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Simulation of Heat Transfer in Nanoscale Flow Using Molecular Dynamics

Abbasi, Hossein Reza | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41847 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Darbandi, Masoud
  7. Abstract:
  8. We investigate heat transfer between parallel plates separated by liquid argon using three-dimensional molecular dynamics (MD) simulations incorporating with 6-12 Lennard-Jones potential between molecule pairs. We use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. Channel walls are maintained at specific temperatures using a recently developed interactive thermal wall model. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the heat transfer between wall and fluid. Heat flux and temperature distribution in nanochannels are calculated for channel height of9σ_Argon. In this study, thermal conductivity of liquid argon in different temperatures using Fourier law is calculated. Temperature jump and slip velocity at the liquid/solid interface are observed. Temperature jump at the interface is characterized as a function of the surface wettability and spring stiffness that is used between wall molecules.
    We investigate driven flow between parallel plates separated by liquid argon using three-dimensional molecular dynamics (MD) simulations. In this study, we propose a nanochannel system, where half of the channel is in low surface wettability, while the other half has a relatively high surface wettability and at the middle of the channel walls, the temperature is high. Three-dimensional molecular dynamics simulations show that fluids in such channels can be continuously driven by a symmetric temperature gradient. High and low surface wettability cause a difference in fluid density along the channel. High temperature in the middle of the channel breaks the balance and because of the difference in density of the fluid, we have driven flow in the channel.
    One of the main objectives of this study is to simulate a nanochannel where the constant heat flux was imposed to the channel walls. To maintain a constant heat flux at the nanochannel walls, we use thermal wall concept in which the atoms at wall are connected to their original positions using linear spring forces model. For applying a constant heat flux, we have used a novel idea which uses a correction factor depends on the thermal velocities of the wall molecules determined by the desired heat flux. The heat flux and temperature distributions are then investigated for a nanochannel with a height of 64A. To improve the efficiency of simulation, we use USHER algorithm for the inlet of the domain. Inlet boundary condition enters molecules with desired temperature and velocity without any need to the periodic boundary condition. With this method, we avoid the entrance of outlet affects to the inlet induced by the periodic boundary condition
  9. Keywords:
  10. Molecular Dynamics ; Heat Transfer ; Nano Channel ; Fluid-Solid Interaction ; Temperature Jump Boundary Condition ; Lennard-jones Potential

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