SOME FLOW AND THERMAL PHENOMENA AT MICRO/NANO SCALE
In order to have deep insight on flow and thermal phenomena at micro/nano scale it is necessary to classify the physical mechanisms of the size effect on the flow and heat transfer into two groups a) the relative importance of factors varies which influence the flow and heat transfer as the characteristic length decreases, even if the continuum assumption is still valid; b) the continuum assumption breaks down as the characteristic length of the flow becomes comparable to the mean free path of the molecules. For the first group, the departure of most flow and thermal phenomena at microscale from conventional ones is because factors related to surface effects have more impact to the flow and heat transfer at small scales. Among these are: the surface friction induced flow compressibility, the surface roughness, the axial heat conduction in the wall, channel surface geometry, surface electrostatic charges, and measurement errors. For the second group, the incontinuity of fluid medium near the wall is the origin of the size effect on the flow and heat transfer. Molecular dynamics simulations show that velocity slips between of the gas flow in the nano channel are determined by fluid property, the Knudsen number, and by the surface roughness as well. In addition, molecular dynamics study indicates that bubble nucleation starts from the nanoscale low-density region in liquid, and only the fluid repulsive nanoparticle with a size close to the critical radius can enhance the bubble nucleation remarkably.
ARHT Digital Library
Illustration of composite TIMs with a percolation of spherical nanoparticles, and high aspect ratio nanowires. NANOSTRUCTURED THERMAL INTERFACES
Photograph of copper/diamond sintered wick structure. RECENT ADVANCES IN TWO-PHASE THERMAL GROUND PLANES
The microchannel with a single pillar used by Jung et al., and an SEM image of the pillar with a flow control slit at 180 deg (facing downstream). ADVANCED CHIP-LEVEL LIQUID HEAT EXCHANGERS
Schematics of thermal boundary conductance calculations. NONEQUILIRIUM MOLECULAR DYNAMICS METHODS FOR LATTICE HEAT CONDUCTION CALCULATIONS
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