Different modes of nanoparticle migration at mixed convection of Al2O3–water nanofluid inside a vertical microannulus in the presence of heat generation/absorption

Abstract

Intensity and direction of nanoparticle migration are able to tune thermophysical properties of nanofluids to improve the thermal performance of heat exchange equipments. The intensity strongly depends on nanoparticle diameter and cannot be actively controlled while different directions of nanoparticle migration are achieved with asymmetric heating. In the current study, the mixed convective heat transfer of Al 2 O 3 -water nanofluid inside a vertical microannulus is investigated theoretically considering different modes of nanoparticle migration. The model employed for the nanoparticle-fluid mixture is able to fully account for the effects of nanoparticle slip velocity relative to the base fluid originating from the thermophoresis (nanoparticle slip velocity due to temperature gradient) and Brownian motion (nanoparticle slip velocity due to concentration gradient). To consider surface roughness in the microannulus, Navier's wall slip condition is employed at the solid-fluid interface. It is revealed that the asymmetric heating at the walls alters the orientation of nanoparticle migration and deforms the symmetry of the flow field. In addition, despite temperature-dependent buoyancy forces, concentration-dependent buoyancy forces have considerable effects on the flow fields and nanoparticle migration.

Evaporation of Water/Alumina Nanofluid Film by Mixed Convection Inside Heated Vertical Channel

“…They consider the effect of the nanoparticle volume rate by using the Buongiorno model. The same authors [29] related the effect of the nano particles migration on the heat exchangers efficiency. With changing the migration modes of the Al 2 O 3 inside water and under the mixed convection of gas in vertical micro channels, they demonstrate the influence of the thermophysical variations on the heat transfer.…”

Nanoparticle Shape Effect on a Sodium–Alginate Based Cu–Nanofluid under a Transverse Magnetic Field

“…Aly et al [5] studied the effects of thermal radiation and suction/injection on the heat transfer flow of water based nanofluid past a vertical plate, and reported that a constant temperature was maintained on the plate. Moshizi et al [6] considered mixed convection of Al 2 O 3 -water nanofluid inside a vertical micro-annulus with two different types of heat fluxes imposed at the walls. They noted that both temperature and concentration dependent buoyancy forces affect flow fields and nanoparticle migration.…”

MHD Convection in a Lid-Driven Cavity Heated Linearly at Bottom

“…Heat transfer using natural convection plays a key role in many engineering applications. It can be found in heat exchanger, desiccation technology, electronic technology, solar energy, and greasing technology [1][2][3][4]. Sivaraj et al [5] analyzed MHD natural convection along with entropy generation using ferro uid and heated plate located centrally in a square cavity.…”