Modelling and Understanding of Highly Energy Efficient Fluids

TL;DR

This paper models nanofluid heat transfer at macro and nano scales, revealing a 7% enhancement in thermal conductivity due to a dense water layer around gold nanoparticles, aiding understanding of nanofluid behaviour.

Contribution

It combines CFD and MD simulations to analyze nanofluid heat transfer, providing new insights into nanoparticle effects on thermal conductivity.

Findings

Maximum 7% heat transfer enhancement at 0.015 gold volume fraction

Dense water layer forms 2nm from gold nanoparticles

Nanoparticle concentration correlates with heat transfer increase

Abstract

Conventional heat carrier liquids have demonstrated remarkable enhancement in heat and mass transfer when nanoparticles were suspended in them. These liquid-nanoparticle suspensions are now known as Nanofluids. However the relationship between nanoparticles and the degree of enhancement is still unclear, thus hindering the large scale manufacturing of them. Understanding of the energy and flow behaviour of nanofluids is therefore of wide interest in both academic and industrial context. In this paper we first model the heat transfer of a nanofluid in convection in a circular tube at macro-scale by using CFD code of OpenFoam. Then we zoon into nano-scale behaviour using the Molecular Dynamics (MD) simulation. In the latter we considered a system of water and Gold nanoparticles. A systematic increase of convective heat transfer was observed with increasing nanoparticle concentration. A maximum enhancement of 7.0% was achieved in comparison to base fluid water. This occurred when the gold volume fraction was 0.015. Subsequent MD simulations confirmed a dense water layer formed 2nm away from the gold nanoparticle boundary. It is speculated that the observed increase in thermal conductivity was principly caused by this dense water layer formed around each nanoparticle.