Molecular Dynamics (MD) simulations of nano-scale flows typically utilize fixed
lattice crystal interactions between the fluid and stationary wall molecules. This
approach cannot properly model thermal interactions at the wall-fluid interface. In order
to properly simulate the flow and heat transfer in nano-scale channels, an interactive
thermal wall model is developed. Using this model, the Fourier’s law of heat conduction
is verified in a 3.24 nm height channel, where linear temperature profiles with constant
thermal conductivity is obtained. The thermal conductivity is verified using the
predictions of Green-Kubo theory. MD simulations at different wall wettability ( εωf /ε )
and crystal bonding stiffness values (K) have shown temperature jumps at the
liquid/solid interface, corresponding to the well known Kapitza resistance. Using
systematic studies, the thermal resistance length at the interface is characterized as a
function of the surface wettability, thermal oscillation frequency, wall temperature and
thermal gradient. An empirical model for the thermal resistance length, which could be
used as the jump-coefficient of a Navier boundary condition, is developed. Temperature distributions in the nano-channels are predicted using analytical solution of the
continuum heat conduction equation subjected to the new temperature jump condition,
and validated using the MD results. Momentum and heat transfer in shear driven nanochannel
flows are also investigated. Work done by the viscous stresses heats the fluid,
which is dissipated through the channel walls, maintained at isothermal conditions.
Spatial variations in the fluid density, kinematic viscosity, shear- and energy dissipation
rates are presented. The energy dissipation rate is almost a constant for εωf /ε < 0.6,
which results in parabolic temperature profiles in the domain with temperature jumps
due to the Kapitza resistance at the liquid/solid interfaces. Using the energy dissipation
rates predicted by MD simulations and the continuum energy equation subjected to the
temperature jump boundary conditions developed in this study, the analytical solutions
are obtained for the temperature profiles, which agree well with the MD results.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-447 |
| Date | 2009 May 1900 |
| Creators | Kim, Bo Hung |
| Contributors | Beskok, Ali, Cagin, Tahir |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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