Numerical and modeling analysis of fluid flow and heat transfer of liquid steel in a tundish with different flow control devices

Fluid flow and heat transfer of liquid steel in a two-strand tundish of a slab caster were analyzed using water modeling and numerical techniques. Three cases were considered: A bare tundish, a tundish equipped with a pair of weirs and a pair of baffles (arrangement W&B) and a tundish equipped with a turbulence inhibitor and a pair of baffles (arrangement TI&B). The water modeling, under isothermal conditions, indicated the existence of a strong bypass-flow for the bare tundish and the W&B arrangement while the TI&B arrangement reported a longer minimum residence time and higher plug flow characteristics. Numerical results verified the trend mentioned with the water model. The numerical study showed also that cold and hot steel affected considerably the flow patterns of steel due to the existence of buoyancy forces. In the case of a step-input of cold steel, bypass-flow was intensified for the bare tundish and the tundish with a W&B arrangement. When a step input of hot steel is introduced into the system buoyancy forces make the steel to flow preferentially near the free surface. The tundish with a TI&B arrangement showed the best flow characteristics with not splashing and negligible turbulence. This arrangement shows a slower response to thermal disturbs coming from the input making the tundish a less exposed reactor to the temperature changes and the consequent changes in flow patterns usually found in real casting operations.