Natural convection heat transfer enhancement using nanofluid and time-variant temperature on the square enclosure with diagonally constructed twin adiabatic blocks

A finite difference based two dimensional numerical investigation of laminar natural convection inside the closed square enclosure filled with copper-water nanofluid and two diagonally placed adiabatic blocks is presented by vorticity-stream function approach. The left and right walls are assumed as hot and the top wall is kept as cold. The temperature of bottom wall varies sinusoidal over time. The variables considered in the present study are Rayleigh number (104 to 106), volumetric fraction of copper particles (0 < phi <4%), amplitude (0< a <0.5) and the period (0.001 < 0.8). The periodic results of fluid flow are elucidated with Streamlines, Isotherms and Nusselt number. The combined effect of nanofluid and timevariant temperature at the bottom wall suppresses the hydrodynamic blockage effect of solid blocks and enhanced the convective heat transfer. The time-averaged local Nu is increased by a maximum of 11% when comparing with pure fluid. (C) 2015 Elsevier Ltd. All rights reserved.