Interface-inspired formulation and molecular-level perspectives on heat conduction and energy storage of nanofluids

Abstract

Aiming for the introduction of stability requirements in nanofluids processing, an interface-based three-step method is proposed in this work. It is theory-based design framework for nanofluids that aims for a minimum tension at the solid-liquid interface by adjusting the polar and dispersive components of the base fluid to meet those of disperse nanomaterial. The method was successfully tested in the preparation of aqueous nanofluids containing single-walled carbon nanotubes that resulted to be stable and to provide good thermal properties, i.e. thermal conductivity increases by 79.5% and isobaric specific heat by 8.6% for a 0.087 vol.% load of nanotubes at 70 °C. Besides, a system for these nanofluids was modelled. It was found to be thermodynamically consistent and computationally efficient, providing consistent response to changes in the state variable temperature in a classical Molecular Dynamics environment. From an analysis of the spatial components of the heat flux autocorrelation function, using the equilibrium approach, it was possible to elucidate that heat conduction through the host fluid is enhanced by phonon propagation along nanotubes longitudinal axes. From an analysis of the structural features described by radial distribution functions, it was concluded that additional heat storage arises from the hydrophobic effect.

Atomic-level breakdown of Green–Kubo relations provides new insight into the mechanisms of thermal conduction

“…Density was underestimated from the experimental values 27 – 30 by between 0.8% (propylene glycol) and 4.6% (propanol). While 10 Å is not unprecedented 31 , a 12 Å cutoff is perhaps more common for studies of this nature 15 , 16 , 20 , 32 , however in tests under the conditions used in this study with ethylene glycol we found the difference in density, thermal conductivity and its components to be negligible under these two cutoff distances. Length of bonds involving one hydrogen bond, and angles involving two hydrogen bonds were fixed using the SHAKE algorithm 33 .…”

Two-Dimensional Tungsten Disulfide-Based Ethylene Glycol Nanofluids: Stability, Thermal Conductivity, and Rheological Properties

“…Such adjustment leads to a minimum tension at the solid–liquid interface by using the non-ionic surfactant Triton X-100 (Panreac Quimica SLU, Barcelona, Spain). This approach showed better stability and an anomalous enhancement in thermo-physical properties based on the molecular dynamic simulation, even at 70 °C [ 40 ]. Meanwhile, in another recent report, Li et al have shown the spacer length optimization of cationic Gemini surfactant that improved the colloidal stability of aqua-based Au and Ag nanofluids, along with the pH dependency of stability.…”

“…Likewise, a molecular dynamic simulation investigation of the Triton X-100 surfactant has also shown ~79.5% enhancement in thermal conductivity for aqua-based carbon nanotube nanofluids at 70 °C. This enhancement was attributed to the better colloidal stability with the inclusion of a surfactant which lowers the interfacial tension between the solid–liquid network [ 40 ].…”

Efficient harmonic oscillator chain energy harvester driven by colored noise

“…While most studies of energy harvesters typically consider uncorrelated environmental noise, the reality is that this limit is an idealisation to describe noises correlated over very short times. However, in many potential applications, like electromagnetic plasmas 30 , non-Newtonian fluids 31 or nanofluidics 32 , the noise fluctuations may exhibit long correlation times. Therefore, energy harvesters that can take advantage of the low end frequency band without the need of fine tuning the device response frequency to the right bandwidth, are most welcome.…”