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He D, Rui Z, Lyu X, Zhuo J, Sun H, Dong Y. Effect of Nanopillars on the Wetting State and Adhesion Characteristics of Molten Aluminum Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:13986-13999. [PMID: 37725795 DOI: 10.1021/acs.langmuir.3c01674] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/21/2023]
Abstract
To solve the adhesion problem between molten aluminum and vacuum ladle liner during the electrolytic aluminum production process, the wetting state and adhesion properties of molten aluminum droplets on substrate surfaces with different nanopillars are investigated based on molecular dynamics. The results show that the adhesion strength of molten aluminum droplets in different wetting states has the pattern Young state > Wenzel state > Cassie state. Effects of increasing nanopillar height or interval are poles apart in the wetting state and adhesion characteristics of aluminum molten droplets. The critical height and critical interval of the nanopillar where the wetting state transition occurs are obtained. The increase of the nanopillar width can induce the wetting state transition from the Cassie state to the Wenzel state. In addition, the phantom wall method is applied to study the variation of the separation force. It is found that a peak in the separation force curve occurs when the molten droplet separates from the bottom of the nanopillar interval or the top of the nanopillar. The separation force curves of the droplets in the Young state and the Cassie state have single peaks, while the droplets in the Wenzel state have double peaks.
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Affiliation(s)
- Dongyun He
- School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
| | - Zhiyuan Rui
- School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
| | - Xin Lyu
- School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
| | - Junting Zhuo
- School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
| | - Huaming Sun
- School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
| | - Yun Dong
- School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
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2
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Zheng SF, Gao YY, Yang LT, Gao SR, Yang YR, Lee DJ, Sunden B, Wang XD. Theoretical and Three-Dimensional Molecular Dynamics Study of Droplet Wettability and Mobility on Lubricant-Infused Porous Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:13371-13385. [PMID: 37675482 DOI: 10.1021/acs.langmuir.3c02078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
Profiting from their slippery nature, lubricant-infused porous surfaces endow with droplets excellent mobility and consequently promise remarkable heat transfer improvement for dropwise condensation. To be a four-phase wetting system, the droplet wettability configurations and the corresponding dynamic characteristics on lubricant-infused porous surfaces are closely related to many factors, such as multiple interfacial interactions, surface features, and lubricant thickness, which keeps a long-standing challenge to promulgate the underlying physics. In this work, thermodynamically theoretical analysis and three-dimensional molecular dynamics simulations with the coarse-grained water and hexane models are carried out to explore droplet wettability and mobility on lubricant-infused porous surfaces. Combined with accessible theoretical criteria, phase diagrams of droplet configurations are constructed with a comprehensive consideration of interfacial interactions, surface structures, and lubricant thickness. Subsequently, droplet sliding and coalescence dynamics are quantitatively defined under different configurations. Finally, in terms of the promotion of dropwise condensation, a non-cloaking configuration with the encapsulated state underneath the droplet is recommended to achieve high droplet mobility owing to the low viscous drag of the lubricant and the eliminated pinning effect of the contact line. On the basis of the low oil-water and water-solid interactions, a stable lubricant layer with a relatively low thickness is suggested to construct slippery surfaces.
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Affiliation(s)
- Shao-Fei Zheng
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Yi-Ying Gao
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Li-Tao Yang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Shu-Rong Gao
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Yan-Ru Yang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Duu-Jong Lee
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong
- Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-li, Taoyuan City 320315, Taiwan
| | | | - Xiao-Dong Wang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
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3
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Xiang H, Yuan Y, Zhu T, Dai X, Zhang C, Gai Y, Liao R. Anti-Icing Mechanism for a Novel Slippery Aluminum Stranded Conductor. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37413794 DOI: 10.1021/acsami.3c04797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
The icing of transmission conductor seriously threatens the safe operation of power grids. Slippery lubricant-infused porous surface (SLIPS) has shown great potential for anti-icing applications. However, aluminum stranded conductors have complex surfaces, and the current SLIPSs are almost prepared and studied on small flat plates. Herein, the construction of SLIPS on the conductor was realized through anodic oxidation and the anti-icing mechanism of the slippery conductor was studied. Compared to the untreated conductor, the SLIPS-conductor reduces the icing weight by 77% in the glaze icing test and shows very low ice-adhesion strength (7.0 kPa). The excellent anti-icing performance of the slippery conductor is attributed to the droplet impact dynamics, icing delay, and lubricant stability. The dynamic behavior of water droplets is most affected by the complex shape of the conductor surface. Specifically, the impact of the droplet on the conductor surface is asymmetric and the droplet can slide along the depression in low-temperature and high-humidity environments. The stable lubricant of SLIPS increases both the nucleation energy barriers and the heat transfer resistance, which greatly delays the freezing time of droplets. Besides, the nanoporous substrate, the compatibility of the substrate with the lubricant, and the lubricant characteristics contribute to the lubricant stability. This work provides theoretical and experimental guidance on anti-icing strategies for transmission lines.
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Affiliation(s)
- Huiying Xiang
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - Yuan Yuan
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - Tao Zhu
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - Xu Dai
- State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Cheng Zhang
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - Yu Gai
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - Ruijin Liao
- State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China
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4
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He X, Li J, Guan Y, Wang Z. Nanodroplet Wetting and Electrowetting Behavior on Liquid-infused Surfaces: A Molecular Simulation Study. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.121157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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5
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Guo L, Sheng Q, Kumar S, Liu Z, Tang G. Lubricant-induced tunability of self-driving nanodroplets on conical grooves. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.121149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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6
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Ye H, Yin C, Wang J, Zheng Y. Controllable and Gradient Wettability of Bilayer Two-Dimensional Materials Regulated by Interlayer Distance. ACS APPLIED MATERIALS & INTERFACES 2022; 14:41489-41498. [PMID: 36001530 DOI: 10.1021/acsami.2c08282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Surfaces with controllable and gradient wettability often require an elaborate design of the microstructure or its response under electrical, thermal, optical, pH, and other stimuli. Generally, the wettability change under these physical or chemical effects relies on a complex mechanism that is difficult to be quantitatively described. In this study, an online controlling strategy for surface wettability and the corresponding theoretical model are put forward based on a bilayer graphene-like atomic structure. Molecular dynamics results indicate that the surface wettability varies toward hydrophilicity after sticking a bottom material regardless of its wettability. But such an influence becomes weak with increasing interlayer distance, and the overall wettability approaches that of the upper layer material gradually. This variation is elucidated by the increase of the work of adhesion, providing new insight into the wetting transparency of graphene. A theoretical model of the governing relationship is established based on the work of adhesion, which correlates the overall surface wettability with the interlayer distance and the wettabilities of individual materials. Moreover, a surface with a uniform wettability gradient is achieved by inclining the bottom material. The spontaneous and steady motion of droplets can be induced by this gradient wettability. The relevant speedup behavior is evaluated through a theoretical model considering the varying interlayer distance, which reveals the critical role of the lower layer. This study proposes a novel strategy for controllable wetting and relevant gradient surfaces using prevailing two-dimensional materials, paving new routes to many applications such as microfluidic chips, virus diagnosis, and intelligent sensors.
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Affiliation(s)
- Hongfei Ye
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
| | - Chenguang Yin
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
| | - Jian Wang
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
| | - Yonggang Zheng
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
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7
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Badr RGM, Hauer L, Vollmer D, Schmid F. Cloaking Transition of Droplets on Lubricated Brushes. J Phys Chem B 2022; 126:7047-7058. [PMID: 36062355 DOI: 10.1021/acs.jpcb.2c04640] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study the equilibrium properties and the wetting behavior of a simple liquid on a polymer brush, with and without the presence of lubricant by multibody Dissipative Particle Dynamics simulations. The lubricant is modeled as a polymeric liquid consisting of short chains that are chemically identical with the brush polymers. We investigate the behavior of the brush in terms of the grafting density and the amount of lubricant present. Regarding the wetting behavior, we study a sessile droplet on top of the brush. The droplet consists of nonbonded particles that form a dense phase. Our model and choice of parameters result in the formation of a wetting ridge and in the cloaking of the droplet by the lubricant; i.e., the lubricant chains creep up onto the droplet and eventually cover its surface completely. Cloaking is a phenomenon that is observed experimentally and is of integral importance to the dynamics of sliding droplets. We quantify the cloaking in terms of its thickness, which increases with the amount of lubricant present. The analysis reveals a well-defined transition point where the cloaking sets in. We propose a thermodynamic theory to explain this behavior. In addition, we investigate the dependence of the contact angles on the size of the droplet and the possible effect of line tension. We quantify the variation of the contact angle with the curvature of the contact line on a lubricant free brush and find a negative value for the line tension. Finally we investigate the effect of cloaking/lubrication on the contact angles and the wetting ridge. We find that lubrication and cloaking reduce the contact angles by a couple of degrees. The effect on the wetting ridge is a reduction in the extension of the brush chains near the three phase contact line, an effect that was also observed in experiments of droplets on cross-linked gels.
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Affiliation(s)
- Rodrique G M Badr
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, D-55099 Mainz, Germany
| | - Lukas Hauer
- Max Plank Institut für Polymer Forschung Mainz, Ackermannweg 10, D-55128 Mainz, Germany
| | - Doris Vollmer
- Max Plank Institut für Polymer Forschung Mainz, Ackermannweg 10, D-55128 Mainz, Germany
| | - Friederike Schmid
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, D-55099 Mainz, Germany
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8
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Gao S, Qu J, Liu Z, Liu W. Nanoscale Thin-Film Boiling Processes on Heterogeneous Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6352-6362. [PMID: 35536686 DOI: 10.1021/acs.langmuir.2c00276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
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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Affiliation(s)
- Shan Gao
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Jian Qu
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Zhichun Liu
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Wei Liu
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
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9
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Yang M, Sheng Q, Zhang H, Tang G. Water molecular bridge undermines thermal insulation of Nano-porous silica aerogels. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118176] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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10
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11
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Zhu H, Cai S, Liao G, Gao ZF, Min X, Huang Y, Jin S, Xia F. Recent Advances in Photocatalysis Based on Bioinspired Superwettabilities. ACS Catal 2021. [DOI: 10.1021/acscatal.1c04049] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Hai Zhu
- Key Laboratory of Catalysis and Energy Materials Chemistry of Education, Hubei Key Laboratory of Catalysis and Materials Science, South-Central University for Nationalities, Wuhan 430074, People’s Republic of China
- China State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, People’s Republic of China
| | - Si Cai
- Key Laboratory of Catalysis and Energy Materials Chemistry of Education, Hubei Key Laboratory of Catalysis and Materials Science, South-Central University for Nationalities, Wuhan 430074, People’s Republic of China
| | - Guangfu Liao
- Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074, People’s Republic of China
| | - Zhong Feng Gao
- Collaborative Innovation Center of Tumor Marker Detection Technology, Equipment and Diagnosis-Therapy Integration in Universities of Shandong, Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, People’s Republic of China
| | - Xuehong Min
- Key Laboratory of Catalysis and Energy Materials Chemistry of Education, Hubei Key Laboratory of Catalysis and Materials Science, South-Central University for Nationalities, Wuhan 430074, People’s Republic of China
| | - Yu Huang
- China State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, People’s Republic of China
| | - Shiwei Jin
- Key Laboratory of Catalysis and Energy Materials Chemistry of Education, Hubei Key Laboratory of Catalysis and Materials Science, South-Central University for Nationalities, Wuhan 430074, People’s Republic of China
| | - Fan Xia
- China State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, People’s Republic of China
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12
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Sun J, Jiang X, Weisensee PB. Enhanced Water Nucleation and Growth Based on Microdroplet Mobility on Lubricant-Infused Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12790-12801. [PMID: 34699236 DOI: 10.1021/acs.langmuir.1c01559] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Lubricant-infused surfaces (LISs) can promote stable dropwise condensation and improve heat transfer rates due to a low nucleation free-energy barrier and high droplet mobility. Recent studies showed that oil menisci surrounding condensate microdroplets form distinct oil-rich and oil-poor regions. These topographical differences in the oil surface cause water microdroplets to rigorously self-propel long distances, continuously redistributing the oil film and potentially refreshing the surface for re-nucleation. However, the dynamic interplay between oil film redistribution, microdroplet self-propulsion, and droplet nucleation and growth is not yet understood. Using high-speed microscopy, we reveal that during water condensation on LISs, the smallest visible droplets (diameter: ∼1 μm, qualitatively representing nucleation) predominantly emerge in oil-poor regions due to a lower nucleation free-energy barrier. Considering the significant heat transfer performance of microdroplets (<10 μm) and transient characteristic of microdroplet movement, we compare the apparent nucleation rate density and water collection rate for LISs with oils of different viscosities and a solid hydrophobic surface at a wide range of subcooling temperatures. Generally, the lowest lubricant viscosity leads to the highest nucleation rate density. We characterize the length and frequency of microdroplet movement and attribute the nucleation enhancement primarily to higher droplet mobility and surface refreshing frequency. Interestingly and unexpectedly, hydrophobic surfaces outperform high-viscosity LISs at high subcooling temperatures but are generally inferior to any of the tested LISs at low temperature differences. To explain the observed nonlinearity between LISs and the solid hydrophobic surface, we introduce two dominant regimes that influence the condensation efficiency: mobility-limited and coalescence-limited. We compare these regimes based on droplet growth rates and water collection rates on the different surfaces. Our findings advance the understanding of dynamic water-lubricant interactions and provide new design rationales for choosing surfaces for enhanced dropwise condensation and water collection efficiencies.
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Affiliation(s)
- Jianxing Sun
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, Saint Louis, Missouri 63130, United States
| | - Xinyu Jiang
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, Saint Louis, Missouri 63130, United States
| | - Patricia B Weisensee
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, Saint Louis, Missouri 63130, United States
- Institute of Materials Science and Engineering, Washington University in St. Louis, Saint Louis, Missouri 63130, United States
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13
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Zhao P, Li X, Tong Y, Dong X, Qi M. Effect of the interface between magnetic particles and carrier liquids on magnetorheological properties and sedimentation of magnetorheological fluids: A molecular dynamics simulation and experimental insights. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117377] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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14
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Mao P, Gao S, Liu W, Liu Z. Head-on Collision of Two Nanodroplets on a Solid Surface: A Molecular Dynamics Simulation Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12346-12355. [PMID: 34648710 DOI: 10.1021/acs.langmuir.1c01849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Most researchers focus on the collision of a single droplet with a solid surface, while it is common for a droplet to collide with a sessile droplet on a solid surface in reality. This study performed the head-on collision of two nanodroplets on a solid surface using the molecular dynamics simulation method. The effects of impact velocity, interaction intensity between solid and liquid atoms, and the solid fraction of the surface on the collision process are studied with independent simulation cases. The maximum spreading factor and the dimensionless maximum spreading time are recorded and calculated to describe the collision process quantitatively. The simulation results indicate that the maximum spreading factor depends more on the solid fraction than the interaction intensity since it does not fundamentally change the wetting state of the droplet at its maximum spreading state. Because of two different effects, the maximum dimensionless spreading time decreases first and then increases with the interaction intensity, and both effects weaken with the increase of impact velocity. As the solid fraction increases, the maximum spreading factor increases significantly at high impact velocity, and the maximum dimensionless spreading time first decreases and then increases because the wetting state of the coalescent droplet at the maximum spreading moment gradually changes from the Wenzel state to the Cassie state. In general, the initial wetting state of the sessile droplet and the wetting state of the coalescent droplet at the maximum spreading moment have important effects on the maximum spreading factor and the maximum spreading time. We establish a theoretical prediction model for the maximum spreading factor on a smooth surface based on energy conservation with quite good accuracy. This research has improved our understanding of the head-on collision process of two nanodroplets on a solid surface.
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Affiliation(s)
- Peng Mao
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Shan Gao
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Wei Liu
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhichun Liu
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
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15
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Pu JH, Wang SK, Sun J, Wang W, Wang HS. Growth and self-jumping of single condensed droplet on nanostructured surfaces: A molecular dynamics simulation. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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16
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Niu D, Gao H, Tang G, Yan Y. Droplet Nucleation and Growth in the Presence of Noncondensable Gas: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9009-9016. [PMID: 34296609 DOI: 10.1021/acs.langmuir.1c00961] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The presence of noncondensable gas (NCG) followed by undesirable heat transfer deterioration cannot be avoided in some situations. In this work, droplet nucleation and growth for the Ar-Ne mixed system are investigated using molecular dynamics simulation. Different droplet state transition modes corresponding to the subcooling degree or NCG content are obtained. The interaction between NCG and a droplet caused by gas enrichment near the solid surface is considered to explain the droplet wetting state during the condensation process. Finally, the disappearance mechanism of the flooding mode on the nanostructured surface under a large amount of NCG is clarified from the nanoscale, which could encourage a clear understanding of the NCG effect on dropwise condensation heat transfer on nanostructured superhydrophobic surfaces.
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Affiliation(s)
- Dong Niu
- Institute of Refrigeration & Cryogenics Engineering, Dalian Maritime University, Dalian 116026, P. R. China
| | - Hongtao Gao
- Institute of Refrigeration & Cryogenics Engineering, Dalian Maritime University, Dalian 116026, P. R. China
| | - Guihua Tang
- MOE Key Laboratory of Thermo-Fluid Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yuying Yan
- Fluids & Thermal Engineering Research Group, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
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17
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Gunjan MR, Kumar A, Raj R. Cloaked Droplets on Lubricant-Infused Surfaces: Union of Constant Mean Curvature Interfaces Dictated by Thin-Film Tension. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:6601-6612. [PMID: 34028279 DOI: 10.1021/acs.langmuir.0c03560] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
It has been recently shown that small-volume droplets on lubricant-infused surfaces (LISs) can be analytically modeled using rotationally symmetric constant mean curvature (CMC) surfaces. While such an approach is available for noncloaked droplets, a similar approach is missing for cloaked droplets that are ubiquitous in a number of LIS-related applications. The presence of a thin cloaking film on the top spherical cap portion and its gradual transition to a bulk meniscus remain unaddressed for its implications on the interfacial profile of cloaked droplets. Here, we take into account the cloaking film tension and the disjoining pressure to present a mean curvature-based framework for modeling cloaked droplets on LISs. The transition of the bulk meniscus to a thin film is formulated as a transition regime, which is then modeled as a single imaginary point akin to the Neumann point of noncloaked droplets. We next show that the shape of a small droplet on a LIS essentially obeys a simple fundamental mean curvature relation that changes forms depending on the regimes of lubrication and whether the droplet is cloaked or noncloaked. We validate our framework with the droplet profiles recorded during the evaporation of cloaked droplets in our experiments, as well as those published in the literature. In addition, we also demonstrate the ability to model the shapes of floating droplets on LISs reported in the literature. In addition to quantifying the effect of disjoining pressure on interfacial profiles, we importantly unmask the behavior of the contact line, which is optically covered by the lubricant meniscus around the droplets on LISs.
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Affiliation(s)
- Madhu Ranjan Gunjan
- Thermal and Fluid Transport Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Patna, R113, Block III, Bihta, Bihar 801103, India
| | - Alok Kumar
- Thermal and Fluid Transport Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Patna, R113, Block III, Bihta, Bihar 801103, India
| | - Rishi Raj
- Thermal and Fluid Transport Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Patna, R113, Block III, Bihta, Bihar 801103, India
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18
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Etha SA, Desai PR, Sachar HS, Das S. Wetting Dynamics on Solvophilic, Soft, Porous, and Responsive Surfaces. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02234] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Sai Ankit Etha
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Parth Rakesh Desai
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Harnoor Singh Sachar
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
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19
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Wang C, Guo Z. A comparison between superhydrophobic surfaces (SHS) and slippery liquid-infused porous surfaces (SLIPS) in application. NANOSCALE 2020; 12:22398-22424. [PMID: 33174577 DOI: 10.1039/d0nr06009g] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Slippery liquid-infused porous surfaces inspired by the Nepenthes pitcher plant exhibit excellent performances and are known for their extremely low contact angle hysteresis (<5°) and smooth surface. In contrast, superhydrophobic surfaces (SHS) exhibit poor pressure stability, difficulty in self-healing, and difficulty in removing low surface tension liquids or organic solvents, which can affect the stable air layer. Thus, these issues can be avoided through the replacement of SHS with slippery liquid infused porous surfaces (SLIPS). In this review, the theoretical models of SHS and SLIPS are classified initially, and several design standards for the preparation of SLIPS are briefly described. Then, we focus on comparing the differences in the application of SHS and SLIPS, such as pressure stability, transparency, and droplet manipulation. However, there are still some problems that need to be improved during the preparation of SLIPS, such as the evaporation of the lubricant layer, the use of a lubricant layer of toxic perfluoropolyether and other substances, and easily lost nanostructured lubricant layer. Accordingly, several new improved methods are proposed in this review, and finally, the potential applications and development prospects of SLIPS are presented.
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Affiliation(s)
- Chenghong Wang
- Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062, P. R. China.
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20
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Tang G, Niu D, Guo L, Xu J. Failure and Recovery of Droplet Nucleation and Growth on Damaged Nanostructures: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13716-13724. [PMID: 33147034 DOI: 10.1021/acs.langmuir.0c02809] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The condensate flooding during dropwise condensation causes serious deterioration in heat transfer performance. In this study, the three-dimensional large-scale molecular dynamics simulation is carried out to investigate the droplet state transition from local flooding mode to Wenzel or from Wenzel to Cassie due to the droplet coalescence under the effect of nanostructure size. In particular, the effect of nanostructure breakage on droplet nucleation and growth is discussed to reveal the mechanism of dropwise condensation heat transfer deterioration. As a potential solution, the lubricant-impregnated surface is proposed to recover the preferred Cassie state by regulating the dynamic wetting characteristics of droplets, and thus the detrimental effect of nanostructure breakage could be effectively avoided.
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Affiliation(s)
- Guihua Tang
- MOE Key Laboratory of Thermo-Fluid Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Dong Niu
- MOE Key Laboratory of Thermo-Fluid Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Lin Guo
- MOE Key Laboratory of Thermo-Fluid Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Jinliang Xu
- Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization, North China Electric Power University, Beijing 102206, China
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