Coupled trapezoidal cover plate and stepped porous structures for enhanced flow boiling in microchannel heat sinks

Two-phase microchannel cooling offers a novel solution to the challenges of managing high heat fluxes and low-cost thermal management in compact electronic devices. Open microchannels provide significant advantages in enhancing heat transfer, reducing pressure drop, and improving flow stability. However, experimental studies on the multi-dimensional enhancement of open microchannel heat sinks are relatively limited. In this work, a stepped porous surface was fabricated using anodized aluminum technology. The concept of coupling the trapezoidal cover plate with a stepped porous surface (TOMP) was proposed for multi-dimensional synergistic enhancement of the heat transfer performance in open microchannels. Using HFE-7100 as the working fluid, the flow boiling characteristics of the TOMP heat sink were tested under different mass fluxes and subcooling conditions. The results show that the TOMP heat sink can significantly maintain various flow patterns over a wider range of heat fluxes. The TOMP heat sink achieves a maximum increase of 82.1 % in critical heat flux (CHF), a temperature reduction of up to 20.3 K, and a maximum enhancement of 209.6 % in the average heat transfer coefficient (HTC). Owing to the presence of more nucleation sites, faster bubble departure, and efficient liquid replenishment, the TOMP heat sink effectively mitigates boiling deterioration on the stepped porous surface, enabling the open microchannel to sustain stable nucleate boiling at high heat fluxes. In addition, the TOMP heat sink has the ability to delay the development of flow patterns, preventing the flow from prematurely entering Type-II stratified flow, thus making the boiling process in the microchannels more orderly and achieving better flow stability. Finally, the proposed TOMP heat sink demonstrates excellent performance in both performance evaluation criteria (PEC) and coefficient of performance (COP) metrics. This collaborative enhancement design provides a new approach for optimizing the performance of open microchannel heat sinks in two-phase heat transfer systems.