Ultra-stable counter flow diverging minichannel heat sink with integrated microstructures for superior cooling performance

Efficient thermal management of miniaturized electronic devices is quite challenging nowadays. It requires dissipation of very high heat flux without considerable elevation of surface temperature. To address this issue, this study proposes the counter flow diverging minichannel heat sink in a compact size of 3 cm². Additionally, two innovative microstructures have been developed and integrated into the bottom surface of the proposed minichannel heat sink: one with gradient micro pin-fins and another combining gradient microcavities with micro pin-fins. Comprehensive flow boiling experiments are conducted under various operating conditions to identify the best configuration with the most appropriate operating condition to dissipate the highest heat flux with minimal pressure drop and stable two-phase flow patterns. The current study reveals that the synergistic effects of gradient micro pin-fins and optimized gradient microcavities achieve a very high heat flux of 746.14 W/cm² and a two-phase heat transfer coefficient of 28.18 W/cm²K under the limitation of wall temperature lower than 132 °C. Additionally, it maintains an exceptionally low pressure drop of 2.35 kPa with stable two-phase flow patterns under a mass flux of 600 kg/m²s and a degree of subcooling of 40 °C. Compared to the bare surface, counter flow diverging minichannels with gradient micro pin-fins and optimized gradient microcavities show excellent enhancements of 201.12 % in the effective heat flux and 124 % in the two-phase heat transfer coefficient, suggesting it is the best design in the present study for advanced cooling applications. © 2024 Elsevier Ltd.