EFFECT OF THE PRESENCE OF POROUS MEDIUM ON THE PARTICLES DISTRIBUTION IN NANOFLUID CONVECTIVE HEAT TRANSFER-CASE STUDY: ELBOW MICRO-CHANNEL

Because of the high thermal conductivity of metal nanoparticles, nanofluids are used to enhance the heat transfer rate. However, due to the drag force, nanoparticles are located far from the walls. One way to bring the particles closer to the walls of the channel is to use a porous medium. In this study, the geometry used was an elbow, equipped with a porous medium in different positions. Microchannel height was 100 μm, the Reynolds number was 500, and the nanofluid was water and Al<sub>2</sub>O<sub>3</sub> at 2% concentration. To determine the effect of the presence of porous medium on the heat transfer rate due to the particle distribution, rather than to the high thermal conductivity of the porous medium, the thermal properties of the porous medium are assumed to be the same as the thermal properties of the base fluid. The porosity and permeability of the porous medium were 0.9 and 10<sup>-10</sup> m<sup>2</sup>, respectively. The governing equations including continuity, momentum, and energy based on Fortchimer-Brinkman-Darcy equations for the porous part and Buongiorno's model for nanofluid were solved numerically using a control volume method. The pressure linked equations solved using SIMPLE method. The results show that the porous part changes the fluid velocity direction toward the walls. This made the particles move toward the walls and caused an increase in the Nusselt number by up to 12%.