Analysis of Directly Measured Heat Transfer Coefficients During Special Experiments to Provide Better Understanding of Secondary Cooling During Continuous Casting Process

摘要

The cooling intensity of spray nozzles is a very important parameter in the secondary cooling zone of a continuous caster since it has strong impact on cast slab quality and operation. This parameter is characterized by the heat transfer coefficient (HTC), which is one of the boundary conditions for the heat conduction problem. At the Heat Transfer and Fluid Flow Laboratory of Brno University the cooling intensity of nozzles is measured on an experimental apparatus [1], [2]. Temperatures in a test plate are obtained from the measurements and surface temperatures as well as heat transfer coefficients are computed from these temperatures by an inverse heat conduction problem. The standard procedure for measuring the HTC is to position the spray nozzles below a preheated plate. In most continuous casters this configuration only exists in the run-out portion of the machine. The sprays in continuous casters are also spraying from above on to the cast slab and can spray onto the surface of the slab when it is in a vertical position and the sprays are perpendicular to slab surface in almost all cases. A series of experiments were conducted to determine the effect of slab surface orientation on the measured heat transfer coefficient.