Zhaojie Shen

Influence of nanoparticle properties on the thermal conductivity of nanofluids by molecular dynamics simulation

The properties of nanoparticles (including shape, size, material, and volume concentration) may significantly influence the thermal properties of nanofluids. Through molecular dynamics simulations, the aim of this study is to investigate the influence of nanoparticle properties on the thermal conductivity of nanofluids and find an effective criterion for predicting thermal conductivity enhancement. By establishing a series of simulation models, thermal conductivities of nanofluids were calculated on the basis of the Green–Kubo formula. It was found that all the nanoparticle properties that have been considered in this work influence the thermal conductivity of nanofluids, and the influence rules were discussed. Furthermore, there is a positive correlation between the distribution of atomic potential energy and the thermal conductivity of nanofluids. Therefore, the ratio of energetic atoms in nanoparticles is proposed to be the criterion for predicting enhancement of the apparent thermal conductivity of nanofluids.

Enhancing Heat Transfer in Internal Combustion Engine by Applying Nanofluids

Nanofluids exhibit novel properties including significant heat transfer properties that make them potentially useful in internal combustion engine cooling. However, although there is a substantial number of mechanisms proposed, modeling works related to their enhanced thermal conductivity, systematic mechanisms, or models that are suitable for nanofluids are still lacked. With molecular dynamics simulations, thermal conductivities of nanofluids with various nanoparticles have been calculated. Influence rule of various factors for thermal conductivity of nanofluids has been studied. Through defining the ratio of thermal conductivity enhancement by nanoparticle volume fraction, Κ, the impacts of nanoparticle properties for thermal conductivity are further evaluated. Furthermore, the ratio of energetic atoms in nanoparticles, E, is proposed to be an effective criterion for judging the impact of nanoparticles for the thermal conductivity of nanofluids. Mechanisms of heat conduction enhancement are investigated by MD simulations. Altered microstructure and movements of nanoparticles in the base fluid are proposed to be the main reasons for thermal conductivity enhancement in nanofluids. Both the static and dynamic mechanisms for heat conduction enhancement in nanofluids have been considered to establish a prediction model for thermal conductivity. The prediction results of the present model are in good agreement with experimental results.

Effect of Temperature on Rheology and Nanoparticle Movements of Water Based Nanofluids by Molecular Dynamics Simulation

Employing nanofluids is an innovative way to enhance heat transfer in cooling system of internal combustion engine. the reasons for the significantly enhanced heat transfer properties of nanofluids are various. On one hand, the markedly increased thermal conductivity is the most apparent reason; on the other hand, the changed rheology properties of base fluid due to the disordered movements of countless nanoparticles is even more important. Because the size scale of nanoparticles is too small, in some cases of computational simulations nanofluids is simplified as single-phase fluids. However, the influence of nanoparticles for flow behaviors of base fluids distinctly should not be ignored. By means of molecular dynamics method, a nano-scale simulation on the rheology of nanofluids could be conducted, therefore the movements of nanoparticles could be directly observed, which is conducive to reveal the influence of movements of nanoparticles for rheology of nanofluids. The present work is intended to perform a molecular dynamic simulation on the rheology of water based nanofluids. By applying temperature difference, the velocity and temperature distribution of fluid zone are calculated to evaluate heat transfer through nanofluids. Moreover, the influence of temperature for the movements of nanoparticle is discussed.Copyright