Natural convection of Al2O3-water nanofluid in an inclined enclosure with the effects of slip velocity mechanisms: Brownian motion and thermophoresis phenomenon

Effects of inclination angle on natural convective heat transfer and fluid flow in an enclosure filled with Al2O3-water nanofluid are studied numerically. The left and right walls of enclosure are kept in hot and cold constant temperature while the other two walls are assumed to be adiabatic. Considering Brownian motion and thermophoresis effect (two important slip velocity mechanisms) the two-phase mixture model has been employed to investigate the flow and thermal behaviors of the nanofluid. The study was performed for various inclination angles of enclosure ranging from gamma = 0 degrees to gamma = 60 degrees, volume fraction from 0% to 3%, and Rayleigh numbers varying from 105 to 10(7). The governing equations are solved numerically using the finite volume approach. The results are presented in the form of streamlines, isotherms, distribution of volume fraction of nanoparticles and Nusselt numbers. They demonstrated that the slip velocity mechanisms have caused the decreasing Nusselt number with increasing volume fraction of nanoparticles. They also indicate important differences between single-phase and two-phase models. In addition, the highest value for Nusselt number is reached at gamma = 30 degrees. Increase in nanoparticle diameter leads to decrease and increase in Nusselt number and non-uniformity, respectively. The investigation of inclination angle effects on natural convection of nanofluid in an enclosure has been carried out for the first time by two-phase mixture model including slip velocity mechanisms (Brownian motion and thermophoresis phenomenon) effects. (C) 2016 Elsevier Masson SAS. All rights reserved.