Numerical Study of the Influence of Geometric Factors on Heat Transfer Using Water-Al2O3 Nanofluid in Microchannels

In this study the heat transfer and fluid flow, water-Al2O3 nanofluid in microchannel, two-dimensional rectangular in volume fractions 2%, 4%, 6% and 8% nanoparticles and Reynolds number from 10 to 50 using computational fluid dynamics (CFD) has been investigated. The governing equations of continuity and momentum and thermal is solved by finite element method and by applying initial and boundary conditions by using COMSOL Multiphysics software. Simulation results have shown, the local Nusselt number water-Al2O3 nanofluid in Reynolds number 6.9 and volume fractions 5% is a good agreement with experimental data [1]. Increasing the Reynolds number leads to increases fluid velocity and increase the density of streamlines in the edge of the baffle and the creation of larger vortex flow that increases the heat transfer coefficient [2]. By increasing the number of baffles leads to the formation of the recirculation zone, which increased outlet temperatures due to better heat exchange fluid to the walls of the microchannel .So that the output of fluid temperature in Reynolds number 40 in the microchannel six baffle and in the microchannel one baffle is 322.35 K and 314.9 K, respectively. By increasing the height of baffle ,increase recirculation zone and then increase the heat transfer coefficient. But also the average output temperature is increased by increasing nano-particle volume fractions and viscosity affected on size zone. But the effect of the distance between the baffles, the average temperature of the microchannel output is low. Numerical method is useful to predict thermal performance microchannel system.