Molecular dynamics study on water evaporation/condensation parameters

Skarbalius, Gediminas; Džiugys, Algis; Misiulis, Edgaras; Navakas, Robertas

doi:10.1007/s10404-021-02482-3

Cited by 8 publications

(5 citation statements)

References 47 publications

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“…[26] and [27] also evaluated the distribution function at points similar to those chosen by Refs. [30] and [31] and the results match well. Furthermore, nonequilibrium thermodynamic analysis has shown that the temperature of the liquid-vapor interface is very close to the temperature of the bulk liquid adjacent to the interface [32].…”

Section: Introductionsupporting

confidence: 59%

“…Frezzotti and Barbante also observed the half-range Maxwellian from their Enskog-Vlasov model calculations [28]. We note that other MD studies appear to contradict these findings [29][30][31], but the discrepancy appears to arise only from the choice of interphase boundary position. References [26] and [27] evaluated the distribution function at the center of the transition layer (the angstrom-scale region where the density transitions from liquid to vapor) while Refs.…”

Section: Introductionmentioning

confidence: 56%

“…References [26] and [27] evaluated the distribution function at the center of the transition layer (the angstrom-scale region where the density transitions from liquid to vapor) while Refs. [30] and [31] explicitly chose a "vapor boundary" in the vapor region outside of the transition layer. In fact, Refs.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Schrage Equation for Kinetically Limited Evaporation and Condensation

Vaartstra

Lienhard

et al. 2022

Journal of Heat Transfer

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The Schrage equation is commonly used in thermofluid engineering to model high-rate liquid-vapor phase change of pure fluids. Although shortcomings of this simple model were pointed out decades ago and more rigorous models have emerged from the kinetic theory community, Schrage's equation continues to be widely used. In this paper, we quantify the accuracy of the Schrage equation for evaporation and condensation of monatomic and polyatomic fluids at the low to moderately high flux operating conditions relevant to thermofluid engineering applications. As a high-accuracy reference, we numerically solve a BGK-like model equation for polyatomic vapors that has previously been shown to produce accurate solutions to the Boltzmann transport equation. We observe that the Schrage equation overpredicts heat/mass fluxes by ~15% for fluids with accommodation coefficients close to unity. For fluids with smaller accommodation coefficients, such as water, the Schrage equation yields more accurate flux estimates. We find that the Mott-Smith-like moment methods developed for liquid-vapor phase change are much more accurate than the Schrage equation, achieving heat/mass flux estimates that deviate by less than 1% (evaporation) and 4% (condensation) from the reference solution. In light of these results, we recommend using the moment-method equations instead of the Schrage equation. We also provide: tables with our high-accuracy numerical data for evaporation of any fluid and condensation of saturated water vapor; engineering equations fit to our data; and code for moment method calculations of evaporation and condensation.

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Section: Introductionsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 56%

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Revisiting the Schrage Equation for Kinetically Limited Evaporation and Condensation

Vaartstra

Lienhard

et al. 2022

Journal of Heat Transfer

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“…In our study, the water accommodation coefficient (α) was calculated by tracking the trajectory and phase-state of water molecules during a 100 ns trajectory for each simulated system. We note that even based on atomistic trajectories determined using MD simulations, there are several possible ways of defining whether an impinging water molecule is absorbed or reflected and, as a result, different reported α-values (ranging from 0.9 to 1.0) even for the flat surface of pure liquid water (Julin et al, 2013;Barclay and Lukes, 2019;Skarbalius et al, 2021;Tsuruta and Nagayama, 2004;Ohashi et al, 2020). To highlight the impacts of curvature, salinity, and organic coatings on α and compare our results with those of other studies, we report normalized values as α * = α/α 0,w , where α 0,w is the value reported for the flat surface of pure liquid water in the same study.…”

Section: Accommodation Coefficient Of Water and Condensation Kineticsmentioning

confidence: 97%

Microphysics of liquid water in sub-10 nm ultrafine aerosol particles

Bourg

2022

Preprint

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Abstract. Ultrafine aerosol particles with sizes smaller than 50 nm have been shown in recent studies to serve as a large source of cloud condensation nuclei (CCN) that can promote additional cloud droplet formation under supersaturation conditions. Knowledge of the microphysics of liquid water in these droplets remains limited, particularly in the sub-10 nm particle size range, due to experimental and theoretical challenges associated with the complexity of aerosol components and the small length scales of interest (e.g., difficulty of precisely sampling the liquid-air interface, questionable validity of mean-field theoretical representations). Here, we carried out molecular dynamics (MD) simulations of aerosol particles with diameters between 1 and 10 nm and characterized atomistic-level structure and water dynamics in well-mixed and phase-separated system with different particle sizes, NaCl salinities, and organic surface loadings as a function of distance from the time-averaged Gibbs dividing interface or instantaneous water-air interface. We define a sphericity factor (Φ) that can shed light on the phase-mixing state of nanodroplets, and we reveal an unexpected dependence of mixing state on droplet size. Our results also evidence an ion concentration enhancement in ultrafine aerosols, which should modulate salt nucleation kinetics in ultrafine sea salt aerosols, and provide detailed characterization of the influence of droplet size on surface tension and on water self-diffusivity near the interface. Analysis of water evaporation free energy and water activity demonstrates the validity of the Kelvin equation and Köhler theory at droplet sizes larger than 4 nm under moderate salinities and organic loadings and the need for further extension to account for ion concentration enhancement in sub-10 nm aerosols, droplet-size-dependent phase separation effects, and a sharp decrease in the cohesiveness of liquid water in sub-4 nm droplets. Finally, we show that an idealized fractional surface coating factor (fs) can be used to categorize and reconcile water accommodation coefficients (α*) observed in MD simulations and experimental results in the presence of organic coatings, and we resolve the droplet-size dependence of α*.

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“…[57] and are listed in Table 1. The long-range electrostatic interactions beyond the cut-off distance were handled by the Particle-particle particle-mesh (PPPM) method with the accuracy of 2 × 10 −5 [58]. To avoid unphysical slab-slab interactions, the system was treated as periodic in z-direction; however, an empty volume was inserted between the channel walls and dipole inter-slab interactions were removed.…”

Section: Poiseuille Flow Simulation Detailsmentioning

confidence: 99%

Molecular Dynamics Study on Water Flow Behaviour inside Planar Nanochannel Using Different Temperature Control Strategies

et al. 2021

Self Cite

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In the present paper, molecular dynamics simulations were performed to study the influence of two temperature control strategies on water flow behaviour inside planar nanochannel. In the simulations, the flow was induced by the force acting on each water molecule in the channel. Two temperature control strategies were considered: (a) frozen wall simulations, in which the dynamics of confining wall atoms was not solved and the thermostat was applied to the water, and (b) dynamic wall simulations, in which the dynamics of confining wall atoms was solved, and the thermostat was applied to walls while water was simulated in the microcanonical ensemble. The simulation results show that the considered temperature control strategies has no effect on the shape of the water flow profile, and flow behaviour in the channel is well described by the Navier–Stokes equation solution with added slip velocity. Meanwhile, the slip velocity occurring at the boundaries of the channel is linearly dependent on the magnitude of the flow inducing force in both frozen wall and dynamic wall simulations. However, the slip velocity is considerably greater in simulations when the wall dynamics are solved in contrast to the frozen wall simulations.

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Molecular dynamics study on water evaporation/condensation parameters

Cited by 8 publications

References 47 publications

Revisiting the Schrage Equation for Kinetically Limited Evaporation and Condensation

Revisiting the Schrage Equation for Kinetically Limited Evaporation and Condensation

Microphysics of liquid water in sub-10 nm ultrafine aerosol particles

Molecular Dynamics Study on Water Flow Behaviour inside Planar Nanochannel Using Different Temperature Control Strategies

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