Numerical study on the influence of slit shapes and sizes between the lower wall and the plate on turbulent flow and heat transfer characteristics

摘要

The results of numerical study of flow structure and heat transfer in turbulent flow of air over a flat plate at q_w = const with a rectangular rib with slit channel of different shapes: confusor, diffusor and const cross-section are presented. The slit channel is located between the plate and the lower wall of the rib. Numerical simulation is performed for an incompressible fluid in the framework of three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations with a Kato-Launder k-ε turbulence model for turbulence closure. The parameter effects, including the slit channel sizes and shapes (confusor, diffusor and plane-parallel), on turbulent flow structure and normalized local heat transfer coefficients on the heat transfer surface are examined. It is established that the rib with a slit, especially with a confusor, substantially reduces the size of the recirculation region behind the rib due to the effect of the generated near-wall jet on main flow. In addition, in the presence of a slit between the wall and the rib, in transverse direction, a pair of symmetrical extended spots with high values of heat transfer coefficients relative to the middle of the plate is observed. Rib with a consfor slit having a longer confusor part (Case B2) provides the best overall heat transfer performance.