Effects of surface temperature and wettability on explosive boiling of nanoscale water film over copper plate

2020 ◽  
Vol 162 ◽  
pp. 120375 ◽  
Author(s):  
Pu Bai ◽  
Leping Zhou ◽  
Xiaoze Du
Keyword(s):  
Surface Temperature ◽  
Water Film ◽  
Copper Plate ◽  
Explosive Boiling

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.

Attachment of Bacteria to Meat Surfaces: A Review

1981 ◽  
Vol 44 (8) ◽  
pp. 602-607 ◽  
Author(s):  
RUTH FIRSTENBERG-EDEN
Keyword(s):  
Surface Temperature ◽  
Bacterial Strain ◽  
Water Film ◽  
Bacterial Attachment ◽  
Time Dependent ◽  
Second Stage ◽  
Strain Type ◽  
Physical Forces ◽  
Increased Strength ◽  
Number Of Bacteria

The mechanism of attachment of bacteria to meat surfaces involves two consecutive stages. During the primary stage, bacterial attachment is probably due to physical forces, and the number of bacteria becoming attached is proportional to the number in the water film over the surface. The second stage is initially characterized by an increased strength of attachment due to polysaccharide formation, which is a time-dependent process. The dependence of attachment on various factors such as bacterial strain, type of meat surface, temperature, culturing method, etc. is discussed. Some potential consequences of attachment on slaughter hygiene, kitchen hygiene and methodology are described.

Molecular Dynamics Simulation of Ultra-Fast Phase Transition in Water Nanofilms

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Malcolm Porterfield ◽  
Diana-Andra Borca-Tasciuc
Keyword(s):  
Morse Potential ◽  
Water Film ◽  
Contact Angles ◽  
Lennard Jones Potential ◽  
Gold Substrate ◽  
Jones Potential ◽  
Explosive Boiling ◽  
Interaction Sites ◽  
Lennard Jones ◽  
Water Films

Abstract Molecular dynamics simulations are used to explore explosive boiling of thin water films on a gold substrate. In particular, water films of 0.7, 1.6, and 2.5 nanometer thickness were examined. Three different surface wettabilities with contact angles of 11 deg, 47 deg, and 110 deg were simulated along with substrate temperatures of 400 K, 600 K, 800 K, and 1000 K. The 11 and 47 deg contact angles were obtained using a Morse interaction potential between the water film and gold substrate while the 47 and 110 deg contact angles were obtained via a Lennard-Jones potential. Evaporation was the first mode of phase change observed in all cases and explosive boiling did not occur until the substrate reached a temperature of 800 K. When explosive boiling was present for all three contact angles, it was consistently shown to occur first for the surface with a 47 deg contact angle and Lennard-Jones potential. These results suggest that explosive boiling onset is strongly dependent on the particularities of the interaction potential. For instance, the Morse potential is smoother when compared to the Lennard-Jones potential, but has more interaction sites per molecule—two hydrogen atoms and one oxygen atom versus one oxygen atom. Thus, even when the water film reaches a higher temperature with the Morse potential, explosive boiling onset is delayed as more interaction sites have to be disrupted. These results suggest that contact angle alone is insufficient and both the interaction strength and the number of atoms interacting at the interface must be considered when investigating trends of explosive boiling with surface wettability.

Molecular Dynamics Simulation of Ultra-Fast Phase Transition in Water Nanofilms

2020 ◽  
Author(s):  
Malcolm Porterfield ◽  
Diana Borca-Tasciuc
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Morse Potential ◽  
Water Film ◽  
Contact Angles ◽  
Gold Substrate ◽  
Explosive Boiling ◽  
Interaction Sites ◽  
Lennard Jones ◽  
Water Films

Abstract Molecular dynamics simulations are used to explore explosive boiling of thin water films on a gold substrate. In particular, water films of 2.5, 1.6 and 0.7 nanometer thickness were examined. Three different surface wettabilities with contact angles of 11, 47 and 110 degrees were simulated along with substrate temperatures of 400K, 600K, 800K and 1000K. The 11 degree contact angle was obtained using a Morse interaction potential between the water film and the gold substrate while the 47 and 110 degree contact angles were obtained via a Lennard-Jones potential. Evaporation was the first mode of phase change observed in all cases and explosive boiling did not occur until the substrate reached a temperature of 800K. When explosive boiling was present for all three contact angles, it was consistently shown to occur first for the surface with a 47 degree contact angle, contrary to the expectation that it would occur first on the substrate with an 11 degree contact angle. These results suggest that explosive boiling onset is strongly dependent on the particularities of the interaction potential. For instance, the Morse potential used to model the surface described by an 11 degree contact angle, is a softer potential as compared with Lennard-Jones, but has more interaction sites per molecule — two hydrogen atoms and one oxygen atom vs one oxygen atom. Thus, although the water film reaches a higher temperature with the Morse potential, explosive boiling onset is delayed as more interaction sites have to be disrupted. These results suggest that both the interaction strength and the number of atoms interacting at the interface must be considered when investigating trends of explosive boiling with surface wettability.

Application of pyrometer and standard sample to determine surface temperature of studied materials

2019 ◽  
pp. 9-13
Author(s):  
V.Ya. Mendeleyev ◽  
V.A. Petrov ◽  
A.V. Yashin ◽  
A.I. Vangonen ◽  
O.K. Taganov
Keyword(s):  
Composite Material ◽  
Surface Temperature ◽  
Relative Error ◽  
Wavelength Range ◽  
Standard Sample ◽  
A Priori ◽  
Temperature Changes ◽  
Surface Temperatures ◽  
Relative Errors ◽  
Normal Emissivity

Determining the surface temperature of materials with unknown emissivity is studied. A method for determining the surface temperature using a standard sample of average spectral normal emissivity in the wavelength range of 1,65–1,80 μm and an industrially produced Metis M322 pyrometer operating in the same wavelength range. The surface temperature of studied samples of the composite material and platinum was determined experimentally from the temperature of a standard sample located on the studied surfaces. The relative error in determining the surface temperature of the studied materials, introduced by the proposed method, was calculated taking into account the temperatures of the platinum and the composite material, determined from the temperature of the standard sample located on the studied surfaces, and from the temperature of the studied surfaces in the absence of the standard sample. The relative errors thus obtained did not exceed 1,7 % for the composite material and 0,5% for the platinum at surface temperatures of about 973 K. It was also found that: the inaccuracy of a priori data on the emissivity of the standard sample in the range (–0,01; 0,01) relative to the average emissivity increases the relative error in determining the temperature of the composite material by 0,68 %, and the installation of a standard sample on the studied materials leads to temperature changes on the periphery of the surface not exceeding 0,47 % for composite material and 0,05 % for platinum.

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