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Experimental investigation of the flow behavior of Lagrangian LED Particles in a 200 l bioreactor
Citation Link: https://doi.org/10.15480/882.4320
Publikationstyp
Bachelor Thesis
Date Issued
2022-04-29
Sprache
English
Author(s)
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2022-05-19
Institut
TORE-DOI
Citation
Technische Universität Hamburg (2022)
Peer Reviewed
false
Lagrangian Sensor Particles are essential in gaining knowledge about process conditions inside of Single-Use Stirred Tank Bioreactors. To facilitate this, the particles should follow the flow of the fluids inside of the reactor.
However, so far it has not been possible to validate their internal means of trajectory determination. To address this problem, in this thesis the positions of LED-equipped tracking particles, called LED Motes, in a 200 L Continuously Stirred Tank Reactor made of acrylic glass are measured visually and their velocities and accelerations calculated.
To this end, LED Motes are designed and manufactured. A mote recognition script as well as a script for removal of distortions in the image through geometric calibration for MATLAB is developed to complement scripts for the calculation of velocity and acceleration values from positional data.
Experiments are performed utilizing two different stirrer setups, one consisting of a Rushton turbine impeller and a pitched blade impeller and the other consisting of two pitched blade impellers. The experiments are performed without aeration and with an aeration rate of 15 l min^-1 and 20 l min^-1 using both a micro and a macro sparger. Thus, a total of 10 combinations of experimental parameters are achieved not accounting for variations in stirrer speed. Experiments utilizing every combination of experimental parameters are performed at four different stirrer speeds of 50, 70, 100 and 120 RPM for a total of 40 experiments.
A high proportion of theoretically possible LED Mote positions are recognized. Only positions that can be assigned to a track of a length of more than 5 positions are evaluated for the calculation of velocity and acceleration values. Up to 94 % of the recognized positions are assigned to such a track. However, for the low-visibility, aerated, cases the percentage of positions assigned to tracks long enough to allow for evaluation is lower, reaching as low as 66 %. For the majority of experiments the percentage of positions used for calculations lies between 80 % and 90 %.
The results show that the tracking of the 2D positions of LED Motes can lead to a good understanding of the dominant flow phenomena inside of a CSTR. The highest calculated mean velocity magnitudes for a single 62~mm by 60~mm interrogation window are approximately half of the stirrer tip speed. The expected flow patterns for the different stirrer types are observed. The Rushton turbine impeller causes high radial velocities while the pitched blade impellers cause high axial velocities. A good resolution of velocity and acceleration data can be achieved even with short experimental run times of only 120~s. However, for the aerated case, obscuration of the LED Motes reduces the quality of the results. A longer experimental run time and an increase in LED-brightness can increase the quality and resolution of the evaluation results even further. Usefulness and quality of data can be increased by the development of 3D tracking techniques using two cameras or a mirror setup to achieve two different viewpoints of the reactors instead of evaluating a single point of view. For this, the produced script lays a solid foundation.
However, so far it has not been possible to validate their internal means of trajectory determination. To address this problem, in this thesis the positions of LED-equipped tracking particles, called LED Motes, in a 200 L Continuously Stirred Tank Reactor made of acrylic glass are measured visually and their velocities and accelerations calculated.
To this end, LED Motes are designed and manufactured. A mote recognition script as well as a script for removal of distortions in the image through geometric calibration for MATLAB is developed to complement scripts for the calculation of velocity and acceleration values from positional data.
Experiments are performed utilizing two different stirrer setups, one consisting of a Rushton turbine impeller and a pitched blade impeller and the other consisting of two pitched blade impellers. The experiments are performed without aeration and with an aeration rate of 15 l min^-1 and 20 l min^-1 using both a micro and a macro sparger. Thus, a total of 10 combinations of experimental parameters are achieved not accounting for variations in stirrer speed. Experiments utilizing every combination of experimental parameters are performed at four different stirrer speeds of 50, 70, 100 and 120 RPM for a total of 40 experiments.
A high proportion of theoretically possible LED Mote positions are recognized. Only positions that can be assigned to a track of a length of more than 5 positions are evaluated for the calculation of velocity and acceleration values. Up to 94 % of the recognized positions are assigned to such a track. However, for the low-visibility, aerated, cases the percentage of positions assigned to tracks long enough to allow for evaluation is lower, reaching as low as 66 %. For the majority of experiments the percentage of positions used for calculations lies between 80 % and 90 %.
The results show that the tracking of the 2D positions of LED Motes can lead to a good understanding of the dominant flow phenomena inside of a CSTR. The highest calculated mean velocity magnitudes for a single 62~mm by 60~mm interrogation window are approximately half of the stirrer tip speed. The expected flow patterns for the different stirrer types are observed. The Rushton turbine impeller causes high radial velocities while the pitched blade impellers cause high axial velocities. A good resolution of velocity and acceleration data can be achieved even with short experimental run times of only 120~s. However, for the aerated case, obscuration of the LED Motes reduces the quality of the results. A longer experimental run time and an increase in LED-brightness can increase the quality and resolution of the evaluation results even further. Usefulness and quality of data can be increased by the development of 3D tracking techniques using two cameras or a mirror setup to achieve two different viewpoints of the reactors instead of evaluating a single point of view. For this, the produced script lays a solid foundation.
Subjects
Image processing
MATLAB
Calibration technique
Stirred tank reactor
Bioreactor agitation
Flow behavior
Lagrangian particle trajectories
DDC Class
620: Ingenieurwissenschaften
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