Practical trainings, student assistants and theses

6-month internship on the experimental investigation of granular mixing (Id 285)

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

Background:
Granular mixing is an important industrial process. In the pharmaceutical industry for instance, the powder that is pressed to make tablets is produced by mixing precise quantities of active substances and excipients in granular state. The mixing needs to be done in such a way that the final powder has a homogeneous composition. Tablets may also need to be coated in a pan coater. Granular mixing also plays a crucial role there, as it greatly affects the thickness of the coating. Granular mixing is also often coupled with heat exchanging and solid-gas or solid-solid reactions, as is the case of rotary kilns in the cement, ceramics and metallurgical industries. The quality of the mixing is then a crucial factor to the efficiency of the overall process.

Objectives:
The objective of the work is to experimentally study the mixing process of two different types of granular particles inside a rotating drum under various operating conditions. More specifically, the mixing process is to be captured with a high-speed camera. The videos are then to be post-processed in order to extract characteristics of the particle velocity fields and mixing efficiency. The mixing facility is already available.

Tasks:
• Literature survey
• Mixing experiments under various operating conditions
• Post-processing of the results with MATLAB

Department: Experimental Thermal Fluid Dynamics

Contact: Papapetrou, Theodoros Nestor

Requirements

• Student of natural sciences or engineering
• Willingness to conduct experimental work

Conditions

Duration: 6 months
Remuneration: available

Online application

Please apply online: english / german

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Experimental investigation of bubble coalesence in salt solutions (Id 284)

Student practical training / Bachelor theses / Master theses / Diploma theses

With the energy turnaround, the demand for rare earth elements (REE) for key technologies such as lithium for electromobility or neodymium for wind turbines is increasing. The effective processing and separation of these valuable minerals represent a challenge for the mineral industry. One possibility for separation is flotation. Flotation separates the value mineral particles from gangue material based on their surface wettability. Hydrophobic valuable particles adhere to gas bubbles and rise as agglomerates. These form a froth which can be skimmed off. The efficiency of this process still remains far below the economically and ecologically desired targets for the separation of REE.

One approach to improve the process efficiency is to inhibit coalescence of bubbles so that more interfacial area is available for the attachment of the hydrophobic particles. This is achieved by adding complex organic compounds in the presence of simple salts. Present experimental study focuses on quantifying the effect of inorganic electrolytes on the coalescence behavior. Images of bubble swarm are captured by means shadowgraphy at different electrolyte concentrations. Bubble diameter distribution is then computed by means of image analysis algorithm and analyzed as a function of electrolyte concentration. The results will improve the understanding of the suppression of coalescence in a flotation cell, leading to a higher efficiency in the separation of REE.

FOCUS OF WORK
• Measurement of bubble diameter at varying concentrations of different electrolytes
• Image analysis of bubble images with ImageJ, Matlab or Python
• Summarization and documentation of the obtained data

Department: Transport processes at interfaces

Contact: Sommer, Anna-Elisabeth, Hossain, Syed Sahil

Requirements

• Studies in process/energy/mechanical engineering
• Interest in practical work
• Experience in programming with MatLab or Python is beneficial
• Good written and oral communication skills in English and German

Conditions

• Start: immediately
• Duration: ca. 6 months

Online application

Please apply online: english / german

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Experimental study on the hydrogen bubble dynamics in electrolysis: electric effect (Id 282)

Master theses / Diploma theses / Student Assistant

Foto: The electric effect in bubble attraction ©Copyright: Aleksandr BashkatovThe growth of hydrogen bubbles in water electrolysis is a particularly interesting problem of high practical relevance due to the prominent role of hydrogen in energy storage via power-to-gas processes. The dynamics even of a single bubble are already multifaceted and associated with a number of interdisciplinary phenomena such as Marangoni convection, bubble-microlayer interaction, or electric effect resulting from the interplay of electric field and surface charge of a bubble.

PROBLEM: Our recent work shows a noticeable role of the electric force in the bubble dynamics, e.g. in bubble oscillations. The electric effect, in that case, was established as a restoring force triggering a return mechanism of the bubble once detached from the electrode surface. In such a way, the depended on the bubble position electric force causes long-lasting position oscillations. As an extension to ongoing work a new phenomenon related to electric effect was preliminary observed. The essence of that is the ability of the bubble moves oppositely to the gravity force direction under the electric force influence and returns back to the electrode from relatively large distances (appx. 300 μm).

OBJECTIVE:
- A systematic experimental study of the phenomenon by the shadowgraphy and electric current measurement techniques
- Data analysis via Matlab

Department: Transport processes at interfaces

Contact: Bashkatov, Aleksandr

Requirements

- Study in fluid dynamics, process engineering, chemical engineering (or comparative field of study)
- Motivation and eagerness
- Good written and oral communication skills in English
- Optimally: experimental experience, Matlab basics

Conditions

Duration ca. 6 months, start: from October. 2020, workplace: HZDR. Possible to combine a student assistant work or internship with Master/ Diploma theses.

Online application

Please apply online: english / german

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Contributions to motion tracking of autonomous flow-following sensor particles in industrial process environments (Id 279)

Student practical training / Bachelor theses / 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 properties such as temperature and electrical conductivity inside the vessel need to be known. This can be achieved by the autonomous flow-following sensor particles developed by HZDR. Equipped with a pressure sensor, an accelerometer, two gyroscopes and a magnetometer, the sensor particle can track the movement inside the vessels and to infer the flow field from that. The analysis of the data is done after a successful recovery from the vessel. Therefore, algorithms of any complexity can be used to track the motion of the sensor particle.

For the extension and especially for the improvement of the motion tracking we offer the following tasks, from which we can agree on a topic for a thesis or an internship:
• Development of motion tracking algorithms
• Characterization and error correction of the sensors
• Intelligent sampling for the sensors
• Experimental investigation of the maximal acceleration on a stirrer
• Development of firmware to cover several data acquisition scenarios
• Development of an end-user program for the configuration and data analysis of the gathered data

Department: Experimental Thermal Fluid Dynamics

Contact: Buntkiel, Lukas

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

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Experimental investigation of the multiphase flow in a stirred tank with PIV and Shadowgraphy (Id 277)

Student practical training / Bachelor theses / Master theses / Diploma theses

Foto: Motivation_StirredTank ©Copyright: Anna-Elisabeth Sommer, Flotation cell: https://www.matsamining.com/innovacion/planta-de-tratamiento/With the energy turnaround, the demand for rare earth elements (REE) for key technologies such as lithium for electromobility or neodymium for wind turbines is increasing. The effective processing and separation of these valuable minerals represent a challenge for the mineral industry. One possibility for separation is flotation. Flotation separates the solid particles based on their surface wettability. Hydrophobic valuable particles adhere to gas bubbles and rise as agglomerates. These form a froth which can be skimmed off. The selective separation is influenced by the hydrodynamics in the flotation cell. The efficiency of this process still remains far below the economically and ecologically desired targets for the separation of REE.

Of particular interest are numerical models of flotation cells. In these models, process parameters can be changed much more versatile and easier than in experimental investigations. For this purpose, however, it is necessary to understand the processes taking place in flotation based on experimental studies and also to generate data for the validation of numerical models. In this work, a comprehensive experimental study of multiphase flow in the stirred tank with Particle Image Velocimetry (PIV) and shadowgraphy, concerning flow conditions and material parameters, is to be carried out. The results will help to improve the understanding of multiphase flow within the stirred tank and provide validation data for numerical models.

FOCUS OF WORK
• Investigation of the influence of solid particles and bubbles on the multiphase flow in the stirred tank with PIV and shadowgraphy
• Development of suitable algorithms for data evaluation with MatLab or Python
• Cooperation with CFD department for comparison of experimental and numerical results

Department: Transport processes at interfaces

Contact: Sommer, Anna-Elisabeth

Requirements

• Studies in process/energy/mechanical engineering
• Interest in practical work
• Experience in programming with MatLab or Python is beneficial
• Good written and oral communication skills in English and German

Conditions

• Start: immediately
• Duration: ca. 6 months

Online application

Please apply online: english / german

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Nonlinear characterization of horizontal gas-liquid flows (Id 266)

Student practical training / Bachelor theses / Master theses / Diploma theses / Compulsory internship / Research Assistant

Foto: Nonlinear characterization of horizontal gas-liquid flows ©Copyright: Dr. Philipp WiedemannHorizontal gas-liquid flows occur in a variety of processes in energy and process engineering. According to the type of fluids, operating conditions and geometrical aspects different flow patterns are observed. These can be identified successfully by means of online monitoring systems when using appropriate measurement techniques and data processing algorithms.
Within the frame of an internship further investigations will focus on the predictability of the future development of the flow patterns on the basis of currently measured data. For that purpose, methods for characterizing nonlinear systems will be applied to available data that was recorded with the aid of an imaging technique.

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Wiedemann, Philipp

Requirements

- studies in mathematics/physics/engineering
- interest in applying sophisticated mathematical methods to engineering problems
- experiences in signal processing and nonlinear systems as well as using Matlab are beneficial
- 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

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Modelling of bubble formation on submillimeter submerged orifice (Id 258)

Student practical training / Bachelor theses / Master theses / Diploma theses

Foto: Bubble Formation ©Copyright: Ehsan Mohseni, Ehsan MohseniBubbles are an inevitable part of almost all chemical and process engineering processes as long as heat and mass transfer or particle separation are concerned. Formation of bubbles from a submerged orifice is a typical fluid dynamic phenomenon, which incorporates the influence of different characteristics of both gas and liquid phases. Although posing as a simple problem in the first sight, the formation process varies dramatically by changing influential parameters such as diameter and geometry of orifice, volume of gas reservoir under the orifice, surface tension, density and viscosity of both continuous and dispersed phases, etc. Among these parameters, the effect of the volume of the gas reservoir under the orifice is highly influential. Within an ongoing investigation, we are experimentally studying the effect of this parameter on the dynamics of bubbles generated at orifices smaller than 1 mm. A sub task of this investigation associates the findings of the experimental studies into a mechanistic model, which is designed to estimate the final bubble size.

Task Spectrum:
• Establishment of a profound scientific knowledge into the phenomena of bubble formation and detachment
• Concept development and establishing solution strategy for the bubble volume
• Implementing the solutions into MATLAB
• Compare and adopting the model based on the experimental results
• Generate scientific documentation

Department: Experimental Thermal Fluid Dynamics

Contact: Mohseni, Ehsan, Dr. Reinecke, Sebastian

Requirements

• Studies in mechanical, chemical, process engineering, and similar engineering courses
• Experience in data analysis and programming with MATLAB
• Independence, self-responsible working methods

Conditions

Duration: 6 Months

Online application

Please apply online: english / german

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Design and operation of liquid metal batteries as large-scale storage option (Id 256)

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

Foto: Study of a liquid metal battery module ©Copyright: Dr. Michael Nimtz, ©Michael NimtzIn contrast to conventional batteries, Liquid Metal Batteries feature all liquid anodes (alkaline or alkaline earth metal), cathodes (transition metal or metal) and electrolytes (molten salts) at a temperature between 400 °C and 600 °C. For the operation of liquid metal batteries as large-scale storage option (frequency control and other applications), the design of the storage system and operation strategies (including a battery management system) need to be implemented and tested using exemplary load curves.
Starting point is an existing model of a battery system in Python.

Note: This is an offer suitable for a bachelor, master or diploma thesis or studentic internships.
Do not apply if you already finished your studies!

Department: Magnetohydrodynamics

Contact: Dr. Nimtz, Michael

Requirements

Study of mechanical engineering, physics, mathematics or similar
Basic knowledge of engineering principles.
Good knowledge of a programming language, preferably python.

Conditions

Start: October 2019
Duration: 4-6 months
Paid according to HZDR-internal tariff

Links:

Online application

Please apply online: english / german

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Smart actuation system for flow following µAUV particles for industrial process environments (Id 175)

Master theses / Diploma theses / Compulsory internship

Foto: flow following sensor particle ©Copyright: Dr. Sebastian ReineckeSmart flow following sensor particles are used for acquisition of spatially distributed process parameters in industrial processes, such as biogas digesters, waste water treatment basins or bioreactors. The aim of the work is the development of an actuator concept for sensor µAUV-particles for the automatic adjustment of buoyancy (buoyancy) and for buoyancy maneuvers under the condition of small size, minimum energy consumption and high reliability. For this, alternative physical and chemical mechanisms should be considered based on the existing electromechanical solution. There are suitable variants to implement and test. Furthermore, the development of sensor intelligence for the actuators in the sensor particles is an essential part of the task. The developed concepts have to be validated experimentally.

We cordially invite you to an on-site conversation to introduce the topic and to agree on further details. Do not hesitate to contact us, because the way is worth it for you.

What can you expect:

In our department, we offer you an attractive work environment to expand your personal and professional skills. The insight into the diverse R&D projects of the department in the areas of sensor and measuring technology as well as energy and process engineering (among others) and the excellent technical equipment of the laboratories offer optimal conditions for this. The possibility of close contact with competent experienced colleagues plays a central role. As part of student work, we have pursued the approach of structured supervision and associated constructive feedback. This includes regular meetings with your supervisor and intermediate presentations in the form of informal "workshop reports" in the extended audience of interested individuals of the department in order to optimally support you in the successful completion of your project. Furthermore, we are open to support outstanding candidates in their continuing academic qualification, such as in doctoral scholarships or in current or upcoming R&D projects.

Subject-related task spectrum:

• Establishment of the scientific and technical principles of mechanical, physical and chemical principles of action for embedded, actuating components
• Concept development for actuators for taring of sensor particles
• Development of sensor intelligence for situation-dependent, automatic buoyancy, for buoyancy maneuvers and for recovery
• Selection, purchase/ composition and comparison of solution variants
• Minimization of size and energy consumption
• Increased reliability when used in particle-loaded biological substrates
• Development of firmware taking into account existing function routines based on an embedded system with 32-bit data structure (e.g. STM32)
• Conception and realization of suitable test scenarios
• Characterization and comparison of implemented variants with regard to accuracy of taring and reliability in long-term use

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Reinecke, Sebastian, Buntkiel, Lukas

Requirements

• Studies in electrical engineering, mechatronics, mechanical engineering and similar engineering courses
• Experience in design and (micro) actuator systems
• Experience in programming microcontrollers for embedded systems (e.g. STM32)
• Experience in control electronics for microdrives and board design for embedded systems
• Fundamentals of (micro) actuator systems, movement of rigid bodies, measurement uncertainties, digital signal processing
• Data analysis optionally in Matlab, Octave or C / C ++
• Independent, self-responsible working method

Links:

Online application

Please apply online: english / german

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Bestimmung von Geschwindigkeitsfeldern aus tomographischen Bilddaten mittels Kreuzkorrelation (Id 164)

Bachelor theses / Master theses / Diploma theses

Foto: ROFEX CAD ©Copyright: Dr. Frank BarthelAm Institut für Fluiddynamik am Helmholtz-Zentrum Dresden-Rossendorf sind zahlreiche Messverfahren für die Untersuchung von Mehrphasenströmungen entwickelt worden. Eines davon ist die ultraschnelle Elektronenstrahl-Röntgen-Computertomographie, welche mit Aufnahmeraten von bis zu 8000 Bildern pro Sekunde eine dedizierte Aufklärung von Strömungsstrukturen erlaubt. Aufgrund der quasi simultanen Aufnahme von Bilddaten aus zwei Messebenen ergibt sich zudem die Möglichkeit, axiale Geschwindigkeiten zu bestimmen, wofür üblicherweise Kreuzkorrelationsverfahren verwendet werden. Im Rahmen dieser Arbeit sollen die Möglichkeiten dieser Methodik in Hinblick auf die Bestimmung von Geschwindigkeitsfeldern in verschiedenen Strömungsszenarienn analysiert werden.

Folgende Teilaufgaben sind zu lösen:
• Studie zu verschiedenen Varianten der Kreuzkorrelation
• Simulation verschiedener Szenarien und Bewertung der Genauigkeit
• Übertragung der Ergebnisse auf reale Messungen

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Bieberle, Martina

Requirements

• Studium der Informatik, Mathematik oder einer Ingenieurwissenschaft
• Interesse an Messverfahren und Datenanalyse
• Selbständiges Arbeiten

Conditions

Bearbeitungszeit 4 bis 6 Monate

Links:

Online application

Please apply online: english / german

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Untersuchung des Einflusses von Regularisierungsmethoden auf Bildrekonstruktionsalgorithmen (Id 57)

Student practical training / Bachelor theses / Master theses / Diploma theses

Bei der tomographische Bildrekonstruktion muss ein diskretes inverses Problem gelöst werden, wofür algebraische Methoden wie zum Beispiel ART und CG-Verfahren verwendet werden können. Dabei spielt die Regularisierung, die den Einfluss von Diskretisierungsfehler und Messdatenrauschen auf die Lösung beschränkt, eine entscheidende Rolle. Deren Einfluss auf die Bildrekonstruktion von Röntgen- und Gamma-CT-Messdaten soll untersucht werden. Dazu sind folgende Teilaufgaben zu lösen:
• Implementierung verschiedener Regularisierungsmethoden
• Anwendung der Programme auf Messdaten
• Parameterstudien um die Regularisierungsmethoden für die Messdatensätze zu optimieren.

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Wagner, Michael, Dr. Bieberle, Martina

Requirements

• Programmierkenntnisse in MATLAB
• Grundkenntnisse zur numerischen Behandlung linearer Gleichungssysteme

Links:

Online application

Please apply online: english / german

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