Numerical simulation of conjugate conduction and natural convection heat transfer of nanofluid inside a square enclosure containing a conductive partition and several disconnected conducting solid blocks using the Buongiorno's two phase model

A two-dimensional numerical analysis of combined heat transfer (convection and conduction) in a nanofluid filled square enclosure is investigated using two phase method. Main attention was paid to the effects of the Rayleigh number (10(4)<= Ra <= 10(7)), diameter (25nm <= d(p <=)145nm), volume fractions (0 <=phi <= 5%) and type of the nanoparticle (Cu, Al2O3, and TiO2), orientation of conductive wall, thermal conductivity ratio (0.2 <= K-r <= 25) and segmentation of conductive obstacle on the velocity, temperature fields and heat transfer characteristic. The results of this investigation showed that by adding several conductive obstacles inside the enclosure, the heat transfer rate decreases especially at low Ra. Moreover, it is found that, orientation of conductive partition has a big impact on the heat transfer rate at high Ra. It is also observed that in general, internal heating/cooling system has a considerably higher rate of the heat transfer compared with external ones. Finally, it is found that, the effect of the thermophoresis force is more pronounced for solid particles with low thermal conductivity like Al2O3 and especially TiO2. (C) 2017 Published by Elsevier B.V.