Flow boiling heat transfer on nanowire-coated surfaces with highly wetting liquid

Shin, Sangwoo; Choi, Geehong; Kim, Beom-Seok; Cho, Hyung Hee

doi:10.1016/j.energy.2014.08.037

Cited by 59 publications

(30 citation statements)

References 24 publications

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“…This non-monotonic behavior of wetting and wicking in turn leads to significant decrease of CHF. This trend was also observed by previous studies using nanowire-coated boiling surfaces on highly-wetting dielectric fluids [20,21]. It may be attributed to coupled interactions between capillary flow and liquid entrainment, which lead to a flow regime transition from the annular flow into a wispy-annular flow or a churn flow.…”

Section: Introductionsupporting

confidence: 72%

Flow boiling heat transfer of HFE-7000 in nanowire-coated microchannels

Yang

Dai

et al. 2016

Applied Thermal Engineering

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Please cite this article as: Fanghao Yang, Wenming Li, Xianming Dai, Chen Li, Flow boiling heat transfer of HFE-7000 in nanowire-coated microchannels, Applied Thermal Engineering (2015), http://dx.doi.org/ABSTRACT: Flow boiling of dielectric fluids in microchannels is among the most promising embedded cooling solutions for high power electronics. However, it is normally limited by their poor thermal conductivity and small latent heat. To promote thin film evaporation and nucleate boiling, the side and bottom walls of five parallel microchannels were structured with nanowires in a silicon chip. A 10-mm-long thin-film heater were built-in to simulate heat source. Wall Page 1 of 28 2 temperatures were measured from adiabatic condition to critical heat flux (CHF) conditions. Compared to the plain-wall microchannels with identical channel dimensions, heat transfer coefficient of HFE 7000 can be substantially enhanced up to 344% at the mass flux ranging from 1018 kg/m 2 •s to 2206 kg/m 2 •s as promoted evaporation and nucleate boiling. Moreover, pumping power was reduced up to 40% owing to the capillarity-enhanced phase separation. CHF was achieved from 92 to 120 W/cm 2 and enhanced up to 14.9% at moderate mass flux of 1018 kg/m 2 •s as a result of annular liquid supply. However, interestingly, this trend is non-monotonic and CHF is reduced at higher mass fluxes. This experimental study is trying to explore an optimal range of working conditions using nanostructures in flow boiling on highly-wetting dielectric fluids. NomenclatureA Area, m 2 D Diameter, m H Height, m h fg Latent heat of vaporization, kJ/kg G Mass flux, kg/m 2 •s L Length, m m

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Section: Introductionsupporting

confidence: 72%

Flow boiling heat transfer of HFE-7000 in nanowire-coated microchannels

Yang

Dai

et al. 2016

Applied Thermal Engineering

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“…We can explain this phenomenon by the fact that microropes are not perpendicular to the surface, and have different angles of inclination. In addition, it was observed that the droplets on the surface have a very large precursor line [27]. We assume that water easily penetrates into relief grooves in the case of Cassie impregnating wetting [28].…”

Section: Resultsmentioning

confidence: 92%

Influence of substrate temperature on the morphology of silicon oxide nanowires synthesized using a tin catalyst

Khmel

Баранов

Zamchiy

et al. 2016

Physica Status Solidi (a)

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Silicon oxide nanowires SiOx were synthesized by the gas‐jet electron beam plasma chemical vapor deposition method. The synthesis of nanostructures was carried out on silicon substrates with thin tin film as a catalyst. The evolution in the morphology of the obtained structures was investigated while changing the substrate temperature in the range 200–415 °C. Dense array of aligned nanowire bundles (microropes) is formed at a temperatures of 335 and 415 °C. With decrease in the temperature to 270 and 245 °C arrays of microropes transform into cocoon‐like structures of nanowires. At a temperature 200 °С, array formed almost entirely consisting of cocoon‐like structures. The results of X‐ray energy dispersive spectroscopy (EDS) of the nanowires show that the ratio of oxygen to silicon is on average Si:O = 1:2.4. At the same time, Fourier Transform Infrared spectroscopy (FTIR) analysis of the obtained nanostructures showed that the synthesized nanowires consist of SiOx with x around 2. Moreover, the composition of the structures remains practically unchanged with the variation of the substrate temperature. The IR spectra show bands due to both Si–OH bonds and water molecules. Measurements of contact angles for water showed that the nanowire film surface synthesized in this work is hydrophilic in nature. When structuring involves the oriented growth microropes, the contact angle is about 20–35°. Decreasing of the substrate temperature and formation of cocoon‐like structures leads to a decrease in the contact angle to 4–12°. The photoluminescence (PL) spectra of nanostructures synthesized at the different substrate temperatures consist of a broad band with a maximum around 2.5 eV when using laser at 325 nm as the exciting source. We assume that the composition of the nanowires is close to SiO2, and the excess of oxygen in structures composition is due to the influence of adsorbed water molecules and hydroxyl groups with the formation of Si–OH bonds. Apparently, these bonds define the photoluminescence spectrum.

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“…Thus the role of the surface structures on the stability of the annular liquid film and on the film evaporation performance needs to be investigated. In addition, while introducing structures on the channel wall offers capillary driven liquid flow, the associated viscous resistance [34][35][36] from the structures, especially in the presence of shear from the vapor, can be significant.…”

Section: Introductionmentioning

confidence: 99%