Microfluidic Flow And Heat Transfer In Microchannel Heat Sinks

Due to its outstanding heat transfer capacity and compact structure, the microchannel heat sink is the best choice for cooling of high-power electron device with small volume. Based on Multiplex Inductively Coupled Plasma Etching technique, an experiment appliance is designed and manufactured, on which experiments of single-phase de-ion water turbulent convection heat transfer and CFC-141b flow boiling heat transfer are carried out.Since continuum hypothesis is still valid for liquid flow in microchannels with hydraulic diameter at about 100 micro-meters, a turbulence convection heat transfer model for single-phase liquid flow in microchannels is established, in which wall surface roughness viscosity is introduced. Then a numerical calculation is done by use of 3D FVM (Finite Volume Method), and the numerical results are compared with those experimental ones. Heat transfer characteristics of a microchannel heat sink with arbitrary base heat flux is analyzed by FEM (Finite Element Method). A coupled arithmetic of FEM and FVM is originated so as to get both velocity and temperature profile in microchannels on condition that the base heat flux is distributed arbitrarily. And an engineering application example is supplied.An flow boiling model in microchannel is foremost developed based on the two-fluid model and a numerical process is programmed, in which the roughness of wall surface effecting on the liquid film is considered and both liquid drop entrainment and deposition involved. MD (Molecular Dynamics) Simulation method is first introduced to explore the bubble formation process and the interface stress between the liquid and vapor during fluid flow boiling in microchannels. And the results indicate MD simulation method is an effectual approach to probe into microscale fluidic flow boiling characteristics. An analytical model for flow boiling instability in microchannel heat sinks is initiated by employing Nyquist theorem of multi-variable system. Experiments of flow boiling instability with 4 parallel microchannel heat sinks are made to validate the analyticalmodel. The results of analytical model and experiments are in good agreement.The microchannel heat sinks considered as porous media model, the total heat transfer resistor expression is induced from the double-equation model of porous media. Aiming at reducing the total heat transfer resistor, optimization of structural parameters for the parallel microchannel heat sinks (aspect ratio, microchannel width, fin width, and so on) is discussed. Four heat transfer enhancement structure for parallel microchannels, such as integrated micro heat pipes, concave convex ribs, the assorted axes of flow passage, are designed and fabricated. By comparison, all the four heat transfer enhanced microchannels shows much lower heat transfer resistor than before enhanced.Two novel fractal network microchannel heat sinks are originated, namely, the biomimetic fractal tree-like microchannel net born of mammiferous aspiratory system and the biomimetic fractal comby microchannel net born of natural honeycomb. Both the heat transfer capacity and pump power of the fractal network microchannel heat sinks are compared with the parallel microchannels and the result shows that both of the two fractal network microchannel heat sinks do much better in heat transfer while requiring less pump power.