The Topology Optimization (TO) has been proved to be an effective method for designing Microchannel Heat Sinks (MCHS). However, due to the relatively high computational cost and poor numerical stability, it is still challenging to design the thermo-fluid TO under high Reynolds number (Re). In this work, we propose a Contour Extraction Based on Topology Optimization (CEBTO) method to optimize the geometry of the fins based on a threshold velocity (Ut, proportional to the maximum velocity Umax) and improve the hydrothermal performance of MCHS under high Re. The 3D conjugate heat transfer numerical models are established to study the fluid flow and heat transfer characteristics of the MCHS generated by the conventional TO method and the CEBTO method. The results showed that due to the elimination of the area of stagnation zones under high Re, the CEBTO-generated heat sinks have a better interaction of fluid with the walls and more uniform velocity distribution compared to the TO-generated ones. However, the elimination of the stagnation zones area also leads to the decrease of channel width, which increases the friction loss in CEBTO-generated heat sinks. Nevertheless, the CEBTO-generated heat sinks have better overall performance compared to the TO designs owing to the smaller total entropy generation rate. For example, the CEBTO-I (Ut=28%Umax) exhibits the best overall performance with 10.1% increment of flow entropy generation rate and 7.1% reduction of thermal entropy generation rate as compared to those of TO-I (i.e., a TO-generated heat sink with alveoli-like shape), leading to the augment entropy generation number of 0.92 (Re = 1715). Finally, the CEBTO-I (Ut=28%Umax) was manufactured by micro milling technology and its hydrothermal performance was investigated experimentally to validate the accuracy of numerical simulation. The pressure drop and temperature of the CEBTO-generated heat sink in the experiment agree well with the numerical simulation.

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