Dynamic Leidenfrost temperature of saturated water drops on textured surfaces

2020 ◽  
Vol 150 ◽  
pp. 119298
Author(s):  
Junseok Park ◽  
Dong Eok Kim
Keyword(s):  
Textured Surfaces ◽  
Saturated Water ◽  
Water Drops ◽  
Leidenfrost Temperature

scholarly journals Water drops bouncing off vertically vibrating textured surfaces

2019 ◽  
Vol 876 ◽  
pp. 1041-1051 ◽  
Author(s):  
Wei Wang ◽  
Chen Ji ◽  
Fangye Lin ◽  
Jun Zou ◽  
S. Dorbolo
Keyword(s):  
Drop Size ◽  
Size Dependence ◽  
Water Drop ◽  
Excitation Frequency ◽  
Textured Surfaces ◽  
Acceleration Threshold ◽  
Water Drops ◽  
Different Shapes ◽  
Vertical Vibrations ◽  
Drop Size Dependence

We investigate the conditions that determine the detachment of a water drop from different vibrating textured plates by using vertical vibrations. The plate surfaces were patterned by a lattice of pillars of different shapes with different geometrical arrangements. The acceleration threshold for the water droplet to bounce off the surfaces was measured as a function of the excitation frequency. In each case, the acceleration threshold presents a minimum at the natural frequency of the droplet. The minimum acceleration required for the take-off is larger for small droplets than for large droplets. Namely, one finds that the value of the threshold depends on the size of the droplet and on the maximum apparent contact area between the droplet and the substrate. The theoretical model takes into account the energy necessary to break the capillary bridges between the droplet and the pillars of the surface. This model captures the main ingredients explaining the drop size dependence of the acceleration threshold for the take-off.

Understanding the Role of Surface Micro-Texture on the Delayed Freezing of Drops on Cold Surfaces

2011 ◽  
Author(s):  
Guoping Fang ◽  
Yadollah Maham ◽  
Alidad Amirfazli
Keyword(s):  
Surface Chemistry ◽  
Surface Temperature ◽  
Water Drop ◽  
Textured Surfaces ◽  
Melting Points ◽  
Scanning Calorimetry ◽  
Cold Surface ◽  
Hydrophilic Surfaces ◽  
Water Drops

Freezing of drops on surfaces has many consequences in icing of various systems, e.g. micro-condensers. It is known that when a water drop is placed on a cold surface and the surface temperature is reduced, it will not necessarily freeze when the surface temperature has reached zero degrees Celsius. The delay in freezing of a drop on a cold surface is not well understood; especially the effect that micro- and nano-texture of a surface has this delay. In this study, freezing and melting points of water drops on various micro-textured surfaces, i.e. superhydrophilic, and superhydrophobic have been measured by differential scanning calorimetry (DSC). A comparison of the experimental results with smooth hydrophilic and hydrophobic surfaces allows us to understand the roles of surface chemistry and roughness in freezing of drops in contact with such surfaces. It is found that when the surface chemistry is hydrophobic, roughness will delay the freezing and a drop may not freeze until the surface temperature has been lower than −15 ° C. On the contrary, for hydrophilic surfaces, roughness will shorten the freezing delay and facilitate formation of ice on the surface. This can explain the benefit of the superhydrophobic surfaces (SHS) in preventing ice formation.

Controlling the Leidenfrost Temperature Through Laser-Assisted Surface Micro/Nano Texturing

2013 ◽  
Author(s):  
Corey Kruse ◽  
Troy Anderson ◽  
Dennis Alexander ◽  
George Gogos ◽  
Sidy Ndao
Keyword(s):  
Stainless Steel ◽  
Smooth Surface ◽  
Steel Surface ◽  
304 Stainless Steel ◽  
Stainless Steel Surface ◽  
Textured Surface ◽  
Textured Surfaces ◽  
Transfer Coefficients ◽  
Surface Features ◽  
Leidenfrost Temperature

In the present work, the effect of surface features and wettability on the Leidenfrost temperature are experimentally investigated. The surface features were fabricated on a 304 stainless steel surface using a femtosecond laser. This technique allows for a wide variety of surface microstructures (spikes, mounds, holes, and pyramids) to be created, ranging in size, shape, and spacing. Changing the fluence and shots of the laser produce different micro/nano textured surfaces. A smooth surface sample was fabricated as a reference surface with a measured Leidenfrost temperature as a benchmark. The droplet lifetime experimental method was employed to determine the Leidenfrost temperature for both the smooth and the textured surfaces. A precision dropper was used to control the droplet size to 4.2 microliters (diameter of 2.0mm) while surface temperatures were measured by means of an embedded thermocouple. In comparison to the smooth stainless steel surface, a shift in the Leidenfrost temperature, as high as 55 °C, was observed with the textured surface. The textured surface hasa high emissivity, compared to the smooth surface. As a result, in addition to the shift in the Leidenfrost temperature, significant enhancement of the film boiling heat transfer coefficients were also observed.

Replication of Wet Objects and Cells

1974 ◽  
Vol 32 ◽  
pp. 102-103
Author(s):  
S. Basu ◽  
D. F. Parsons
Keyword(s):  
Water Vapor Pressure ◽  
High Vacuum ◽  
Polystyrene Latex ◽  
Vacuum System ◽  
Saturated Water Vapor ◽  
Replication Method ◽  
New Methods ◽  
Saturated Water ◽  
Water Vapors ◽  
Intermediate Chamber

We are approaching the invasiveness of cancer cells from the studies of their wet surface morphology which should distinguish them from their normal counterparts. In this report attempts have been made to provide physical basis and background work to a wet replication method with a differentially pumped hydration chamber (Fig. 1) (1,2), to apply this knowledge for obtaining replica of some specimens of known features (e.g. polystyrene latex) and finally to realize more specific problems and to improvize new methods and instrumentation for their rectification. In principle, the evaporant molecules penetrate through a pair of apertures (250, 350μ), through water vapors and is, then, deposited on the specimen. An intermediate chamber between the apertures is pumped independently of the high vacuum system. The size of the apertures is sufficiently small so that full saturated water vapor pressure is maintained near the specimen.

Membrane-bound vesicles associated with the microvilli in the midgut of the freshwater microcrustacean, Daphnia magna

1983 ◽  
Vol 41 ◽  
pp. 480-481
Author(s):  
Patricia L. Jansma
Keyword(s):  
Daphnia Magna ◽  
Intestinal Epithelial Cells ◽  
Uranyl Acetate ◽  
Intestinal Epithelial ◽  
Chlamydomonas Reinhardii ◽  
Thin Sections ◽  
Saturated Water ◽  
Cacodylate Buffer ◽  
Membrane Bound ◽  
Ethanol Series

The presence of the membrane bound vesicles or blebs on the intestinal epithelial cells has been demonstrated in a variety of vertebrates such as chicks, piglets, hamsters, and humans. The only invertebrates shown to have these microvillar blebs are two species of f1ies. While investigating the digestive processes of the freshwater microcrustacean, Daphnia magna, the presence of these microvillar blebs was noticed.Daphnia magna fed in a suspension of axenically grown green alga, Chlamydomonas reinhardii for one hour were narcotized with CO2 saturated water. The intestinal tracts were excised in 2% glutaraldehyde in 0.2 M cacodyl ate buffer and then placed in fresh 2% glutaraldehyde for one hour. After rinsing in 0.1 M cacodylate buffer, the sample was postfixed in 2% OsO4, dehydrated with a graded ethanol series, infiltrated and embedded with Epon-Araldite. Thin sections were stained with uranyl acetate and Reynolds lead citrate before viewing with the Philips EM 200.

ESEM - A multipurpose surface Electron Microscope

1986 ◽  
Vol 44 ◽  
pp. 632-633 ◽  
Author(s):  
G.D. Danilatos
Keyword(s):  
Electron Microscope ◽  
Room Temperature ◽  
Environmental Scanning ◽  
Gas Composition ◽  
Saturated Water Vapor ◽  
Surface Electron ◽  
Current State ◽  
Saturated Water ◽  
New Type ◽  
Temperature And Pressure

Over recent years a new type of electron microscope - the environmental scanning electron microscope (ESEM) - has been developed for the examination of specimen surfaces in the presence of gases. A detailed series of reports on the system has appeared elsewhere. A review summary of the current state and potential of the system is presented here.The gas composition, temperature and pressure can be varied in the specimen chamber of the ESEM. With air, the pressure can be up to one atmosphere (about 1000 mbar). Environments with fully saturated water vapor only at room temperature (20-30 mbar) can be easily maintained whilst liquid water or other solutions, together with uncoated specimens, can be imaged routinely during various applications.

In-Situ Observation of Clay Minerals Hydrated and Intercalated With Liquid Chemicals Using Film-Sealed Environmental Cell

1980 ◽  
Vol 38 ◽  
pp. 208-209 ◽  
Author(s):  
K. Fukushima ◽  
N. Kohyama ◽  
A. Fukami
Keyword(s):  
Carbon Film ◽  
Resolving Power ◽  
In Situ Observation ◽  
Interlayer Water ◽  
Saturated Water ◽  
Structure Changes ◽  
Environmental Cell ◽  
Gas Layer ◽  
20 Nm

A film-sealed high resolution environmental cell(E.C) for observing hydrated materials had been developed by us(l). Main specification of the E.C. is as follows: 1) Accelerated voltage; 100 kV. 2) Gas in the E.C.; saturated water vapour with carrier gas of 50 Torr. 3) Thickness of gas layer; 50 μm. 4) Sealing film; evaporated carbon film(20 nm thick) with plastic microgrid. 5) Resolving power; 1 nm. 6) Transmittance of electron beam; 60% at 100 kV. The E.C. had been successfully applied to the study of hydrated halloysite(2) (3). Kaolin minerals have no interlayer water and are basically non-expandable but form intercalation compounds with some specific chemicals such as hydrazine, formamide and etc. Because of these compounds being mostly changed in vacuum, we tried to reveal the structure changes between in wet air and in vacuum of kaolin minerals intercalated with hydrazine and of hydrated state of montmori1lonite using the E.C. developed by us.

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