Temperature profiles and heat fluxes observed in molecular dynamics simulations of force-driven liquid flows

Abstract

This paper concentrates on the unconventional temperature profiles and heat fluxes observed in non-equilibrium molecular dynamics (MD) simulations of force-driven liquid flows in nano-channels. Using MD simulations of liquid argon flows in gold nano-channels, we investigate the manifestation of the first law of thermodynamics for the MD system, and compare it with that of the continuum fluid mechanics. While the energy equation for the continuum system results in heat conduction determined by viscous heating, the first law of thermodynamics in the MD system includes an additional slip-heating term. Interaction strength between argon and gold molecules is varied in order to investigate the effects of slip-velocity on the slip-heating term and the resulting temperature profiles. Heat fluxes and temperature profiles from "continuum", "continuum augmented with slip-heating", and "heat conduction due to the power input by the driving force" are modeled and compared with the MD results. The continuum model can neither predict the heat fluxes nor the temperature profiles from MD simulations. While the continuum model augmented with slip-heating matches the MD heat fluxes, the resulting temperature profiles do not agree with the MD predictions. Overall the analytical model based on "heat conduction due to power input by the driving force" matches the heat fluxes from MD simulations, while the temperature profiles match MD predictions using an effective thermal conductivity that is about 70% of the thermodynamic value. Using different liquid-wall pairs affects the slip velocity, temperature jump, and the resulting thermal conductivity of the fluid, but results in similar physical observations. The inability of the MD method in mimicking continuum fluid mechanics in energy transport for force-driven liquid flows is scale independent, and it is more likely a numerical artifact.

Heat Conduction Characteristic of Rarefied Gas in Nanochannel

“…This heat transfer should be considered in the simulations and cannot be neglected (Liu et al, 2007;Matthes, Knigge, & Talke, 2014;Myo, Zhou, Yu, & Hua, 2011;Zhou, Liu, Yu, & Hua, 2010;Zhou, Yu, Hua, & Myo, 2013). Unlike the gas, it should be noted that the heat transfer characteristics through the liquid medium have been studied extensively by implementation of thermal wall on the channel (Amani, Karimian, & Seyednia, 2017;Cao, Sun, Chen, & Guo, 2009;Faraji & Rajabpour, 2017;Fu & Wang, 2018;Ge, Gu, & Chen, 2015;Ghorbanian & Beskok, 2017;Jepps, Bhatia, & Searles, 2004;Wang, Cheng, & Quan, 2016).…”

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

“…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.…”

Numerical Solution of Non-Newtonian Fluid Flow Due to Rotatory Rigid Disk

“…Their values are obtained by build in command in Mathematica while we have used self-coded algorithm (shooting method with R-K scheme) subject to Casson nanofluid flow induced by solid rotating disk. Beside this one can extend idea to computational fluid dynamics in context of industrial and standpoints, see References [32][33][34][35][36][37][38][39][40][41][42].…”