A Physical Model to Study the Effects of Nozzle Design on Dense Two-Phase Flows in a Slab Mold Casting Ultra-Low Carbon
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nt paper[1] the dispersed two-phase flows, argon and liquid steel in a slab mold, influenced by the nozzle design were studied using a water–air model. The findings of this study indicated that in dispersed flows bubble–bubble interactions are observed only in the proximities of the discharging ports. Nozzle design influences the sizes of bubbles which follow normal distributions through the mold volume, from the discharging ports to the narrow wall. Velocities in the proximities of the meniscus reach magnitudes which may go from two- to threefold those measured in single-phase flows (not air flow). The angle of the resultant velocity vectors of the liquid in the meniscus increases with the presence of a gas load, even if this is small, due to the buoyancy forces provided by the
MARI´A M. SALAZAR-CAMPOY and VALENTI´N CEDILLOHERNA´NDEZ are with the Department of Metallurgy and Materials Engineering, Instituto Polite´cnico Nacional-ESIQIE, Ed. 7 UPALM, Colonia Zacatenco, C.P. 07738 Mexico, DF, Mexico. Contact e-mails: [email protected], [email protected] R.D. MORALES is with the Department of Metallurgy and Materials Engineering, Instituto Polite´cnico Nacional-ESIQIE, Ed. 7 UPALM, Colonia Zacatenco, C.P. 07738 Mexico, DF, Mexico. A. NA´JERABASTIDA is with Metallurgy Engineering, Instituto Polite´cnico Nacional, UPIIZ, C.P. 98160 Mexico, ZAC, Mexico. J.C. DELGADOPURECO is with Arcelor Mittal Steel, Francisco J. Mujica 1B, Cd. La´zaro Ca´rdenas, C.P. 60950 Mexico, MICH, Mexico. Manuscript submitted August 17, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
bubbles. Breakup of bubbles is influenced directly by the physical properties of the fluid (kinematic viscosity and surface tension) and by the flow (dissipation rate of kinetic energy). Moreover, it was found that the turbulent dissipation rate of kinetic energy is a characteristic parameter of a given nozzle, which influences directly bubble size through shearing stresses on the bubble surface. Dispersed two-phase flows in the mold drag bubbles close to the narrow face of the mold and some nozzle designs have more influence on this phenomenon than others. Therefore, for casting ultralow carbon steels (ULC steels), a nozzle which minimizes the dragging effect on gas bubbles is required, in order to avoid the trapping of argon bubbles by the dendritic structure of the shell. In spite of the large differences of physical properties between steel–argon and water–air systems, it was discussed that the latter is a preferable choice to study the first using full scale models instead of non-wetting liquids in small scale models. Although non-wettability of liquids for modeling steel may be attractive, studies in small scale models may overestimate the role of the surface tension. In the second part, the study of two-phase flows dense gas–liquid flows will be considered using a water–air model of a slab mold testing different nozzles designs. Rising the gas loads will lead to changes on the dynamics of the flows including, bubble size distribution functions, fluid veloci
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