Rodrigo Béttega

Three-Dimensional Numerical Simulation of Semi-Cylindrical and Cylindrical Spouted Bed Hydrodynamics

Understanding of detailed transport phenomena occurring in spouted beds is necessary and fundamental for increasing the range of industrial applications. Especially for drying processes, detailed information about hydrodynamics is important, because it is closely related to heat and mass transfer. The use of semi-cylindrical spouted beds is a classical technique that emerged as an alternative to obtaining experimental data on the fluid dynamics of full-column spouted beds. This technique has been questioned, because the geometry of the bed must be altered for the visualization of the hydrodynamics occurring inside it, which, nevertheless, is the only way to obtain visual information on solid dynamics behavior inside the column. Therefore, the objective of this study was to revisit the semi-cylindrical spouted bed technique using computational fluid dynamics to perform numerical simulations and verifying these results against experimental results obtained in cylindrical and semi-cylindrical beds. Both simulated and experimental results were compared for the fluid dynamics of each system. The simulated results indicated that the flat wall had a great influence on the solid velocity, which is in accordance with the experimental observations already presented in the literature. However, little influence of this wall on static pressure, porosity profiles, and spout channel shape was observed in the simulated results, indicating a high fluid dynamic similarity between cylindrical and semi-cylindrical systems.

Velocity Profile in Fixed Beds: A Study on the Representativeness of the Experimental Measurement of Downstream Flow Characteristics

Although considerable progress has been made in the development of experimental techniques for investigating velocity distribution inside a fixed bed, these techniques were limited to special cases. Consequently, the velocity distribution is normally measured at downstream of the fixed bed and then this measurement is considered to be representative for the flow inside the bed. To evaluate the representativeness of this technique, this work presents a study of the change in the flow characteristics, starting from the boundary of the fixed bed within the pipe to a downstream position where the experimental measurement is taken, by using simulations based on computational fluid dynamics methods.

Drying kinetics, structural characteristics and vitamin C retention of dedo-de-moça pepper (Capsicum baccatum) during convective and freeze drying

The main objective of this study was to evaluate the effect of the drying process on the vitamin C levels and physical properties of dedo-de-moca pepper. The drying kinetics and the structural properties were determined as a function of moisture content. Convective drying was compared with freeze-drying in terms of product quality, structural properties, retention of vitamin C and rehydration characteristics. Empirical and semi-empirical equations were used to describe the drying and rehydration kinetics. Nonlinear analysis applied to results of convective drying, based on curvature measures and bias measures, showed that the only equation that gives good inference results based on least squares estimators is the Overhults equation. The characterization of the rehydration process was done by determining the indexes that take into account the water absorption capacity and solutes losses. The material dried by lyophilization show greater potential to rehydrate.

Global performance parameters for different pneumatic bioreactors operating with water and glycerol solution: experimental data and CFD simulation.

Global variables play a key role in evaluation of the performance of pneumatic bioreactors and provide criteria to assist in system selection and design. The purpose of this work was to use experimental data and computational fluid dynamics (CFD) simulations to determine the global performance parameters gas holdup (

AVALIAÇÃO DA HIDRODINÂMICA DE UM LAVADOR VENTURI: DADOS EXPERIMENTAIS E SIMULAÇÃO NUMÉRICA

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BB 06. Avaliação do tempo de circulação em biorreatores airlift com região de mistura expandida

α¯G) and volumetric oxygen transfer coefficient (kLa), and conduct an analysis of liquid circulation velocity, for three different geometries of pneumatic bioreactors: bubble column, concentric-tube airlift, and split tube airlift. All the systems had 5 L working volumes and two Newtonian fluids of different viscosities were used in the experiments: distilled water and 10 cP glycerol solution. Considering the high oxygen demand in certain types of aerobic fermentations, the assays were carried out at high flow rates. In the present study, the performances of three pneumatic bioreactors with different geometries and operating with two different Newtonian fluids were compared. A new CFD modeling procedure was implemented, and the simulation results were compared with the experimental data. The findings indicated that the concentric-tube airlift design was the best choice in terms of both gas holdup and volumetric oxygen transfer coefficient. The CFD results for gas holdup were consistent with the experimental data, and indicated that kLa was strongly influenced by bubble diameter and shape.

Use of Fluid Dynamic Simulation to Improve the Design of Spouted Beds

Abstract The aim of this study was to evaluate different intermittency ratios applied to a spouted bed used to dry alumina, from the energy perspective. Two types of intermittency (reduction and total interruption of the air flow) and five different intermittency profiles were evaluated, including the use of time-variant intermittency ratios. The use of intermittency provided higher energy efficiency and better use of the energy supplied, compared to the continuous process. Reductions of energy consumption in the range from 13.2% to 67.2% were obtained, relative to the continuous process. The findings showed that the use of intermittency is a promising way to optimize energy consumption in spouted beds.

Scale-up study of spouted beds using computational fluid dynamics

O lavador Venturi é um equipamento de reconhecida eficiência na remoção de micropartículas de efluentes gasosos. O seu princípio de funcionamento envolve a injeção de um líquido de lavagem que é responsável pela captura das partículas. O líquido, geralmente introduzido através de pequenos orifícios, quando entra em contato com o ar em altas velocidades gera inúmeras gotas. A distribuição uniforme das gotas no lavador promove o contato adequado entre líquido e partícula, influenciando a eficiência de coleta. Desta forma, estudos acerca de condições operacionais considerando o uso apropriado de líquido e a sua distribuição no lavador, bem como modelos computacionais para sua previsão, são relevantes. Neste contexto, o presente estudo tem por objetivo avaliar experimentalmente e numericamente a distribuição de líquido em um lavador Venturi operando em diferentes condições. O comportamento fluidodinâmico do escoamento ar-água foi simulado utilizando o pacote comercial ANSYS FLUENT 14.0 através da implementação de um modelo de trajetória para fase discreta. Os resultados simulados acerca da hidrodinâmica do equipamento apresentaram desvios baixos quando comparados com os experimentais, já que tanto o perfil de pressão, a dispersão de líquido, quanto à porcentagem de filme aderido as paredes apresentaram comportamento em concordância com os previstos nas simulações.