Simulation of the velocity and temperature distribution in tundishes with electric arc heating
The flow in a continuous casting distributor with a capacity of 69 t steel melt was investigated. Since investigations of the real melt flow in the steelworks are not feasible due to the extreme boundary conditions and the lack of optical accessibility, these investigations were carried out in compliance with the characteristic similarities on a reduced water model distributor on a scale of 1:3. Particle image velocimetry was used as the measuring method. The numerical calculations were performed with the commercial flow solver FLUENT based on the RANS equations. The numerical and physical simulation of the stationary casting showed that very heterogeneous areas with strong vortices are present in the distributor. The dominant flows are dependent on thermal boundary conditions. The transient casting is investigated over the entire casting period (casting of the first ladle, stationary casting phase and ladle change). The results show that the thermal conditions in the two strand distributor are influenced by the casting conditions and the casting duration. This results in changing flows over the casting time which have a significant influence on the distribution characteristics. Additional measures to increase the melt temperature by means of electric arcs also lead to a significant thermal stratification, which leads to a sharp increase in the temperature of a part of the melt. The heat supplied is mainly transported via heat conduction. Only in the inlet area does the shadow tube jet lead to mixing and thus to a more homogeneous temperature distribution. This method represents a possibility to increase the temperature of the melt flowing out of the distributor. However, due to the slow heat conduction phenomena compared to convection, this system has a long reaction time. The comparison between the experimental and numerical investigations carried out for both stationary and transient casting shows that with FLUENT it is possible to correctly reproduce the flow in the continuous casting distributor. However, it is important to use realistic boundary conditions. In transient casting, this means that self-programmed boundary conditions are integrated into the model. These include, among other things, the heat losses via the surface and walls as well as the thermal energy supplied by means of arcs.
The project was funded by the Deutsche Forschungsgemeinschaft (DFG) under the reference number PF 394/7–1.