Practical trainings, student assistants and theses

Characterizing overflowing froth using ultrasonic reflectometry (Id 347)

Bachelor theses / Master theses / Diploma theses / Compulsory internship / Volunteer internship

Froth flotation is a widely applied process in the separation of materials. There, the froth phase which consists of foam with particles has a
tremendous impact on the overall process performance. An efficient control in such processes requires suitable measurement systems. However, resulting from the opaque nature of such multiphase systems, on-line monitoring of the froth in industrial settings displays a major challenge and is mostly done by means of optical systems.
As an alternative for froth characterization, the use of acoustic measurements could provide a simple solution. It was observed, that a sound wave which is sent towards the froth/air interface will be reflected and the strength of the reflected signal contains information on the froth composition. This has the potential for advanced measurement systems.
In the next step, a deeper understanding of the relationship between reflected signal strength and the froth composition is required. Additionally, the influence of the froth surface has to be studied in more detail. The work aims at investigating this relationship and the influencing parameters in a laboratory flotation cell. This includes acquisition and processing of ultrasonic signals and parallel optical measurement of the froth's surface.

Department: Transport processes at interfaces

Contact: Knüpfer, Leon, Dr. Heitkam, Sascha

Requirements

  • Field of study: process engineering, mechanical engineering, or similar focus in chemistry or physics
  • Interest in experimental work
  • Experience with data processing using python is beneficial

Conditions

  • Work in multidisciplinary and international environment
  • Compensation as for HZDR conditions
  • Duration: at least 3 months

Online application

Please apply online: english / german

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Calculation of multi-phase flow using the GENTOP model with FLUENT (Id 346)

Student practical training / Master theses / Diploma theses

Foto: Fig. 1: Boiling pipe flow (left: disperse gas volume fraction, right: continuous gas volume fraction) from Setoodeh et al., Applied Thermal Engineering 204 (2022) 117962 ©Copyright: Dr. Thomas HöhneAs a member of the Helmholtz Association of German Research Centers, the HZDR employs about 1,400 people. The Center's focus is on interdisciplinary research in the areas energy, health and matter. The Institute of Fluid Dynamics is conducting basic and applied research in the fields of thermo-fluid dynamics and magnetohydrodynamics in order to improve the sustainability, the energy efficiency and the safety of industrial processes.

Multiphase flows are important part of many industrial applications, whereas modelling of them is a challenging and complex task. For flow situations with higher void fractions, HZDR developed a new generalized concept for the CFD-simulations including flow regime transitions. The GENTOP (Generalized Two-Phase Flow) approach is able to simulate co-existing large-scaled (continuous) and small-scaled (polydispersed) structures (Fig. 1). Previous results were performed with the CFD code CFX and compared against DEBORA validation data.

The goal of the thesis would be to apply and improving the existing state of the simulations in the Fluent GENTOP framework.

We offer an interesting task dealing with complex physical phenomena, work in an international team using state-of-the-art calculation and programming methods.

We are looking for a motivated student (f/m/d) (master thesis) able to perform CFD simulations, understand and program code to generalize/parametrize CFD simulations, work with experimental data sets, document and present the work in an appropriate manner. Useful but not required is a knowledge of the following software tools: CFD codes CFX and Fluent, Python, GIT.

The task is supervised by Framatome and HZDR.

FRAMATOME is a designer and supplier of nuclear steam supply system and nuclear equipment, services and fuel for high levels of safety and performance. Framatome is a major international player in the nuclear energy market recognized for its innovative solutions and value-added technologies for designing, building, maintaining, and advancing the global nuclear fleet. The company designs, manufactures, and installs components, fuel and instrumentation and control systems for nuclear power plants and offers a full range of reactor services. With 14,000 employees worldwide, every day Framatome's expertise helps its customers improve the safety and performance of their nuclear plants and achieve their economic and societal goals.

Department: Computational Fluid Dynamics

Contact: Dr. Höhne, Thomas, Dr. Lucas, Dirk

Requirements

  • Studies in Engineering, Computer Science or comparable
  • Interest in numerical work
  • Good communication skills in both written and spoken English
  • Useful but not required is a knowledge of the following software tools: CFD codes CFX and Fluent, Python, GIT.

Conditions

  • A vibrant research community in an open, diverse, and international work environment.
  • Scientific excellence and extensive professional networking opportunities.
  • Compensation as student researcher (working hours to be determined).
  • Working place will be Dresden and/or Erlangen Germany.

Online application

Please apply online: english / german

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Application of flow modulation technique to trickle bed reactors (Id 345)

Master theses / Diploma theses / Student Assistant / Compulsory internship / Volunteer internship

Trickle bed reactors are subjected to dispersion phenomena on both the gas and liquid phase. In the last decades, several models have been proposed to describe the hydrodynamics of trickle bed reactors, involving up to six parameters, as reviewed by Gianetto et al. (1978). However, the axial dispersion model remains the most practical, accepted and used one. This model assumes dispersion as a stochastic phenomenon and uses the axial liquid dispersion coefficient as the sole parameter.
Traditionally, axial dispersion coefficients are measured using the residence time behaviour of inserted tracer substances. However, such methods are hardly universally applicable considering also production units. Tracer substances can alter the physical properties of the system and may cause detrimental impurities or process downtimes.
The flow modulation technique (FMT) has been proposed by Hampel (2015) and was recently applied by Do ß et al. (2017) for measuring the axial gas dispersion coefficient in bubble columns. However, it has never been applied for measuring the axial liquid dispersion coefficient in trickle bed reactors. Using the FMT, no tracer substances are injected; instead, a marginal sinusoidal modulation is superimposed to the inlet flow rate and used as a virtual tracer. This way, the modulation introduces a sinusoidal variation of the liquid holdup in time, called holdup wave. Along the reactor, the holdup wave gets damped in amplitude and shifted in phase due to liquid dispersion. Amplitude damping and phase shift can be measured and related to the value of the axial liquid dispersion coefficient via the above mentioned dispersion model. A schematic sketch of the working principle of liquid flow modulation is shown in the figure below. The approach is a new, non invasive and easy to apply experimental approach.
The candidate (f/m/d) will experimentally test the applicability of the (liquid) flow modulation approach in trickle bed reactors of different sizes, using gamma ray densitometry as a measurement technique. For comparison purposes, conductivity based tracer measurements will be performed as well. Liquids of different viscosities will be tested and the impact of viscosity on the value of the liquid axial dispersion coefficient will be evaluated.

Department: Experimental Thermal Fluid Dynamics

Contact: Marchini, Sara

Requirements

  • Studies in chemical engineering or comparable
  • Interest in experimental work
  • Good communication skills in both written and spoken English

Conditions

  • Start in September/October 2022
  • Work in multidisciplinary and international environment
  • Compensation as for HZDR conditions

Online application

Please apply online: english / german

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Motion tracking of autonomous sensor particles in industrial vessels (Id 335)

Master theses / Diploma theses / Compulsory internship

Foto: AutoSens_StirredReactor ©Copyright: fwdf (Mailgruppe)Data acquisition in large industrial vessels such as biogas fermenters or wastewater treatment plants is limited to local measurement points due to limited access to the vessel and the non-transparency of the fluid. To optimize these kinds of plants, the three-dimensional flow field and the spatial distribution of fluid properties such as temperature and electrical conductivity inside the vessel must be known. This can be achieved by the autonomous flow-following sensor particles developed by the HZDR. Equipped with a pressure sensor, an accelerometer, two gyroscopes and a magnetometer, the sensor particle can track the movement inside the vessels and derive the flow field from that. Additionally, the sensor particle gets position information by an ultra-wide-band based localization module (like GPS) as soon as it is on the fluid surface. The motion of the sensor particle is currently tracked with an error-state Kalman filter and yields a reliable tracking of the velocity and position, respectively. However, the tracking time is limited by the propagation of uncertainties of the inertial sensors through the filter. The objective of this master thesis is to extend this tracking time by the use of more advanced tracking algorithms like particle filter or other types of Kalman filters. This includes the following tasks:

  • Literature review of advanced filters for motion tracking
  • Theoretical comparison and implementing the most promising algorithm in Python
  • Verification and performance analysis based on experimental data

Department: Experimental Thermal Fluid Dynamics

Contact: Buntkiel, Lukas, Dr. Reinecke, Sebastian

Requirements

Studies in the area of electrical, mechatronic, mechanical engineering or similar

  • Basics of measurement uncertainty, digital signal processing
  • Data analysis in Python
  • Independent and structured way of working

Conditions

  • Start possible at any time
  • Duration according to the respective study regulations

Links:

Online application

Please apply online: english / german

Druckversion


Experimental investigation of influence of interfacial viscoelasticity on the dripping to jetting transition (Id 333)

School practical training / Student practical training / Bachelor theses / Master theses / Compulsory internship

Foto: Capillary with jetting liquid-liquid interface ©Copyright: Milad EftekhariLiquid jets are unstable and eventually form droplets to minimize the surface energy with the surrounding fluid. The transition from dripping to jetting and dynamics of the droplet pinch-off have been studied extensively for various systems, from pure Newtonian fluids to complex non-Newtonian liquids. The jetting process has received significant attention as it is a critical step in various three-dimensional (3D) printing techniques such as dropwise additive manufacturing and the direct ink writing method. In most of the applications surface active materials such as surfactants, nanoparticles, and polymers exist in the systems. The presence of surface-active materials reduces the liquid-fluid surface energies and in some cases generates a viscoelastic layer at the interface.
In this research, we aim to study the influence of interfacial viscoelasticity on the dripping to jetting transition. The study is conducted by the injection of an aqueous phase (nanoparticle dispersions) into an oil phase that contains surfactants over a wide range of flow rates. We tune the magnitude of interfacial viscoelasticity by changing the concentration of surfactants and nanoparticles.
Research question:
Does the dripping to jetting transition (critical flow rate) linearly increase by increasing the interfacial viscoelasticity?

Experiments:
1. Measurements of interfacial tension and surface elasticity for a range of particle and surfactant concentration using Profile analysis tensiometry, and Langmuir trough.
2. Dripping to jetting experiments for the selected systems using high-speed cameras and in-house setups.

Department: Transport processes at interfaces

Contact: Eftekhari, Milad, Dr. Schwarzenberger, Karin

Requirements

  • Field of study: chemical engineering, process engineering, fluid mechanics, or similar focus in chemistry or physics
  • Experience with laboratory work and imaging measurement techniques is beneficial

Conditions

  • Working in an international team
  • Duration: at least 6 months
  • Location: Dresden-Rossendorf

Online application

Please apply online: english / german

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Techno-ökonomische Bewertung eines hybriden Energiespeichersystems basierend auf einem batteriegestützten Power-to-Methanol Prozess und erneuerbaren Energien (Id 331)

Master theses / Diploma theses

Das Institut für Fluiddynamik des Helmholtz-Zentrums Dresden-Rossendorf (HZDR) beschäftigt sich unter anderem mit Fragen der Modellbildung und Simulation von verfahrenstechnisch eng gekoppelten Power-to-X-Systemen bestehend aus den Teilprozessen Hochtemperaturelektrolyse (Solid Oxide Electrolyzer Cells) und heterogen katalysierten Syntheseprozessen von synthetischen Energieträgern der Zukunft (Methanol, Methan, usw.) unter stofflicher Nutzung anthropogener Kohlenstoffdioxidemissionen und regenerativ produziertem Strom. Auf Basis eines bereits existierenden Modells eines Power-to-Methanol Prozesses und eines ebenfalls vorliegenden techno-ökonomischen Teilmodells (TEA) soll die Wirtschaftlichkeit der dezentralen Produktion von Methanol mit Hilfe von erneuerbarem Strom in Kopplung mit großen Batteriespeichern untersucht werden.
Zur Realisierung dieser Aufgabe bietet die Abteilung Experimentelle Thermofluiddynamik für Studenten der unten genannten Studiengänge studienbegleitende Tätigkeiten zur beschriebenen Thematik an. Die Voraussetzung ist die Anfertigung einer Diplom- oder Masterarbeit.

Folgende Teilarbeiten sind durchzuführen:

  • Literaturrecherche zu hybriden Energiespeichersystemen basierend auf Power-to-Methanol Prozessen und Batteriespeichern hinsichtlich Prozessdesign und Wirtschaftlichkeit,
  • Literaturrecherche zur mathematisch-physikalischen Modellierung von Batteriespeichern und Erstellung eines einfachen Batteriespeichermodells mittels Matlab,
  • Ermittlung der ökonomischen Randbedingungen für großskalige Batteriespeicher auf Basis von Literaturdaten,
  • Untersuchung der Wirtschaftlichkeit des hybriden Energiespeichersystems für ein vorgegebenes Anschlussszenario für den Betrieb mit erneuerbaren Energiequellen.

Department: Experimental Thermal Fluid Dynamics

Contact: Fogel, Stefan

Requirements

  • Student (w/m/d) der Studiengänge Wirtschaftsingenieurwesen, Chemieingenieurwesen, Verfahrenstechnik, Energietechnik, Maschinenbau oder ähnlicher fachlicher Ausrichtung,
  • Grundkenntnisse in Matlab wünschenswert,
  • Sorgfältige, kreative und selbstständige Arbeitsweise,
  • Gute Sprachfertigkeiten (oral/schriftlich) in englischer und deutscher Sprache,
  • Freude an der wissenschaftlichen und eigenständigen Arbeit.

Conditions

Bearbeitungszeit: 6 Monate (Beginn ab sofort)

Online application

Please apply online: english / german

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Experimental investigation of two-phase flow on fixed valve trays for distillation columns (Id 317)

Bachelor theses / Master theses / Diploma theses / Compulsory internship

Foto: Eye-Catcher Single Valve ©Copyright: Dr. Philipp WiedemannDistillation columns are used for the thermal separation of multicomponent mixtures in the chemical industry. Owing to increased energy supply from renewable sources a more flexible operation of such apparatuses is already demanded. However, enlarged over- and under load modes are challenging with respect to design, since a high separation efficiency needs to be attained anyway. Especially in case of fixed valve trays there are presently no reliable methods for estimating the influence of the tray design on the complex two-phase flow of liquid and vapor. Therefore, a current research project aims at detailed investigations of the two-phase flow at single valves in order to evaluate their performance.
Within the frame of a student internship experimental investigations will be carried out using an existing lab-scale test rig. The phase distribution of gas and liquid will be measured around different valves with high temporal and spatial resolution by specifically developed sensors. Subsequently, measured data will be used to quantify and model the momentum transfer from the gas inlets to the liquid phase. The results will be used in future developments of numerical models to predict the two-phase flow on such trays.

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Wiedemann, Philipp

Requirements

  • studies in chemical/process/energy/mechanical engineering
  • interest in experimental work
  • creativity
  • good written and oral communication skills in English and German

Conditions

  • start: from Sept. 2022
  • working in a multi-disciplinary team
  • remuneration according to HZDR internal regulations

Links:

Online application

Please apply online: english / german

Druckversion


Construction and test of a reference measurement system for an industrial wire-mesh sensor for multiphase flow measurements (Id 313)

Student practical training / Bachelor theses / Diploma theses / Compulsory internship / Volunteer internship

Foto: reference measurements for multiphase measurement systems ©Copyright: Dr. Philipp WiedemannWire-mesh sensors allow for measuring the phase distribution of gas-liquid flows with high spatial and temporal resolution. For industrial applications (e.g. in power plants or chemical plants) previous projects already focussed on the development of data processing algorithms that convert the huge data sets into user friendly information, i.e. average void fraction and flow pattern. Hence, plant operators can now benefit from advanced process monitoring and operate their processes more efficiently.
The current developments focus on an enhanced system that includes online reference measurements in order to compensate drifts, which may result from changes of fluid properties when dealing with dynamic operation modes of the process. For this purpose, an existing concept should be converted into a final design, constructed and finally tested within the frame of an internship.

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Wiedemann, Philipp

Requirements

  • interest in practical work
  • manual skills
  • creativity
  • studies in process/energy/mechanical/electrical engineering
  • good written and oral communication skills in English AND German

Conditions

  • start: immediately
  • working in a multi-disciplinary team
  • remuneration according to HZDR internal regulations

Links:

Online application

Please apply online: english / german

Druckversion