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When designing microscale heat exchangers, the reduction of energy dissipation and improved system performance in terms of heat transfer and fluid flow should be considered. Some methods, such as the use of nanofluids and convergent walls in the microchannel heat sinks, can be helpful. In this study, the hydrothermal performance and entropy generation of alumina‐silica/water hybrid nanofluid in the double‐layer tapered microchannel are investigated using the three‐dimensional simulation. The flow Re number and the volumetric fraction of the nanoparticles vary in the ranges of 50 to 400 and 0% to 5%, respectively. Numerical results show that by using the convergent microchannel, in addition to decreasing the maximum base surface temperature, the temperature gradient also becomes more uniform. Boosting the volumetric fraction of nanoparticles and decreasing the tapered factor (TF) reduce the thermal resistance of the system but cause higher pumping powers. At Re = 400 and φ = 5%, when the convergence factor of the channel reduces from 1 to 0.4, pumping power will increase 149% but the thermal resistance reduction about 12%. At lower Re numbers, the effects of channel convergence on enhancing the mean Nu number are greater than the cases with higher Re numbers. In general, boosting the convergence of the channel increases the frictional entropy generation and diminishes the thermal entropy generation. At Re = 200 and φ = 5%, by decreasing the tapered ratio from TF = 1 to TF = 0.4, the frictional entropy generation will double and the thermal entropy generation will reduce by 7.9%.

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