Effects of Electrostatic Force, Relative Humidity, Heating Surface Temperature, and Size and Shape on Droplet Evaporation Rate

1969 ◽  
Vol 8 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Don Aylor ◽  
W. S. Bradfield
Keyword(s):  
Relative Humidity ◽  
Surface Temperature ◽  
Evaporation Rate ◽  
Electrostatic Force ◽  
Heating Surface ◽  
Droplet Evaporation ◽  
Size And Shape

scholarly journals Peculiarities in Leidenfrost water droplet evaporation

2020 ◽  
Author(s):  
Tadeusz Orzechowski
Keyword(s):  
Surface Temperature ◽  
Orthogonal Projection ◽  
Water Droplet ◽  
Linear Time ◽  
Heating Surface ◽  
Droplet Evaporation ◽  
Measuring System ◽  
Main Element ◽  
Bottom Surface ◽  
Good Representation

Abstract The investigations involved a large water droplet deposited on the heating surface, the temperature of which was higher than the Leidenfrost point. The main element of the experimental setup was the heating cylinder with K-type shielded thermocouple located in its centre just below the surface. The measuring system was located on highly sensitive scales. The analysis of the droplet behaviour in time was conducted based on measured droplet mass changes over time and also photographic data recorded with high resolution digital camera. The energy balance equation is given for the assumption that evaporation from the droplet upper surface is small compared with the amount of heat dissipated from the bottom surface. The formula for the heat transfer coefficient depends on two slope values and an orthogonal projection of the drop onto the heating surface. The slopes are estimated based on the droplet diameter linear time dependence and mass versus the contact zone relationship. The solution provides a good representation of droplet evaporation under Leidenfrost conditions. The investigations, reported in the study, which concern water droplet at atmospheric pressure deposited on a hot surface with the temperature higher than the Leidenfrost point, indicate the following regularities: droplet orthogonal projection onto the heating surface changes linearly with the droplet mass, evaporation of the same amount of mass decreases linearly with an increase in the heating surface temperature, slope of the graph showing mass loss versus the heating surface temperature successively decreases.

Modeling of Sessile Droplet Evaporation on Engineered Surfaces

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Jyoti Prakash ◽  
Basant Singh Sikarwar
Keyword(s):  
Experimental Study ◽  
Relative Humidity ◽  
Evaporation Rate ◽  
Sessile Drop ◽  
Droplet Evaporation ◽  
Contact Angles ◽  
Surface Wettability ◽  
Aluminum Surface ◽  
Complex Nature ◽  
Wide Range

The evaporation of sessile drop has a wide range of application that includes printing, washing, cooling, and coating. Due to the complex nature of drop evaporation process, this phenomenon is reliant on several parameters such as ambiance and physiochemical properties of liquid and surface. In the present study, a mathematical model of water droplet evaporation on an engineered aluminum surface is developed. Experimental study is carried out for the validation of code. The data obtained from the simulation is validated against the data obtained from an experimental study as well as the data available in the literature and good agreement was found among them. Post-validation, the effect of surface wettability and environment conditions on a droplet evaporation rate is estimated. It is inferred from the outcomes that the temperature at the apex of the drop varies linearly with the increasing relative humidity. Droplet volume has a significant impact on the evaporation rate and comparatively higher evaporative flux for a smaller volume of the drop with large contact angles. This unveils the possibility of achieving the required evaporation rate by controlling surface wettability and relative humidity conditions near the drop.

Experimental Study of Brine Droplet Evaporation and Crystallization at Various Temperatures and Humidity Using EDB Method and Pendant Droplet Method

2019 ◽  
Author(s):  
Jie Qu ◽  
Luis Escobar ◽  
Zhonghao Rao ◽  
Ben Xu
Keyword(s):  
Relative Humidity ◽  
High Speed ◽  
Evaporation Rate ◽  
Crystallization Process ◽  
Dynamic Balance ◽  
Pure Water ◽  
Test Chamber ◽  
Droplet Evaporation ◽  
Water Molecules ◽  
Droplet Method

Abstract In this study, both electro-dynamic balance (EDB) method and pendant droplet method were employed to study the evaporation and crystallization process of brine droplet. The EDB setup was used to levitate the charged micrometer sized droplets to study the evaporation process. The pendant droplet method could hang millimeter sized droplet to study the crystallization process. The evaporation of brine droplets with different mass concentrations was visualized by a high speed camera under different temperatures and relative humidity in the test chamber. The results showed that EDB method could get the accurate droplet evaporation results which obeyed the classic D2-law. It was found that the evaporation was increased with the decrease of relative humidity. Due to the attractive force provided by sodium and chloride ion on water molecules, evaporation rate of brine droplet was smaller than pure water, therefore the evaporation rate decreased with the increase of mass concentration by showing a linear relationship. In addition, a salt shell could be formed at the outside of droplet which still contained some amount of salt solution inside. Consequently, the water molecules need to overcome the pressure difference inside and outside the salt shell, and diffuse through the shell for further evaporation. For a higher relative humidity, a more round shell would be formed during the evaporation, and the growth of crystallization along the filament is weaker than that of smaller relative humidity. We hope this study can provide a different perspective to the heat transfer community about the evaporation of brine droplet.

Leidenfrost Evaporation of Liquid Nitrogen Droplets

1994 ◽  
Vol 116 (4) ◽  
pp. 999-1006 ◽  
Author(s):  
S. Chandra ◽  
S. D. Aziz
Keyword(s):  
Surface Temperature ◽  
Liquid Nitrogen ◽  
Glass Surface ◽  
Evaporation Rate ◽  
Ambient Pressure ◽  
Droplet Diameter ◽  
Droplet Evaporation ◽  
Copper Surface ◽  
Droplet Impact ◽  
Bubble Nucleation

The evaporation of a single droplet of liquid nitrogen, levitated during film boiling above a solid, impervious surface, was studied experimentally. The droplet initial diameter (1.9 mm), surface temperature (~20°C), ambient temperature (~20°C), and ambient pressure (~0.1 MPa) were held constant. The principal parameters varied were the surface material (copper or glass), and roughness (0.35 to 50 μm). Measurements were made of the droplet diameter evolution and the surface temperature variation during droplet impact. Predictions from existing models of droplets in Leidenfrost evaporation agree well with measurements of the droplet evaporation rate. The droplet lifetime was found to be slightly longer on the glass surface than it was on the copper surface, corresponding to the greater cooling of the glass surface during droplet impact. The droplet evaporation rate was unchanged by small increases in surface roughness. However, ridges on the surface with a height of the same magnitude as the thickness of the vapor film under the drop caused vapor bubble nucleation in the droplet, and significantly reduced the droplet evaporation time.

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 Experimental study on the evaporating progress of hexane lens on immiscible liquid：Spreading and receding

2021 ◽  
Vol 321 ◽  
pp. 01017
Author(s):  
Aiqiang Chen ◽  
Jinghong Yin ◽  
Huiqin Wang ◽  
Bin Liu ◽  
Rachid Bennacer
Keyword(s):  
Evaporation Rate ◽  
Droplet Evaporation ◽  
Immiscible Liquid ◽  
Deionized Water ◽  
Maximum Diameter ◽  
Evaporation Process ◽  
Droplet Spreading ◽  
Minimum Diameter ◽  
Base Solution ◽  
Evaporation Intensity

The change of evaporation liquid on another immiscible liquid has important guiding significance for many applications. In this experiment, the geometric temperature distribution and evaporation rate of n-hexane droplets were observed and recorded by changing the temperature of deionized water. The results show that with the increase of temperature of deionized water-based solution, the maximum diameter of n-hexane droplet spreading after titration increases gradually, while the minimum diameter of n-hexane droplet disappearing decreases gradually. Meanwhile, the evaporation rate of n-hexane droplet is constant during the whole evaporation process. It should also be mentioned that if the base solution is changed from deionized water to a certain concentration of salt solution, the maximum diameter of n-hexane droplet spreading will be reduced, and the evaporation intensity will be relatively reduced. These experimental results will give us a better understanding of the mechanism and characteristics of droplet evaporation.

scholarly journals Optimization of bioinspired triangular patterns for water condensation and transport

2019 ◽  
Vol 377 (2150) ◽  
pp. 20190127 ◽  
Author(s):  
Dong Song ◽  
Bharat Bhushan
Keyword(s):  
Relative Humidity ◽  
Pressure Gradient ◽  
Surface Temperature ◽  
Dew Point ◽  
Laplace Pressure ◽  
Theme Issue ◽  
Water Condensation ◽  
Water Collection ◽  
Condensed Water ◽  
Droplet Condensation

Water condenses on a surface in ambient environment if the surface temperature is below the dew point. For water collection, droplets should be transported to storage before the condensed water evaporates. In this study, Laplace pressure gradient inspired by conical spines of cactus plants is used to facilitate the transport of water condensed in a triangular pattern to the storage. Droplet condensation, transportation and water collection rate within the bioinspired hydrophilic triangular patterns with various lengths and included angles, surrounded by superhydrophobic regions, were explored. The effect of relative humidity was also explored. This bioinspired technique can be used to develop efficient water collection systems. This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology (part 2)’.

Modelling the Natural Evaporation of the Concentrated Seawater after Desalinized

2015 ◽  
Vol 713-715 ◽  
pp. 2989-2992
Author(s):  
Xue Kui Wang ◽  
Ying Zhou ◽  
Ling Li ◽  
Tian Cheng Gao ◽  
Na Tang
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Artificial Neural Network ◽  
Relative Humidity ◽  
Evaporation Rate ◽  
Evaporation Model ◽  
Irradiation Intensity ◽  
Artificial Neural ◽  
Good Agreement

The influence of natural evaporation factors (the irradiation intensity, speed of the wind, temperature of the brine, temperature and relative humidity of the air) on the desalinated seawater evaporation rate was measured experimentally. A natural evaporation model was built by correlating the experimental data using the artificial neural network. This model was well correlated with the influence of natural evaporation factors, and it showed a good agreement of the results and evaporation theory.

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