23 de mar de 2010

Artigo em Destaque

AIChE Journal - Fluid Mechanics and Transport Phenomena

Estimation of mass transfer velocity based on measured turbulence parameters
Johannes G. Janzen 1 *, H. Herlina 2, Gerhard H. Jirka 2, Harry E. Schulz 3, John S. Gulliver 4
1Dept. of Environmental Engineering, Federal University of Rondônia, Jardim dos Migrantes, Ji-Paraná 76900-726, RO, Brazil
2Institute for Hydromechanics, University of Karlsruhe, Karlsruhe 76128, Germany
3Centre of Thermal Engg. and Fluids, Dept. of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Carlos 13560-970, SP, Brazil
4Dept. of Civil Engineering, University of Minnesota, Minneapolis, MN 55455

The aim of this study is to quantify the mass transfer velocity using turbulence parameters from simultaneous measurements of oxygen concentration fields and velocity fields. The surface divergence model was considered in more detail, using data obtained for the lower range of  (surface divergence). It is shown that the existing models that use the divergence concept furnish good predictions for the transfer velocity also for low values of , in the range of this study. Additionally, traditional conceptual models, such as the film model, the penetration-renewal model, and the large eddy model, were tested using the simultaneous information of concentration and velocity fields. It is shown that the film and the surface divergence models predicted the mass transfer velocity for all the range of the equipment Reynolds number used here. The velocity measurements showed viscosity effects close to the surface, which indicates that the surface was contaminated with some surfactant. Considering the results, this contamination can be considered slight for the mass transfer predictions. © 2009 American Institute of Chemical Engineers AIChE J, 2010


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