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by Lyle Long
1999, Journal of Thermophysics and Heat Transfer
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1998, Journal of Thermophysics and Heat Transfer
1997, 35th Aerospace Sciences Meeting and Exhibit
This work presents a method to predict transport properties of supercritical and near critical fluids using a microscopical approach by molecular dynamics with Green-Kubo method. The first results were obtained for argon. The fluid was modeled by spherical Lennard-Jones pair-potentials with parameters adjusted to experimental vapor liquid equilibrium. Good agreement between predictions from simulation and experimental data from NIST is found for shear viscosity and thermal conductivity. The method can be extended for other fluids and mixtures and can be an useful tool to predict properties when experimental data is not available.
1997, 33rd Joint Propulsion Conference and Exhibit
2005, The Journal of Supercritical Fluids
2010, Industrial Engineering Chemistry Research
2009
Endohedral adsorption properties of ethylene and ethane onto single-walled carbon nanotubes were investigated using a united atom (2CLJQ) and a fully atomistic (AA-OPLS) force fields, by Grand Canonical Monte Carlo and Molecular Dynamics techniques. Pure fluids were studied at room temperature, T=300 K, and in the pressure ranges 4×10−4<p<47.1 bar (C2H4) and 4×10−4<p<37.9 bar (C2H6). In the low pressure region, isotherms differ quantitatively depending on the intermolecular potential used, but show the same qualitative features. Both potentials predict that ethane is preferentially adsorbed at low pressures, and the opposite behavior was observed at high loadings. Isosteric heats of adsorption and estimates of low pressure Henry’s constants, confirmed that ethane adsorption is the thermodynamically favored process at low pressures. Binary mixtures of C2H4/C2H6 were studied under several (p,T) conditions and the corresponding selectivities towards ethane, S, were evaluated. Small values of S<4 were found in all cases studied. Nanotube geometry plays a minor role on the adsorption properties, which seem to be driven at lower pressures primarily by the larger affinity of the alkane towards the carbon surface and at higher pressures by molecular volume and packing effects. The fact that the selectivity towards ethane is similar to that found earlier on carbon slit pores and larger diameter nanotubes points to the fact that the peculiar 1-D geometry of the nanotubes provides no particular incentive for the adsorption of either species.
2014, Journal of Chemical & Engineering Data
2020, ScienceDirect
This paper presents molecular dynamics simulations to study on the effects of external driving force and boundary wall temperature on the density, velocity and temperature profiles of Argon fluid atoms, flowed in a platinum microchannel with square section. The Argon atoms are structured in three regions. Two thin liquid film of Argon sandwich central vapor zone. Applying wall temperatures in the range of 84K to 133K prepares boiling condition which causes liquid atoms move from lateral layers to central bins of microchannel. Afterward, density of central layers of microchannel increases which is highlighted by sampling data after equilibrium condition of system energy in 4 time steps. It is concluded that augmentation of external driving forces on the Argon atoms from 0.002 to 0.01 and 0.02 eV/Angstrom can increase flow temperature from 180K to 1920K and 7570K, respectively which is noticeable for practical application such as medical especially in Cryosurgery. Moreover, augmentation of external forces can increase velocity profiles of Argon fluid flow. Generally, density was independent from variation of external force and boundary wall temperature in the studied limits. Also, alteration of boundary wall temperature does not play very important role on the velocity and temperature of Argon fluid inside microchannel.
2015, The Journal of Physical Chemistry B
2007, Asia-Pacific Journal of Chemical Engineering
2016, Journal of Propulsion and Power
Large-eddy simulations are carried out for the coaxial injection of liquid nitrogen and preheated hydrogen at supercritical pressures. The conditions are similar to that in typical liquid-propellant rocket combustors. By using nitrogen as a model gas, the mixing process is studied without the interference with chemical reactions. An analysis of the thermodynamic conditions that arise in the shear layer reveals that local phase separation may occur if the injection condition is transcritical. A novel volume-translation method on the basis of the cubic Peng–Robinson equation of state is introduced for the use in multispecies large-eddy simulations and is tested for both trans- and supercritical injection conditions. The new thermodynamic model corrects the deficiencies of the Peng–Robinson equation of state in the transcritical regime at minimal extra computational cost. Two independently developed large- eddy simulation codes are used for the simulations and the results are compared. The outcome indicates that the flowfield is mainly controlled by the turbulence on the resolved scales, and an accurate model for the fluid’s thermodynamic state is more important than the subgrid-scale turbulence model or the details of the code architecture. A comparison with available experimental data shows that important flow features are well predicted.
The accurate knowledge of thermophysical properties of natural gas mixtures is of great importance for practical purposes for the gas industry from exploration stages to final customer use (Jaescke et al., 2002; Wagner & Kleinrahm, 2004; Gallagher, 2006). Two main properties are required by the oil and natural gas industry: i) phase equilibria and ii) pressure–density–temperature (PρT) data.
2007
We present non-equilibrium molecular dynamics simulations of liquid argon flow through nano-channels formed by two infinite krypton plates. Density, velocity and temperature distributions across the channel are studied for channels widths in the range 2.65σ-18.58σ (σ is the argon atom diameter). For small channels (2.65σ-7.9σ) the fluid is ordered in layers and this ordering persists close to the walls even for wider channels. Velocity profiles in small channels deviate from the parabolic behavior predicted by continuum theory. The no-slip condition breaks down in small channels for all external forces and system temperatures studied while for large channels it is always satisfied. For channels of intermediate width the validity of the no-slip condition depends on the system temperature and the magnitude of the driving force. Temperature distribution remains uniform across the channel for values of the driving force below a threshold value which depends on channel width. We calculated also the diffusion coefficient, D, along the flow (x-direction) and across the channel (z-direction). The ratio Dz/Dx increases as the channel width increases with diffusion being higher in layers close to the center of the flow. Acknowledgment: The authors acknowledge financial support of the Hellenic Secretariat for Research & Technology under grant pened-03-uth-3337.
2006, Chemical Physics
2008, Molecular Simulation
2006, The Journal of Chemical Physics
2009, Physical Review B
We report nonequilibrium molecular dynamics study of heat transfer in binary Lennard-Jones superlattices. The influence of the characteristic height of the interface roughness and the superlattice period on the in-plane thermal conductivity is reported. We observe that in-plane thermal conductivity first decreases with an increase in the characteristic height of the roughness. For perfectly periodic roughness, it seems that the
2010, The Journal of chemical physics
2010, Journal of Chemical and Engineering Data
2016, ScienceDirect
LAMMPS code is used to simulate three-dimensional Poiseuille flow. Velocity, temperature and density profiles have been obtained, and agglutination of nanoparticles has been discussed. Using of nanoparticles raises thermal conduction in the channel. a b s t r a c t In this paper, simulation of Poiseuille flow within nanochannel containing Copper and Platinum particles has been performed using molecular dynamic (MD). In this simulation LAMMPS code is used to simulate three-dimensional Poiseuille flow. The atomic interaction is governed by the modified Lennard-Jones potential. To study the wall effects on the surface tension and density profile, we placed two solid walls, one at the bottom boundary and the other at the top boundary. For solid-liquid interactions, the modified Lennard-Jones potential function was used. Velocity profiles and distribution of temperature and density have been obtained, and agglutination of nanoparticles has been discussed. It has also shown that with more particles, less time is required for the particles to fuse or agglutinate. Also, we can conclude that the agglutination time in nanochannel with Copper particles is faster that in Platinum nanoparticles. Finally, it is demonstrated that using nanoparticles raises thermal conduction in the channel.
2019, ScienceDirect
Present work studies effects of presence of surface roughness elements with cone geometry on the boiling flow behavior of Argon fluid inside microchannels which are affected by different boundary wall temperatures using molecular dynamic simulation method. Firstly, microchannel is simulated with smooth surfaces under boundary wall temperatures of 84 K, 96 K, 108 K, 114 K and 133 K to prepare boiling condition for Argon atoms. Microchannel surfaces are roughened by cone shape of roughness elements and mentioned temperatures are applied on the roughened microchannel walls to be comparable with smooth one. Also, an external driving force of 0.002 eV/Å is applied on the Argon atoms at the entrance of both rough and smooth microchannels for all cases of wall temperatures. Statistical approach is employed to compare results of both microchannels. It is reported that adding roughness elements on the smooth surfaces of microchannel can extend contact surfaces of energy transfer which empowers boiling process of fluid flow. Presence of cone geometry of roughness elements causes fluid flow velocity reduction as much as 0.5-1.5%. Also, it is observed that roughness elements results in enhancement of temperature profiles of fluid. Moreover, it is found that role of roughness element in low time steps is stronger than high time step. Therefore, evolution of boiling process can reduce consequences of roughness on the flow behavior. Finally, due to ignorable consequences of roughness element on the boiling flow behavior, it is concluded that preparing very smooth surfaces is not economical for practical application such as medical micro probes to destroy abnormal or diseased tissues.
2005, The Journal of Physical Chemistry B
2005, The Journal of Chemical Physics
2011
2006, Energy Conversion and Management
2008, The Journal of Physical Chemistry B
2006, Journal of Physics-condensed Matter
2000, Chemical Physics
A new momentum impulse relaxation method for obtaining the shear viscosity of Newtonian fluids using molecular dynamics simulations is introduced. The method involves the resolution of a decaying coarse-grain Gaussian velocity profile in a properly thermostated simulation box. This localized velocity profile, along with a modification of the periodic boundary conditions, allows computations in a periodic box with minimal phonon
In this work it is presented a detailed description of the thermogravitational installation for high pressures, which is constructed with the aim to determine the influence of pressure on the thermogravitational effect. The column has been validated at atmospheric pressure with binary mixtures which coefficients are well known in the literature (4). Moreover, experimental results of the work to study the separation of binary mixtures of hydrocarbons in terms of pressure carried out in the new installation would be presented for first time.
2000, Acta Physica Slovaca. Reviews and Tutorials
2005, The Journal of Physical Chemistry B
2008, Fluid Phase Equilibria
2009, High Performance Computing in Science and Engineering '08
2006, Journal of Physics: Condensed Matter
2019, ScienceDirect
The present study used molecular dynamics (MD) simulation to study the effects of external forces on the fluid flow passing through a nanochannel with different shapes of the interior wall. To this end, molecular dynamics simulation was employed to investigate the atomic arrangement and stability of the fluid inside a nanochannel in both presence and absence of rectangular and square cuboid, ellipsoid, and hemispheroid roughness. Moreover, the number density, velocity and temperature of argon flowing inside a Platinum nanochannel were investigated for a time step of 1,000,000 at external forces of 0.002, 0.0018, 0.0017, and 0.0014 eV/Å. The results obtained for each of the aforementioned models were compared with respect to the different thrust forces. Our results show that as the driving force increases from 0.0014 to 0.002 eV/Å, the velocity at the center of the nanochannel is increased approximately from 1.7 to 3.6 Å/ps while the velocity near the wall increases approximately from 0.5 to 1.4 Å/ps. Also, the temperature at the center of the nanochannel increases approximately from 355.2 to 536 K while the temperature near the wall increases approximately from 206.5 to 237.6 K.
2012, Journal of Molecular Liquids
The approach of using molecular dynamics (MD) for mimicking the dynamics of nanoparticles dispersion in different fluids is increasing since last decade. This vast increment utilizes computational softwares to mimick distictive aspects of experimental conditions. The technique of MD further makes it easier for understanding conditions of physical and chemical interactions that exist in nanofluid system. However, this review explains the procedure and implication on how to simulate the nanofluid system using molecular dynamics. Further, it is made easier for the reader for applying the technique, by good software recommendations and step by step procedure are given for utilization of successful nanofluid simulations.