Enhancing Flow Boiling Heat Transfer in Microchannels for Thermal Management with Monolithically-Integrated Silicon Nanowires

Abstract

Thermal management has become a critical issue for high heat flux electronics and energy systems. Integrated two-phase microchannel liquid-cooling technology has been envisioned as a promising solution, but with great challenges in flow instability. In this work, silicon nanowires were synthesized in situ in parallel silicon microchannel arrays for the first time to suppress the flow instability and to augment flow boiling heat transfer. Significant enhancement in flow boiling heat transfer performance was demonstrated for the nanowire-coated microchannel heat sink, such as an early onset of nucleate boiling, a delayed onset of flow oscillation, suppressed oscillating amplitudes of temperature and pressure drop, and an increased heat transfer coefficient.

Surface Structure Enhanced Microchannel Flow Boiling

“…To suppress flow instability and to enhance heat transfer, recent studies have focused on incorporating various structures in microchannels, such as inlet restrictors [12][13][14], artificial nucleation sites [14,15], vapor venting membranes [16][17][18], micro pin fins [19][20][21], and nanowire-coated surfaces [22][23][24] integrated into the microchannel.…”

“…In fact, in pool boiling, superhydrophilic micro and nanostructures have demonstrated significantly increased CHF [25][26][27][28][29][30][31] and biphilic patterned surfaces have shown large enhancements in heat transfer coefficients [32,33]. In flow boiling, silicon nanowire-coated channel surfaces have been reported to reduce temperature fluctuations [22], increase the heat transfer coefficient and CHF, and decrease the pressure drop across the microchannels with water as the working fluid [23,24]. The enhancement mechanism was mainly attributed to both increased wettability in delaying CHF and nucleation sites formed by the nanowire bundles to improve the heat transfer coefficient in the nucleate boiling regime.…”

Nanotechnology on Boiling Heat Transfer for a Next-generation Cooling Technology

“…Boiling heat transfer has been considered as a powerful method for high-thermal load dissipations accompanying vigorous phase-change of liquid coolant on a hot spot surface [1,2]. The technique with much higher heat transfer coefficients compared to typical single-phase convective cooling methods like natural and forced convection via gasor liquid-phase coolant, has contributed to the appearance of modern electronic devices with astonishing performances [3,4].Since the middle of 2000s, nanotechnologies have been magnified as a novel innovative approach to improve the cooling performance of boiling heat transfer [5][6][7]. Based on thermo-physical fundamentals on boiling heat transfer, we can present two principal factors which dominantly determine the cooling performance; one is surface roughness and the other is wettability characteristics.…”

“…Since the middle of 2000s, nanotechnologies have been magnified as a novel innovative approach to improve the cooling performance of boiling heat transfer [5][6][7]. Based on thermo-physical fundamentals on boiling heat transfer, we can present two principal factors which dominantly determine the cooling performance; one is surface roughness and the other is wettability characteristics.…”

“…Based on thermo-physical fundamentals on boiling heat transfer, we can present two principal factors which dominantly determine the cooling performance; one is surface roughness and the other is wettability characteristics. Herein, the manipulated surface morphology via nanoscale structures, like vertically aligned nanowires [6][7][8][9][10], is able to increase the roughness extremely and intensify the hydrophilicity towards super-wetting regime which is clearly favorable to wetting of the target surface by liquid-phase coolant. At first, higher heat dissipation capacity can be attributed to the increase of surface roughness, which means the extended interfacial contact area between the solid surface and the liquid coolant.…”