Numerical optimization of nozzle ports to improve the fluidynamics by controlling backflow in a continuous casting slab mold

In order to improve the fluid flow patterns inside the mold, a better understanding of the backflow phenomenon and its controlling parameters is necessary; then a mathematical simulation of the fluidynamics in the mold and the submerge entry nozzle (SEN) are carried out considering two typical nozzle designs and different modifications applied to the outlet ports. The numerical model considers isothermal three dimensional continuity and the Navier-Stokes equations in Cartesian co-ordinates, which are solved together with the k-a standard turbulence and the Volume of Fluid (VOF) models through the volume finite method. The results show that the backflow phenomenon emerges from an inadequate SEN port design, when a boundary layer separation is generated before the steel is delivered to the mold. This separation occurs at the upper internal side of the port inducing a low pressure zone with high levels of kinetic energy dissipation, producing the backflow phenomenon. From the analysis, it is concluded that the implementation of a radius at the internal upper side of the port avoids the separation of the boundary layer, eliminating the backflow phenomenon which allows the use of the complete effective exit area of the port; this is reflected in a velocity decrease of the jets and consequently a velocity decrement of the bulk flow. Furthermore, the size of the radius controls the penetration angle of the jets, the impact point position and the meniscus deformation; which avoids the need of the inclination angle of the port.