Proposta de uma nova metodologia para a determinação da transição catarateamento-centrifugação utilizando partículas esféricas e não-esféricas em um tambor rotatório via técnicas de CFD

• Autor(a) principal: Benedito, Wanessa Mendonça
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/10450
• topic: Modelo Euleriano Granular Multifásico (MEGM); Viscosidade friccional; Formato da partícula; Efeito de parede; Regimes de escoamento em tambores; Multiphase Granular Eulerian Model (MGEM); Frictional viscosity; Particle shape; End-caps effect; Drum flow regimes.; ENGENHARIAS::ENGENHARIA QUIMICA

Rotary drums are widely utilized in several industrial processes, such as drying, mixing, milling, granulation, among others. The widespread frequent use of rotary drums is due to their simple design and their capability to handle materials characterized by broad size distributions with significant differences in their physical properties. The granular flow inside rotary drums can be classified in different forms: sliding, slumping, rolling, cascading, cataracting, and centrifuging regimes. This classification depends on the drum operating conditions and the physical properties of the particulate material envolved in the granular flow. There are have been no reposts in the literature that presents a precise methodology for cataracting-centrifuging transition identification in rotary drums. This identification is carried out exclusively by visual and subjective way. In this context, the present work aims the proposition of a methodology for the cataracting-centrifuging transition identification, for different particle shapes, using the Multiphase Granular Eulerian Model (MGEM), implemented by CFD simulations. When compared to the Lagrangian model (DEM), the mainly difficult associated with Eulerian model is the particle shape representation, since the solid phase is treated as continuous in CFD simulations. The particle shape for non-spherical particles was indirectly represented in the MGEM using the critical solid fraction (αsc), a parameter associated with the Schaeffer’s frictional model. The present work is also dedicated to overcoming this difficulty. The drum length effect on the cataracting-centrifuging transition was also analyzed. Using the methodology herein proposed was verified that the particle shape and the drum length influence the cataracting-centrifuging transition behavior. For nonspherical particles was required lower values of rotation speed to reach the centrifuging regime condition when compared with spherical particles. It was verified that the lower the drum length, the higher the facility associated with the transition for centrifuging regime for both particle shapes.