Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 25 for “"Leidenfrost"”.
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Leidenfrost Drop Ratchet Impact Dynamics
… the movement of impacting droplets in this Leidenfrost state. We propose a model for the behavior of droplets impacting a micro scale ratchet structure. In particular, we theorize that surface roughness can lead to an inconsistent vapor layer, allowing for propulsion resulting from contact …
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The evaporation of drops from super-heated nano-engineered surfaces
In pool boiling and spray cooling the Leidenfrost point marks the transition from nucleate boiling, in which the evaporating liquid is in contact with the surface, and film boiling, in which a layer of vapor separates the fluid from the surface. For a single evaporating drop, the Leidenfrost point …
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Investigation of a Reproducible Boiling Phenomenon with Relevance to Volcanic Lightning
… the continuation, in this investigation, of the Leidenfrost form of boiling and the discovery of an associated charging process. This discovery resolves a two centuries long dispute as to whether the Leidenfrost phenomenon of boiling produces charge as well as showing its important relevance to …
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Electrostatic control and enhancement of film boiling heat transfer
… layer at the surface, commonly known as the Leidenfrost effect. Heat transfer is limited to a critical heat flux (CHF); higher heat fluxes lead to surface dryout and temperature excursions. An externally applied electric field in the vapor layer can significantly enhance boiling heat transfer …
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Flow characteristics and phase interactions of evaporating sprays in gas-solid suspensions
… the preheated temperature of solids beyond the Leidenfrost temperature, the heat transfer into spray droplets and resulted vaporization can be greatly restricted by the film boiling characteristics that are in turn coupled with collision dynamics. So far few studies on these complex yet …
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Tailoring hydrodynamics of non-wetting droplets with nano-engineered surfaces
… Another class of non-wetting droplet, the Leidenfrost drop, is studied with textured super-wetting surfaces. The liquid drop loses its contact to the solid by its own vapor, created by a large superheat from the solid. The Leidenfrost effect is undesirable in cooling applications as the …
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Passive and active approaches to sustained turbulent hydrodynamic drag reduction using superhydrophobic surfaces
… approach, a submerged body is heated past its Leidenfrost temperature to form a thick, continuous film of steam between itself and the water. I continue to employ superhydrophobic surfaces, but now exploit their unique heat transfer properties (i.e. the insulation to heat transfer provided by …
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Three-Phase and Unidirectional Heat Transfer
… a critical temperature referred to as the ``Leidenfrost temperature'', the highly effective nucleate boiling is completely replaced by insulating film boiling, causing a dramatic decrease in the essential cooling rate of water pool boiling and spray quenching. In chapter 2, after noting the …
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Heat transfer from molten materials to liquids
… were observed at nucleate boiling crisis and the Leidenfrost point respectively. Results indicate that heat transfer from molten metals to sub-cooled water is a function of temperature and coolant depth and not a direct function of the physical properties of the metals. Heat transfer in the …
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Droplet levitation and underwater plastron restoration using aerophilic surface textures
… pinning of water droplets on surfaces is the Leidenfrost effect, wherein the droplets are levitated on a cushion of vapor over the surface. But this typically requires the substrate to withstand high temperatures and also results in the loss of the droplet volume due to thermal evaporation. In …
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Development of an experimental technique to investigate droplet cooling phenomena on accident tolerant fuel materials
… with micro- and nanostructures may affect the Leidenfrost point temperature of water and thus the efficiency of droplet cooling by altering the wettability of the surfaces. In this project, smooth and rough chromium surfaces were subjected to droplet cooling at temperatures ranging from 100 to …
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Intricate Dynamics of Droplet-Substrate Interactions Beyond Conventional Limitations
… behaviors similar to the high-temperature Leidenfrost effect. Unlike the traditional Leidenfrost effect, which occurs above 230 °C, fin-array-like micropillars enable water microdroplets to levitate and jump off the surface within milliseconds at just 130 °C, triggered by the …
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Droplet-based Two-phase Thermal Management
… on a heated post in the nucleate boiling and Leidenfrost regimes to investigate the influence of the surface structure on the heat transfer and hydrodynamics. We find that the post substrate leads to a shorter droplet lifetime and a 20℃ higher dynamic Leidenfrost temperature compared to a flat …
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Evaporating crossflow sprays in gas-solid flows
… particles. Part of this study is focused on the Leidenfrost collisions between evaporating droplets and solid particles, which are involved in many multiphase flow applications, e.g., petroleum refinery, surface coating, and fire quenching. In this study, an analytical model has been developed to …
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Development of High-Performance Optofluidic Sensors on Micro/Nanostructured Surfaces
… on micro/nano-structured surfaces and the Leidenfrost effect, this doctoral research focuses on developing high-performance optofluidic sensing systems, including optical beam adaptive steering, whispering gallery mode (WGM) optical sensing, and surface-enhanced Raman spectroscopy (SERS) …
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Hydrophobic coatings for film boiling based drag reduction on a torpedo model
… long as the surface temperature stays above the Leidenfrost point. This vapor layer has poor heat transfer characteristics but has the potential to reduce drag by acting as a buffer between the solid surface and the liquid. The goals of this research were to quantify the drag reduction due to …
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Tartaglia, Zigzag et Flips : les particules denses à haut Reynolds
… a fluid particle with the particular case of a Leidenfrost liquid ring. A such object is created by approaching an annular magnet from a paramagnetic liquid oxygen drop. The closing dynamics of this non wetting ring is described with by the way of a potential flow approach.
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Heat transfer during spray water cooling using steady experiments
… during the spray heating-cooling cycle. The Leidenfrost temperature is found to be around at 850oC.
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Effects of surface parameters on boiling heat transfer phenomena
… to enhance critical heat flux (CHF) and Leidenfrost point (LFP) have been shown successful in previous studies. However, the enhancement mechanisms are not well understood, partly due to many surface parameters being altered at the same time, as in the case for nanofluids. Therefore, the …
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Nanolaminated Plasmonics: from Passive to Active Nanophotonics Devices
… and measure the analyte in water droplets. Leidenfrost evaporation-assisted SERS sensing on the hierarchical substrates provides the way for ultrafast and ultrasensitive biochemical detections without a need for additional surface modifications and chemical treatments.
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