Effect of natural convection hybrid nanofluid flow on the migration and deposition of MWCNT-Fe[formula omitted]O[formula omitted] in a square enclosure

Abstract

In the present study, the migration and deposition of multi-walled carbon nanotube (MWCNT)-Fe3O4 nanocomposite particles in a square enclosure for natural convection hybrid nanofluid flow are analysed numerically using the Eulerian–Lagrangian model with one-way coupling. The governing equations are solved by the finite volume method and Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. The location and velocity of 3000 selected composite particles in the host nanofluid are obtained by employing the Lagrangian approach. The influences of Rayleigh number and nanoparticle volume fraction on the thermal and flow behaviours of the system are presented. It is observed that the increasing volume fraction leads to a rise in the average Nusselt number at low Rayleigh numbers, while the case of ϕ=0.1% is the optimum volume fraction of nanoparticle in terms of heat transfer enhancement and strength of flow structure at Ra≥104. The simulations of Lagrangian particle tracking demonstrate that the minimum deposition rate of composite particles with dp=0.5 μm is obtained for a given Rayleigh number. The number of deposited large composite particles for the case of ϕ=0.1% is slightly more than for ϕ=0.3%, while the deposition rate of ultra-fine composite particles gets a higher value in the case of ϕ=0.3%. Moreover, the thermophoresis force plays a more significant role in small particle deposition than the Brownian random force.