Investigation of transient fluid flow and heat transfer in a continuous casting tundish by numerical analysis verified w
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I. INTRODUCTION
PHYSICAL and mathematical models are used commonly to simulate the flow of liquid steel in continuous casting (CC) tundishes. Numerous studies with reduced scale or full scale water models of different tundishes have been carried out under isothermal conditions, i.e., with water at room temperature.[1–4] By investigating momentum transfer (by the water) and concentration (by a tracer), both the liquid flow pattern and residence time distribution (RTD) can be derived. This provides useful information for optimizing the tundish design. However, there are still other important transport phenomena, such as heat transfer, which cannot be simulated with a uniform temperature distribution model. Thus, in recent years, several researchers have attempted to use nonisothermal models to simulate the thermal effects.[5,6,7] The nonisothermal research results clearly show that different flow patterns result when compared with the isothermal case. This is due to the effects of the thermal buoyancy force. There have also been significant efforts in the field of mathematical modeling of transport processes in the tundish. Most of these works have considered steady-state conditions and forced convection.[8,9,10] Hence, the momentum equations and the equations for conservation of thermal energy were solved separately. However, according to the characteristics of the tundish process given previously, the temperature of the steel in the tundish varies due to the following reasons: (a) variations in the temperature of the discharged steel; (b) heat losses to the atmosphere by conduction through the tundish walls, as well as by radiation from the bath surface; and (c) external heating and cooling caused by operations to regulate the temperature and the composition in the tundish.
may have a significant effect on the overall fluid flow behavior. Hence, a more complete mathematical model is necessary, a model that allows for coupling of fluid flow and heat transfer under three-dimensional (3-D), transient, nonisothermal conditions. Some initial transient calculations have been published earlier.[11,12] These results confirm that the predicted flow patterns under transient and isothermal conditions are quite different from those obtained for steady state, isothermal conditions. The temperature and liquid steel flow during continuous casting are the basic factors governing operation and quality control. The nonisothermal behavior of liquid steel in the tundish may bring about significant changes in the average residence time of the steel, temperature distribution, and movement of inclusions. These could directly influence the final products. Hence, the present work is a detailed study of the behavior of transient, nonisothermal steel flow, including heat transfer, in the CC tundish. This investigation work is performed using both physical modeling and mathematical modeling. A model tundish has been designed, maintaining geometric, dynamic, and thermal similarity with an industrial scale tundish.[13] In addition, a 3-D math
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