Molecular dynamics simulation of effective thermal conductivity of vapor-filled nanogap and nanocavity

Abstract

The effect of adsorption on momentum a u and thermal a T accommodation coefficients and effective thermal conductivity ͗k f ͘ of Ar vapor-filled Pt nanogap and nanocavity is examined using nonequilibrium molecular dynamics ͑MD͒ simulations. For the accommodation coefficients, the increase in solid-fluid or fluid-fluid interatomic interactions within adsorbed layer causes transitions in magnitudes of a u and a T near Ar triple-point temperature. In the nanogap, ͗k f ͘ MD results are in close agreement with the available closed-form solution for transition-flow regime, i.e., Knudsen number 0.1Ͻ Kn L Ͻ 10, using the MD results of a T. In the nanocavity, the adiabatic sidewalls do not significantly alter the gas mean free path and ͗k f ͘, and the sparse adsorption coverage on the sidewalls results in a negligibly small fluid circulation by surface diffusion under a temperature gradient.

First-Principles Informed Atomistic-Scale Calculations of Equilibrium Energy Accommodation Coefficients for Aluminum–Noble Gas Systems

“…It then attains a minimum value and then increases gradually with further increase in the temperature. A qualitatively similar trend has been reported elsewhere. − Furthermore, the accommodation coefficient is generally lowest for helium and greatest for xenon. The temperature corresponding to the minimum value of the accommodation coefficient is also lowest for helium and greatest for xenon.…”

Nanoscale thermal transport. II. 2003–2012

“…45 A similar relationship between the interfacial conductance and the interfacial bonding strength was observed in a number of MD simulation on interfacial systems, including hard solid-polymer, 42 solid-solid, 46 solid-SAM-solid, 47,48 carbon nanotube on silica substrate, 49 and for gas-solid interfaces. 50 Within the theoretical treatment, the effect of interfacial bonding on the phonon transmission coefficients and consequently on the interfacial thermal conductance can be demonstrated via an analysis of a simple model of semi-infinite one-dimensional chains of masses connected by springs. 51 A calculation based on this model shows that the interfacial phonon transmission coefficient for a typical phonon representing those carrying the majority of the heat strongly increases with increasing interfacial stiffness.…”

Improvement of heat transfer efficiency at solid-gas interfaces by self-assembled monolayers

“…(2), we set an imaginary plane 11 Å (cutoff distance) away from the solid surface. 18 The incident (or reflected) gas atoms pass through the imaginary plane and indicate the start or finish of the energy exchange process. The temperature of incident (or reflected) gas atoms is obtained by dividing the average kinetic energy of the incident (or reflected) atoms by 2k B .…”