Computational fluid dynamics simulation of precipitation processes

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2004-01-01
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Wang, Liguang
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Rodney O. Fox
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Chemical and Biological Engineering

The function of the Department of Chemical and Biological Engineering has been to prepare students for the study and application of chemistry in industry. This focus has included preparation for employment in various industries as well as the development, design, and operation of equipment and processes within industry.Through the CBE Department, Iowa State University is nationally recognized for its initiatives in bioinformatics, biomaterials, bioproducts, metabolic/tissue engineering, multiphase computational fluid dynamics, advanced polymeric materials and nanostructured materials.

History
The Department of Chemical Engineering was founded in 1913 under the Department of Physics and Illuminating Engineering. From 1915 to 1931 it was jointly administered by the Divisions of Industrial Science and Engineering, and from 1931 onward it has been under the Division/College of Engineering. In 1928 it merged with Mining Engineering, and from 1973–1979 it merged with Nuclear Engineering. It became Chemical and Biological Engineering in 2005.

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1913 - present

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  • Department of Chemical Engineering (1913–1928)
  • Department of Chemical and Mining Engineering (1928–1957)
  • Department of Chemical Engineering (1957–1973, 1979–2005)
    • Department of Chemical and Biological Engineering (2005–present)

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Abstract

First, an experimental and computational investigation of the effects of local fluid shear rate on the aggregation and breakage of ~10 mum latex spheres suspended in an aqueous solution undergoing laminar and turbulent Taylor-Couette flow was carried out, according to the following program. First, computational fluid dynamics (CFD) simulations were performed and the flow field predictions were validated with data from particle image velocimetry experiments. Subsequently, the quadrature method of moments (QMOM) was implemented into the CFD code to obtain predictions for mean particle size that account for the effects of local shear rate on the aggregation and breakage. These predictions were then compared with experimental data for latex sphere aggregates (using an in-situ optical imaging method) and with predictions using spatial average shear rates. The mean particle size evolution predicted by CFD and QMOM using appropriate kinetic expressions that incorporate information concerning the particle morphology (fractal dimension) and the local fluid viscous effects on aggregation collision efficiency matches well with the experimental data. Second, CFD simulation of turbulent reactive precipitation in a poorly micromixed plug-flow reactor has been investigated in this work. The predictions of multi-environment and transported PDF models are compared. For the first time, DQMOM is formulated and applied to approximate the composition PDF transport equation. When properly chosen, the resulting DQMOM correction terms enforce agreement between selected lower-order moments of the mixture-fraction PDF and the exact moment transport equations. Likewise, for reacting scalars, the multi-environment PDF model provides a closure for the chemical source term, and the DQMOM correction terms enforce the correct behave of the lower-order moments under the influence of turbulent diffusivity. Results for reactive precipitation show that the DQMOM-IEM model agrees closely with a transported PDF model. Since the multi-environment PDF model is much less computationally intensive than the transported PDF model, it is easy and extremely promising to couple the simple Eulerian-based multi-environment PDF models with a commercial CFD code for realistic industrial problems. Third, a novel algorithm, in-situ adaptive tabulation, has been implemented in a CFD code for the integration of reactive precipitation. A speed-up of ~10 was achieved.

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Thu Jan 01 00:00:00 UTC 2004