Molecular Dynamics Simulation of Nanofilm Boiling on Graphene‐Coated Surface

Abstract

Molecular dynamics (MD) simulations are conducted to investigate the effect of graphene coating on nanofilm boiling on an atomically smooth surface. Transition of boiling modes from normal evaporation to explosive boiling is observed on both bare and graphene-coated surfaces. The onset temperature of explosive boiling on the graphene-coated surface is approximately 170 K, which is extremely close to the value of approximately 160 K on the bare surface. A hydrophobic surface is also artificially fabricated to verify the effect of surface wettability on nanofilm boiling and the significance of graphene coating. The onset temperature of explosive boiling on the hydrophobic surface is much higher than that on the hydrophilic and graphene-coated surfaces. Additionally, the critical heat flux of the nanofilm boiling on the graphene-coated surface is slightly lower than that on the bare hydrophilic surface. Results confirm that graphene coating is almost useless, and even harmful to the heat transfer enhancement of the nanofilm boiling. Simulation MethodThree simulation systems, namely hydrophilic Cu, hydrophobic Cu, and graphene-coated Cu systems, are developed and shown in Figure 1. The initial configurations of the three systems are cuboid confinements with the same size of 8.39 nm (x) × 9.68 nm

Surface Topography Effects on Pool Boiling via Non-equilibrium Molecular Dynamics Simulations

“…As a result, only two regimes can be defined: nucleate boiling and film-like (or nanofilm) boiling, an observation consistent with the literature. 23,24,26 This transition to film-like boiling takes place when the energy provided through the solid wall causes rapid vapor-phase expansion, which is not balanced by an adequate supply of liquid in the proximity of the solid−liquid interface.…”

“…Molecular dynamics (MD) has been widely employed in the last few years to provide molecular-scale insights into the complexity of boiling phase change at the nano/micro-scale. ,− Previous attempts at the MD level investigated extensively the role of wettability in heat transfer performances for Lennard–Jones (LJ) liquid argon systems. Tang et al studied the effect of bare and graphene-coated surfaces for atomically smooth solid wall systems and their influence on the critical heat flux (CHF) and transition to film (explosive) boiling for liquid LJ argon. A local, non-uniform heating spot was investigated by Yamamoto and Matsumoto with particular attention to wettability heterogeneities on smooth (flat) solid walls.…”

“…42 We investigate the effect of the wall superheat, ΔT wall , defined as which represents the difference between the wall temperature, T wall , and the liquid saturation temperature, T sat , that corresponds to about 1.01 at the investigated operating conditions and is in line with that of other studies performed on LJ systems. 23 As common practice, 23,24 T sat is determined by NVT simulations at increasing fluid temperatures T. T sat corresponds to the minimum temperature beyond which a nucleus appears within the limit of the simulation time. We are aware that the saturated temperature will change in a nontrivial manner as the system is heated, at different points of the fluid.…”

Molecular Dynamics Investigation of Liquid and Vapor Interactions Near an Evaporating Interface: A Theoretical Genetics Perspective

“…MD simulation models calculate the trajectories of atoms and molecules over time and hence provide the detailed physics of phase transition at interfacial regions between two phases. [44][45][46][47][48][49][50] To gain insights on the atomistic picture of phase transition process, we use MD models that simulate an evaporating thin liquid film on nanostructures, as illustrated in Figure 2a. The detailed view in Figure 2b shows the interactions between liquid and vapor molecules at the interface, representing accommodation and reflection processes.…”

Molecular Dynamics Study of Phase Transition Heat Transfer in Water Nanofilm on Nanorough Surfaces

“…Qasemian et al [19] studied the explosive boiling of a thin argon nanofilm on conical Al-Cu-based nanostructures and found that the surface with a Cu-Al nanostructure has better heat transfer efficiency than the surface with a single-metal nanostructure. Tang et al [20] investigated the boiling of nanofilm on a single-layer graphene-coated Cu-like surface, and found that the heat transfer of the nanofilm during boiling is barely affected by the single-layer graphene coating. However, Refs.…”