Enhanced Flow Boiling in Microchannels Integrated with Hierarchical Structures of Micro-Pinfin Fences and Nanowires.

Two-phase flows in microchannels have been extensively investigated due to their wide range of applications including the fluid process and thermal management in electronic devices. In this study, silicon nanowires (SiNWs) were directly integrated with all the inner microchannel surfaces including walls and micro-pinfins (μ-pinfin) to form SiNW-pinfin hierarchical structures. The objective of this study is to explore if the SiNW-decorated surfaces can further enhance flow boiling through promoting local capillary flows with a better managed pressure drop. Experimental results illustrate that the critical heat flux in the proposed SiNW-pinfin microchannels can be promoted up to 483, 71.7, and 25.5% at a mass flux of 303 kg/m2 s compared with the traditional plain-wall, SiNW-coated plain-wall, and plain-wall with inlet orifice microchannels, respectively. Moreover, the heat-transfer rate of the flow boiling can be enhanced up to 122% at a mass flux of 303 kg/m2 s compared to that of inlet orifice microchannels with an effectively managed pressure drop. The capillary-induced periodic and rapid liquid wetting is believed to be the primary enhancement mechanism.