Effect of Reynolds number on flow and heat transfer in incompressible forced convection over a 3D backward-facing step

A three-dimensional incompressible numerical model for the case of the 3D backward-facing step flow is established to investigate the characteristics of fluid flow and heat transfer in the low and middle Reynolds number ranges (200 ≤ Re≤1400). The governing equations, including continuous, unsteady Navier-Stokes and energy equations, are solved by the finite volume method in FLUENT. The simulation results show that the time averaged reattachment length reaches the peak value at Re = 1000, and subsequently decreases as the increase of Re. The formation of secondary peak Nu influenced by flow instability has a better contribution to the heat transfer at the center area. Taking away the hot fluid and carrying the cold fluid into the floor wall, which is caused by periodic instability, have positive effects on heat transfer enhancement.