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296 results on '"Boreyko, Jonathan B."'

12. Unstable Leidenfrost Drops on Roughened Surfaces

Author

Boreyko, Jonathan B. and Chen, Chuan-Hua

Subjects
Physics - Fluid Dynamics
Abstract

Drops placed on a surface with a temperature above the Leidenfrost point float atop an evaporative vapor layer. In this fluid dynamics video, it is shown that for roughened surfaces the Leidenfrost point depends on the drop size, which runs contrary to previous claims of size independence. The thickness of the vapor layer is known to increase with drop radius, suggesting that the surface roughness will not be able to penetrate the vapor layer for drops above a critical size. This size dependence was experimentally verified: at a given roughness and temperature, drops beneath a critical size exhibited transition boiling while drops above the critical size were in the Leidenfrost regime. These Leidenfrost drops were unstable; upon evaporation down to the critical size the vapor film suddenly collapsed., Comment: 2 videos included, one large size and one small, both are MPEG-4

Published
2010

14. Bio‐Inspired Fog Harvesting Meshes: A Review.

Author

Kennedy, Brook S. and Boreyko, Jonathan B.

Subjects
*WATER harvesting, *WATER shortages, *CONDENSATION (Meteorology), *SORBENTS, *FRESH water
Abstract

Freshwater scarcity has become a critical global challenge affecting some of the most vulnerable populations. In response, significant effort has focused on ways to increase access to this precious resource. Within the context of geographical, cultural, political, and technological factors governing freshwater availability, atmospheric water harvesting (AWH) has demonstrated tremendous promise to help address these shortages. Specifically, mesh‐based fog harvesters have received considerable attention for their passive qualities compared with their energy‐dependent technological siblings (sorbents, condensation, etc.), yet their specific water yield (SY) has developed only modestly in recent decades. While the plant and animal kingdom provide diverse examples of passive fog collection, and science has developed a remarkable understanding of these processes, much of this knowledge has yet to be translated practically at scale. This is partially due to challenges in mass‐producing complex (often micro‐scale) structures observed in nature. Fortunately, manufacturing technology is catching up with scientific understanding, especially at the scale of mesh design. To this end, the review begins by surveying bioinspired research in fog harvesting. Afterward, this study identifies milestones in developing bioinspired fog harvesting meshes, concluding in a discussion of future mesh research opportunities connecting bioinspiration and emerging advanced manufacturing techniques. [ABSTRACT FROM AUTHOR]

Published
2024
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18. Coalescence‐Induced Jumping Bubbles during Pool Boiling.

Author

Park, Hyunggon, Ahmadi, S. Farzad, Foulkes, Thomas P., and Boreyko, Jonathan B.

Subjects
EBULLITION, HEAT transfer coefficient, NUCLEATE boiling, HEAT flux, MICROBUBBLES, SURFACE potential
Abstract

Surfaces with micro/nano‐structures significantly enhance the critical heat flux of nucleate boiling by increasing the wickability of the liquid phase to delay film boiling. An alternative strategy, of removing surface bubbles at smaller sizes, is largely ignored. Here, they fabricate a rationally designed micro‐structured surface that enables the coalescence‐induced departure of microscopic vapor bubbles during the pool boiling of water at diameters an order of magnitude smaller than single‐bubble buoyant departure. Arrays of micro‐cavities or micro‐grooves serve as tailored nucleation sites to nucleate close‐packed vapor bubbles, which coalesce at unusually small sizes compared to a homogeneous surface. Two different modes of coalescence‐induced bubble departure are observed and modeled: capillary‐inertial jumping for smaller micro‐bubbles and buoyant‐inertial liftoff for larger micro‐bubbles. Capillarity‐enhanced pool boiling on micro‐structured surfaces has the potential to dramatically enhance the heat transfer coefficient and critical heat flux of pool boiling. [ABSTRACT FROM AUTHOR]

Published
2024
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28. Planar Bridging-Droplet Thermal Diode

Author

Boreyko, Jonathan B., Edalatpour, Mojtaba, Murphy, Kevin, Mukherjee, Ranit, Boreyko, Jonathan B., Edalatpour, Mojtaba, Murphy, Kevin, and Mukherjee, Ranit

Abstract

This disclosure provides a thermal diode including a first plate having a first surface defining a wick structure. The thermal diode can include a second plate having a smooth surface facing the wick structure, the smooth surface and the wick structure defining a chamber for accommodating a phase-change liquid. The thermal diode also can include a separator positioned between the first plate and the second plate to separate the wick structure from the smooth surface by a gap that is less than a capillary length of the phase-change liquid.

Published
2021

29. Reducing Frost during Cryoimaging Using a Hygroscopic Ice Frame

Author

Lowery, Adam W., Ambi, Ashwin, Miller, Lisa M., Boreyko, Jonathan B., Lowery, Adam W., Ambi, Ashwin, Miller, Lisa M., and Boreyko, Jonathan B.

Abstract

Cryomicroscopy is commonly hampered by frost accumulation, reducing the visual clarity of the specimen. Pulling a vacuum or purging with nitrogen gas can greatly reduce the sample chamber's humidity, but at cryogenic temperatures, even minute concentrations of water vapor can still result in frost deposition. Here, a hygroscopic ice frame was created around the specimen to suppress frost growth during cryomicroscopy. Specifically, fluorescently tagged rat brain vessels were frozen on a silicon nitride window with an ice frame, and the luminescence of the fluorescent tag was improved by a factor of 6 compared to a similar specimen in only a nitrogen purge environment. These findings suggest that the simple implementation of a hygroscopic ice frame surrounding the specimen can substantially improve the visual clarity for cryomicroscopy, beyond that of a vacuum or nitrogen purge system.

Published
2022

30. Fog Harvester Having a Vertical Wire Array and Uses Thereof

Author

Virginia Tech Intellectual Properties, Inc., Boreyko, Jonathan B., Kennedy, Brook, Shi, Weiwei, Tulkoff, Joshua, Anderson, Mark, Virginia Tech Intellectual Properties, Inc., Boreyko, Jonathan B., Kennedy, Brook, Shi, Weiwei, Tulkoff, Joshua, and Anderson, Mark

Abstract

Described herein are fog harvesters having a vertical wire array and systems thereof. The fog harvesters described herein can be used to harvest liquid from the air, such as from fog. The fog harvesters can, in some aspects, have improved performance in one or more aspects as compared to fog harvesters having a mesh design.

Published
2022

36. Optimizing Fog Harps

Author

Kowalski, Nicholas G., primary, Shi, Weiwei, additional, Kennedy, Brook S., additional, and Boreyko, Jonathan B., additional

Published
2021
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