Abstract
In the past two decades, the radioactive particle tracking (RPT) measurement technique has been proven to visualize flow fields of most multiphase flow systems of industrial interest. The accuracy of RPT, and hence the data obtained, depend largely on the calibration process, which stands here as a basis for two subsequent processes: tracking and reconstruction. However, limitations in the RPT calibration process can be found in different experimental constrains and in assumptions made in the classical Monte Carlo approach used to simulate number of counts received by the detectors. Therefore, in this work, we applied a GEANT4-based Monte Carlo code to simulate the RPT calibration process for an investigated multiphase flow system (i.e., gas–liquid bubble column). The GEANT4 code was performed to simulate the number of counts received by 28 scintillation detectors for 931 known tracer positions while capturing all the types of photon interaction and overcoming solids’ angle limitations in classical approaches. The results of the simulation were validated against experimental data obtained using an automated RPT calibration device. The results showed a good agreement between the simulated and experimental counts, where the maximum absolute average relative deviation detected was about 5%. The GEANT4 model typically predicted the number of counts received by all the detectors; however, it over-estimated the counts when the number of primary events applied in the model was not the optimal.
Highlights
Radioisotope-based measurement techniques have found many applications in different sectors of industry as well as in research and development
The radioactive particle tracking (RPT) technique is a Lagrangian measurement technique, used to track the movement of a single radioactive tracer by means of detectors to obtain the velocity field of a multiphase flow system such as gas–liquid bubble column [3], gas–solid spouted beds [4,5], gas–solid riser [6,7,8], and gas–solid fluidized beds [9,10]. It has been proven through research studies and practical experimentation that the RPT is the only non-invasive technique that can provide a full description of a 3D flow field of highly opaque multiphase flow systems [2]
In the RPT experiment, counts recorded by the detector result from the number of photons incident on the detector, which is determined by the intrinsic efficiency of the detector
Summary
Radioisotope-based measurement techniques have found many applications in different sectors of industry as well as in research and development. The authors of [20] adopted the Monte Carlo approach for the first time in the RPT framework to compute the absolute detector efficiencies in the presence of intervening medium, and generating the counting map of the RPT calibration process. The impact on the phase’s distributions due to alteration in the applied operating conditions was taken as constant [20] Considering this state-of-the-art technique, Monte Carlo calculations found in the literature for the RPT calibration process are rather simplified by assumptions/estimations. More accurate models are needed for sufficiently accurate RPT calibration process, and successful RPT experimentation and reliable data can be obtained Such models should be able to capture all the types of photon interaction with matter and should not be limited to solids angle determined by the detectors. The data obtained from the GEANT4 simulation will be compared against experimental data obtained using advanced automated RPT technique for the same investigated system at identical selected operating conditions as in a previous study [3]
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