Numerical Investigation of Combined Convection and Nanofluids Flow Over Backward Facing Step in a Channel Having a Blockage

The effects of two dimensional laminar and turbulent combined convection nanofluids flows over backward facing step in a channel having a blockage are numerically investigated. The continuity, momentum and energy equations are solved using finite volume method (FVM) with the SIMPLE algorithm scheme. The duct has a step height of 0.01, and an expansion ratio of 2. The Reynolds number was in the range of 100-1900 (laminar flow) and in the range of 4000-10000 (turbulent flow). The effect of the blockage shape (circular, square and triangular) on the flow and heat transfer characteristics is examined. The effects of various types of nanoparticles such as Al2O3, SiO2, CuO, and ZnO dispersed in a base fluid (water), volume fraction of nanoparticles in the range of 1% to 4% and nanoparticle diameter in the range of 25 nm to 80 nm are also studied. It is inferred that the circular blockage has the highest Nusselt number compared to other two shapes. The reattachment point is found to move downstream far from the step as Reynolds number increases. Nanofluid of SiO2 is observed to have the highest Nusselt number and skin friction coefficient among other nanofluids types, while nanofluid of CuO nanoparticles has the lowest Nusselt number and skin friction coefficient.