Comparative analysis of methods for calculating the heat transfer coefficient through the copper wall of the MNLZ crystallizer

The crystallizer of a continuous casting machine (CCM) is the most critical component of the system, as it is where the solid shell of the cast strand is formed. The crystallizer walls are made of copper-containing material, which exhibits high thermal conductivity, enabling the removal of up to 25% of the heat generated during metal solidi-fication to the cooling water. Research and development of reliable methods for calculating heat transfer processes in slab crystallizers remain an urgent challenge. When analyzing the thermal performance of the crystallizer, knowledge of the heat transfer coefficient between its working surface and the cooling water is crucial. This coefficient allows for the selection of optimal water cooling regimes under varying metal casting parameters and prevents overheating of the copper-containing wall’s working surface beyond its weakening temperature.The aim of this work is to perform a comparative analysis of existing analytical and numerical methods for calculating the heat transfer coefficient through the copper wall of a CCM crystallizer with slotted channels to the cooling water. Three primary analytical algorithms for determining the heat transfer coefficient through the copper wall of the CCM crystallizer are examined. A mathematical model for calculating the thermal state of the crystallizer wall with slotted channels was developed, along with a computer program to determine the heat transfer coefficient through the copper wall.A comparative analysis of all methods for calculating the heat transfer coefficient for narrow and wide copper walls of a slab crystallizer revealed that, within the practical water velocity range of 4–9 m/s in the channels, the heat transfer coefficients obtained by different methods differ by an average of no more than 12–13%. It was also established that a wear-resistant Co–Ni coating with a thickness of 0.67–2 mm on the copper crystallizer walls increases thermal resistance, thereby reducing the heat transfer coefficient by 7–23%.