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

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

Druckversion


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