Mathematical Analysis of Inclusion Removal from Liquid Steel by Gas Bubbling in a Casting Tundish

The mechanism of inclusion removal from liquid steel by gas bubbling and bubble attachment in the tundish is complex due to the great number of variables involved, and it is even more difficult to study because of the turbulent flow conditions. The main objective of this work is to analyze and improve the understanding of the alumina inclusion removal rate by bubble attachment and by gas bubbling fluid dynamics effects. The results show that the inclusion collection probability mainly depends on the attachment mechanism by collision. This parameter was determined by calculating the induction time, which is shorter when the rupture time and the formation time of a stable three phases contact (particle/liquid/gas) are ignored than when it is fully considered, affecting the attachment probability. In addition, to achieve acceptable inclusion removal, a smaller bubble diameter is required, such as 1 mm. This consideration is almost impossible to achieve during tundish operation; a more realistic bubble diameter around 10 mm is employed, resulting in a very inefficient inclusion removal process by bubble attachment. Nevertheless, in a real casting tundish the inclusion removal rate employing argon bubbling is efficient; is mainly due to the fluid flow pattern changes rather than bubble attachment. Consequently, it is imperative to consider the summation of both removal mechanisms to compute a better approximation of this important operation

Comparison of experimental and Computational Fluid Dynamics (CFD) studies of slug flow in a vertical riser

This paper presents a comparison of the results obtained from experiments and CFD studies of slug flow in a vertical riser. A series of two experimental investigations were carried out on a 6 m vertical pipe with a 0.067 m internal diameter charged with an air–silicone oil mixture. For the first set of experiments, the riser was initially full of air, and then liquid and gas flows set to liquid and gas superficial velocities = 0.05 and 0.344 m/s, respectively, electrical capacitance tomography (ECT) and wire mesh sensor (WMS) transducers were employed. In the second one, the riser was initially full of (static) liquid, and then liquid and gas flows set to liquid and gas superficial velocities = 0.05 and 0.344 m/s, respectively, only ECT was used. A characterisation of the observed slug flow regimes was carried out. This includes the evaluation of the instantaneous distribution of the phases over the pipe cross-section, the Probability Density Function (PDF) of void fraction, time series of cross-sectional void fraction, Power Spectral Density (PSD), structure velocity of the Taylor bubble, lengths of the liquid slug and Taylor bubble and void fractions in the liquid slug and Taylor bubble. The simulation results were validated both qualitatively and quantitatively against experimental data. A reasonably good agreement was observed between the results of the experiment and CFD

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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Miradas y voces de la investigación educativa I

Fil: Ferreyra, Horacio Ademar. Universidad Católica de Córdoba. Facultad de Educación; ArgentinaFil: Calneggia, María Isabel. Universidad Católica de Córdoba. Facultad de Educación; ArgentinaFil: Di Francesco, Adriana Carlota. Universidad Católica de Córdoba. Facultad de Educación; Argentin

“DISEÑO DEL SISTEMA DE MEDICIÓN Y CONTROL DE UN PROTOTIPO DE STATCOM BASADO EN UN DSC”

El presente trabajo se enfoca al diseño del sistema de medición y control de un STATCOM, asi como la construccion del prototipo. Para realizar el control se ha puesto especial atención en el modelado matemático del STATCOM. Apoyados en la transformacion de Park se diseñaron controladores desacoplados para la potencia real y reactiva, los cuales fueron diseñados en el dominio discreto usando retroalimentacion de estado. Integrando estos controladores se diseñó un controlador PI para regular el voltaje del capacitor. El hardware construido básicamente se compone de dos etapas: la etapa de procesamiento de las señales que proporciona información del STATCOM y del sistema eléctrico esta etapa está constituida por dos tarjetas una para los transductores y otra para el filtrado y acondicionamiento de nivel de las señales provenientes de los transductores, la otra etapa se encarga de suministrar las señales de control al puente convertidor trifásico en el cual basa su operación el STATCOM. Esta etapa se compone de dos partes, una que se denomina controladora del puente convertidor (la cual fue dividida en tres tarjetas una para cada fase) y la otra parte es la tarjeta del puente convertidor trifásico la cual se construyó con transistores IGBTs como dispositivo de conmutación. La construcción del hardware se realizó con un enfoque para que en un futuro se implemente el sistema de control en un controlador digital de señales TMS320F28335 fabricado por Texas Instruments. Las aportaciones de este trabajo son importantes debido a que el hardware construido servirá para validar modelos matemáticos simulados digitalmente, tambien para experimentar diferentes esquemas de control. Como aportación inmediata el hardware diseñado servirá en la construccion de un sistema de transmision HVDC Light. Mas adelante se presenta la simulación de dos casos de estudio, los cuales sirven para validar el sistema de control implementado. Estos casos de estudio pueden servir para comparar los resultados del STATCOM con otros compensadores de potencia reactiva