Molecular Dynamics Simulations of Translational Thermal Accommodation Coefficients for Time-Resolved LII

2008 ◽  
Author(s):  
K. J. Daun ◽  
F. Liu ◽  
G. J. Smallwood
Keyword(s):  
Molecular Dynamics ◽  
Accommodation Coefficient ◽  
Dynamics Simulation ◽  
Gas Temperature ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Precise Knowledge ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Dynamics Simulations

Time-resolved laser-induced incandescence demands precise knowledge of the thermal accommodation coefficient, but little is known about the gas-surface scattering physics underlying this parameter. This paper presents a molecular dynamics simulation that shows how the thermal accommodation coefficient is influenced by gas molecular mass and the gas temperature. The MD results also define scattering kernels that form boundary conditions in DSMC simulations of heat and momentum transfer between soot aggregates and surrounding gas molecules.

Quantifying the Thermal Accommodation Coefficient for Iron Surfaces Using Molecular Dynamics Simulations

2015 ◽  
Author(s):  
T. A. Sipkens ◽  
K. J. Daun ◽  
J. T. Titantah ◽  
M. Karttunen
Keyword(s):  
Molecular Dynamics ◽  
Accommodation Coefficient ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Contemporary Science ◽  
Depth Analysis ◽  
Laser Induced Incandescence ◽  
Important Field ◽  
Thermal Accommodation Coefficient ◽  
Dynamics Simulations

With nanotechnology becoming an increasingly important field in contemporary science, there is a growing demand for a better understanding of energy exchange on the nanoscale. Techniques, such as time-resolved laser-induced incandescence, for example, require accurate models of gas-surface interaction to correctly predict nanoparticle characteristics. The present work uses molecular dynamics to define the thermal accommodation coefficient of various gases on iron surfaces. A more in depth analysis examines the scattering distributions from the surfaces and examines how well existing scattering kernels and classical theories can represent these distributions. The molecular dynamics-derived values are also compared to recent experimental time-resolved laser-induced incandescence studies aimed at evaluating the thermal accommodation coefficient across a range of surface-gas combinations.

Thermal Accommodation Coefficients Between Nitrogen and Soot in Laser-Induced Incandescence Experiments

2008 ◽  
Author(s):  
K. J. Daun
Keyword(s):  
Md Simulation ◽  
Accommodation Coefficient ◽  
Monte Carlo Integration ◽  
Detailed Knowledge ◽  
Gas Temperature ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient

Time-resolved laser-induced incandescence demands detailed knowledge of the thermal accommodation coefficient, but to date little is understood about the gas/surface scattering physics underlying this parameter. We present a molecular dynamics (MD) simulation that models nitrogen molecules as rigid rotors and soot as crystalline graphite at 3000 K. A Monte Carlo integration over incident gas molecular speeds and surface atomic vibrational phases yields a simulated thermal accommodation coefficient that matches the experimentally-measured value. The MD simulation is then extended to assess how α changes with gas temperature, and finally to define a Cercingnani-Lampis-Lord scattering kernel.

Thermal Accommodation Coefficients for Time-Resolved Laser-Induced Incandescence Sizing of Metal Nanoparticles in Monotomic Gases

2012 ◽  
Author(s):  
T. A. Sipkens ◽  
K. J. Daun ◽  
J. T. Titantah ◽  
M. Karttunen
Keyword(s):  
Metal Nanoparticles ◽  
Accommodation Coefficient ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Fundamental Relationship ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Molybdenum Nanoparticles ◽  
First Time

There is recent interest in adapting time-resolved laser-induced incandescence (TiRE-LII) to measure aerosolized metal nanoparticles, which requires knowledge of the thermal accommodation coefficient between the gas and the laser-energized particle. This paper presents accommodation coefficients for various metal particles in monatomic gases derived using molecular dynamics (MD). A comparative analysis of different gas/metal systems reveals a fundamental relationship between the thermal accommodation coefficient and the potential well depth. Finally, MD derived accommodation coefficients are used, for the first time, to recover particle sizes from TiRe-LII measurements made on molybdenum nanoparticles in helium and argon atmospheres.

Molecular Dynamics Simulation of Thermal Accommodation Coefficients for Laser-Induced Incandescence Sizing of Nickel Nanoparticles

2011 ◽  
Author(s):  
K. J. Daun ◽  
M. Karttunen ◽  
J. T. Titantah
Keyword(s):  
Molecular Dynamics ◽  
Nickel Nanoparticles ◽  
Accommodation Coefficient ◽  
Dynamics Simulation ◽  
Nickel Surface ◽  
Carbonaceous Particles ◽  
Thermal Accommodation ◽  
Gas Molecule ◽  
Laser Induced Incandescence ◽  
Thermal Accommodation Coefficient

While time-resolved laser-induced incandescence is most often used to characterize the size and concentration of aerosolized carbonaceous particles, it has recently been applied to aerosols containing metal nanoparticles. This calculation requires the thermal accommodation coefficient, however, which is often difficult to determine experimentally. This paper presents a molecular dynamics investigation of the thermal accommodation coefficient between laser-energized nickel nanoparticles immersed in argon, and the underlying the gas-surface scattering physics. The predicted interaction between gas molecules and the laser-energized surface depends strongly on the potential between the gas molecule and a surface atom: a Lennard-Jones 6–12 potential derived using the Lorentz-Berthelot combination rules overestimates the potential well due to a bond-order effect in the nickel, resulting in strong trapping-desorption and near-perfect thermal accommodation. A Morse potential with parameters obtained directly from ab initio free energies predicts a relatively brief interaction between the gas molecule and nickel surface, on the other hand, and a lower thermal accommodation coefficient similar to experimentally-derived values for laser-energized iron nanoparticles in argon reported in the literature.

Investigation of Thermal Accommodation Coefficients in Time-Resolved Laser-Induced Incandescence

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
K. J. Daun ◽  
G. J. Smallwood ◽  
F. Liu
Keyword(s):  
Particle Size ◽  
A Priori ◽  
Accommodation Coefficient ◽  
Particle Sizing ◽  
Time Resolved ◽  
Polyatomic Gases ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient

Accurate particle sizing through time-resolved laser-induced incandescence (TR-LII) requires knowledge of the thermal accommodation coefficient, but the underlying physics of this parameter is poorly understood. If the particle size is known a priori, however, TR-LII data can instead be used to infer the thermal accommodation coefficient. Thermal accommodation coefficients measured between soot and different monatomic and polyatomic gases show that the accommodation coefficient increases with molecular mass for monatomic gases and is lower for polyatomic gases. This latter result indicates that surface energy is accommodated preferentially into translational modes over internal modes for these gases.

Time Resolved Laser Induced Incandescence for Sizing Aerosolized Iron Nanoparticles

2014 ◽  
Author(s):  
T. A. Sipkens ◽  
N. R. Singh ◽  
K. J. Daun ◽  
N. Bizmark ◽  
M. Ioannidis ◽  
...  
Keyword(s):  
Iron Nanoparticles ◽  
Accommodation Coefficient ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Ab Initio Potentials ◽  
Thermal Accommodation Coefficient ◽  
Carrier Gases ◽  
Pneumatic Atomizer

This paper summarizes the results of Time-Resolved Laser-Induced Incandescence (TiRe-LII) measurements of iron nanoparticles in He, Ne, Ar, N2, CO, CO2, and N2O. The iron nanoparticles are formed in solution and then aerosolized with a pneumatic atomizer using various carrier gases, so the nanoparticle size is the same for each aerosol and the TiRe-LII signal only differs due to the different thermal accommodation coefficient (TAC). Thermal accommodation coefficients for the Fe-Ar, and Fe-N2 aerosols, derived from molecular dynamics using ab initio potentials, are compared with values inferred from the TiRe-LII measurements.

scholarly journals Measurement of Thermal Accommodation Coefficients Using Laser-Induced Incandescence

2007 ◽  
Author(s):  
K. J. Daun ◽  
P. H. Mercier ◽  
G. J. Smallwood ◽  
F. Liu ◽  
Y. Le Page
Keyword(s):  
Deformation Rate ◽  
Surface Deformation ◽  
Accommodation Coefficient ◽  
Polyatomic Gases ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Translational Mode ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Gas Molecules

Laser-induced incandescence (LII) is used to measure the thermal accommodation coefficient between soot sampled from a well-characterized flame and various monatomic and polyatomic gases. These measurements show that the thermal accommodation coefficient between soot and monatomic gases increases with molecular mass due to the decreasing speed of incident gas molecules and corresponding decrease in surface deformation rate, and that energy is transferred preferentially from the surface to the translational mode of the polyatomic gas molecules over internal energy modes.

Heat Transfer Predictions for Micro-/Nanochannels at the Atomistic Level Using Combined Molecular Dynamics and Monte Carlo Techniques

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
S. V. Nedea ◽  
A. J. Markvoort ◽  
A. A. van Steenhoven ◽  
P. A. J. Hilbers
Keyword(s):  
Molecular Dynamics ◽  
Heat Flux ◽  
Monte Carlo ◽  
Boundary Conditions ◽  
Accommodation Coefficient ◽  
Monte Carlo Techniques ◽  
Effective Coefficients ◽  
Accommodation Coefficients ◽  
Dynamics Simulations ◽  
Wall Interactions

The thermal behavior of a gas confined between two parallel walls is investigated. Wall effects such as hydrophobic or hydrophilic wall interactions are studied, and the effect on the heat flux and other characteristic parameters such as density and temperature is shown. For a dilute gas, the dependence on gas-wall interactions of the temperature profile between the walls for the incident and reflected molecules is obtained using molecular dynamics (MD). From these profiles, the effective accommodation coefficients for different interactions and different mass fluid/wall ratio are derived. We show that Monte Carlo (MC) with Maxwell boundary conditions based on the accommodation coefficient gives good results for heat flux predictions when compared with pure molecular dynamics simulations. We use these effective coefficients to compute the heat flux predictions for a dense gas using MD and MC with Maxwell-like boundary conditions.

scholarly journals The Thermal Accommodation Coefficient of Graphite

1973 ◽  
Vol 52 ◽  
pp. 311-315 ◽  
Author(s):  
Kenrick L. Day
Keyword(s):  
Carbon Dioxide ◽  
Atomic Hydrogen ◽  
Accommodation Coefficient ◽  
Sticking Coefficient ◽  
Thermal Accommodation ◽  
Significant Process ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Theoretical Paper ◽  
Very High

An experiment has been performed to determine the thermal accommodation coefficients for the gases hydrogen, oxygen, methane, and carbon dioxide on graphite, in the temperature range 273–77 K. The experimental results are compared to those indirectly predicted in a theoretical paper by Hollenbach and Salpeter, and agreement is found to be satisfactory. A sticking coefficient for atomic hydrogen on a graphite grain is derived which would support the conclusion that recombination of hydrogen on grain surfaces could be a significant process. The very high measured thermal accommodation coefficients for the heavier gases supports the popular assumption that retention of such gases on grain surfaces should be considered extremely likely.

Sign in / Sign up

Export Citation Format

Share Document