Effective utilization of MWCNT-water nanofluid for the enhancement of laminar natural convection inside the open square enclosure

A finite difference based two dimensional numerical analysis of laminar natural convection inside the open square enclosure containing nanofluid of water with multi-walled carbon nanotube (MWCNT) is presented by stream function-vorticity approach. The left wall is subjected to sinusoidal time-variant temperature. The top and bottom walls are considered as adiabatic and the right wall is kept as ambient. The flow is diagonally downward and opposed by the buoyancy force. In the numerical analysis, Xue [30] model of thermal conductivity is coupled with modified Krieger and Dougherty (K-D) model of viscosity based on rheology of suspension of particles. The variables considered in the present study are Rayleigh number (10(4)-10(6)), volumetric fraction of MWCNT (0 < phi < 1.5%), amplitude (0 < a < 0.5) and the period (tau = 0.2). The periodic results of fluid flow are elucidated with streamlines, isotherms and time averaged Nusselt number. The heat transfer intensifies when both the Rayleigh number and percentage of MWCNT increases. The effect of amplitude on the rate of heat transfer is remarkable on the hot wall but is subtle on the opposite cold wall. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.