Dynamics of inner bubble during water droplet evaporation on conical micro-pillars surfaces

2022 ◽  
Vol 131 ◽  
pp. 105841
Author(s):  
Linsong Gao ◽  
Jizu Lyu ◽  
Zhifu Zhou ◽  
Yang Li ◽  
Dongdong Gao ◽  
...  
Keyword(s):  
Water Droplet ◽  
Droplet Evaporation ◽  
Micro Pillars

scholarly journals Study of water droplet evaporation in a mini-channel with gas flow

2016 ◽  
Vol 92 ◽  
pp. 01002
Author(s):  
Evgeniy Orlik ◽  
Ekaterina Isachenko
Keyword(s):  
Water Droplet ◽  
Gas Flow ◽  
Droplet Evaporation

Assessment of Water Droplet Evaporation Mechanisms on Hydrophobic and Superhydrophobic Substrates

Langmuir ◽  
2013 ◽  
Vol 29 (51) ◽  
pp. 15831-15841 ◽  
Author(s):  
Zhenhai Pan ◽  
Susmita Dash ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Water Droplet ◽  
Droplet Evaporation

Enhanced Evaporation of Microscale Droplets With an Infrared Laser

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Luis A. Ferraz-Albani ◽  
Alberto Baldelli ◽  
Chrissy J. Knapp ◽  
Wolfgang Jäger ◽  
Reinhard Vehring ◽  
...  
Keyword(s):  
Water Droplet ◽  
Droplet Evaporation ◽  
Radiant Flux ◽  
Droplet Temperature ◽  
Ambient Conditions ◽  
Drying Time ◽  
Proposed Model ◽  
Environment Temperature ◽  
Order Of Magnitude ◽  
Surface Area Change

Enhancement of water droplet evaporation by added infrared radiation was modeled and studied experimentally in a vertical laminar flow channel. Experiments were conducted on droplets with nominal initial diameters of 50 μm in air with relative humidities ranging from 0% to 90% RH. A 2800 nm laser was used with radiant flux densities as high as 4 × 105 W/m2. Droplet size as a function of time was measured by a shadowgraph technique. The model assumed quasi-steady behavior, a low Biot number liquid phase, and constant gas–vapor phase material properties, while the experimental results were required for model validation and calibration. For radiant flux densities less than 104 W/m2, droplet evaporation rates remained essentially constant over their full evaporation, but at rates up to 10% higher than for the no radiation case. At higher radiant flux density, the surface-area change with time became progressively more nonlinear, indicating that the radiation had diminished effects on evaporation as the size of the droplets decreased. The drying time for a 50 μm water droplet was an order of magnitude faster when comparing the 106 W/m2 case to the no radiation case. The model was used to estimate the droplet temperature. Between 104 and 5 × 105 W/m2, the droplet temperature changed from being below to above the environment temperature. Thus, the direction of conduction between the droplet and the environment also changed. The proposed model was able to predict the changing evaporation rates for droplets exposed to radiation for ambient conditions varying from dry air to 90% relative humidity.

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.

scholarly journals Investigation of Regularities of Heat and Mass Transfer and Phase Transitions during Water Droplets Motion through High-Temperature Gases

2014 ◽  
Vol 6 ◽  
pp. 865856 ◽  
Author(s):  
Roman S. Volkov ◽  
Olga V. Vysokomornaya ◽  
Genii V. Kuznetsov ◽  
Pavel A. Strizhak
Keyword(s):  
Mass Transfer ◽  
Phase Transitions ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Water Droplet ◽  
Small Neighborhood ◽  
Droplet Evaporation ◽  
Optical Methods ◽  
Water Droplets ◽  
Two Phase

The macroscopic regularities of heat and mass transfer and phase transitions during water droplets motion through high-temperature (more than 1000 K) gases have been investigated numerically and experimentally. Water droplet evaporation rates have been established. Gas and water vapors concentrations and also temperature values of gas-vapor mixture in small neighborhood and water droplet trace have been singled out. Possible mechanisms of droplet coagulation in high-temperature gas area have been determined. Experiments have been carried out with the optical methods of two-phase gas-vapor-droplet mixtures diagnostics (“Particle Image Velocimetry” and “Interferometric Particle Imaging”) usage to assess the adequateness of developed heat and mass transfer models and the results of numerical investigations. The good agreement of numerical and experimental investigation results due to integral characteristics of water droplet evaporation has been received.

Numerical Study of Water Droplet Heat Removal and Dynamics During its Impact Onto the Micro-Pillar Array at Elevated Temperature

2018 ◽  
Author(s):  
Beni Mehrdad Shahmohammadi ◽  
Shangzhen Xie ◽  
Jiyun Zhao
Keyword(s):  
Heat Transfer ◽  
Level Set Method ◽  
Level Set ◽  
Solid Surface ◽  
Water Droplet ◽  
Heat Removal ◽  
Spray Cooling ◽  
Optimal Size ◽  
Droplet Dynamics ◽  
Micro Pillars

The spray cooling and heat removal efficiency is one of the important aspect of nuclear thermalhydraulics and safety, especially for passive containment cooling after severe accidents. In order to design and optimize these systems effectively, computer modelling of the underlying mechanism of the liquid drop interaction with the hot solid surface would be necessary. Therefore, completeness, accuracy and reliability of the models that are being used in such sensitive areas are vital to the society and environment. Furthermore, the current powerful computer resources need to be fully exploited, so that the precision and the accuracy of the obtained computational results would be further enhanced. Nowadays, Volume-Of-Fluid (VOF) method is widely used in simulating the droplet dynamics, however these models provide estimations that are different in certain extents compare to the experimental results. In present work, we have used the level-set method to study the droplet dynamics and heat removal when the water droplet impact on the surface with different morphologies. The developed model which is based on the finite element method (FEM) has been benchmarked with previously performed experiments regarding the droplet bouncing on a flat hydrophobic surface; these estimations were in a good agreement with the previously published results. Moreover, hot solid surfaces with presence of micro-pillar has been considered to perform sensitivity study for different sizes of the micro-pillars and water droplets. In addition, it has been found that the heat transfer and droplet dynamic behavior would significantly vary in scenarios when the micro-pillars are presents in compare to a flat solid surface; it is observed that a better droplet spreading can be obtained with optimal size of micro-pillars that are present underneath of the droplet axial trajectory. The present study and the model would add valuable information to the field of heat transfer in aspect of spray cooling by investigating the feasibility of using the level-set method for a better estimation of fluid and heat transfer related results.

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