Nanofluid forced convection in entrance region of a baffled channel considering nanoparticle migration

In the present paper, forced convection flow of Al2O3-water nanofluid in the entrance region of a two-dimensional baffled channel is numerically investigated. A constant heat flux is imposed on the channel wall and a scalar equation is added to conservation equations to determine nanoparticle distribution throughout the channel. The energy equation is modified by considering terms related to Brownian motion and thermophoresis phenomenon. The effect of Reynolds number, nanoparticle concentration and diameter on particle distribution, velocity and temperature fields, heat transfer coefficient, and pressure drop is evaluated. Results reveal that the addition of nanoparticle into basefluid decreases wall temperature and more uniformity of temperature can be obtained. The particle concentration decreases in the vicinity of wall and a layer of agglomerated nanoparticles is formed exactly over the baffles. Although the intensity of recirculation region increases with rising particle concentration, the flow moves toward less distance to reach the channel surface, resulting in shorter length of recirculation region. The reduction of particle diameter improves thermal properties and, on the other hand, increases inlet velocity for constant Reynolds number due to increased viscosity; consequently the heat transfer is enhanced at the expense of higher pressure drop and pumping power. The finding of this study proves the potential of nanoparticle in thermal performance improvement of baffled channel with short length. (C) 2016 Elsevier Ltd. All rights reserved.