Dimensional Crossover of Thermal Transport in Nanoconfined Liquids Driven by the Interplay of Quasi-One-Dimensional Structure and Wall Dissipation

Abstract

Heat transport in nanoconfined liquids can deviate from ordinary Fourier behavior because confinement alters liquid structure and interfacial dissipation. Although such changes may lead to quasi-one-dimensional transport or overdamped sound relaxation, the conditions under which length-dependent transport persists remain unclear. Here we use molecular dynamics simulations of monatomic liquid argon confined in carbon nanotubes with systematically varied radii and lengths. We find a radius-controlled crossover: length-dependent axial thermal conductivity persists over long tube lengths in single-file and single-shell states, but is strongly truncated or nearly saturated once mixed-shell or multilayer packing develops. This crossover is accompanied by the loss of clear acoustic-like axial modes and enhanced wall--liquid friction. Thus, tube radius controls whether length-dependent heat transport persists or is truncated by coupling confined-liquid structure to wall-induced dissipation.