Stanovení okrajových podmínek rovnice vedení tepla v sekundární oblasti chlazení ZPO

Abstract

The thesis deals with the determination of boundary conditions of the heat equation applicable in the secondary cooling zone on the steel billet in the continuous casting machine. The description of the secondary cooling zone, physical modelling of various parameters which influence heat removal from the billet in the secondary cooling, and determination of the correlation dependence between physical quantities measured using physical models are addressed.

Series of test measurements for the determination of the physical quantities using a set of the physical models from Department of Thermal Engineering, Faculty of Metallurgy and Materials Engineering VŠB-Technical University of Ostrava were performed. Water nozzles in real configurations in which they occur in the casting machine were subjected to the experimental testing.

The linear spraying intensity, which gives the distribution of cooling water across the width of the solidifying billet is determined by using the cold physical model. The model also allows for determination of the size of the areal spraying intensity, which defines the quantity of cooling water to the width of blanks and in the direction of casting.

The hot physical model allows for determination of the heat transfer coefficient, depending on the current position of the nozzle on the cooled surface. The knowledge of the distribution of the heat transfer coefficient is important for determination of the total heat removal in the secondary cooling zone. The heat removal in this part of cooling is mainly realized by partial evaporation of the cooling water, which reaches the surface of the billet.

Based on the experimental and calculated physical parameters correlation dependencies are obtained, which can be used for faster and less energy consuming determination of the heat transfer coefficient from the knowledge of the linear spraying intensity and the knowledge of the reference value of the HTC, which is measured at the center of the nozzle spray pattern. Thus, it is possible to perform a partial replacement of testing using the expensive hot physical model by testing on the faster and less energy consuming cold physical model.