Mathematical and physical modelling of fluid flow and heat transfer in steel ladles during holding and teeming

University dissertation from Luleå : Luleå tekniska universitet

Abstract: Fluid flow and heat transfer in industrial steel ladles during holding and teeming periods were simulated by using three mathematical numerical models and a physical hot-water model. Firstly, based on a finite-difference method, a one-dimensional heat conduction numerical model was established for predicting the heat loss fluxes through ladle wall, bottom and top slag layer. Secondly, by means of a computational fluid dynamics (CFD) modelling method and employing the predicted heat loss fluxes as thermal boundary conditions, a two-dimensional CFD numerical model was developed for simulating natural convection and resulted thermal stratification phenomena in steel ladles during the holding period before teeming. Thirdly, a three-dimensional CFD numerical model was further developed for simulating fluid dynamics in steel ladles with drainage flows during teeming. The developed mathematical models were validated by industrial experiments. With these mathematical models, factorial numerical experiments were performed to investigate important parameters influencing steel ladle heat loss rate, thermal stratification and teeming stream temperature. Furthermore, a systematic analysis on the similarity between steel ladles and hot-water models regarding natural convection phenomena was made using the CFD numerical simulation results. On the basis of this similarity analysis, the criteria governing the similarity between water models and steel ladles regarding the flow and heat transfer phenomena of interest were obtained. Obeying these criteria, a 1/4-scale hot-water model was set up in the laboratory for simulation of fluid flow and heat transfer in industrial 107-tonne steel ladles. The water model can also be used for further validation of the CFD numerical models. With the help of the established mathematical and physical models, flow patterns and temperature distributions in steel ladles during holding and teeming periods were successfully studied.

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