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UBC Theses and Dissertations

Characterization of heat transfer in the secondary cooling system of a continuous slab caster Hibbins, Stephen George


Air-purged radiation pyrometers have been installed at several locations below the mould of a continuous slab-casting machine. In each secondary cooling zone, slab surface temperatures have been measured under normal and modified water spray cooling practices. A one-dimensional heat-transfer model of the casting process has been developed, based on the implicit finite-difference method, and used to convert the measured temperature profiles into overall heat-transfer coefficients which incorporate the effects of both the sprays and rolls. Regression equations have been determined for each secondary cooling zone which relate the overall coefficients to the spray water fluxes obtained. The results of this study indicate that unstable film-boiling heat transfer occurs in parts of the secondary cooling system of the machine which was studied. This behaviour results in a large scatter in the spray heat-transfer coefficients and slab surface temperatures. The results also indicate, that current spray cooling practices may exacerbate surface cracking problems. Modifications to the present secondary cooling system are suggested so that better control of slab surface temperatures and better slab quality will be obtained.

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