Natural Convection in Evaporating Minute Drops

1982 ◽  
Vol 104 (4) ◽  
pp. 656-662 ◽  
Author(s):  
Nengli Zhang ◽  
Wen-Jei Yang
Keyword(s):  
Room Temperature ◽  
Evaporation Rate ◽  
Flow Structures ◽  
Interfacial Flow ◽  
Flat Plates ◽  
Liquid Drops ◽  
Ripple Formation ◽  
Air Interface ◽  
Flow Map ◽  
Interface Type

Interfacial flow structures in small liquid drops evaporating on flat plates are cinematographically investigated using the methods of direct photography and laser shadowgraphy. Various liquids of relatively low boiling point were evaporated on glass and copper plates at room temperature. The laser shadowgraph records the flow patterns simultaneously at both the liquid-air interface and the liquid-solid interface, from which the evaporation rate is determined. It reveals the existence of three distinct flow structures at the liquid air interface: stable, substable, and unstable. An interfacial flow map is constructed. The direct photography is employed to study the morphology during the entire process of the unstable-interface type evaporation. The mechanism of ripple formation which enhances the evaporation rate is found to be caused by hydrophilicity of the liquid.

scholarly journals Experience in registration of evaporation of liquid drops on a substrate by the capacitive method

2021 ◽  
Vol 2119 (1) ◽  
pp. 012077
Author(s):  
A V Kokorin ◽  
A D Nazarov ◽  
A F Serov
Keyword(s):  
Evaporation Rate ◽  
Particle Concentration ◽  
Sio2 Nanoparticles ◽  
Integrated Approach ◽  
Optical Recording ◽  
Time Interval ◽  
Evaporation Time ◽  
Liquid Drops ◽  
Complete Evaporation ◽  
Evaporation Of Droplets

Abstract This paper presents the results of an experimental study of the dynamics of evaporation of nanofluid droplets based on distilled water with a mass concentration of SiO2 nanoparticles of 0.1%, 0.5%, and 7% lying on a metal surface. The drop height was changed over time using original equipment, which is based on an integrated approach to the combined use of capacitive and optical recording methods. The experimental results show that the change in the height of nanofluid droplets with concentrations of 0.1%, 0.5%, and 7% is linear over the main part of the evaporation time interval. A deviation from the linear law is observed at the final stage, at the time interval of complete evaporation. The time for complete evaporation of droplets of nanofluids with a concentration of 0.1% increases by 20%, for droplets with a concentration of 0.5%, it increased by 28% in comparison with the evaporation of droplets of the base liquid. The particle concentration of 7% does not lead to an increase in the evaporation time of droplets in comparison with the evaporation of low concentration droplets. Before the formation of a jelly-like residue of nanoparticles, the evaporation rate of droplets with a particle concentration of 7% is comparable to the evaporation rate of droplets with a concentration of 0.1%.

Strip Cladding of Propeller Shafts with Nickel Alloy 625 by Electroslag Surfacing

1993 ◽  
Vol 9 (03) ◽  
pp. 173-180
Author(s):  
J. H. Devletian ◽  
Y. P. Gao ◽  
Q. H. Zhao ◽  
W. E. Wood
Keyword(s):  
Nickel Alloy ◽  
Room Temperature ◽  
Cost Effective ◽  
Flat Plates ◽  
Alloy 625 ◽  
Silicon Carbon ◽  
Class 1 ◽  
Comprehensive Comparison ◽  
Bend Tests ◽  
Submerged Arc

A comprehensive comparison between electroslag surfacing (ESS) and submerged arc surfacing (SAS) using 30-mm-wide (1.2 in.) χ 0.5-mm-thick (0.020 in.) nickel alloy 625 strip was conducted in both the as-deposited and stress relieved (at 650°C [1200°F]) conditions. In most cases, exactly duplicate cladding conditions were used to best compare ESS with SAS. Nickel alloy 625 strip was deposited on 10-cm-thick (4 in.) flat plates and 64-cm-diameter (25 in.) shafting (both MIL-S-23284 Class 1 steel) using optimized ESS and SAS processes. Tension and face and side bend tests were performed on as-welded and stress-relieved cladding at room temperature. Microstructural analyses of the clad specimens were performed using optical and electron microscopy. Cladding parameters were found to affect the dilution, deposition rate, and penetration. Although ESS and SAS cladding possessed similar strength levels, the cladding deposited by ESS was shown to have greater ductility than that by SAS. Also, the resistance to solidification cracking of cladding by ESS was superior to SAS because of the reduced silicon, carbon, oxygen, and impurity levels which promote interdendritic Laves phase, niobium-rich MC carbides and inclusions. Compared with SAS, the ESS method proved to be not only more metallurgically favorable but also cost-effective.

scholarly journals Influence of Magnetic Field on Evaporation Rate and Surface Tension of Water

2018 ◽  
Vol 2 (4) ◽  
pp. 68 ◽  
Author(s):  
Emil Chibowski ◽  
Aleksandra Szcześ ◽  
Lucyna Hołysz
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Water Evaporation ◽  
Water Molecules ◽  
Surface Tension Data ◽  
Ring Magnet ◽  
The Magnetic Field

Using neodymium ring magnets (0.5–0.65 T), the experiments on the magnetic field (MF) effects on water evaporation rate and surface tension were performed at room temperature (22–24 °C). In accordance with the literature data, the enhanced evaporation rates were observed in the experiments conducted in a period of several days or weeks. However, the evaporated amounts of water (up to 440 mg over 150 min) in particular experiments differed. The evaporated amounts depended partially on which pole of the ring magnet was directed up. The relatively strong MF (0.65 T) caused a slight decrease in surface tension (−2.11 mN/m) which lasted longer than 60 min and the memory effect vanished slowly. The surface tension data reduced by the MF action are reported in the literature, although contrary results can be also found. The observed effects can be explained based on literature data of molecular simulations and the suggestion that MF affects the hydrogen bonds of intra- and inter-clusters of water molecules, possibly even causing breakage some of them. The Lorentz force influence is also considered. These mechanisms are discussed in the paper.

Surface exciton polaritons supported by a J-aggregate-dye/air interface at room temperature

2017 ◽  
Vol 42 (19) ◽  
pp. 3876 ◽  
Author(s):  
Kentaro Takatori ◽  
Takayuki Okamoto ◽  
Koji Ishibashi ◽  
Ruggero Micheletto
Keyword(s):  
Room Temperature ◽  
Air Interface ◽  
Exciton Polaritons

Large Heat Transport Due to Spontaneous Gas Oscillation Induced in a Tube With Steep Temperature Gradients

1983 ◽  
Vol 105 (4) ◽  
pp. 889-894 ◽  
Author(s):  
T. Yazaki ◽  
A. Tominaga ◽  
Y. Narahara
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Helium ◽  
Heat Conductivity ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Large Heat

This paper describes experimental studies of heat transfer due to the oscillations of gas columns that are spontaneously induced in a tube with steep temperature gradients. The tube (∼3 m in length) is closed at both ends and bent into U-shaped form at the midpoint. The temperature distribution along the tube is step-functional and symmetrical with respect to the midpoint. The warm part (closed-end sides) is maintained at room temperature and the cold one is immersed in liquid helium (4.2 K). The heat transported from the warm part to the cold is estimated from the evaporation rate of liquid helium. The heat flux by the oscillations is proportional to the square of the pressure amplitude, and the effective heat conductivity can be several orders of magnitude larger than the molecular heat conductivity of gas. The experimental results are compared with the theory of the second-order heat flux proposed by Rott and are found to be in satisfactory agreement with this.

A Runback Criterion for Water Drops in a Turbulent Accelerated Boundary Layer

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Edward B. White ◽  
Jason A. Schmucker
Keyword(s):  
Leading Edge ◽  
Reynolds Numbers ◽  
Critical Parameters ◽  
Challenging Problem ◽  
Aircraft Icing ◽  
Liquid Drops ◽  
Air Interface ◽  
Displacement Thickness ◽  
Water Drops ◽  
Accelerated Flow

Predicting the runback threshold for liquid drops in aerodynamic boundary layers is a challenging problem with numerous applications including aircraft icing simulations. The critical parameters that govern drop runback are investigated in this experiment by using a wind tunnel that provides a turbulent accelerated flow similar to flows near an unswept wing’s leading edge. The experiments feature water drops on aluminum with a contact angle of 70±5deg. Results show that significant water∕air interface unsteadiness precedes drop runback. This is likely due to air-flow separation in the drop wakes. For displacement-thickness-scaled Reynolds numbers ranging from 348 to 429, a constant-Weber-number runback threshold We=3.45±0.09 is found to adequately correlate the runback results.

The preparation and some properties of transparent conducting ZnO for use in solar cells

1982 ◽  
Vol 60 (10) ◽  
pp. 1387-1390 ◽  
Author(s):  
J. H. Morgan ◽  
D. E. Brodie
Keyword(s):  
Solar Cells ◽  
Glow Discharge ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Dc Glow Discharge ◽  
Electron Carrier ◽  
Glass Substrates ◽  
Transparent Conducting Films ◽  
Transparent Conducting ◽  
Evaporation Technique

The fabrication of transparent conducting films of ZnO is described. These films are deposited on room temperature glass substrates using an enhanced reactive evaporation technique in which the power in a dc glow discharge, the oxygen pressure, and the zinc evaporation rate are controlled separately. Each of these parameters is adjusted to optimize the required film property.Films with ρ = 0.0014 Ω cm and an absorption of ~ 1% at 550 nm and 40 Ω/ have been prepared with no annealing. The electron carrier densities are ~ 1.3 × 1020 cm−3 and the mobilities are ~ 34 cm2/(Vs) with a variation of less than ~ 15% between −120 and +150 °C.

scholarly journals Reynolds number influence on the formation of vortical structures on a pitching flat plate

2017 ◽  
Vol 7 (1) ◽  
pp. 20160079 ◽  
Author(s):  
Alexander Widmann ◽  
Cameron Tropea
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Flow Structures ◽  
Flat Plates ◽  
Time Resolved ◽  
Flow Phenomena ◽  
Wall Interaction ◽  
The Impact

The impact of chord-based Reynolds number on the formation of leading-edge vortices (LEVs) on unsteady pitching flat plates is investigated. The influence of secondary flow structures on the shear layer feeding the LEV and the subsequent topological change at the leading edge as the result of viscous processes are demonstrated. Time-resolved velocity fields are measured using particle image velocimetry simultaneously in two fields of view to correlate local and global flow phenomena in order to identify unsteady boundary-layer separation and the subsequent flow structures. Finally, the Reynolds number is identified as a parameter that is responsible for the transition in mechanisms leading to LEV detachment from an aerofoil, as it determines the viscous response of the boundary layer in the vortex–wall interaction.

scholarly journals Evaporation with the formation of chains of liquid bridges

2018 ◽  
Vol 837 ◽  
pp. 703-728 ◽  
Author(s):  
C. Chen ◽  
P. Joseph ◽  
S. Geoffroy ◽  
M. Prat ◽  
P. Duru
Keyword(s):  
Porous Media ◽  
Evaporation Rate ◽  
Phase Distribution ◽  
Pore Space ◽  
Liquid Films ◽  
Bulk Liquid ◽  
Pure Liquid ◽  
Liquid Bridges ◽  
Flat Plates ◽  
Evaporation Kinetics

The objective of the present work is to study the drying of a quasi-two-dimensional model porous medium, hereafter called the micromodel, initially filled with a pure liquid. The micromodel consists of cylinders measuring $50~\unicode[STIX]{x03BC}\text{m}$ in both height and diameter, radially arranged as a set of neighbouring spirals and sandwiched between two horizontal flat plates. As drying proceeds, air invades the pore space and elongated liquid films trapped by capillary forces form along the spirals. These films consist of ‘chains’ of liquid bridges connecting neighbouring cylinders. They provide hydraulic connectivity between the central bulk liquid cluster and the external rim of the cylinder pattern, where evaporation takes place during a first constant-evaporation-rate drying stage. The first goal of the present paper is to describe experimentally the phase distribution during drying, notably the evolution of liquid films, which controls the evaporation kinetics (e.g. the depinning of the films from the external rim signals the end of the constant-evaporation-rate period). Then, a viscocapillary model for the drying process is presented. It is based on numerical simulations of a liquid film capillary shape and viscous flow within a film. The model shows a reasonably good agreement with the experimental data. Thus, the present study is a step towards direct modelling of the effect of films on the drying of more complex porous media (e.g. packing of beads) and should be of interest for multiphase flow applications in porous media, involving transport within liquid films.

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