Practical trainings, student assistants and theses

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

Druckversion


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 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