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Numerical experiments on evaporation and explosive boiling of ultra-thin liquid argon film on aluminum nanostructure substrate.

Wang W, Zhang H, Tian C, Meng X - Nanoscale Res Lett (2015)

Bottom Line: Those simulations begin with an initial configuration for the complex liquid-vapor-solid system, followed by an equilibrating system at 90 K, and conclude with two different jump temperatures, including 150 and 310 K which are far beyond the critical temperature.The space and time dependences of temperature, pressure, density number, and net evaporation rate are monitored to investigate the phase transition process on a flat surface with and without nanostructures.The simulation results reveal that the nanostructures are of great help to raise the heat transfer efficiency and that evaporation rate increases with the nanostructures' height in a certain range.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Mechanical Engineering, Xidian University, No. 2 South Taibai Road, Xi'an, Shaanxi 710071 China ; State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, No. 99 Yanxiang Road, Xi'an, Shaanxi 710054 China ; Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.

ABSTRACT
Evaporation and explosive boiling of ultra-thin liquid film are of great significant fundamental importance for both science and engineering applications. The evaporation and explosive boiling of ultra-thin liquid film absorbed on an aluminum nanostructure solid wall are investigated by means of molecular dynamics simulations. The simulated system consists of three regions: liquid argon, vapor argon, and an aluminum substrate decorated with nanostructures of different heights. Those simulations begin with an initial configuration for the complex liquid-vapor-solid system, followed by an equilibrating system at 90 K, and conclude with two different jump temperatures, including 150 and 310 K which are far beyond the critical temperature. The space and time dependences of temperature, pressure, density number, and net evaporation rate are monitored to investigate the phase transition process on a flat surface with and without nanostructures. The simulation results reveal that the nanostructures are of great help to raise the heat transfer efficiency and that evaporation rate increases with the nanostructures' height in a certain range.

No MeSH data available.


Related in: MedlinePlus

Temperature variation of the wall and argon regions for the case with a 310 K heated source.
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Fig3: Temperature variation of the wall and argon regions for the case with a 310 K heated source.

Mentions: For the case of high superheated temperature, the heat source is set to a fixed temperature of 310 K, which is much higher than the critical liquid temperature, so the liquid film will enter into explosive boiling in a certain time period. The simulation results of the historical temperature of the solid, liquid, and vapor regions are shown in Figure 3. From 0.5 to 1 ns, the simulation domain is in an initial equilibrium state at 90 K, then the heat source is set to a high temperature of 310 K at 1 ns, and the solid surface quickly responds to achieve the target temperature in less than 0.1 ns. Meanwhile, the temperatures of the argon liquid films for surfaces 1 to 3 also have a rapid increase at the onset of the explosive boiling, but for surface 0, the temperatures of the argon liquid films increase slower than those of the other three surfaces which results from the absence of nanoposts. After a few tenths of a nanosecond, the temperatures of the argon region with nanostructure have an obvious drop, which indicates that the liquid argon atoms start to get away from the solid wall surface. It is a quick rise in the wall surface temperature that promotes the liquid argon layer adjacent to the solid wall surface to exceed the critical temperature point and to boil, but the other argon layers are still in liquid phase. The vaporized argon with high pressure pushes the liquid to separate from the solid surface. The low-density vapor region adjacent to the solid surface prevents the energy flow from the wall to the separated liquid, and because of sudden expansion, the liquid argon region temperature falls in an interval time. Subsequently, the liquid region temperature keeps increasing to evaporate because of energy transmission by atom collisions. It can be drawn from Figure 3 that the nanostructured surfaces, including surfaces 1, 2, and 3, lead to higher temperatures of liquid and vaporize argon atoms as a result of increased interaction area between solid surface and liquid. Furthermore, with increasing height of nanoposts, the argon temperature increases further and it spends less time to reach equilibrium.Figure 3


Numerical experiments on evaporation and explosive boiling of ultra-thin liquid argon film on aluminum nanostructure substrate.

Wang W, Zhang H, Tian C, Meng X - Nanoscale Res Lett (2015)

Temperature variation of the wall and argon regions for the case with a 310 K heated source.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401484&req=5

Fig3: Temperature variation of the wall and argon regions for the case with a 310 K heated source.
Mentions: For the case of high superheated temperature, the heat source is set to a fixed temperature of 310 K, which is much higher than the critical liquid temperature, so the liquid film will enter into explosive boiling in a certain time period. The simulation results of the historical temperature of the solid, liquid, and vapor regions are shown in Figure 3. From 0.5 to 1 ns, the simulation domain is in an initial equilibrium state at 90 K, then the heat source is set to a high temperature of 310 K at 1 ns, and the solid surface quickly responds to achieve the target temperature in less than 0.1 ns. Meanwhile, the temperatures of the argon liquid films for surfaces 1 to 3 also have a rapid increase at the onset of the explosive boiling, but for surface 0, the temperatures of the argon liquid films increase slower than those of the other three surfaces which results from the absence of nanoposts. After a few tenths of a nanosecond, the temperatures of the argon region with nanostructure have an obvious drop, which indicates that the liquid argon atoms start to get away from the solid wall surface. It is a quick rise in the wall surface temperature that promotes the liquid argon layer adjacent to the solid wall surface to exceed the critical temperature point and to boil, but the other argon layers are still in liquid phase. The vaporized argon with high pressure pushes the liquid to separate from the solid surface. The low-density vapor region adjacent to the solid surface prevents the energy flow from the wall to the separated liquid, and because of sudden expansion, the liquid argon region temperature falls in an interval time. Subsequently, the liquid region temperature keeps increasing to evaporate because of energy transmission by atom collisions. It can be drawn from Figure 3 that the nanostructured surfaces, including surfaces 1, 2, and 3, lead to higher temperatures of liquid and vaporize argon atoms as a result of increased interaction area between solid surface and liquid. Furthermore, with increasing height of nanoposts, the argon temperature increases further and it spends less time to reach equilibrium.Figure 3

Bottom Line: Those simulations begin with an initial configuration for the complex liquid-vapor-solid system, followed by an equilibrating system at 90 K, and conclude with two different jump temperatures, including 150 and 310 K which are far beyond the critical temperature.The space and time dependences of temperature, pressure, density number, and net evaporation rate are monitored to investigate the phase transition process on a flat surface with and without nanostructures.The simulation results reveal that the nanostructures are of great help to raise the heat transfer efficiency and that evaporation rate increases with the nanostructures' height in a certain range.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Mechanical Engineering, Xidian University, No. 2 South Taibai Road, Xi'an, Shaanxi 710071 China ; State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, No. 99 Yanxiang Road, Xi'an, Shaanxi 710054 China ; Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.

ABSTRACT
Evaporation and explosive boiling of ultra-thin liquid film are of great significant fundamental importance for both science and engineering applications. The evaporation and explosive boiling of ultra-thin liquid film absorbed on an aluminum nanostructure solid wall are investigated by means of molecular dynamics simulations. The simulated system consists of three regions: liquid argon, vapor argon, and an aluminum substrate decorated with nanostructures of different heights. Those simulations begin with an initial configuration for the complex liquid-vapor-solid system, followed by an equilibrating system at 90 K, and conclude with two different jump temperatures, including 150 and 310 K which are far beyond the critical temperature. The space and time dependences of temperature, pressure, density number, and net evaporation rate are monitored to investigate the phase transition process on a flat surface with and without nanostructures. The simulation results reveal that the nanostructures are of great help to raise the heat transfer efficiency and that evaporation rate increases with the nanostructures' height in a certain range.

No MeSH data available.


Related in: MedlinePlus