Orientador: Amauri Garcia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T22:38:42Z (GMT). No. of bitstreams: 1 Santos_NewtonSilva_M.pdf: 11404473 bytes, checksum: e3fa93c65cc03106c6ee4c62e3694589 (MD5) Previous issue date: 2005 / Resumo: O presente trabalho descreve o desenvolvimento de um simulador físico estático do processo de lingotamento contínuo rotativo, como parte de uma metodologia experimental auxiliada por um modelo matemático para a determinação de coeficientes transitórios globais de transferência de calor metal/molde ao longo da solidificação. Através desta metodologia, investigou-se a influência da formação do gap de ar entre as paredes do molde e o metal, na cinética total do processo. O simulador fisico foi construído na mesma escala do processo industrial e constitui-se de um trecho de um equipamento de lingotamento contínuo rotativo Properzi. O simulador é equipado com um sistema de refrigeração à água por bicos pulverizadores, canal de vazamento e termopares acoplados a um sistema de aquisição de dados, onde foram realizados experimentos com ligas utilizadas na indústria de condutores elétricos de alumínio. Para a determinação dos coeficientes transitórios de transferência de calor, após o mapeamento experimental das temperaturas, empregou-se o método de comparação teórico-experimental de perfis térmicos (método IHCP) através de um modelo numérico baseado na técnica de diferenças finitas, aplicada em um volume de controle do sistema experimental. Os resultados obtidos demonstraram consistência da metodologia, permitindo a caracterização destes coeficientes e com isso a possibilidade de se prever a evolução da solidificação em processos industriais / Abstract: The present study describes the development of a static experimental set-up representing the solidification system of a Rotary Continuous Caster, as part of a metholology, which connected to a numerical model permits to determine transient global metal/mold heat transfer coefficients along solidification. By using this methodology the influence of air gap formation between mold walls and metal surface on process kinetics has been investigated . The static simulator has the same escale of an industrial caster and is constituted of a Properzi copper wheel sector, equipped with a spray cooling system, a pouring system and a thermocouple arrangement connected to a data aquisition system. Experiments were performed using aluminum alloys of the electrical conductors industry. The heat transfer coefficients were obtained by using a method base don com pari sons of numerically calculated and experimental thermal profiles (lHCP method). The used numerical model is based on a finite difference technique and applied on a control volume from the experimental system. The results have shown that the used methodology is consistent, permitting the characterization of metal/mold heat transfer coefficients and as a consequence, to predict the solidification evolution in industrial processes / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Continuous casting is an important process to transform molten metal into solid. Arrays of spray nozzles are used along the process to remove heat from the slab letting it solidify. Efficient and uniform heat removal without slab cracking is desired during steel continuous casting, and air-mist sprays could help to achieve this goal.Air-mist nozzles are one of the important keys for determining the quality of steel as well as energy consumption for pumping the water. Based on industrial data, it is estimated that a 1% reduction in scrapped production due to casting related defects can result in annual savings of 40.53 million dollars in the U.S. Computational simulations studies can minimize defects in steel such as cracks, inclusions, macro-segregations, porosity, and others, which are closely related to the heat transfer between water droplets and hot slab surface.<div><br></div><div>Conducting multiple spray experiments in order to find optimum operating conditions might be impractical and expensive in some cases. Thus, Computational Fluid Dynamics (CFD) simulation is aimed to be used for simulating the air-mist spray process. Because it is a challenging process due to strong air and water interaction, then numerical models have been developed to simulate water droplets. The first model involves air and water phases which then are transformed in single-phase water droplets. To do so, a Volume of Fraction (VOF) to the Discrete Phase Model (DPM) is used.<br></div><div><br></div><div>VOF-TO-DPM transition model involves the primary and secondary breakup which occurs in the water atomization process, starting with a single water core, followed by a smaller compact mass of water known as lumps or ligaments due to the interaction of air, and finally converted into water droplets.The second model is using the Nukiyama-Tanasawa function size distribution which injects water droplets based on defined size range and velocity profile. A validation of droplet size and velocity against experimental data has been accomplished. The models can avoid acquiring expensive equipment in order to understand nozzle spray performance, and droplets generated. Quality, water droplet velocity, size, energy, and water consumption are the core of the current study. Last but not least, the methodology for this model can be used in any other air-mist nozzle design.<br></div>

This work includes the development of computational fluid dynamic (CFD) and finite element analysis (FEA) models to investigate fluid flow , solidification, and stress in the shell within the mold during continuous casting. The flow and solidification simulation is validated using breakout shell measurements provided by an industrial collaborator. The shell can be obtained by the solidification model and used in a FEA stress model. The stress model was validated by former research related to stress within a solidifying body presented by Koric and Thomas. The work also includes the application of these two models with a transient solidification model and a carbon percentage investigation on both solidification and deformation.