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.

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.

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.

Nano Sized Bubble Formation, Growth and Collapse in Liquid Water by Central Heating: A Molecular Dynamics Simulation

2019 ◽  
Author(s):  
Muhammad Rubayat Bin Shahadat ◽  
AKM M. Morshed ◽  
Amitav Tikadar ◽  
Titan C. Paul ◽  
Jamil A. Khan
Keyword(s):  
Molecular Dynamics ◽  
Liquid Water ◽  
Structural Parameters ◽  
Bubble Formation ◽  
Dynamics Simulation ◽  
Central Heating ◽  
Simulation Domain ◽  
Short Period ◽  
Different Temperatures ◽  
Non Equilibrium Molecular Dynamics

Abstract Non-equilibrium Molecular Dynamics (NEMD) Simulation has been employed to investigate the nanobubble generation, growth and collapse in liquid water. The center molecules (240 water molecule) of the simulation domain were heated at five different temperatures (400K, 800K, 1500K, 2100K and 2800K) by velocity scaling for a very short period of time and the radius of the nano sized bubble was calculated. At 400K temperature, no nano bubble is formed but as temperature increases, nano bubble forms and the radius of the nano bubble increases. TIP-3P potential model has been used to predict the structural parameters of water molecules. The SHAKE algorithm has been employed to hold the bonds of O-H and H-O-H as rigid. The results obtained from the simulation were then compared with the results got from Rayleigh-Plesset Equation in order to show the discrepancy of MD simulation and the Hydrodynamic model. The simulation results indicate that Rayleigh-Plesset equation is not valid for prediction the formation, growth and collapse of nano bubble in liquid water because of its uncertainty in predicting the surface tension and ignoring the viscosity.

Enhanced Mechanism of Water Evaporation Through Nanoporous Membrane

2021 ◽  
Author(s):  
Runkeng Liu ◽  
Zhenyu Liu
Keyword(s):  
Water Film ◽  
Dynamics Simulation ◽  
Natural Phenomenon ◽  
Water Evaporation ◽  
Water Molecules ◽  
Multilayer Graphene ◽  
Evaporation Process ◽  
Research Attention ◽  
Nanoporous Membrane ◽  
Film Evaporation

Abstract Evaporation through nanoporous membrane has attracted tremendous research attention as a ubiquitous natural phenomenon, which can be used in numerous applications. In this work, we explored the ultrathin water film evaporation process on nanoporous membrane based on non-equilibrium molecular dynamics simulation. A heat localization design of multilayer graphene coated at the bottom of membrane was implemented to reduce the heat loss along the non-evaporation direction. The underlying mechanism of water evaporation through nanoporous membrane was investigated after analysis of the average number of hydrogen bonds per water molecule, the temperature variation and the mean squared displacement of water molecular during the evaporation process. The results showed that the change of pore size will affect the water molecules structure. We also discussed the effect of heat localization design on ultrathin water film evaporation process. The result suggested that water molecules are more active and evaporation efficiency is improved correspondingly. This work reveals the feasibility of the novel nanoporous membrane structure design for enhancing heat and mass transfer, which can be adopted in efficient thermal management and low-cost approaches for water desalination.

scholarly journals Gas Transport in Shale Nanopores with Miscible Zone

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Xiang Li ◽  
Sai Xu ◽  
Youzhi Hao ◽  
Daolun Li ◽  
Detang Lu ◽  
...  
Keyword(s):  
Water Flow ◽  
Flow Model ◽  
Water Film ◽  
Velocity Profiles ◽  
Water Velocity ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Flow Models ◽  
Gas Molecules ◽  
Physical Phenomena

Based on the results of molecular dynamics simulation, in a gas-water miscible zone, the velocity profiles of the flowing water film do not increase monotonously but increase first and then decrease, which is due to the interaction between water and gas molecules. This exhibits a new physical mechanism. In this paper, we firstly propose a gas-water flow model that takes into account the new physical phenomena and describes the distribution of gas-water velocity in the whole pore more accurately. In this model, a decreasing factor for water film in the gas-water miscible zone is used to describe the decrease of water velocity in the gas-water miscible zone, which leads to the gas velocity decrease correspondingly. The new flow model considers the interaction among gas and water molecules in the miscible zone and can provide more accurate velocity profiles compared with the flow models not considering the miscible region. Comparison calculation shows that the previous model overestimates the flow velocity, and the overestimation increases with the decrease of the pore radius. Based on the new gas-water flow model, a new permeability correction factor is deduced to consider the interaction among gas and water molecules.

Hydrodynamic Lubrication in a Nanoscale Bearing

2009 ◽  
Vol 60-61 ◽  
pp. 1-5 ◽  
Author(s):  
Chang Zheng Xiang ◽  
Yu Juan Wang ◽  
Yun Fei Chen
Keyword(s):  
Liquid Water ◽  
Effective Viscosity ◽  
Hydrodynamic Lubrication ◽  
Load Capacity ◽  
Water Film ◽  
Hydrodynamic Pressure ◽  
Shear Velocity ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
High Shear

Nonequilibrium molecular dynamics simulation is used to simulate the hydrodynamics lubrication in the nanoscale bearing. A physical model of the nanascale bearing that the thin liquid water film confined between two solid walls has been set up. The simulation results indicate that the hydrodynamic pressure profiles as the macroscopic state are formed in nanoscale bearings. The hydrodynamic pressure increases with increasing shear velocity, and corresponding load capacity also increases with increasing sliding velocity of the upper driven wall. These results are in accordance with classical Reynolds’ theory about hydrodynamic lubrication. On the other hand, the shear thinning behavior of the liquid water film appears, so that effective viscosity decreases under high shear velocity. Although effective viscosity of water film decreases under high shear velocity, this phenomenon doesn’t affect the hydrodynamic lubrication of the nanoscale bearing.

Sign in / Sign up

Export Citation Format

Share Document