Heat transfer performance of water flowing over "V"-shaped micro-channel with different dimensions is studied using two three-dimensional numerical methods, i.e. traditional CFD (computational fluids dynamics) and LBM (lattice Boltzmann method) in this paper. The inlet flow is considered to be laminar. We altered the inclined angle and the height of the "V"-shaped micro-groove and simulated the corresponding water flow in it. The CFD code is based on the platform of Fluent and the LB method is self coded. Simulation results show that the two approaches can produce reasonable and agreed results. It also suggests that in our geometrical dimension varying range, micro-channel heat transfer performance increases with the micro-groove height monotonically. However, with the increase of inclined angle, the heat transfer performance decreases firstly and increases secondly. This can be intuitively explained as the result of changed surface area. We introduced the novel concept of field synergy principle to have an insight view of the convective flow field and temperature result. It is found that it is the synergy level between velocity and temperature gradient that finally results in the different heat transfer performance for different sized "V"-shaped micro-grooves. The pressure loss is also investigated using the two methods proposed in this paper. It is found that the pressure loss varies for different sized micro-grooves, and the pressure loss results exhibit a similar trend with that of the temperature field. This implies that to gain better heat transfer performance by altering the geometrical dimensions, the corresponding cost is quite considerable pressure loss. The widely studied perpendicularity "V"-shaped micro-channel has the lowest heat transfer performance compared with the inclined ones depicted in this study, but its pressure loss is the lowest. In contrast, the structure with the best heat transfer performance in this research possesses the largest pressure loss.
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