Abstract
Adding a small amount of nanoparticles to conventional fluids (nanofluids) has been proved to be an effective way for improving capability of heat transferring in base fluids. The change in micro structure of base fluids and micro motion of nanoparticles may be key factors for heat transfer enhancement of nanofluids. Therefore, it is essential to examine these mechanisms on microscopic level. The present work performed a Molecular Dynamics simulation on Couette flow of nanofluids and investigated the microscopic flow characteristics through visual observation and statistic analysis. It was found that the even-distributed liquid argon atoms near solid surfaces of nanoparticles could be seemed as a reform to base liquid and had contributed to heat transfer enhancement. In the process of Couette flow, nanoparticles moved quickly in the shear direction accompanying with motions of rotation and vibration in the other two directions. When the shearing velocity was increased, the motions of nanoparticles were strengthened significantly. The motions of nanoparticles could disturb the continuity of fluid and strengthen partial flowing around nanoparticles, and further enhanced heat transferring in nanofluids.
Highlights
Nanofluids have received much attention in recent years due to the significantly improved heat transferring ability compared to conventional fluids, which offer important economic benefits
Molecular dynamics (MD) method is an effective way for examining the microscopic mechanisms of flow characteristics and heat transfer enhancement in flowing nanofluids
Plenty of literatures based on MD simulation of liquids have been reported; few of them focus on the simulation of flow characteristics in nanofluids flow. Since these are important for understanding the mechanism of enhanced heat transferring in nanofluids, based on our previous studies the present paper presents a MD simulation on Couette flow of Cu-Ar nanofluids and discusses in detail the microscopic flow characteristics of nanofluids
Summary
Nanofluids have received much attention in recent years due to the significantly improved heat transferring ability compared to conventional fluids, which offer important economic benefits. A spot of uniformly dispersed and stably suspended nanoparticles could dramatically improve the thermal properties of base fluids. This new class of nanotechnology-based heat transfer fluids could meet the requirements of ultrahigh-performance cooling in many industrial technologies. Theories of fluid dynamics and heat transfer in macroscale are based on continuous medium hypothesis They are not suitable for nanofluids, for when it comes to nanoscale, small size effect appears and surface forces tend to predominate in fluids. The basic principle of MD method is solving molecular (or atomic) Newton equations of motion regarding effects of interaction potential between molecules (or atoms) and external restriction By this method, time-evolving microscopic process of system is simulated; and equilibrium parameters and transport properties could be statistical computed. Ahadian et al [7] performed
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