Effect of temperature difference between channel walls on the heat transfer characteristics of nanoscale-confined gas

Abstract

We present molecular dynamics simulations of stationary argon gas in nanoscale confinement and under various temperature differences between walls. For a channel of 5.4 nm height, we vary the gas density and find that in addition to the temperature difference between the walls, the absolute temperature of each wall plays an important role in the determination of the gas molecule distribution regardless of the level of rarefaction. The combined effect of the wall force field, the temperature difference between the walls and the wall temperature leads to the fact that the normalized temperature profile along the channel height does not coincide for various temperature differences between the walls. As the gas density is increased, it is observed that the wall force field effect on the density and temperature profiles reduces considerably due to the increment in the magnitude of the gas force field for all implemented temperature differences. Considering the temperature profiles and the distribution of the effective local thermal conductivity (ELTC) along the channel height, it is inferred that a diffusive transport mechanism is dominant throughout the dense gas medium. Besides, as the gas becomes rarefied, ballistic transport in the bulk region and diffusive transport in the regions close to the walls are observed. Furthermore, the effective thermal conductivity is a function of the implemented temperature differences between the walls and its value at 300 K varies from 0.18 to 12 mW/mK as the bulk gas density changes from 1.95 to 196 kg m 3 ⁄ .

Effect of wall stiffness, mass and potential interaction strength on heat transfer characteristics of nanoscale-confined gas

“…Besides, it should be considered that as stated before, the top and bottom walls are at 308K and 288K; respectively and consequently, the gas mean temperature is around298K. As the temperature difference between the walls increases, the atom distribution along the channel height varies considerably which changes the induced heat flux [49].…”

“…Similarly, forK S ¼ 900er À2 , these density peaks become 5:84kg=m 3 and 6:24kg=m 3 for the hot and cold walls, respectively. It should be considered that as the temperature difference increases, the difference between the density peaks increases [46,49].…”

“…Besides, it should be noted that there is a small kink in the temperature profile near each wall in 0:2nm < y < 0:4nm which can be named as the near-wall layer. The reduction in gas temperature in the near-wall layer occurs due to the strong repulsive force between the wall/gas atoms in the adjacent vicinity of the walls [46,48,49]. Fig.…”

“…It was depicted that the distribution of the gas atoms along the channel height is a function of both the temperature differences between the channel walls and the absolute temperature of each wall. Besides, the distribution of the effective local thermal conductivity and temperature profile reveals that while the diffusive transport regime exists for the dense gas, the ballistic transport regime governs the bulk region and diffusive transport is observed in the near wall region of the rarefied gas [49].…”

Nanoconfined Fluids: What Can We Expect from Them?

“…Abe et al even measured the dynamic properties of water confined in an ionic liquid by using the incoherent quasielastic neutron scattering. Related studies on the transport properties of NCFs and their dependence on the molecular structures and other factors are continuously released, − and more researchers are expected to be involved in this cutting-edge area to fill in the gaps currently faced by bulk fluids. The correlations of the transport properties considering the effects of thermodynamics state parameters (temperature, pressure, etc .…”