This paper presents a numerical study of mixed convection melting and solidification with conjugate heat transfer inside a molten-metal bath. Our interest for this problem was sparked by the necessity to understand the basic heat transfer and fluid flow phenomena that lead to the formation of slag banks inside electric-arc furnaces. If symmetry is assumed, the transport processes can be represented in a two-dimensional plane (Fig.1). Circulation in the metal pool is caused chiefly by a combination of buoyancy forces and momentum of the impinging plasma jet. As the liquid metal flows along the surface of the bath and downward near the furnace wall, it looses heat, its temperature decreases and solidification may take place forming a slag bank. The thickness and the shape of the bank is dependent on the heat input from the electrode, the heat losses at the surface of the bath and through the brick walls as well as the flow circulation. The slag bank serves as a protective coating for the refractory brick wall thereby prolonging the active life of the furnace. On the other hand, too thick a slag bank is detrimental to the furnace production as the smelting volume available in the bath is reduced. Predicting the formation and the behaviour of the slag bank is therefore crucial in the operation and control of electric-arc furnaces Over the last two decades, solid-liquid phase change in enclosures with natural conveciton in the liquid phase has received considerable research attention (1,2,3,4). These studies have provided conclusive evidence that during melting, natural convection heat transfer controls the rate of melting and the shape of the solid-liquid interface. Comparatively little attention was devoted however to the study of mixed convection melting and solidification (5). The present paper remedy this situation by examining the melting and solidification processes that take place in an enclosure in which natural convection and forced convection prevail simultaneously. The objective is to delineate the effect of these forces and of the boundary conditions on the size and the shape of the resulting bank. A nenthalpy method is used to take into account the phase change which occurs at the wall-bath interface. A validation problem is first presented. Then, the effects of the heat input at the top surface on the bank formation is studied. Results shows that a bank forms in a limited range of heat input. Further details on the numerical model and the results of the simulations are provided in the full paper.
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