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%.

WATER DROPLET EVAPORATION IN A CHAMBER ISOLATED FROM THE EXTERNAL ENVIRONMENT

2020 ◽  
Vol 6 (3) ◽  
pp. 8-22
Author(s):  
KSENIA A. Batishcheva ◽  
ATLANT E. Nurpeiis
Keyword(s):  
Water Vapor ◽  
Evaporation Rate ◽  
External Environment ◽  
Heat Removal ◽  
Droplet Evaporation ◽  
Droplet Volume ◽  
Evaporation Time ◽  
Aluminum Alloy Amg6 ◽  
Evaporation Of Droplets ◽  
Contact Diameter

With an increase in the productivity of power equipment and the miniaturization of its components, the use of traditional thermal management systems becomes insufficient. There is a need to develop drip heat removal systems, based on phase transition effects. Cooling with small volumes of liquids is a promising technology for microfluidic devices or evaporation chambers, which are self-regulating systems isolated from the external environment. However, the heat removal during evaporation of droplets into a limited volume is a difficult task due to the temperature difference in the cooling device and the concentration of water vapor that is unsteady in time depending on the mass of the evaporated liquid. This paper presents the results of an experimental study of the distilled water microdrops’ (5-25 μl) evaporation on an aluminum alloy AMg6 with the temperatures of 298-353 K in an isolated chamber (70 × 70 × 30 mm3) in the presence of heat supply to its lower part. Based on the analysis of shadow images, the changes in the geometric dimensions of evaporating drops were established. They included the increase in the contact diameter, engagement of the contact line due to nano roughening and chemical composition inhomogeneous on the surface (90-95% of the total evaporation time) of the alloy and a decrease in the contact diameter. The surface temperature and droplet volume did not affect the sequence of changes in the geometric dimensions of the droplets. It was found that the droplet volume has a significant effect on the evaporation time at relatively low substrate temperatures. The results of the analysis of droplet evaporation rates and hygrometer readings have shown that reservoirs with salt solutions can be used in isolated chambers to control the concentration of water vapor. The water droplets evaporation time was determined. The analysis of the time dependences of the evaporation rate has revealed that upon the evaporation of droplets in an isolated chamber under the conditions of the present experiment, the air was not saturated with water vapor. The latter did not affect the evaporation rate.

scholarly journals An experimental study of the evaporation rate of nanofluid droplets with SiO2 nanoparticles

2020 ◽  
Vol 1675 ◽  
pp. 012046
Author(s):  
E M Bochkareva ◽  
N B Miskiv ◽  
A D Nazarov ◽  
V V Terekhov ◽  
V I Terekhov
Keyword(s):  
Experimental Study ◽  
Evaporation Rate ◽  
Sio2 Nanoparticles

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 Spatial Evolution of Prosopis Invasion and its Effects on LULC and Livelihoods in Baringo, Kenya

2019 ◽  
Vol 11 (10) ◽  
pp. 1217 ◽  
Author(s):  
Purity Rima Mbaabu ◽  
Wai-Tim Ng ◽  
Urs Schaffner ◽  
Maina Gichaba ◽  
Daniel Olago ◽  
...  
Keyword(s):  
Integrated Approach ◽  
Well Being ◽  
Time Interval ◽  
Wet Season ◽  
Alien Plant ◽  
Random Forest Classification ◽  
Lulc Changes ◽  
Forest Classification ◽  
Landsat Satellite ◽  
Gains And Losses

Woody alien plant species have been deliberately introduced globally in many arid and semi-arid regions, as they can provide services and goods to the rural poor. However, some of these alien trees and shrubs have become invasive over time, with important impacts on biodiversity, ecosystem services, and human well-being. Prosopis was introduced in Baringo County, Kenya, in the 1980s, but since then, it has spread rapidly from the original plantations to new areas. To assess land-use and land-cover (LULC) changes and dynamics in Baringo, we used a combination of dry and wet season Landsat satellite data acquired over a seven-year time interval between 1988–2016, and performed a supervised Random Forest classification. For each time interval, we calculated the extent of Prosopis invasion, rates of spread, gains and losses of specific LULC classes, and the relative importance of Prosopis invasion on LULC changes. The overall accuracy and kappa coefficients of the LULC classifications ranged between 98.1–98.5% and 0.93–0.96, respectively. We found that Prosopis coverage increased from 882 ha in 1988 to 18,792 ha in 2016. The highest negative changes in LULC classes were found for grasslands (−6252 ha; −86%), irrigated cropland (−849 ha; −57%), Vachellia tortilis-dominated vegetation (−3602 ha; −42%), and rainfed cropland (−1432 ha; −37%). Prosopis invasion alone directly accounted for over 30% of these negative changes, suggesting that Prosopis invasion is a key driver of the observed LULC changes in Baringo County. Although the management of Prosopis by utilization has been promoted in Baringo for 10–15 years, the spread of Prosopis has not stopped or slowed down. This suggests that Prosopis management in Baringo and other invaded areas in East Africa needs to be based on a more integrated approach.

scholarly journals Экспериментальное исследование влияния наночастиц на процессы испарения жидкостей

2020 ◽  
Vol 90 (1) ◽  
pp. 33
Author(s):  
А.В. Минаков ◽  
А.С. Лобасов ◽  
М.И. Пряжников ◽  
Л.С. Тарасова ◽  
Н.Я. Василенко ◽  
...  
Keyword(s):  
Evaporation Rate ◽  
Volume Concentration ◽  
Experimental Studies ◽  
Aluminium Oxide ◽  
Average Diameter ◽  
Sio2 Nanoparticles ◽  
Zro2 Nanoparticles ◽  
Al2o3 Nanoparticles ◽  
Distilled Water ◽  
Diamond Nanoparticles

Evaporation of nanofluids based on distilled water and the silicium and zirconium dioxides, aluminium oxide as well as the diamond has been experimentally studied. The average diameter of the SiO2 nanoparticles was 25 nm, of the ZrO2 nanoparticles was 105 nm, of the Al2O3 nanoparticles was 43 nm and of the diamond nanoparticles was 5 nm. The synchronous thermoanalyser STA 449 С Jupiter was used in the investigation of the evaporation processes. The dependences of the evaporation rate on the volume concentration of the nanoparticles were obtained as a result of the experimental studies. It was shown that as the nanoparticles volume concentration increases the nanofluids evaporation rates monotonically increase too.

Recent developments in hydrodynamic stability of two-phase flows

2012 ◽  
Vol 9 (1) ◽  
pp. 125-130
Author(s):  
A.N. Osiptsov ◽  
S.A. Boronin
Keyword(s):  
Boundary Layer ◽  
Particle Concentration ◽  
Volume Fraction ◽  
Time Interval ◽  
Dusty Gas ◽  
Two Phase Flows ◽  
Two Phase ◽  
Layer Width ◽  
Dispersed Flows ◽  
Optimal Disturbances

In the framework of two-continuum model, the stability of plane-parallel dispersed flows is analyzed. Several flow configurations are considered and several new factors are analyzed. The factors include: particle velocity slip and particle concentration non-uniformity in the main flow, non-Stokesian components of the interphase force and finite volume fraction of the dispersed phase. It is found that the new factors modify significantly the parameters of the fastest growing mode and change the critical Reynolds number of two-phase flows. A method for studying algebraic (non-modal) instability and optimal disturbances to dispersed flows is proposed. While studying the non-modal instability of the dusty-gas boundary-layer flow with a non-uniform particle concentration, we found that the disturbances with the maximum energy gain at a limited time interval are streamwise-elongated structures (streaks). As compared to the flow of a particle-free fluid, optimal disturbances to the dusty-gas flow gain much larger kinetic energy even at the boundary layer width-averaged mass concentration of ten percent, which leads to significant amplification of non-modal instability mechanism due to the presence of suspended particles.

scholarly journals Defensive interactions in soccer small-sided games: an integrated approach between the fundamental tactical principles and the social network analysis

2019 ◽  
Vol 20 (5) ◽  
pp. 422-431 ◽  
Author(s):  
Gibson Moreira Praça ◽  
Raphael Brito e Sousa ◽  
Sarah Da Glória Teles Bredt ◽  
Filipe Manuel Clemente ◽  
Israel Teoldo ◽  
...  
Keyword(s):  
Social Network ◽  
Social Network Analysis ◽  
Network Analysis ◽  
Integrated Approach ◽  
Clustering Coefficient ◽  
Time Interval ◽  
Page Rank ◽  
Sports Club ◽  
The Social ◽  
Tactical Knowledge

This study aimed to 1) present a new analysis of the interactions between the tactical principles of defensive coverage and delay using the Social Network Analysis (SNA); 2) compare the defensive cooperation patterns presented by players of different categories during a 3vs.3 soccer small-sided games SSG; 3) compare the level of defensive prominence presented by defenders, midfielders, and forwards in 3vs.3 SSG within and between different categories. Twenty-eight soccer athletes from U-13 (n=14) and U-14 (n=14) categories of a sports club performed 3vs.3 SSG for the analysis of the defensive tactical principles. Defensive interactions were considered successful defensive coverage and a delay actions performed within the same time interval. Macro (density and clustering coefficient) and micro (degree centrality, degree prestige and page rank) analyses were used as SNA measures. Results indicated no significant differences between categories for the macro and micro analyses. Only in the U-14 category, midfielders presented higher prominence levels than the other playing positions (p=0.004). We concluded that U-13 and U-14 athletes are not different regarding defensive cooperation patterns. A higher positional tactical knowledge obtained through deliberate practice is essential to induce different defensive interactions between playing positions, as shown by significant differences only in the U-14 category.

scholarly journals Influence of microphysical schemes on atmospheric water in the Weather Research and Forecasting model

2014 ◽  
Vol 7 (1) ◽  
pp. 147-160 ◽  
Author(s):  
F. Cossu ◽  
K. Hocke
Keyword(s):  
Water Vapour ◽  
Evaporation Rate ◽  
The Other ◽  
Shortwave Radiation ◽  
Weather Research And Forecasting ◽  
Time Interval ◽  
High Mountain ◽  
Atmospheric Water ◽  
Surface Evaporation ◽  
Weather Research

Abstract. This study examines how different microphysical parameterization schemes influence orographically induced precipitation and the distributions of hydrometeors and water vapour for midlatitude summer conditions in the Weather Research and Forecasting (WRF) model. A high-resolution two-dimensional idealized simulation is used to assess the differences between the schemes in which a moist air flow is interacting with a bell-shaped 2 km high mountain. Periodic lateral boundary conditions are chosen to recirculate atmospheric water in the domain. It is found that the 13 selected microphysical schemes conserve the water in the model domain. The gain or loss of water is less than 0.81% over a simulation time interval of 61 days. The differences of the microphysical schemes in terms of the distributions of water vapour, hydrometeors and accumulated precipitation are presented and discussed. The Kessler scheme, the only scheme without ice-phase processes, shows final values of cloud liquid water 14 times greater than the other schemes. The differences among the other schemes are not as extreme, but still they differ up to 79% in water vapour, up to 10 times in hydrometeors and up to 64% in accumulated precipitation at the end of the simulation. The microphysical schemes also differ in the surface evaporation rate. The WRF single-moment 3-class scheme has the highest surface evaporation rate compensated by the highest precipitation rate. The different distributions of hydrometeors and water vapour of the microphysical schemes induce differences up to 49 W m−2 in the downwelling shortwave radiation and up to 33 W m−2 in the downwelling longwave radiation.

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