D125 Examination of Indirect Extinguishment by Water Vapor Produced from Water Droplet Impacting on Heated Wall

Novel hydrophobic/hydrophilic Janus fibrous membranes, the poly[4,4′-methylenebis (phenylisocyanate)-alt-1,4-butanediol/di(propylene glycol)/plycaprolactone] (PU) fibrous membrane as the hydrophobic layer and cellulose acetate (CA) fibrous membrane as the hydrophilic layer, were fabricated by the so-called “layer-by-layer” electrospinning technology. A series of the PU/CA Janus membranes with different electrospinning time of the CA layers by which the thickness of hydrophilic layer can be controlled were also prepared to uncover its influence on the directional water vapor transmission. The results showed that water vapor transmission capability from the hydrophobic side to the hydrophilic side of the PU/CA Janus fibrous membrane was enhanced rather than that from the reverse direction of the same membrane. The optimal water vapor transmission capacity existed when the electrospinning time of CA fibrous membrane reached 15 min. Such enhanced water vapor transmission originated because of the asymmetric wettability of the Janus membrane and the strong force to draw tiny water droplet from the hydrophobic side to the hydrophilic side. The novel understanding is useful for facile designing and fabrication of efficient moisture permeable fabrics and clothing.

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Evaporation of layers of salt solutions

MATEC Web of Conferences ◽

10.1051/matecconf/201819401041 ◽

2018 ◽

Vol 194 ◽

pp. 01041

Author(s):

S. Y. Misyura ◽

V. S. Morozov

Keyword(s):

Heat Flux ◽

Water Vapor ◽

Wall Temperature ◽

Ambient Air ◽

Heated Wall ◽

Equilibrium Partial Pressure ◽

Salt Solutions ◽

Significant Drop ◽

Initial Concentration ◽

Evaporation Stage

Nonisothermal evaporation of layers of water and aqueous salts solutions of H2O/LiBr, H2O/CaCl2 and H2O/LiCl was studied experimentally. The liquid layer was placed on a horizontal heated wall. The initial concentration of salt C0 was 10 %. The wall temperature Tw = 75 °C and ambient air pressure was 1 bar. It was shown that the heat flux q increases for water for the final evaporation stage and falls for salt solutions due to the increase in salt concentration C and due to a significant drop in the equilibrium partial pressure of water vapor.

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Freezing of water droplets colliding with kaolinite particles

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-4295-2009 ◽

2009 ◽

Vol 9 (13) ◽

pp. 4295-4300 ◽

Cited By ~ 28

Author(s):

E. A. Svensson ◽

C. Delval ◽

P. von Hessberg ◽

M. S. Johnson ◽

J. B. C. Pettersson

Keyword(s):

Water Vapor ◽

Relative Humidity ◽

Water Droplet ◽

Supercooled Water ◽

Dust Particles ◽

Freezing Process ◽

Water Droplets ◽

Electrodynamic Balance ◽

Dry Conditions

Abstract. Contact freezing of single supercooled water droplets colliding with kaolinite dust particles has been investigated. The experiments were performed with droplets levitated in an electrodynamic balance at temperatures from 240 to 268 K. Under relatively dry conditions (when no water vapor was added) freezing was observed to occur below 249 K, while a freezing threshold of 267 K was observed when water vapor was added to the air in the chamber. The effect of relative humidity is attributed to an influence on the contact freezing process for the kaolinite-water droplet system, and it is not related to the lifetime of the droplets in the electrodynamic balance. Freezing probabilities per collision were derived assuming that collisions at the lowest temperature employed had a probability of unity. Mechanisms for contact freezing are briefly discussed.

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High-resolution neutron imaging reveals kinetics of water vapor uptake into a sessile water droplet

Matter ◽

10.1016/j.matt.2021.04.013 ◽

2021 ◽

Author(s):

Jae Kwan Im ◽

Leekyo Jeong ◽

Jan Crha ◽

Pavel Trtik ◽

Joonwoo Jeong

Keyword(s):

Water Vapor ◽

High Resolution ◽

Water Droplet ◽

Neutron Imaging ◽

Kinetics Of

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New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010006427x ◽

1971 ◽

Vol 29 ◽

pp. 44-45

Author(s):

R. C. Moretz ◽

G. G. Hausner ◽

D. F. Parsons

Keyword(s):

Electron Microscopy ◽

Water Vapor ◽

Electron Diffraction ◽

Water Vapor Pressure ◽

Biological Materials ◽

Thin Membrane ◽

Reliable System ◽

System A ◽

Water Films ◽

Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

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Hydration Chamber for Jeolco 200 Kv Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069703 ◽

1970 ◽

Vol 28 ◽

pp. 542-543

Author(s):

V. R. Matricardi ◽

G. G. Hausner ◽

D. F. Parsons

Keyword(s):

Electron Microscope ◽

Water Vapor ◽

Vapor Pressure ◽

Pressure Gradient ◽

Room Temperature ◽

List Type ◽

Type Number ◽

Equilibrium Vapor Pressure

In order to observe room temperature hydrated specimens in an electron microscope, the following conditions should be satisfied: The specimen should be surrounded by water vapor as close as possible to the equilibrium vapor pressure corresponding to the temperature of the specimen.The specimen grid should be inserted, focused and photo graphed in the shortest possible time in order to minimize dehydration.The full area of the specimen grid should be visible in order to minimize the number of changes of specimen required.There should be no pressure gradient across the grid so that specimens can be straddled across holes.Leakage of water vapor to the column should be minimized.

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