scholarly journals Effect of the Hybrid Hydrophobic-Hydrophilic Nanostructured Surface on Explosive Boiling

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 212
Author(s):  
Ming-Jun Liao ◽  
Li-Qiang Duan
Keyword(s):  
Liquid Film ◽  
Coating Thickness ◽  
Bubble Nucleation ◽  
Onset Temperature ◽  
Dynamics Simulation ◽  
Hydrophilic Surface ◽  
Pillar Width ◽  
Nanostructured Surface ◽  
Explosive Boiling ◽  
Hydrophobic Coating

The influence of different wettability on explosive boiling exhibits a significant distinction, where the hydrophobic surface is beneficial for bubble nucleation and the hydrophilic surface enhances the critical heat flux. Therefore, to receive a more suitable surface for the explosive boiling, in this paper a hybrid hydrophobic–hydrophilic nanostructured surface was built by the method of molecular dynamics simulation. The onset temperatures of explosive boiling with various coating thickness, pillar width, and film thicknesses were investigated. The simulation results show that the hybrid nanostructure can decrease the onset temperature compared to the pure hydrophilic surface. It is attributed to the effect of hydrophobic coating, which promotes the formation of bubbles and causes a quicker liquid film break. Furthermore, with the increase of the hydrophobic coating thickness, the onset temperature of explosive boiling decreases. This is because the process of heat transfer between the liquid film and the hybrid nanostructured surface is inevitably enhanced. In addition, the onset temperature of explosive boiling on the hybrid wetting surface decreases with the increase of pillar width and liquid film thickness.

Explosive Boiling of Water on a Hot Copper Plate: A Molecular Dynamics Simulation Study

2020 ◽  
Vol 35 ◽  
pp. 18-28
Author(s):  
Muhammad Rubayat Bin Shahadat ◽  
A.K.M.M. Morshed
Keyword(s):  
Molecular Dynamics ◽  
Water Vapor ◽  
Liquid Water ◽  
Hydrophobic Surface ◽  
Copper Plate ◽  
Dynamics Simulation ◽  
Hydrophilic Surface ◽  
Explosive Boiling ◽  
Different Temperatures ◽  
Simulation Results

Non-equilibrium molecular dynamics simulations have been employed to study the explosive boiling phenomena of water over a hot copper plate. The molecular system was comprised of three sections: solid copper wall, liquid water, and water vapor. A few layers of the liquid water were placed on the solid Cu surface. The rest of the simulation box was filled with water vapor. Initially, the water molecules were equilibrated by using Berendsen thermostat at 298 K. Then heat was given to the copper plate at different temperatures so that explosive boiling occurs. After achieving the equilibrium by performing the previous two steps, the liquid water at 298 K is suddenly dropped on the hot plate. NVE ensemble was used in the simulation and the temperature of the copper plate was controlled to different temperatures with phantom atom thermostat. Four temperatures (400K, 500K, 650 K and 1000K) were taken to study the explosive boiling. The simulation results show that, the explosive boiling temperature of water on Cu plate is 500 K temperature. At this point, the energy flux was found 1.79x108 J/m3 which is very promising with the experimental results. Moreover, if the temperature of the surface was increased the explosive boiling occurred at a faster rate. The simulation results also show that explosive boiling occurs earlier for the hydrophilic surface than hydrophobic surface as for the hydrophilic surface the water attracted the Cu plate more than the hydrophobic surface and so the amount of energy transfer is more for the hydrophilic surface.

Molecular Dynamics Simulation of Explosive Boiling on Concave Nanostructured Surface

2018 ◽  
Author(s):  
Pengfei Ji ◽  
Mengzhe He ◽  
Yiming Rong ◽  
Yuwen Zhang ◽  
Yong Tang
Keyword(s):  
Surface Area ◽  
Flat Surface ◽  
Liquid Argon ◽  
Copper Surface ◽  
Heat Transfer Process ◽  
Dynamics Simulation ◽  
Nanostructured Surface ◽  
Explosive Boiling ◽  
Nanostructured Surfaces ◽  
Set Up

Explosive boiling occurs when a liquid film contacts with the wall at extremely high temperature, which is detrimental to continuous heat transfer process. In this paper, five kinds of nanostructured surfaces with equal distance between neighboring nano-concaves and flat surface are set up to study the explosive boiling of liquid argon on copper surface. For all the five cases with concave nanostructured surface, the ratio of concave nanostructured surface area to flat surface area is kept as a constant. The temporal and spatial distributions of temperature, atomic motion and number density are recorded to study the effects of different nanostructured surface designs on explosive boiling. From the perspective of reducing explosive boiling, the most favorable nanostructured surface is determined.

Molecular Dynamics Study on Explosive Boiling of Thin Liquid Argon Film on Nanostructured Surface Under Different Wetting Conditions

2016 ◽  
Vol 138 (1) ◽  
Author(s):  
Sheikh Mohammad Shavik ◽  
Mohammad Nasim Hasan ◽  
A. K. M. Monjur Morshed
Keyword(s):  
Heat Transfer ◽  
Molecular Dynamics ◽  
Liquid Film ◽  
Solid Surface ◽  
Thin Liquid Film ◽  
Liquid Argon ◽  
Spatial And Temporal Variation ◽  
Phase System ◽  
Hydrophilic Surface ◽  
Explosive Boiling

Molecular dynamics (MDs) simulations have been performed to investigate the boiling phenomena of thin liquid film adsorbed on a nanostructured solid surface with particular emphasis on the effect of wetting condition of the solid surface. The molecular system consists of liquid and vapor argon and solid platinum wall. The nanostructures which reside on top of the solid wall have shape of rectangular block. The solid–liquid interfacial wettability, in other words whether the solid surface is hydrophilic or hydrophobic, has been altered for different cases to examine its effect on boiling phenomena. The initial configuration of the simulation domain comprises a three-phase system (solid platinum, liquid argon, and vapor argon), which was equilibrated at 90 K. After equilibrium period, the wall temperature was suddenly increased from 90 K to 250 K which is far above the critical point of argon and this initiates rapid or explosive boiling. The spatial and temporal variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat flux normal to the solid surface was also calculated to illustrate the effectiveness of heat transfer for different cases of wetting conditions of solid surface. The results show that the wetting condition of surface has significant effect on explosive boiling of the thin liquid film. The surface with higher wettability (hydrophilic) provides more favorable conditions for boiling than the low-wetting surface (hydrophobic), and therefore, the liquid argon responds quickly and shifts from liquid to vapor phase faster in the case of hydrophilic surface. The heat transfer rate is also much higher in the case of hydrophilic surface.

Molecular Dynamics Simulation for Bubble Nucleation of Water and Liquid Nitrogen in Explosive Boiling

2008 ◽  
Author(s):  
Yu Zou ◽  
Xiulan Huai ◽  
Shiqiang Liang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Potential Energy ◽  
Liquid Nitrogen ◽  
Equilibrium Temperature ◽  
Bubble Nucleation ◽  
Dynamics Simulation ◽  
Molecular Cluster ◽  
Hydrogen Atoms ◽  
Explosive Boiling

Molecular dynamics simulation is carried out for the bubble nucleation of water and liquid nitrogen in explosive boiling. The heat is transferred into the simulation system by rescaling the velocity of the molecules. When heat is added into the molecular cluster, liquid initial equilibrium temperature and molecular cluster size can affect the energy conversion in the process of bubble nucleation. The potential energy of the system violently varies at the beginning of the bubble nucleation, and then varies around a fixed value. At the end of the bubble nucleation, the potential energy of the system slowly increases. In the process of bubble nucleation of explosive boiling, the lower initial equilibrium temperature leads to the bigger size of the molecular cluster. With more heat added into the system of the simulation cell, the potential energy varies in a larger range. The primary potential of water molecules includes Lennard-Jones potential energy and Columbic force caused by static charges of oxygen and hydrogen atoms. This is the reason why the bubble nucleation of water is different from that of liquid nitrogen. Pressure controlling is applied in the simulation of water, which makes the bubble more fully extended than that of liquid nitrogen.

Molecular Simulation on Explosive Boiling of Water on a Hot Copper Plate

2013 ◽  
Author(s):  
Yijin Mao ◽  
Yuwen Zhang
Keyword(s):  
Liquid Film ◽  
Liquid Water ◽  
Water Film ◽  
Copper Plate ◽  
Dynamics Simulation ◽  
Bulk Liquid ◽  
Water Molecules ◽  
Confined Space ◽  
Explosive Boiling ◽  
Short Period

In this paper, molecular dynamics simulation is carried out to study the explosive boiling of liquid water film heated by a hot copper plate in a confined space. A more physically-sound thermostat is applied to control the temperature of the metal plate and then to heat water molecules that are placed in the elastic wall confined simulation domain. The results show that liquid water molecules close to the plate are instantly overheated and undergo an explosive phase transition. A huge pressure in the region between liquid film and hot copper plate formed at the beginning and leads to a low density vapor region by partially vaporizing water film. A non-vaporization molecular layer, with a constant density of 0.2 g/cm3, tightly attached to the surface of the plate is observed. The z-component of COM (center of mass) trajectory of the liquid film in the confined space is tracked and analyzed. The one-dimensional density profile indicates the water film have a piston-like motion after short period of explosive boiling. Temperatures at three corresponding regions, which are vapor, liquid, and vapor from the top plate surface, are also computed and analyzed along with the piston-like motion of the bulk liquid film.

A Molecular Dynamics Simulation of Bubble Nucleation on Solid Surface in Explosive Boiling

2009 ◽  
Author(s):  
Yu Zou ◽  
Xiulan Huai
Keyword(s):  
Molecular Dynamics ◽  
Solid Surface ◽  
Liquid Water ◽  
Water System ◽  
Bubble Nucleation ◽  
Dynamics Simulation ◽  
Explosive Boiling ◽  
Surface Molecules ◽  
Underwater Blast ◽  
Ghost Atom

A bubble nucleation on solid surface in explosive boiling is simulated by molecular dynamics method. Liquid water on a solid surface is heated until a bubble is nucleated. Liquid water is represented by 10368 simple point charge molecules, and the solid surface is represented by three layers of harmonic molecules which are arranged in an fcc style. The increasing rate of temperature is realized by the temperature control technology of the solid surface molecules. Temperature and pressure of water system is calculated in the process of bubble nucleation. A “ghost atom” is used to estimate the volume of the bubble void, and the diameters of the cavitation are calculated. The bubble growth rate is determined by statistics on the bubble diameters. It indicates that expanding and shrinking alternate all the time, which has a same trend as in an underwater blast. The nucleation rate of the simulation is estimated at 30 orders of magnitude by calculating the nucleation time and the volume of the bubble void. Radial distribution function in the process of nucleation indicates a measure of the structure of the water system in the process of bubble nucleation.

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