Untersuchung der Strömungsformen im Spalt zwischen einer rotierenden Scheibe und einer ruhenden Gegenscheibe

The flow in the gap between a rotating and a parallel static opposite disk is simulated for a small gap width and without flow rate by using computational fluid dynamics. The velocity distribution for different flow regimes is presented. Based on the simulation results the velocity profiles in the turbulent region with “separate boundary layers” are described by approximate equations.     

Three‐Dimensional CFD Simulation of Stratified Two‐Fluid Taylor‐Couette Flow

Two‐fluid Taylor‐Couette flow, with either one or both of the co‐axial cylinders rotating, has potential advantages over the conventional process equipment in chemical and bio‐process industries. This flow has been investigated using three‐dimensional CFD simulations. The occurrence of radial stratification, the subsequent onset of centrifugal instability in each phase, the cell formation and the dependency on various parameters have been analyzed and discussed. The criteria for the stratification, Taylor cell formation in each phase have been established. It can be stated that the analysis of single‐phase flow acts as the base state for the understanding of radial stratification of the two‐fluid flows. The extent of interface deformation also has been discussed. A complete energy balance has been established and a very good agreement was found between dissipation rate by CFD predictions and the energy input rate through the cylinder/s rotation.     

Numerische Simulationen der katalytischen Methanisierung von CO2 in einem pseudo‐homogenen Strömungsrohr

Power to gas is an attractive option for storing excess energy from fluctuating renewable energy sources. In recent years, the concept has gained great interest. An essential part of the process chain of power to gas is the methanation of CO₂. Within this work the catalytic methanation of pure CO₂ and of biogas is modeled in a three‐dimensional polytropic pseudo‐homogeneous flow tube and numerically simulated at different loads. The results represent axial and radial quantitative information about the reaction behavior under the different boundary conditions.     

CFD‐Simulation zur Berechnung der durch Gewebestrukturen induzierten Strömungsfelder mithilfe der Immersed‐boundary‐Methode

Woven structures are often used for separation of solid particles. The solid phase is separated when the fluid flows through the woven structure. Knowing the nature of the flow can be profitably used for the optimization of these structures (e.g., reduction of the pressure loss) and to predict the separation efficiency. In general, computational fluid dynamics allows the calculation of the flow field. In this paper, the immersed boundary method is shown as an efficient way to simulate the flow field within woven structures and reduce modeling efforts compared to the standard CFD method.     

Numerical Simulation of Sterilization Processes for Shear‐Thinning Food in Taylor‐Couette Flow Systems

The performance of the Taylor‐Couette flow apparatus as a heat sterilizer is numerically investigated. The destruction of Clostridium botulinum and thiamine (vitamin B1) was selected as model reaction. When Taylor vortices were formed in the annular space, the heat transfer significantly enhanced as compared to the case without vortex flow. As a result, the equivalent lethality calculated from the temperature field increased, which is regarded as a quantum leap. Conversely, the improvement of heat transfer induced destruction of thiamine. These results suggest that there is a trade‐off relationship between the enhancement of heat transfer and the avoidance of thermal destruction of nutritional components. In conclusion, the Taylor‐Couette flow sterilizer has the potential for process intensification in heat sterilization processes.     

Modellierung und Simulation von Strömungen und biologischen Reaktionen innerhalb eines Belebtschlammbeckens

With the aim to increase the efficiency of the aeration tanks of municipal wastewater treatment plants, the implementation of a biological model system (ASM1) into the CFD code ANSYS CFX® is presented for modeling a full‐scale aeration tank and verified with experimental data. Taking into account the biological processes, hydrodynamics and gas‐liquid mass transfer, simulations were performed and compared to experimental concentration profiles for ammonium and nitrate. The assumptions made are explained in detail. While the simulated ammonium concentration profile is in good agreement with the measured values, deviations occur for the nitrate profile. However, the CFD simulations exceed the prediction accuracy of conventional 0D simulation software.     

Regimes of Multiple Emulsions of W1/O/W2 and O1/W/O2 Type in the Continuous Couette‐Taylor Flow Contactor

The flow regimes of multiple emulsions in the continuous Couette‐Taylor flow (CTF) contactor and characterization of the dispersion state are reported. The proposed method of multiple emulsion preparation is a one‐step procedure on the contrary to the classical two‐step procedure. The effect of operating parameters in the CTF contactor on multiple emulsion appearance, structure (drop size and packing), and rheological behavior is discussed. The key factors affecting multiple emulsion preparation in the CTF apparatus were the phases ratio, the rotational flow, and an annular gap width. The influence of an axial flow was more significant in the range of small rotational rates. The operating conditions were optimized to find the best characteristic multiple emulsions (largest interfacial area). The paper presents the same exemplary data of using W₁/O/W₂ emulsions as emulsion liquid membranes (ELMs) in the extraction process and O₁/W/O₂ for control active agent (drug) release.     

Effect of Rotor Disc Diameter on Holdup,Axial Dispersion and Droplet Size in a Taylor‐Couette Disc Contactor

Application of liquid‐liquid extraction is on a steady rise. Although there are considerable designs of extraction devices, equipment design and optimization is still on the research agenda. Utilization in the biorefinery industry or metallurgy requires robust technologies and equipment. The simple design and stable operation performance of the Taylor‐Couette disc contactor suffices the technical needs for these harsh operation conditions. The effect of different rotor disc diameter on the dispersed phase holdup, axial dispersion, and droplet size was investigated. It was shown that with smaller rotor disc diameter stable operation is still feasible but higher axial backmixing has to be expected.     

CFD‐Simulation und LDA‐Messung der Strömungsvorgänge beim Fluidphasenresonanzmischen

The principle of fluid phase resonance mixing is to apply harmonic oscillating pressure via a gas cushion on a liquid phase in a vessel and thus to cause the liquid phase to start oscillating. This principle is simulated as an unsteady flow of two separate phases with open source CFD software OpenFOAM and the results are verified with measurements by Laser Doppler Anemometry.