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Positron Emission Particle Tracking (positron + emission_particle_tracking)
Selected AbstractsGas-solid Two-phase Mixtures Flowing Upward through a Confined Packed Bed,PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3-4 2006Yurong He Abstract This paper deals with flows of a gas-solid two-phase mixture through a confined packed bed. Both experimental work and numerical modelling are performed on the behaviour of suspended particles within the packed bed. The experimental work is carried out with a non-intrusive Positron Emission Particle Tracking (PEPT) technique, which tracks particle motion at the single particle level for a prolonged period thus allows both the microscopic and macroscopic solids behaviour to be analysed under the steady-state conditions. A continuous based model is used to simulate the flow behaviour. The model uses a newly proposed porosity model and treats the suspended and packed particles as a binary mixture with the packed particles being at zero velocity. The results show that the model captures the main features of solids behaviour in terms of the radial distributions of the suspended particle concentration and the axial solids velocity. Both the experiments and modelling suggest that the wall effect on the motion of suspended particles be limited to a small region close to the wall (,0.5,1 packed particle diameter). However, deviations exist between the model predictions and experiments; more work is therefore proposed to improve the interaction terms in the model between the suspended and packed particles. [source] Measuring velocity distributions of viscous fluids using positron emission particle tracking (PEPT)AICHE JOURNAL, Issue 7 2004S. Bakalis Abstract Positron emission particle tracking (PEPT) can be used to trace the path of a radioactive particle within opaque fluids in pilot-scale equipment; the method can track particles through several centimeters of metal. PEPT has been successfully used to follow isokinetic tracers in viscous fluids and thus to measure velocity distributions under both isothermal and nonisothermal conditions in pipe flow. The accuracy of the method decreased as the measured velocities increased; the faster the particle traveled, the less accurate its detection. For velocities of up to 0.5 m/s the accuracy of the method was acceptable. Agreement between experimentally measured and theoretical velocity distributions was very good, for a range of fluids and process conditions. As tracer particles are used, there were problems ensuring that all parts of the measurement volume were sampled. This is possible to overcome to an extent by adjusting particle size; 600-,m tracers did not pass within 1 mm from the tube wall, whereas 240-,m particles passed much closer to the boundaries of the flow. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1606,1613, 2004 [source] Following the path of hydrophobic and hydrophilic particles in a Denver Cell using positron emission particle trackingASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009K. E. Waters Abstract Positron emission particle tracking (PEPT) has been used to track the movement of single particles of galena and quartz in a Denver Cell batch flotation system. The particles were labeled with a radionuclide, 18F, and using an ADAC Forte positron camera the positions of the particles were determined during mixing, and once air was added to the cell at a constant rate. The hydrophobic galena particle entered the froth readily, attached to air bubbles, and overflowed the weir. Detachment from an air bubble in the froth was also observed, and this is presumed to be due to coalescence events occurring. The hydrophilic quartz particle did not overflow the weir when the air flow was on. When the particle did enter the froth, it was along the sides of the vessel following the flow of the water. This gives a potential indication of one of the methods of the entrainment of gangue minerals in froth flotation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Single-particle motion and heat transfer in fluidized bedsAICHE JOURNAL, Issue 12 2006Yee Sun Wong Abstract Fluidized beds are particularly favored as chemical reactors because of their ability to exchange heat through immersed heat-exchange surfaces. However, little is known about how the heat-exchange process works on a single-particle level. The most commonly applied theory of fluidized bed heat exchange is that developed by Mickley and Fairbanks in the 1950s,the so-called packet model. The work described in this article is an attempt to understand the process of heat transfer by solids convection, using positron emission particle tracking to follow the trajectory of a single tracer particle in the bed. In particular, the residence time of particles in the vicinity of the surface is determined here for the first time. Using these data, the observed heat-transfer variations are interpreted mechanistically. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Measuring velocity distributions of viscous fluids using positron emission particle tracking (PEPT)AICHE JOURNAL, Issue 7 2004S. Bakalis Abstract Positron emission particle tracking (PEPT) can be used to trace the path of a radioactive particle within opaque fluids in pilot-scale equipment; the method can track particles through several centimeters of metal. PEPT has been successfully used to follow isokinetic tracers in viscous fluids and thus to measure velocity distributions under both isothermal and nonisothermal conditions in pipe flow. The accuracy of the method decreased as the measured velocities increased; the faster the particle traveled, the less accurate its detection. For velocities of up to 0.5 m/s the accuracy of the method was acceptable. Agreement between experimentally measured and theoretical velocity distributions was very good, for a range of fluids and process conditions. As tracer particles are used, there were problems ensuring that all parts of the measurement volume were sampled. This is possible to overcome to an extent by adjusting particle size; 600-,m tracers did not pass within 1 mm from the tube wall, whereas 240-,m particles passed much closer to the boundaries of the flow. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1606,1613, 2004 [source] Positron Imaging Studies of Rotating DrumsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2005David J. Parker Abstract The potential of the radioisotope tracer technique of positron emission tomography (PET) and the related techniques of positron emission projection imaging (PEPI) and positron emission particle tracking (PEPT) is illustrated with reference to laboratory scale studies of particulate motion in rotating drums, operating either in batch or continuous flow modes. Sand grains, glass beads and TiO2 granules down to 0.5mm diameter were labelled. Using PEPT the transition between rolling and slumping modes has been identified and the velocity profile within the active layer has been determined for a range of drum diameters. PEPI has been used to measure and explain residence time distributions, while all three techniques have been used to study segregation based on particle size, both radially and axially within the drum. Data on particle motion within a novel baffled drum is also presented. Le potentiel de la technique de traçage par radio-isotopes en tomographie par émission de positrons (PET) et les techniques associées de l'imagerie par projection des émissions de positrons (PEPI) ou le traçage des particules par émission de positrons (PEPT), est illustré en référence à des études à l'échelle de laboratoire du déplacement de particules dans des tambours rotatifs, fonctionnant soit en mode d'écoulement discontinu ou continu. Des grains de sable, des billes de verre et des granules de TiO2 aussi petits que 0,5 mm de diamètre ont été marqués. À l'aide de la technique PEPT, la transition entre les modes roulant et glissant a été identifiée et le profil de vitesse à l'intérieur de la couche active a été déterminé pour une gamme de diamètres de tambours. La technique PEPI a été utilisée pour mesurer et expliquer les distributions de temps de séjour, tandis que les trois techniques ont servi pour l'analyse de la ségrégation d'après la taille des particules, à la fois radialement et axialement dans le tambour. Des données sur le déplacement des particules dans un nouveau tambour à chicanes sont également présentées. [source] Following the path of hydrophobic and hydrophilic particles in a Denver Cell using positron emission particle trackingASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009K. E. Waters Abstract Positron emission particle tracking (PEPT) has been used to track the movement of single particles of galena and quartz in a Denver Cell batch flotation system. The particles were labeled with a radionuclide, 18F, and using an ADAC Forte positron camera the positions of the particles were determined during mixing, and once air was added to the cell at a constant rate. The hydrophobic galena particle entered the froth readily, attached to air bubbles, and overflowed the weir. Detachment from an air bubble in the froth was also observed, and this is presumed to be due to coalescence events occurring. The hydrophilic quartz particle did not overflow the weir when the air flow was on. When the particle did enter the froth, it was along the sides of the vessel following the flow of the water. This gives a potential indication of one of the methods of the entrainment of gangue minerals in froth flotation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||