Enhanced flow boiling heat transfer performance of counter-flow interconnected microchannels via microporous copper surfaces

Abstract

Enhancing flow boiling performance within microchannels is crucial for cooling high-power electronic devices. Based on the concept of “equalizing channel dryness”, a counter-flow interconnected microchannel structure was proposed to enhance flow boiling. To investigate the flow boiling heat transfer characteristics, enhancement effects, and mechanisms of the combination of microporous layer-modified surfaces formed by copper powder sintering and counter-flow interconnected microchannels, this study employed microporous layers formed on microchannel sidewalls as an enhancement method. A detailed study was conducted on the effects of microporous layer morphology, copper powder particle size, sintering thickness, and sintering position on flow boiling heat transfer characteristics. Additionally, a mechanistic analysis of the capillary wicking process within the sintered copper powder surface was performed. The results show that, compared to smooth surface counter-flow connected microchannels, the microporous layer formed by copper powder sintering significantly enhances flow boiling heat transfer performance, as evidenced by a lower onset boiling superheat, increased critical heat flux (q_CHF), and improved heat transfer coefficient (HTC-h_tp). Furthermore, microchannels with microporous layer sidewalls exhibit a relatively uniform liquid film distribution, which helps maintain annular flow, promotes thin film evaporation, and effectively prevents local dryout caused by film rupture or bubble nucleation. The wicking ability (V΄) of the microporous layer is found to have a strong linear relationship with the critical heat flux (CHF).