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Ozsipahi M, Beskok A. Nanoscale Meniscus Dynamics in Evaporating Thin Films: Insights from Molecular Dynamics Simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:18499-18508. [PMID: 38048562 DOI: 10.1021/acs.langmuir.3c02830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2023]
Abstract
Evaporation studies are focused on unraveling heat transfer and flow dynamics near the solid-liquid-vapor contact line, particularly focusing on the meniscus, which encompasses the nonevaporating adsorbed layer, thin-film, and bulk meniscus regions. Continuum models assume that there are no evaporating adsorbed layers due to the strong intermolecular forces. However, recent molecular dynamics (MD) simulations have unveiled the significant role of adsorbed layers in thin-film evaporation. Leveraging a recently published energy-based interface detection method, the current study presents nonequilibrium MD simulation results for thin-film evaporation from a phase-change-driven nanopump using liquid argon confined between parallel platinum plates. Notably, unlike the transient simulations often encountered in the literature, the simulation system achieves a statistically steady transport. In this context, we showcase the shapes of the evaporating menisci for two distinct channel heights, 8 and 16 nm, and elucidate the underlying flow physics through velocity vectors and temperature contours. This comprehensive investigation advances our understanding of thin-film evaporation and its mechanisms, offering insights that span from nanoscale phenomena to broader thermal management applications.
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Affiliation(s)
- Mustafa Ozsipahi
- U.S. DEVCOM Army Research Laboratory, Adelphi, Maryland 20783-1197, United States
| | - Ali Beskok
- Southern Methodist University, Dallas, Texas 75205, United States
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Yesudasan S. The Critical Diameter for Continuous Evaporation Is between 3 and 4 nm for Hydrophilic Nanopores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6550-6560. [PMID: 35580311 DOI: 10.1021/acs.langmuir.2c00159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Evaporation studies of water using classical molecular dynamics simulations are largely limited due to their high computational expense. This study addresses that issue by developing coarse-grained molecular dynamics models based on Morse potential. Models are optimized based on multi-temperature and at room temperature using machine learning techniques like Genetic Algorithm, Nelder-Mead algorithm, and Strength Pareto Evolutionary Algorithm. The multi-temperature-based model named as Morse-D is found to be more accurate than the single temperature model in representing the water properties at higher temperatures. Using this Morse-D water model, evaporation from hydrophilic nanopores with pore diameter varying from 2 to 5 nm is studied. Our results show that the critical diameter to initiate continuous evaporation at nanopores lies between 3 and 4 nm. A maximum heat flux of 21.3 kW/cm2 is observed for a pore diameter of 4.5 nm and a maximum mass flow rate of 16.2 ng/s for a pore diameter of 5 nm. The observed heat flux is an order of magnitude times larger than the currently reported values from experiments in the literature for water, which indicates that we need to focus on nanoscale evaporation to enhance the critical heat flux.
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Affiliation(s)
- Sumith Yesudasan
- Department of Engineering Technology, Sam Houston State University, Huntsville, Texas 77341, United States
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Ozsipahi M, Akkus Y, Nguyen CT, Beskok A. Energy-Based Interface Detection for Phase Change Processes of Monatomic Fluids in Nanoconfinements. J Phys Chem Lett 2021; 12:8397-8403. [PMID: 34435788 DOI: 10.1021/acs.jpclett.1c02517] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
An energy-based liquid-vapor interface detection method is presented using molecular dynamics simulations of liquid menisci confined between two parallel plates under equilibrium and evaporation/condensation conditions. This method defines the liquid-vapor interface at the location where the average kinetic energy of atoms first exceeds the average potential energy imposed by all neighboring molecules. This definition naturally adapts to the location of the menisci relative to the walls and can properly model the behavior of the liquid adsorbed layers. Unlike the density cutoff methods frequently used in the literature that suffer from density layering effects, this new method gives smooth and continuous liquid-vapor interfaces in nanoconfinements. Surface tension values calculated from the equilibrium MD simulations match the Young-Laplace equation better when using the radius of curvatures calculated from this method. Overall, this energy-based liquid-vapor interface detection method can be used in studies of nanoscale phase change processes and other relevant applications.
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Affiliation(s)
- Mustafa Ozsipahi
- Southern Methodist University, Dallas, Texas 75205, United States
| | | | | | - Ali Beskok
- Southern Methodist University, Dallas, Texas 75205, United States
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Liu R, Liu Z. Enhanced Evaporation of Ultrathin Water Films on Silicon-Terminated Si 3N 4 Nanopore Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10046-10051. [PMID: 34383493 DOI: 10.1021/acs.langmuir.1c01212] [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
Water evaporation confined in nanoscale is a ubiquitous phenomenon in nature and has crucial importance in a broad range of technical applications. With the nonequilibrium molecular dynamics simulation, we elucidate nanothin water film evaporation characteristics on a silicon nitride nanopore membrane considering the effects of pore size and pore chemistry. Pore chemistry plays the main role in regulating the evaporation flux. The terminated Si atoms on the pore surface lead to a higher evaporation intensity than the N ones. We attribute this enhancement to the transition of the structural properties of fluid, where liquid molecules are packed loosely and disorderedly under the inducement of terminated silicon atoms. The findings in the present work can contribute to the fundamental understanding of the nanopore-enhanced evaporation process and provide new guidance to the design of advanced nanopore membrane materials.
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Affiliation(s)
- Runkeng Liu
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Zhenyu Liu
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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Davoodabadi A, Ghasemi H. Evaporation in nano/molecular materials. Adv Colloid Interface Sci 2021; 290:102385. [PMID: 33662599 DOI: 10.1016/j.cis.2021.102385] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 02/17/2021] [Accepted: 02/18/2021] [Indexed: 12/29/2022]
Abstract
Evaporation is a physical phenomenon with fundamental significance to both nature and technology ranging from plant transpiration to DNA engineering. Various analytical and empirical relationships have been proposed to characterize evaporation kinetics at macroscopic scales. However, theoretical models to describe the kinetics of evaporation from nano and sub-nanometer (molecular) confinements are absent. On the other hand, the fast advancements in technology concentrated on development of nano/molecular-scale devices demand appropriate models that can accurately predict physics of phase-change in these systems. A thorough understanding of the physics of evaporation in nano/molecular materials is, thus, of critical importance to develop the required models. This understanding is also crucial to explain the intriguing evaporation-related phenomena that only take place when the characteristic length of the system drops to several nanometers. Here, we comprehensively review the underlying physics of evaporation phenomenon and discuss the effects of nano/molecular confinement on evaporation. The role of liquid-wall interface-related phenomena including the effects of disjoining pressure and flow slippage on evaporation from nano/molecular confinements are discussed. Different driving forces that can induce evaporation in small confinements, such as heat transfer, pressure drop, cavitation and density fluctuations are elaborated. Hydrophobic confinement induced evaporation and its potential application for synthetic ion channels are discussed in detail. Evaporation of water as molecular clusters rather than isolated molecules is discussed. Despite the lack of experimental investigations on evaporation at nanoscale, there exist an extensive body of literature that have applied different simulation techniques to predict the phase change behavior of liquids in nanoconfinements. We infer that exploring the effect of electrostatic interactions and flow slippage to enhance evaporation from nanoconduits is an interesting topic for future endeavors. Further future studies could be devoted to developing nano/molecular channels with evaporation-based gating mechanism and utilization of 2D materials to tune energy barrier for evaporation leading to enhanced evaporation.
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Pu JH, Wang SK, Sun J, Wang W, Wang HS. Stable and Efficient Nanofilm Pure Evaporation on Nanopillar Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:3731-3739. [PMID: 33730854 DOI: 10.1021/acs.langmuir.1c00236] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
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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Affiliation(s)
- Jin Huan Pu
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Si Kun Wang
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Jie Sun
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Wen Wang
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Hua Sheng Wang
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, United Kingdom
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Temperature Effect on Capillary Flow Dynamics in 1D Array of Open Nanotextured Microchannels Produced by Femtosecond Laser on Silicon. NANOMATERIALS 2020; 10:nano10040796. [PMID: 32326234 PMCID: PMC7221948 DOI: 10.3390/nano10040796] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/13/2020] [Accepted: 04/14/2020] [Indexed: 01/04/2023]
Abstract
Capillary flow of water in an array of open nanotextured microgrooves fabricated by femtosecond laser processing of silicon is studied as a function of temperature using high-speed video recording. In a temperature range of 23-80 °C, the produced wicking material provides extremely fast liquid flow with a maximum velocity of 37 cm/s in the initial spreading stage prior to visco-inertial regime. The capillary performance of the material enhances with increasing temperature in the inertial, visco-inertial, and partially in Washburn flow regimes. The classic universal Washburn's regime is observed at all studied temperatures, giving the evidence of its universality at high temperatures as well. The obtained results are of great significance for creating capillary materials for applications in cooling of electronics, energy harvesting, enhancing the critical heat flux of industrial boilers, and Maisotsenko cycle technologies.
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Affiliation(s)
- Sumith Yesudasan
- Department of Mechanical Engineering, University of Jamestown, Jamestown, ND, USA
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Kolegov KS, Barash LY. Joint effect of advection, diffusion, and capillary attraction on the spatial structure of particle depositions from evaporating droplets. Phys Rev E 2019; 100:033304. [PMID: 31640055 DOI: 10.1103/physreve.100.033304] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Indexed: 11/07/2022]
Abstract
A simplified model is developed, which allows us to perform computer simulations of the particles transport in an evaporating droplet with a contact line pinned to a hydrophilic substrate. The model accounts for advection in the droplet, diffusion, and particle attraction by capillary forces. On the basis of the simulations, we analyze the physical mechanisms of forming of individual chains of particles inside the annular sediment. The parameters chosen correspond to the experiments of Park and Moon [Langmuir 22, 3506 (2006)LANGD50743-746310.1021/la053450j], where an annular deposition and snakelike chains of colloid particles have been identified. The annular sediment is formed by advection and diffusion transport. We find that the close packing of the particles in the sediment is possible if the evaporation time exceeds the characteristic time of diffusion-based ordering. We show that the chains are formed by the end of the evaporation process due to capillary attraction of particles in the region bounded by a fixing radius, where the local droplet height is comparable to the particle size. At the beginning of the evaporation, the annular deposition is shown to expand faster than the fixing radius moves. However, by the end of the process, the fixing radius rapidly outreaches the expanding inner front of the ring. The snakelike chains are formed at this final stage when the fixing radius moves toward the symmetry axis.
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Affiliation(s)
- K S Kolegov
- Astrakhan State University, 414056 Astrakhan, Russia.,Volga State University of Water Transport, Caspian Institute of Maritime and River Transport, 414014 Astrakhan, Russia.,Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia
| | - L Yu Barash
- Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia.,National Research University Higher School of Economics, 101000 Moscow, Russia
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Koklu A, El Helou A, Raad PE, Beskok A. Characterization of Temperature Rise in Alternating Current Electrothermal Flow Using Thermoreflectance Method. Anal Chem 2019; 91:12492-12500. [DOI: 10.1021/acs.analchem.9b03238] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Anil Koklu
- Department of Mechanical Engineering, Southern Methodist University, Dallas, Texas 75205, United States
| | - Assaad El Helou
- Department of Mechanical Engineering, Southern Methodist University, Dallas, Texas 75205, United States
| | - Peter E. Raad
- Department of Mechanical Engineering, Southern Methodist University, Dallas, Texas 75205, United States
| | - Ali Beskok
- Department of Mechanical Engineering, Southern Methodist University, Dallas, Texas 75205, United States
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