Interplay of confinement and density on the heat transfer characteristics of nanoscale-confined gas

TL;DR

This study uses molecular dynamics simulations to explore how confinement and density influence heat transfer in nanoscale argon gas, revealing the dominant role of wall effects and interfacial resistance across different conditions.

Contribution

It provides new insights into the interplay of confinement, density, and Knudsen number on nanoscale gas thermal properties, highlighting the significance of wall force fields and interfacial resistance.

Findings

Wall force fields significantly affect density and temperature distributions within 1 nm of walls.

Normalized effective thermal conductivity is consistent across different methods of changing Knudsen number.

Interfacial and wall resistance dominate total thermal resistance even in near micrometer channels.

Abstract

The effect of changing the Knudsen number on the thermal properties of static argon gas within nanoscale confinement is investigated by three-dimensional molecular dynamics simulations. Utilizing thermalized channel walls, it is observed that regardless of the channel height and the gas density, the wall force field affects the density and temperature distributions within approximately 1 nm from each channel wall. As the gas density is increased for constant channel height, the relative effect of the wall force field on the motion of argon gas atoms and, consequently, the maximum normalized gas density near the walls is decreased. Therefore, for the same Knudsen number, the temperature jump for this case is higher than what is observed for the case in which the channel height changes at a constant gas density. The normalized effective thermal conductivity of the argon gas based on the heat flux that is obtained by implementation of the Irving-Kirkwood method reveals that the two cases give the same normalized effective thermal conductivity. For the constant density case, the total thermal resistance increases as the Knudsen number decreases while for the constant height case, it reduces considerably. Meanwhile, it is observed that regardless of the method used to change the Knudsen number, a considerable portion of the total thermal resistance refers to interfacial and wall force field thermal resistance even for near micrometer sized channels.