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978-3-8439-0015-7, Reihe Verfahrenstechnik
Neue Messtechniken und Simulationen für die Strömungsvorgänge und den örtlichen Stoffübergang in nicht-Newtonschen Fluiden
170 Seiten, Dissertation Universität Hohenheim Stuttgart-Hohenheim (2010), Softcover, A5
Flow and transport phenomena in non-Newtonian fluids are of significant industrial interest. As a kind of static mixer, spacers play an important role in process engineering concerning problems of mixing, homogenizing and dispersing in connection with residence time behavior up to the enhancement of heat and mass transfer. However, the efficiency of such spacers strongly depends on fluid properties, the characteristic geometry and operating conditions. Additionally, it is very difficult to respond to changed operating conditions for such spacers and ill-designed feed spacers can hinder the realization of a high performance.
Here, experimental and numerical methods were introduced for the investigation of flow phenomena and mass transfer for non-Newtonian fluids in spacer-filled channels.
Based on a coupled chemisorption reaction between the sulfonic acid group of Acidol-Blue and the -NH2- group of Polyamide, an experimental mass transfer method was used to visualize the flow phenomena, determine the local mass transfer, quantify the mixing behavior and determine the homogeneity of mass transfer for Newtonian fluid flow. This method is extended to the case of non-Newtonian fluids in spacer-filled channels in this study.
Numerical methods were also introduced in this study. Three-dimensional computations based on a commercial computational fluid dynamics (CFD) code have been conducted to study the flow phenomena and local mass transfer for non-Newtonian fluids in spacer-filled channels. The simulations focus on a single characteristic diamond of the spacer, which plays an important role in saving computer resources as well as computing time and provides immediate information on the effect of the spacer geometry. Due to the existence of a high viscosity in the non-Newtonian fluids, the laminar flow for low Reynolds number is of the most interest. Equations for the laminar boundary layer with periodic interfaces for steady state were solved three-dimensionally in this study. The equations were coupled with a diffusive transport equation, Acidol-Blue was added as a specific additional variable into computations, when mass transfer was taken into account. Diffusion coefficients for different concentrations of METHOCEL® K15M, determined by PFG-NMR, were used in these calculations.