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Item type:Publication, Access status: without files , Experimental investigation and force balance modelling of wet particle collisions(2018-04); ; ; ; Knowledge about collision dynamics of particles is fundamental for describing and modelling particulate processes. If liquids are additionally involved in the collisions, the rebound dynamics strongly depend on the liquid properties. However until now, wet particle collisions are still not fully understood. Hence, influence of liquid properties, particle attributes and impact conditions on rebound behavior of dry particles from wet walls is investigated experimentally and a force balance model is described, which can predict collision dynamics on a physical basis. The results of this proceeding were already published in [1].Publicationtype: Conference Paper61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Detection of Fluidization with Real-Time Magnetic Resonance ImagingUnfluidized areas (dead zones) within gas-solid fluidized beds can deteriorate the mixing and heat transfer between the gas phase and the solid phase, and thus lower the performance, homogeneity and efficiency of the desired process. A thorough understanding of the conditions that lead to the formation of dead zones is therefore key in order to design, operate and scale fluidized bed reactors reliably. The experimental detection of dead zones inside three-dimensional (3D) fluidized beds can provide valuable information to validate theories and numerical models. However, due to the opacity of most granular materials, such measurements are challenging and require the use of intrusive probes1,2 or non-intrusive tomographic techniques, e.g. x-ray tomography3, electric capacitance tomography (ECT), positron emission particle tracking (PEPT)4 or magnetic resonance imaging (MRI)5. While intrusive probes perturb the granular dynamics, the tomographic techniques suffer from limitations in either their ability to measure particle motion (x-ray CT, ECT, PEPT) or from poor temporal resolution (MRI)6.Publicationtype: Conference Paper39 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Dynamic wetting of multicomponent particle systems(2018-04-22); ; ; ; Publicationtype: Conference Paper125 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Experimental and numerical investigation of a three-dimensional prismatic spouted bed with liquid injection(2018-04-22); ; ; ; In this contribution, a three-dimensional prismatic spouted bed for coating purposes is investigated experimentally and numerically. Spouting behavior was experimentally investigated by means of Fourier transform of the pressure drop signal. The spouting stability could be increased by two parallel draft plates and influenced by using binary or ternary mixtures of different particle sizes. Simulations were performed with a coupled CFD-DEM approach, whereby droplets were injected in a post-processing step, which allowed the estimation of the liquid surface coverage of the used Y-AI2O3 particles. It was found that the insertion of draft plates results in a broader liquid distribution in the first ten seconds of the process. By applying the recurrence CFD (rCFD) method, the broader liquid distribution could be confirmed for a process duration of 1 hour.Publicationtype: Conference Paper175 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Functionalization of aerogel particles by coating in a spouted bed(2018-04-22); ; ; Aerogels are porous and light-weighting materials with high specific surface area. Due to their properties they have been investigated as carriers of active ingredients. However, open pore structure limits their application because of changing their structure when they are exposed to liquids. Therefore, there is a protective layer on the surface of the aerogels needed, which preserves loaded drug or enables storage in liquid containing media. Furthermore, the knowledge of thickness of the applied coating layer is essential in order to predict the storage or release behavior. In this work a novel technique for measurement of coating layer thickness of fine particles is presented. This method is based on cross-sectioning of single coated particles in micrometer size range with focused ion beam (FIB). This technique has been tested on two batches of produced aerogel particles coated with thin coating layers in a spouted bed.Publicationtype: Conference Paper172 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Magnetic Resonance Imaging and Modeling of Liquid-Solid FluidizationAlthough less studied than gas-solid fluidized beds, liquid-solid fluidized beds have a variety of applications ranging from particle separation to thermal energy storage to bioreactors1. On a fundamental level, liquid-solid fluidized beds typically exhibit homogeneous fluidization, making them an ideal candidate for studying particle motion in a granular gas2. Studies of liquid-solid fluidized beds have been somewhat limited by difficulties in studying particle and liquid motion in the interior of 3D opaque systems. Here, we use rapid magnetic resonance imaging (MRI) to study both liquid and particle dynamics inside of a 3D liquid-solid fluidized bed. MRI techniques are used to create instantaneous maps of particle and liquid velocity over time3, as well as the distribution of particle and liquid velocities4 in the system at the molecular level. The findings are compared with various theories for fluid and particle motions in a granular gas. Additionally, the results are compared with computational fluid dynamics – discrete element method (CFD-DEM)5 simulations to understand the abilities and deficiencies of such a model in capturing liquid and solid dynamics in a liquid-solid fluidized bed.Publicationtype: Conference Paper48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fluidization characterisitcs of cohesive powder in a pilot plant scale vibrated fluidized bed dryer at low vibration frequencies(2018-04-22); ; ; ; Mechanical vibration is often applied in industrial scale fluidized bed dryers in food and pharmaceutical processes to overcome operational problems due to cohesiveness. However, the understanding of the process is still insufficient regarding detailed modelling, apparatus design, up-scaling and process optimization. Almost all of the experimental research in the field of vibrating fluidized beds is conducted on a lab-scale. Within the current project a pilot plant scale unit with a cross section of 250 x 500 mm2 and a total height of 3 m was built. The influence of process parameters, such as gas velocity, vibration intensity, powder moisture content and bed mass, on the fluidization characteristics of whole milk powder was investigated. In order to characterize the lower limit of fluidization from an operational point of view, the velocity of full fluidization (uff) was introduced. It is defined as the lowest superficial gas velocity at which the entire bed is fully fluidized. It could be observed that an increase in powder moisture content results in significant increase of utr. Introduction of mechanical vibration into the bed resulted in the reduction of Uff, expansion of the bed and reduction of bubble volume fraction. This expansion of the suspension phase explains reported increase in heat and mass transfer in vibrated fluidized beds.Publicationtype: Conference Paper133 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the Mechanism of Anomalous Sphere Sinking in Apparently Fixed Particle Beds (Discrete Particle Simulation and Ultra-Fast MRI Measurement)It is well known that a particle bed behaves as a fluid in the case it is aerated with gas velocity higher than the minimum fluidization velocity Umf. This is called as a fluidized bed and widely used in a large number of industrial processes. Under Umf, on the contrary, gravity force working on a particle overcomes fluid force and a particle bed behaves as a solid. Oshitani et al. (Phys. Rev. Lett., 116, 068001, 2016) reported anomalous sinking of intruder spheres in granular beds aerated under but close to Umf. They observed deep and slow sinking of spheres in the case density of sphere is close to the bulk density of the bed. They attributed this phenomena to local fluidization around the spheres while its detailed mechanism was not clear due to opaque nature of granular beds. In the present study, anomalous sinking and stopping mechanism of intruder spheres in an apparently fixed bed aerated just below Umf were explored and revealed in detail by means of discrete particle simulation and ultra-fast MRI measurement. Our numerical simulation and MRI measurement enable us to observe detailed flow dynamics and forces working on the spheres with sufficient spatial and temporal resolutions. Fluid force, contact force from surrounding particles and the gravity force working of the sphere are almost balanced in the case sphere density matches with the bulk density of a bed and small deviations from the equilibrium make slow sinking. The deviation is due to the detachment of small bubbles from the sphere surface. Bubble detachment from the sphere surface loosens local gas pressure gradient that supports the sphere weight and the sphere falls at the time.Publicationtype: Conference Paper34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fabrication of highly-filled composites by spouted bed coating and study of the influence of particle shape on mechanical properties of the materials(2018-04-22); ; ; In this work the mechanical properties, as modulus of elasticity, strength and fracture toughness, of copper-composite materials was studied. The volume fraction of copper was between 60 and 83 %. The study was carried out with two types of composites. The first type were composites containing spherical copper particles. The second type were composites with copper particles, which were rolled before pressing to a bulk material. The analysis of fracture toughness shows, that the composites with spherical particles have the highest fracture toughness of 1.58 MPa·m l/2 . The composites with higher aspect ratios of particles have the highest fracture toughness of 2.64 MPa·m 1/2 . It corresponds to an increasing over 65 % for the highest values of the toughness referred to composites with spherical particles.Publicationtype: Conference Paper75