A molecular dynamics study of heat transfer over an ultra-thin liquid film with surfactant between solid surfaces

Guo, Yuting; Surblys, Donatas; Kawagoe, Yoshiaki; Matsubara, Hiroki; Ohara, Taku

doi:10.1063/1.5123583

Cited by 19 publications

(17 citation statements)

References 31 publications

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“…Figure shows the TBRs, R interface i , and mean values of the interfacial potential energy per unit area, which is the total energy between the solid wall and remaining atoms, at the Pt/PAA and Pt/PEI interfaces as functions of the degree of ionization. The TBR at the solid/polymer interface decreases with increasing absolute value of the interfacial potential energy due to the higher degree of ionization, and a similar tendency was reported in the previous works for solid/simple liquid interfaces. − For TBR at a solid/liquid interface in general, the amount of adsorbed molecules is also an important factor. However, as shown in Figure , the density profiles are almost the same for various ionization conditions.…”

Section: Resultssupporting

confidence: 80%

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

et al. 2020

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A material with anisotropic heat conduction characteristics, which is determined by molecular scale structure, provides a way of controlling heat flow in nanoscale spaces. As such, here, we consider layer-by-layer (LbL) membranes, which are an electrostatic assembly of polyelectrolyte multilayers and are expected to have different heat conduction characteristics between cross-plane and in-plane directions. We constructed models of a poly(acrylic acid)/polyethylenimine (PAA/PEI) LbL membrane sandwiched by charged solid walls and investigated their anisotropic heat conduction using molecular dynamics simulations. In the cross-plane direction, the thermal boundary resistance between the solid wall and the LbL membrane and that between the constituent PAA and PEI layers decrease with increasing degree of ionization (solid surface charge density and the number of electric charges per PAA/PEI molecule). When the degree of ionization is low, the cross-plane thermal conductivity of a constituent layer is higher than that of the bulk state. As the degree of ionization increases, however, the cross-plane thermal conductivity of PAA, a linear polymer, decreases because of the increase in the number of in-plane oriented polymer chains. In the in-plane direction, we investigated the heat conduction of each layer and found the enhancement of effective in-plane thermal conductivity again due to the in-plane oriented chain alignment. The heat conduction in the LbL membrane is three-dimensionally enhanced compared to those in the bulk states of the constituent polymers because of the electrostatic interactions in the cross-plane direction and the molecular alignment in the in-plane direction.

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Section: Resultssupporting

confidence: 80%

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

et al. 2020

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“…We only calculate the first term of eq because the second term cannot be obtained by LAMMPS correctly when the control volume is small. Similar calculations of respective contributions to heat flux have been done in our previous studies. ,, …”

Section: Simulation Methodssupporting

confidence: 70%

“…Temperature jump Δ T is the difference between the temperature of a silica wall and liquid at the interface as shown in Figure . The interface temperatures of the silica wall and the liquid were obtained by the linear extrapolation method used in our previous studies. ,, The local temperatures of liquid near the interface were obtained layer by layer, whereas those for the bulk liquid area were obtained by binning the volume into slabs with a thickness of 10 Å. The local temperatures of silica walls were obtained from binning the volume into slabs with a thickness of 4 Å.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Molecular dynamics (MD) simulation is a powerful tool for this aim. Our previous MD studies using monatomic surfactant and solvent molecules , showed that when surfactant molecules have a high affinity with solid surfaces and solvent, the solid–liquid interfacial thermal resistance is significantly reduced. While these studies clarified a basic mechanism of thermal energy transfer enhancement aided by a surfactant, it is not possible for systems of monatomic molecules to provide the details of the effect of molecular structure on the heat conduction and molecular packing near the interface.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface

et al. 2020

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The addition of surfactants to polymer-based thermal interface materials applied to improve the heat dissipation efficiency of chip surfaces in contact has attracted attention for the microelectronic processing technology. In the present study, the mechanism by which a long-chain surfactant affects heat transfer across the interface between solid surface and polymer liquid was investigated by non-equilibrium molecular dynamics simulation. We constructed a system where tetracosane was used as a solvent and contained alcohol molecules as a surfactant, and they were placed between two flat silica surfaces under a thermal gradient. The effect of the hydrophilicity of silica surface, the concentration of the surfactant, and chain length of the surfactant on silica–liquid interfacial thermal resistance R b were examined. Alcohol surfactant molecules preferred to adsorb onto the hydrophilic silica (Si–OH) surface due to hydrogen bonding between alcohol and silanol hydroxyl groups. It was found that R b reduced not only with the adsorption amount of alcohol molecules but also with the chain length of alcohol. The van der Waals interaction contribution was dominant for solid–liquid and liquid–liquid heat conduction near the interface. The hydroxyl terminals of alcohol molecules were vertically adsorbed onto the Si–OH surface due to hydrogen bonds, which produced a heat path from silanols to the hydroxyl groups of alcohol. Furthermore, heat was also exchanged between alcohol hydroxyl and alkyl groups via intramolecular interaction and between the alcohol alkyl groups and nearby solvent molecules via van der Waals (vdW) intermolecular interaction. This resulted in an efficient heat path from solid surface silanols to liquid bulk. As the alcohol chain length increased without changing the number of adsorbed alcohol molecules, the heat transfer through this heat path increased, which led to a decrease in R b. These results provided insight toward the guiding principle for the molecular design of complex surfactants to enhance the interfacial heat transfer.

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“…Similar observations were also reported by shah et al for the rGO/EG based nanofluids [ 28 ]. Moreover, it was described that the surfactants added into liquids became adsorbed onto solid surfaces and caused less friction [ 48 ]. More recently, ceria/EG nanofluids showed ~33% viscosity reduction along with a critical temperature limit of ~65 °C.…”

Section: Resultsmentioning

confidence: 99%

Rheological and Thermal Conductivity Study of Two-Dimensional Molybdenum Disulfide-Based Ethylene Glycol Nanofluids for Heat Transfer Applications

et al. 2022

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The rheological behavior of two-dimensional (2D) MoS2-based ethylene glycol (EG) nanofluids (NFs) was investigated at low volume concentrations (0.005%, 0.0075%, and 0.01%) in a wide temperature range of 0–70 °C and at atmospheric pressure. A conventional two-step method was followed to prepare NFs at desired volume concentrations. Based on the control rotational (0.1–1000 s−1 shear rate) and oscillation (0.01–1000% strain) methods, the viscoelastic flow curves and thixotropic (3ITT (three interval thixotropic) and hysteresis loop) characteristics of NFs were examined. Shear flow behavior revealed a remarkable reduction (1.3~14.7%) in apparent dynamic viscosity, which showed concentration and temperature dependency. Such remarkable viscosity results were assigned to the change in activation energy of the ethylene glycol with the addition of MoS2. However, the nanofluids exhibited Newtonian behavior at all temperatures for concentrations below 0.01% between 10 and 1000 s−1. On the other hand, strain sweep (@1Hz) indicated the viscoelastic nature of NFs with yielding, which varied with concentration and temperature. Besides, 3ITT and hysteresis loop analysis was evident of non-thixotropic behavior of NFs. Among all tested concentrations, 0.005% outperformed at almost all targeted temperatures. At the same time, ~11% improvement in thermal conductivity can be considered advantageous on top of the improved rheological properties. In addition, viscosity enhancement and reduction mechanisms were also discussed.

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A molecular dynamics study of heat transfer over an ultra-thin liquid film with surfactant between solid surfaces

Cited by 19 publications

References 31 publications

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface

Rheological and Thermal Conductivity Study of Two-Dimensional Molybdenum Disulfide-Based Ethylene Glycol Nanofluids for Heat Transfer Applications

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