Effect of pattern geometry on bubble dynamics and heat transfer on biphilic surfaces

Pontes, Pedro; Cautela, Ricardo; Teodori, Emanuele; Moita, Ana S.; Liu, Yan; Moreira, A.L.N.; Nikulin, Artem; Barrio, Elena Palomo del

doi:10.1016/j.expthermflusci.2020.110088

Cited by 44 publications

(24 citation statements)

References 17 publications

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“…Images obtained by high-speed visualization and time-resolved thermography are consistent with those recently reported by Reference [ 50 ]. Hence, there is a peak in the heat flux that is dissipated at each event of bubble departure, as a result of the induced fluid convection.…”

Section: Resultssupporting

confidence: 90%

“…For this distance between superhydrophobic regions, which was established following the recommendations of Reference [ 50 ], the coalescence actually promotes surface cooling, which is clearly identified in the thermographic images by a temperature drop at the surface, during bubbles detachment and coalescence. The coalescence also helps promote the early detachment of the bubbles, thus increasing frequency and recirculation.…”

Section: Resultsmentioning

confidence: 99%

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Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

et al. 2021

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This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

et al. 2021

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“…The experimental observation and characterization of the bubble growth is detailed in our previous work [36] and is in overall agreement with the numerical simulation.…”

Section: Image Based Analysis Of the Resultssupporting

confidence: 80%

“…A more detailed analysis of the surface topography performed by Laser Scanning Confocal Microscopy (using a confocal microscope model SP8 from Leica) further shows a complex structure with cavities, that is presented in our previous work [36]. Also in [36], further analysis was done to the surface of the coating with scanning electron microscope (SEM), using a FEI-QUANTA 200FEG operated in high vacuum mode at 20 kV (images were captured by a BackScattered Electron Detector -BSED, Everhart-Thornley Detector -ETD and in a combined mode of BSED and ETD) further identified a hierarchical structure, consisting of larger cracks (around 30-500 µm in length and 2-40 µm in width) and cavities (around 2-90 µm in diameter) which are covered by a "spongelike" porous mesh (with pores of the order of 5-75 nm in diameter). This complex hierarchical structure strongly aids the formation of a stable superhydrophobic coating, as detailed for instance in [6], who describe a similar hierarchical structure for the English weed leaves.…”

Section: Surface Manufacturing and Characterizationmentioning

confidence: 63%

“…In this model, the liquid and vapour phases are treated as incompressible, Newtonian fluids. The used solver has been previously validated with other multi-phase interactions [26,30,[36][37]. These include cases of adiabatic and diabatic bubble and droplet dynamics, which were compared against experimental data and analytical solutions.…”

Section: Governing Equationsmentioning

confidence: 99%

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Bubble Dynamics and Heat Transfer on Biphilic Surfaces: Experiments and Numerical Simulation

et al. 2020

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Wettability is known to play a major role in enhancing pool boiling heat transfer. In this context bioinspired surfaces can bring significant advantages in pool boiling applications. This work addresses a numerical investigation of bubble growth and detachment on a biphilic surface pattern, namely in a superhydrophobic region surrounded by a hydrophilic region. Surface characteristics resemble bioinspired solutions explored in our research group, mainly considering the main topographical characteristics. This numerical approach is intended to provide additional information to an experimental approach, allowing to obtain temperature, pressure and velocity fields in and around the bubble, which help to describe bubble dynamics. The model was validated based on experimental data obtained with extensive image processing of synchronized high-speed video and high-speed thermographic images. The results obtained here clearly evidence that combining enhanced direct numerical simulations with high-resolution transient experimental measurements is a promising tool to describe the complex and intricate hydrodynamic and heat transfer phenomena governing pool boiling on heated biphilic surfaces.

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Superbiphilic Laser‐Microengineered Surfaces with A Self‐Assembled Monolayer Coating for Exceptional Boiling Performance

Hadžić,

Može,

Zupančič

et al. 2023

Adv Funct Materials

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The rapid advancement of engineering systems has spurred the search for innovative thermal management solutions. Boiling, as a phase‐change heat transfer method, has shown promise in heat dissipation, but non‐functionalized surfaces struggle with increasing cooling demands. To improve heat dissipation efficiency across different heat loads, functionalized surfaces with tailored wettability have been proposed. Separately, superhydrophilic and superhydrophobic surfaces each offer benefits and drawbacks in boiling applications but combining them on a single “biphilic” surface simultaneously harnesses their advantages. In this study, laser‐functionalized copper surfaces with spatially tailored wettability are developed by combining two‐step laser texturing with a self‐assembled monolayer coating, while focus is placed on the impact of the size and pitch of superhydrophobic spots. The developed functionalized surfaces exhibit exceptional boiling performance with heat transfer coefficients up to 299 kW m−2 K−1, a 434% enhancement over untreated surfaces. Optimal ratios of superhydrophilic and superhydrophobic areas and optimal spot pitch are identified. Additionally, varying behavior at different heat flux levels is observed, emphasizing the importance of considering thermal loads when determining the optimal surface pattern. This advancement in performance, along with the rapid and cost‐effective functionalization process, represents a significant breakthrough for enhanced thermal management applications.

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Effect of pattern geometry on bubble dynamics and heat transfer on biphilic surfaces

Cited by 44 publications

References 17 publications

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Bubble Dynamics and Heat Transfer on Biphilic Surfaces: Experiments and Numerical Simulation

Superbiphilic Laser‐Microengineered Surfaces with A Self‐Assembled Monolayer Coating for Exceptional Boiling Performance

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