Conjugate-mixed convection heat transfer in a two-sided lid-driven cavity filled with nanofluid using Manninen's two phase model

Abstract

A numerical study is carried out concerning conjugate mixed convection heat transfer of various type of the nanofluid in a two-dimensional square enclosure using Manninen's model (Two phase mixture model). In the both cases of internal/external heating and cooling, hot and cold surfaces are kept at different constant temperatures while other walls of the enclosure are thermally insulated. Two-dimensional Navier–Stokes, energy and volume fraction equation are solved using the finite volume method and SIMPLE algorithm. This study has been conducted to investigate the effects of the certain pertinent parameters such as: Richardson number (10 − 2 ≤ Ri ≤ 102), thermal conductivity ratio (0.1 ≤ Kr ≤ 10), presence of the conductive obstacles, number of the hot obstacles, volume fraction (0 ≤ ϕ ≤ 0.05), size (25 nm ≤ dp ≤ 145 nm) and type (Cu, Al2O3 and TiO2) of the nanoparticles on the fluid flow and heat transfer characteristics. The simulation results indicate that depending on the boundary conditions of the problem, there is an optimal volume fraction of the solid particles at which the maximum heat transfer rate can be obtained within the enclosure. It is also observed that at high Richardson numbers, the particle distribution is fairly non-uniform while by decreasing the Richardson number and nanoparticles diameter, distribution of solid particles becomes uniform. Moreover, it is found that at low values of Richardson numbers, type of the nanoparticles has nominal effect on heat transfer rate while at high Ri by increasing the thermal conductivity of the solid particles, the total Nusselt number and optimal particle loading increase. Finally, the results demonstrate that, adding a vertical conductive wall into the enclosure leads to a significant reduction of the heat transfer rate at all values of Richardson numbers.