Molecular Dynamics Study of Bubble Nucleation on an Ideally Smooth Substrate

Chen, Yujie; Chen, Xue-Jiao; Yu, Bo; Zou, Yu; Tao, Wen‐Quan

doi:10.1021/acs.langmuir.0c02832

Cited by 20 publications

(6 citation statements)

References 33 publications

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“…Figure shows that bubble nuclei first originate at the base corner of nanopillars on the surface R o . To analyze the behaviors of bubble nucleation, we computed the potential energy , U of one single water molecule at the solid–liquid interface. Taking the surface R o for example, as shown in Figure b, we chose a structural unit (one single pillar) and calculated the potential energy between one single water molecule and all solid atoms according to the 12-6 LJ potential function.…”

Section: Resultsmentioning

confidence: 99%

“…Unlike traditional computational fluid dynamics simulations, the MD method can directly explore the nanoscopic origins, elucidate phenomena from a molecular perspective, and provide a fundamental understanding that is not accessible by experiments; thus, it has been widely used to investigate various interfacial phenomena, such as droplet wetting, , impact, − coalescence, , and evaporation, , as well as liquid boiling − and vapor condensation. ,− In this paper, nonequilibrium molecular dynamics simulations were performed to investigate the nanoscale thin-film boiling process. Aiming at understanding the initial bubble behaviors and the heat and mass transfer performance, this work was conducted and illustrated around the following objectives: (1) capturing the triple-phase interface to record the lifetime of nanobubbles, (2) visualizing the internal fluid flow and thermal characteristics, (3) studying the effects of surface physicochemical properties on boiling performance, and (4) revealing the essential regulation mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale Thin-Film Boiling Processes on Heterogeneous Surfaces

Gao

Liu

et al. 2022

Langmuir

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Acquiring rapid and efficient boiling processes has been the focus of industry as they have the potential to improve the energy efficiency and reduce the carbon emissions of production processes. Here, we report nanoscale thin-film boiling on different heterogeneous surfaces. Through nonequilibrium molecular dynamics simulation, we captured the triple-phase interface details, visualized the bubble nucleation, and recorded the internal fluid flow and thermal characteristics. It is found that nanoscale thin-film boiling without the occurrence of bubble nucleation shows excellent heat and mass transfer performance, which differs from macroscale boiling. In general, rough structures advance the onset time of stable boiling and improve the efficiency. The heat transfer coefficient and heat flux on a rough hydrophilic surface respectively reach to 7.43 × 104 kW/(m2·K) and 1.3 × 106 kW/m2 at a surface temperature of 500 K, which are 100-fold higher than those of micrometer-scale thin-film boiling. However, due to the resultant vapor film trapped between the liquid and the surface, the rough hydrophobic surface leads to heat transfer deterioration instead. It is revealed that the underlying mechanism of regulatory effects resulting from surface physicochemical properties is originated from the variation of interfacial thermal resistance. It is available to reduce the overall interfacial resistance and further improve the heat and mass transfer efficiency through increasing surface roughness, enhancing surface wettability, and increasing the area proportion of the hydrophilic region. This work provides guidelines to achieve rapid and efficient thin-liquid-film boiling and serves as a reference for the optimized design of surfaces utilized for high-heat flux removal through vaporization processes.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanoscale Thin-Film Boiling Processes on Heterogeneous Surfaces

Gao

Liu

et al. 2022

Langmuir

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“…Due to strong solid–fluid wettability, nanobubbles do not originate from the solid surface and there is a nonevaporation ultrathin film covering in the solid surface, which is also observed in other studies. , To further understand this, the potential energy contour of fluid is calculated (see Figure ). From energy point of view, , low potential energy means large energy barrier for evaporation or boiling and only when liquid overcomes their potential barrier can the bubble nucleus form. As can be seen in Figure , fluid close to the solid surface owes much low potential energy, which strongly impedes the evaporation and boiling.…”

Section: Resultsmentioning

confidence: 99%

“…33,34 To further understand this, the potential energy contour of fluid is calculated (see Figure 7). From energy point of view, 35,36 low potential energy means large energy barrier for evaporation or boiling and only when liquid overcomes their potential barrier can the bubble nucleus form. As can be seen in Figure 7, fluid close to the solid surface owes much low potential energy, which strongly impedes the evaporation and boiling.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

Stable and Efficient Nanofilm Pure Evaporation on Nanopillar Surfaces

Wang

Sun

et al. 2021

Langmuir

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Molecular dynamics simulations were conducted to systematically investigate how to maintain and enhance nanofilm pure evaporation on nanopillar surfaces. First, the dynamics of the evaporation meniscus and the onset and evolution of nanobubbles on nanopillar surfaces were characterized. The meniscus can be pinned at the top surface of the nanopillars during evaporation for perfectly wetting fluid. The curvature of the meniscus close to nanopillars varies dramatically. Nanobubbles do not originate from the solid surface, where there is an ultrathin nonevaporation film due to strong solid–fluid interaction, but originate and evolve from the corner of nanopillars, where there is a quick increase in potential energy of the fluid. Second, according to a parametric study, the smaller pitch between nanopillars (P) and larger diameter of nanopillars (D) are found to enhance evaporation but also raise the possibility of boiling, whereas the smaller height of nanopillars (H) is found to enhance evaporation and suppress boiling. Finally, it is revealed that the nanofilm thickness should be maintained beyond a threshold, which is 20 Å in this work, to avoid the suppression effect of disjoining pressure on evaporation. Moreover, it is revealed that whether the evaporative heat transfer is enhanced on the nanopillar surface compared with the smooth surface is also affected by the nanofilm thickness. The value of nanofilm thickness should be determined by the competition between the suppression effect on evaporation due to the decrease in the volume of supplied fluid and the existence of capillary pressure and the enhancement effect on evaporation due to the increase in the heating area. Our work serves as the guidelines to achieve stable and efficient nanofilm pure evaporative heat transfer on nanopillar surfaces.

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“…Though similar studies on evaporation of water or different aqueous films can be found in the literature, significantly less research has been done in understanding the film boiling and at the molecular level in the presence of an electric field. Similarly, molecular-level study of nucleate boiling on smooth surfaces, on surfaces with cavities, and on surfaces with varying wettabilities can be seen in the literature, but the effect of an electric field is yet to be explored. Hence, in the present paper, molecular dynamics simulations have been performed in an attempt to understand and control film and nucleate boiling using an electric field.…”

Section: Introductionmentioning

confidence: 99%

Electric Charge-Induced Active Control of Nucleate and Rapid Film Boiling at the Nanoscale: a Molecular Perspective

2021

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An effort has been made to understand the nucleate and the rapid film boiling phenomena under the influence of an electric field using a molecular viewpoint. The behavior of water molecules with a solid copper surface during the film boiling process in the presence of an electric field of different intensities has been studied. The molecular reasoning behind the suppression of the Leidenfrost phenomenon upon application of a uniform electric field along the heating substrate is established. Furthermore, the effect of surface characteristics with different wettabilities on film boiling in the presence of an electric field has also been studied. The electric field produces a finger-like water column besides thinning of the water film over a non-wetting surface. A similar phenomenon is also evident over a hydrophilic surface only after reaching a threshold value of electric charge intensity. Molecular simulations have explained the phenomenon of nucleate boiling of water on hydrophilic or non-wetting surfaces. Finally, the ability to control the bubble formation and suppression at a required location using an electric field has also been demonstrated. The water molecules near the surface experience dispersion at a lower electric field and an attraction force at a higher electric field, mimicking bubble nucleation and suppression, respectively.

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Molecular Dynamics Study of Bubble Nucleation on an Ideally Smooth Substrate

Cited by 20 publications

References 33 publications

Nanoscale Thin-Film Boiling Processes on Heterogeneous Surfaces

Nanoscale Thin-Film Boiling Processes on Heterogeneous Surfaces

Stable and Efficient Nanofilm Pure Evaporation on Nanopillar Surfaces

Electric Charge-Induced Active Control of Nucleate and Rapid Film Boiling at the Nanoscale: a Molecular Perspective

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