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Dal'Toe A.T.O.,Federal University of Santa Catarina | Padoin N.,Federal University of Santa Catarina | Ropelato K.,Engineering Simulation and Scientific Software Ltda. ESSS | Soares C.,Federal University of Santa Catarina
International Journal of Heat and Mass Transfer | Year: 2015

Realistic mathematical modeling of multicomponent mixtures is highly complex due to diffusive phenomena (cross diffusion effects) not described by Fick's law. The Maxwell-Stefan equations and generalized Fick's law can represent all possible interactions in multicomponent mixtures and, thus, the effects of cross diffusion are considered. The present work was planned to study the interfacial heat and mass transfer and cross diffusion effects in a multicomponent mixture. For this purpose, three computational routines based on a constant diffusion coefficient model, on the effective diffusivity model and on the Maxwell-Stefan equations along with the generalized Fick's law were developed. The models were applied to study mass and heat transfer in a binary air-water mixture and in a multicomponent mixture composed of methane, n-pentane, n-hexane and n-octane. The equilibrium achieved in the CFD studies was verified with data obtained from a psychrometric chart, (for the binary mixture), and the values obtained by the process simulator PRO/II® (for the multicomponent mixture). It was found that the cross diffusion effects were not significant in the mixture studied, leading to the conclusion that simpler approaches, such as the effective diffusivity model, can be used to describe the mass transfer in ideal multicomponent mixtures. © 2015 Elsevier Ltd. All rights reserved. Source


Padoin N.,Federal University of Santa Catarina | Souza A.Z.D.,Federal University of Santa Catarina | Ropelato K.,Engineering Simulation and Scientific Software Ltda. ESSS | Soares C.,Federal University of Santa Catarina
Chemical Engineering Research and Design | Year: 2016

Microchannel technology has attracted great interest due to its potential for process intensification and design of compact devices. In this study, isothermal gas-liquid flow patterns (Taylor and stratified) developed in a rectangular microchannel were numerically evaluated through the volume of fluid (VOF) model. Hydrophilic (θw = 25°) and hydrophobic (θw = 105°) microchannels were investigated. The numerical results were compared with experimental data. A comparison between numerical and experimental data and some available correlations showed good agreement. At similar feeding conditions, the model was able to capture the different gas-liquid flow patterns expected when the wall contact angle is varied. Thus, this work elucidated the use of CFD for the evaluation of the impact of variations of the wall wettability on isothermal gas-liquid flow patterns developed in microchannels. This procedure can be used as a source of preliminary information on the flow morphology expected in microfluidic devices subjected to superficial treatment. © 2016 The Institution of Chemical Engineers. Source


Monteiro H.C.,Engineering Simulation and Scientific Software Ltda. ESSS | Rangel L.P.,Engineering Simulation and Scientific Software Ltda. ESSS | Da Silva A.F.C.,Federal University of Santa Catarina | Pereira J.C.,Federal University of Santa Catarina | And 3 more authors.
13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery 2010, ISROMAC-13 | Year: 2010

This work concerns the transient steam flow simulation in a steam turbine bladed disk for a blade fatigue analysis of a thermoelectric power plant. The purpose of this work is to obtain the transient flow pressure due to steam over the 5 th stage blades of this turbine using a Computational Fluid Dynamics analysis at a commercial code ANSYS CFX 12. In the present work, the turbulent and compressible flow is solved for the gathered 4 th and 5 th stages of the turbine. The medium and the alternating stresses induced by the transient flow pressure fluctuation must be used in an ulterior fatigue analysis of the 5 th stage blades. The fatigue analysis will be performed after the end of this prior work has been validated. Copyright © 2010 by ISROMAC-13. Source


Padoin N.,Federal University of Santa Catarina | Dal'Toe A.T.O.,Federal University of Santa Catarina | Rangel L.P.,Engineering Simulation and Scientific Software Ltda. ESSS | Ropelato K.,Engineering Simulation and Scientific Software Ltda. ESSS | Soares C.,Federal University of Santa Catarina
International Journal of Heat and Mass Transfer | Year: 2014

Heat and mass transfer take place in a large number of processes. These phenomena are encountered in systems comprised of two or more phases, in which at least one of them is a mixture of many chemical species. The predictability of such multiphase and multicomponent systems plays a major role in the efficient design and operation of equipment and processes, where CFD has been frequently applied successfully over the past decade. Modeling multicomponent flow remains a challenge in relation to both micro or macro systems. In this study, simulations were carried out with the commercial code ANSYS® CFD (FLUENT®), version 14.0, and customized functions developed to predict the equilibrium compositions and temperature of a vapor-liquid system. A preliminary study on a binary mixture (water/air) was conducted in order to validate the results obtained with the commercial code using the data obtained from a standard psychrometric chart. In addition, simulations were carried out for a mixture of four pure hydrocarbons (methane, n-pentane, n-hexane and n-octane). Thus, a complete multicomponent mass transfer theory, based on Maxwell-Stefan's equations, was applied as a customized function code, which can be used to calculate high flux corrections and the convective mass flux. The results were verified with predicted values obtained using the steady-state process simulator PRO/II®, version 8.2. © 2014 Elsevier Ltd. All rights reserved. Source

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