  In the past few decades, great efforts have been devoted to studying heat
transfer on the nanoscale due to its importance in multiple technologies such
as thermal control and sensing applications. Heat conduction through the
nanoconfined gas medium differs from macroscopic predictions due to several
reasons. The continuum assumption is broken down; the surface forces which
extend deeper through the gas medium become prominent due to the large
surface-to-volume ratio, and, finally, the gas molecules are accumulated
nonuniformly on the solid surfaces. In this work, to better understand the
combination of these phenomena on the heat conduction through the nanoconfined
gas medium, we present a series of molecular dynamics simulations of argon gas
confined between either metals or silicon walls. The gas density is set so that
gas experiences a wide range of Knudsen numbers from continuum to the free
molecular regime. It is observed that the intrinsic characteristics of the
solid determine the gas density distribution near the walls and consequently in
the bulk region, and these distributions control the heat conduction through
the gas medium. While the nanochannel walls have their most significant impact
on the density and temperature distributions of the rarefied gas, the pressure
and the heat flux across the gas domain converge toward a plateau as the gas
becomes denser. We propose new analytical formulas for calculating the gas
pressure, induced heat flux, and effective thermal conductivity through the
strongly nanoconfined gas, which incorporates the wall force field impacts on
the gas transport characteristics for the Knudsen number in the range of 0.05
to 20.
