The effects of fin width

cavity width and Reynolds number (Re) on the convective heat transfer characteristics in the microchannels with cavities and fins were studied by field synergy and entropy generation principle. The heat transfer enhancement mechanism of micro structures was analyzed

and the comprehensive performance of the microchannel was assessed. The results showed that the increase of fin width and cavity width was able to reduce the heat transfer synergy angle

improve the synergy relationship between flow field and temperature field obviously and enhance the convective heat transfer. However

the local vortexes caused the decrease of flow synergy angle and increased the pressure drop of the microchannels; the increase of fin width was helpful to improve the energy utilization efficiency and enhance heat transfer associated with the increase of the entropy generation rate of fluid friction; increasing the cavity width properly was able to reduce the entropy generation rate of heat transfer

but the extremely large cavity width led to the increase of the heat transfer irreversibility and flow friction; considering the pump power

relative fin width and relative cavity width

new correlation of the thermal resistance was proposed; the microchannel heat sink with relative fin width 0.2 and relative cavity width 2 yielded the lowest thermal resistance and the best overall performance.