Numerical analysis of the effect of baffle on heat transfer enhancement nanofluid flow over a backward facing step: A correlation for the average Nusslet number

In this paper, the effect of baffle on the flow field and heat transfer enhancement of forced convection of Cu-water nanofluid flow in the laminar regime over a backward facing step is numerically investigated. In this study, the influence of baffle geometrical parameters as height, width and number of baffles, as well as the Reynolds number and the volume fraction of nanoparticles on the flow filed and heat transfer are evaluated. Also, to evaluate the simultaneous of the heat transfer enhancement and pressure drop, the Performance Evaluation Index (η) is calculated. The results indicated that in presence of baffle, the η is higher than 1 for all cases, and it is clear that the presence of baffle is effective on thermal efficiency. It is obvious that by increasing the Reynolds number and decreasing the volume fraction of nanoparticles, the Performance Evaluation Index is increased. For all cases, the average Nusselt number and the Performance Evaluation Index for wb=2H are higher than other cases about 7.6% and 15% respectively. The results show that using 2 baffles must be more beneficial than other number of baffles. Finally, a correlation for the Num/Num0 as a function of Reynolds number (Re), volume fraction of nanoparticles (φ), number of baffles (N), baffle height (hb) and baffle width (wb) is presented with an average error of 2.88%.