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Applied Research


Basic Research
[conference paper: 9th OpenFOAM® Workshop, Zagreb, Croatia, 06/2014] [download]
Continuous mixtures are characterized by a large amount of components with similar properties such that it is not feasible to determine each one of them. These mixtures can be represented by a continuous component using a distribution function to characterize its composition. Examples of continuous mixtures are oil fractions and polymer solutions. The semicontinuous mixture is defined as a multicomponent mixture with continuous component and discrete components with known compositions. In order to solve the mass transport equation of a continuous component using the conventional discrete component approach, the distribution function has to be described by pseudocomponents which are usually determined by quadrature based methods. However, the elevated number of pseudocomponents required to capture the composition changes during mass transfer process still represents a drawback for Computational Fluid Dynamics (CFD) simulations. The present work consists on the implementation of the DQMoM for the solution of mass transport equation for the continuous component. It is based on the extension of the adaptive Quadrature Method of Moments (QMoM) for continuous thermodynamics to field problems. It was implemented in the OpenFOAM1.6ext as a compressible ideal gas flow solver. The DQMoM for continuous component were compared with the conventional discrete component model (DCM) in a mixing flow of a mixture of 57 hydrocarbons with nitrogen. It was shown that 4 adaptive DQMoM pseudocomponents were enough to reproduce the DCM mixture properties with a 3% accuracy. Furthermore, the DQMoM CFD solution was approximately two times faster than the conventional solution for the mixture flow.
[Doctoral Thesis in Chemical Engineering at the Federal University of Rio de Janeiro, Advisors: Paulo L. C. Lage, Luiz Fernando L. R. Silva, 05/2014] [download (Portuguese only)]
CFD simulation of transient flow of semicontinuous mixtures is still a major challenge due to the high computational cost associated with the excessive number of pseudocomponents needed to accurately characterize the continuous component. Continuous mixtures are represented by a continuous component using a distribution function for its composition. In order to solve the mass transport equations of such mixtures using the conventional discrete component approach, the distribution function has to be discretized into pseudocomponents that are usually determined by quadrature based methods. In the present work, a new method was developed to solve the mass transfer in the flow of a semicontinuous multicomponent mixture. The continuous component was adaptively characterized using the DQMoM (Direct Quadrature Method of Moments). The main contribution is a method to solve the compressible flow with mass transfer of a semicontinuous mixture using the DQMoM and the Fick or MaxwellStefan diffusion models. The new method has been validated for a mixing process in a ``T" channel in a laminar and isothermal flow of an ideal gas. Preliminary results show that the DQMoM using the MaxwellStefan model and 6 pseudocomponents is 10 times faster than the conventional solution of a mixing flow with 58 components, reproducing the conventional thermodynamic mixture properties, such as dew and bubble pressures, with a 2% error. On the other hand, the DQMoM using the Fick model and 6 pseudocomponents is 1.5 times faster and showed an error of 1.5% in the thermodynamic properties of the mixture.
[article: Computers & Chemical Engineering, vol. 64, pg 153166, 05/2014] [ link ]
We developed a method for the solution of the compressible flow with mass transfer of semicontinuous mixtures and it is based on the Quadrature Method of Moments (QMoM) for continuous thermodynamics. The method extends the adaptive characterization of the continuous mixture to field problems and solves the mass transport equation for the continuous component. The method is referred as Direct QMoM, or DQMoM, for continuous thermodynamics. It was implemented in the OpenFOAM® as a compressible ideal gas flow solver. The DQMoM was applied to the mixing flow of two gas streams with different compositions of a mixture with 57 hydrocarbons diluted in nitrogen. We showed that 4 adaptive components reproduced the mixture properties within 3% accuracy. Furthermore, the DQMoM CFD solution was approximately two times faster than the solution using 58 discrete components.
[conference paper: AIChE Annual Meeting, San Francisco, USA, 11/2013] [ download ]
Continuous mixtures are characterized by a large amount of components with similar properties which makes the determination of its exact composition unfeasible. These mixtures can be represented by a continuous component using a distribution function to characterize its composition. The distribution variable can be the molar mass or any other convenient property. Examples of continuous mixtures are oil fractions and polymer solutions. If the mixture has some known components, it is treated as a semicontinuous mixture. In order to solve the mass transport equation of a continuous component using the conventional discrete component approach, the distribution function has to be described by pseudocomponents which are usually determined by quadrature based methods. However, the elevated number of pseudocomponents required to capture the composition changes during mass transfer process still represents a drawback for CFD simulations. The present work developed the mathematical model and numerical solution of the multicomponent mass transport equations for the flow of semicontinuous mixtures. The model is an extension of the adaptive Quadrature Method of Moments (QMoM) for continuous thermodynamics to field problems. The method is called Direct QMoM for continuous thermodynamics. It was implemented in a CFD opensource package (OpenFOAM) as a compressible ideal gas flow solver. The DQMoM for continuous thermodynamics was compared with the conventional discrete component model (DCM) in a mixing flow of two mixtures consisting of 57 hydrocarbons and nitrogen. It was shown that 4 adaptive DQMoM pseudocomponents were enough to reproduce the properties of the DCM mixture with a 2% accuracy. Furthermore, the DQMoM CFD solution was approximately two times faster than the DCM solution for the mixture flow.