Fluid heating in a nano-scale Poiseuille flow: A non-equilibrium molecular dynamics study

et al. 2020

JAFM

Nonequilibrium molecular dynamics simulations is applied to investigate the simultaneous effect of rarefaction and wall force field on the heat conduction characteristics of nano-confined rarefied argon gas. The interactive thermal wall model is used to specify the desired temperature on the walls while the Irving-Kirkwood expression is implemented for calculating the heat flux. It is observed that as the temperature differences between the walls increases by lowering the temperature of the cold wall, the number of adsorbed gas atoms on the cold wall increases notably due to the increment in the residence time of the gas atoms. Consequently, the interfacial thermal resistance between the gas and the cold wall reduces which results in a reduction of the temperature jump. Meanwhile, the increase in the temperature of the hot wall leads to a reduction of the residence time of gas atoms in the near-wall region which decreases the number of absorbed gas atoms on the hot wall. This results in an increase in interfacial thermal resistance which leads to a higher temperature jump. It is observed that the bulk, wall force field and interface regions form approximately 10%, 45% and 45% of the total thermal resistance, respectively. Furthermore, unlike the interfacial thermal resistance, the bulk and the wall force field thermal resistance are approximately independent of the implemented temperature difference.

Section: Introductionmentioning

confidence: 99%

Heat Conduction Characteristic of Rarefied Gas in Nanochannel

et al. 2020

JAFM

“…The heat transfer mechanism between these two limiting conditions in the presence of the wall force field has not been studied in detail to the best of our knowledge, yet. A literature review reveals that while the heat transfer in liquid confined nanoscale media has been studied extensively by using appropriate wall/liquid interaction potentials, the heat transfer in nanoscale-confined gas has not been studied as well in details [19,20,[29][30][31][32][33][34][35][36][21][22][23][24][25][26][27][28]. This might be due to the fact that the simulation of a nanoscale confined gas requires a very large dimension in the periodic direction which leads to an enormous number of wall molecules in comparison with a nanoscale confined liquid simulation.…”

Section: Introductionmentioning

confidence: 99%

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

International Journal of Thermal Sciences

et al. 2019

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 ⁄ .

“…Due to the cold wall nature of these methods, the above-mentioned simulations were limited to hydrodynamic properties and no heat transfer in the gas medium could be tackled [28,33]. A comprehensive literature review reveals that while the studies of heat transfer in a nanoconfined rarefied gas medium are restricted by the channel length in the periodic direction resulting enormous computational time, heat transfer in the nanoconfined liquid medium has been extensively studied considering appropriate wall/fluid interactions [34][35][36][37][38][39][40][41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

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

International Journal of Heat and Mass Transfer

et al. 2020

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