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2 Journal of Mechanical and Energy Engineering

2 2019

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Measurement of flow parameters in a Taylor-Couette configuration using UDV measurement technology

Meironke Heiko, Klembt Daniel

Journal of Mechanical and Energy Engineering

2019

Vol. 3, No 3

259--266

In the context of the investigations of multiphase flows, e.g. in cooperation with the local brewery, the convective transport phenomena during the fermentation are investigated. Due to the strong turbidity of the medium, the measurement of velocity profiles is complicated. The difficulties of an investigation with a biological fermentation fluid are the many complex interactions between the different three phases (solid, gas, liquid). Furthermore, natural convection processes are superimposed by rising gas bubbles and the high turbidity of the fluid only allow an acoustic velocity measurement. This leads to high requirements for the measurement technology and the following evaluation. In previous investigation, ultrasonic transducers are used for the non-contact determination of velocity fields in fluids. The results of these past projects show that the measurement signals of the ultrasonic transducers used can be influenced by many factors. In order to verify the results of the transducers and to investigate the existing uncertainties, a flow configuration with a relatively stable reproducible flow pattern is required. In this study, a calibration system for ultrasonic transducers is developed, manufactured and validated by means of optical measurement technology such as the LDA. The experimental setup in this study produces a constantly reproducible Taylor Couette fluid flow. Geoffrey I. Taylor observed in 1923 that at a certain Reynolds number regular ring vortices are superimposed on the base flow. Along the axis, these vortices occur at the same distance, but with an alternating sense of rotation. Finally, a measurement using Ultrasonic Doppler Velocimetry in a model fluid will be compared with an optical measurement technique.

Experimental and numerical investigations of natural convection phenomena in a fermentation tank

Klembt Daniel, Meironke Heiko

Journal of Mechanical and Energy Engineering

2019

Vol. 3, No 3

235--244

In the context of investigations of real multiphase flows, the university has its own 350 litre fermentation tank with comprehensive acoustic flow and temperature measurement technology for the systematically investigation, of the influence of the fermentation activity, distribution of yeast and occurring convection phenomena. Due to the many problems with the optical (e.g. PIV) and acoustic (e.g. UDV) measurement in a real fermenting fluid the numerical simulation was already used in earlier publications. To validate the numerical models, extensive experimental investigations were carried out which show that the flow in the fermenter is caused only by the reaction products of the yeast and the cooling panels and controls the yeast distribution. In this paper, both the numerical (CFD) and the experimental investigations serve as a starting point to influence the yeast distribution. The described convection flow can only temporarily guarantee the uniform distribution of the yeast in the fermenter until the sedimentation of the yeast at the tank bottom (bottom-fermenting yeast) finally begins. The aim of the investigation is to influence the convection flow in certain zones by targeted cooling or heating of the jackets in such a way that a uniform spatial distribution of the yeast over the entire fermentation process is ensured and thus optimal conditions for its metabolic processes are given. Finally, the numerical simulation is validated with the experimental data.