surfaces in which direct contact is avoided by a thin vapor layer...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/27858052/electric-field-makes-leidenfrost-droplets-take-a-leap
#14
Sander Wildeman, Chao Sun
Leidenfrost droplets, i.e. droplets whose mobility is ensured by a thin vapor film between the droplet and a hot plate, are exposed to an external electric field. We find that in a strong vertical electric field the droplet can start to bounce progressively higher, defying gravitational attraction. From the droplet's trajectory we infer the temporal evolution of the amount of charge on the droplet. This reveals that the charge starts high and then decreases in steps as the droplet slowly evaporates. After each discharge event the charge is in a fixed proportion to the droplet's surface area...
December 6, 2016: Soft Matter
https://www.readbyqxmd.com/read/27802872/cognitive-status-and-profile-validity-on-the-personality-assessment-inventory-pai-in-offenders-with-serious-mental-illness
#15
Tatiana M Matlasz, Jamie L Brylski, Corey M Leidenfrost, Matt Scalco, Samuel J Sinclair, Ronald M Schoelerman, Valerie Tsang, Daniel Antonius
Cognitive impairment among seriously mentally ill offenders has implications for legal matters (e.g., competency to stand trial), as well as clinical treatment and care. Thus, being able to identify potential cognitive concerns early in the adjudication process can be important when deciding on further interventions. In this study, we examined the validity scales of the Personality Assessment Inventory (PAI), scores on the Wechsler Adult Intelligence Scale-IV (WAIS-IV), and competency findings in male inmates (n=61) diagnosed with a serious mental illness...
October 29, 2016: International Journal of Law and Psychiatry
https://www.readbyqxmd.com/read/27757417/sustained-drag-reduction-in-a-turbulent-flow-using-a-low-temperature-leidenfrost-surface
#16
Dhananjai Saranadhi, Dayong Chen, Justin A Kleingartner, Siddarth Srinivasan, Robert E Cohen, Gareth H McKinley
Skin friction drag contributes a major portion of the total drag for small and large water vehicles at high Reynolds number (Re). One emerging approach to reducing drag is to use superhydrophobic surfaces to promote slip boundary conditions. However, the air layer or "plastron" trapped on submerged superhydrophobic surfaces often diminishes quickly under hydrostatic pressure and/or turbulent pressure fluctuations. We use active heating on a superhydrophobic surface to establish a stable vapor layer or "Leidenfrost" state at a relatively low superheat temperature...
October 2016: Science Advances
https://www.readbyqxmd.com/read/27739833/noise-induces-rare-events-in-granular-media
#17
Evgeniy Khain, Leonard M Sander
The granular Leidenfrost effect [B. Meerson, et al., Phys. Rev. Lett. 91, 024301 (2003)PRLTAO0031-900710.1103/PhysRevLett.91.024301; P. Eshuis et al., Phys. Rev. Lett. 95, 258001 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.258001] is the levitation of a mass of granular matter when a wall below the grains is vibrated, giving rise to a hot granular gas below the cluster. We find by simulation that for a range of parameters the system is bistable: the levitated cluster can occasionally break and give rise to two clusters and a hot granular gas above and below...
September 2016: Physical Review. E
https://www.readbyqxmd.com/read/27721527/effect-of-different-fluids-on-rectified-motion-of-leidenfrost-droplets-on-micro-sub-micron-ratchets
#18
Jeong Tae Ok, Junseo Choi, Emily Brown, Sunggook Park
Leidenfrost droplets, liquid droplets placed on a hot flat surface above the Leidenfrost temperature of the liquid, are an interesting model system to understand and achieve frictionless motion of droplets on a surface. Controlled unidirectional motion of otherwise random Leidenfrost droplets can be achieved by replacing the flat surface by a surface with topological ratchets. In this study, we show how an increase in the vapor layer thickness below the Leidenfrost droplet influences the droplet motion for underlying ratchets with various periods ranging from 1...
June 1, 2016: Microelectronic Engineering
https://www.readbyqxmd.com/read/27708341/nano-inspired-fluidic-interactivity-for-boiling-heat-transfer-impact-and-criteria
#19
Beom Seok Kim, Geehong Choi, Sangwoo Shin, Thomas Gemming, Hyung Hee Cho
The enhancement of boiling heat transfer, the most powerful energy-transferring technology, will lead to milestones in the development of high-efficiency, next-generation energy systems. Perceiving nano-inspired interface functionalities from their rough morphologies, we demonstrate interface-induced liquid refreshing is essential to improve heat transfer by intrinsically avoiding Leidenfrost phenomenon. High liquid accessibility of hemi-wicking and catalytic nucleation, triggered by the morphological and hydrodynamic peculiarities of nano-inspired interfaces, contribute to the critical heat flux (CHF) and the heat transfer coefficient (HTC)...
October 6, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27661694/leidenfrost-vapor-layers-reduce-drag-without-the-crisis-in-high-viscosity-liquids
#20
Ivan U Vakarelski, Joseph D Berry, Derek Y C Chan, Sigurdur T Thoroddsen
The drag coefficient C_{D} of a solid smooth sphere moving in a fluid is known to be only a function of the Reynolds number Re and diminishes rapidly at the drag crisis around Re∼3×10^{5}. A Leidenfrost vapor layer on a hot sphere surface can trigger the onset of the drag crisis at a lower Re. By using a range of high viscosity perfluorocarbon liquids, we show that the drag reduction effect can occur over a wide range of Re, from as low as ∼600 to 10^{5}. The Navier slip model with a viscosity dependent slip length can fit the observed drag reduction and wake shape...
September 9, 2016: Physical Review Letters
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