Effectiveness in incorporating Brownian and thermophoresis effects in modelling convective flow of water-Al2O3 nanoparticles

Purpose - Nanofluids are widely used in heat transfer phenomena owing to the higher rate of heat removal as compared to their base fluids. Nanoparticle's motion in nanofluids is analysed by slip mechanisms that consider physical properties, which can be found in literature. It is assumed that among few, only Brownian motion and thermophoresis affect the slip mechanism to produce a relative velocity between the nanoparticles and the base fluid. The purpose of this paper is to study the effects of Brownian motion and thermophoresis in a square cavity by considering it pure fluid as well as porous cavity. Design/methodology/approach - A finite element method is used to solve the flow porous equations together with the heat transfer equation and the mass transfer equation numerically. The heat and mass transfer equations were modified to take into consideration the Brownian motion as well as the thermophoresis effect. Findings - A negligible amount of Brownian motion and thermophoresis effect has been found by considering 1 to 3 Vol.% of aluminium oxide as nanoparticles suspended in base fluid of water. Practical implications - This study has provided an interesting insight into the importance of Brownian motion as well as the thermophoresis effect in heat enhancement. Originality/value - The present study is believed to be an interesting and original contribution on nanofluid thermal behaviours.