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Enhancement of Pool Boiling Heat Transfer Using Aligned Silicon Nanowire Arrays

Year: 2017

Journal: ACS Appl. Mater. Interfaces, Volume 9, MAY 24, page 17596–17603

Authors: Il Shim, Dong; Choi, Geehong; Lee, Namkyu; Kim, Taehwan; Kim, Beom Seok; Cho, Hyung Hee

Organizations: Center for Advanced Meta Materials (CAMM) - Center for Advanced Meta Materials (CAMM) funded by the Ministry of Science, ICT and Future Planning [NRF-2014M3A6B3063716]; Korea Institute of Energy Technology Evaluation and Planning (KETEP) - Korean Government's Ministry of Trade, Industry, and Energy [20144030200560]

Keywords: Surface modification; aligned nanowires; heat transfer enhancement; interfacial wicking; boiling heat transfer

Enhancing the critical heat flux (CHF), which is the capacity of heat dissipation, is important to secure high stability in two-phase cooling systems. Coolant supply to a dry hot spot is a major mechanism to prevent surface bum-out for enhancing the CHF. Here, we demonstrate a more ready supply of coolant using aligned silicon nanowires (A-SiNWs), with a high aspect ratio (> 10) compared to that of conventional random silicon nanowires (R-SiNWs); which have a disordered arrangement, for additional CHF improvement. We propose the volumetric wicking rate, which represents the coolant supply properties by considering both the liquid supply velocity and the amount of coolant (i.e., wicking coefficient and wetted volume, respectively). Through experimental approaches, we confirm that the CHF is enhanced as the volumetric wicking rate is increased. In good agreement with the fabrication hypothesis, A-SiNWs demonstrate higher coolant supply abilities than those of R-SiNWS. The longest (7 mu m) A-SiNWs have the highest volumetric wicking rate (25.11 x 10(-3) mm(3)/s) and increase the CHF to 245.6 W/cm(2), which is the highest value obtained using nanowires among reported data (178 and 26% enhanced vs unmodulated plain surface and R-SiNWs, respectively). These well-aligned SiNWs can increase the CHF significantly with efficient coolant supply, and it can ensure high stability in extremely high thermal load systems. Moreover, our study provides nanoscale interfacial design strategies for further improvement of heat dissipation.