The entrainment by pulsed or rather so-called synthetic wall jets can be used to sustain a pressu... more The entrainment by pulsed or rather so-called synthetic wall jets can be used to sustain a pressure-less transport of thin liquid layers along ducts. These jets exhibit zero-net-mass-flow conditions and lead to a break of symmetry in the flow pattern during one oscillation cycle. Therefore, only a net impulse is transferred in jet direction and induces a directed movement of the ambient liquid by entrainment according to the jet direction. The aim is to investigate the applicability of the principle to counter-current contactors as an alternative to pressure drop or gravity as driving forces typically applied e.g. in counter-current liquid-liquid contactors. Experiments are performed with an apparatus containing wall-jet flow drives with a multitude of narrow slit-openings (slit-width s = 190 μm) along a channel for synthetic wall jet generation. Firstly, one single wall-jet flow drive is investigated regarding its conveying performance at different related oscillation amplitudes (eslit/s = 7–25) and frequencies (f = 1–5 Hz). Subsequently, the apparatus is extended by a second identical device, arranged in parallel but above and oriented in the opposite conveying direction. This is to demonstrate the applicability of synthetic wall jets for counter-current operations.
A summary of results is presented from experiments in granular systems, which are excited by vert... more A summary of results is presented from experiments in granular systems, which are excited by vertical and/or horizontal vibrations. The transitions between different dynamic states depend on internal properties of the granular system like the density of particles as well as external parameters of the driving shakers. Characteristic for granular systems are counterintuitive phenomena like the crystallization by increasing the vibration amplitude and thereby the energy input, or the rise of large particles in a sea of smaller ones (Brazil-nut effect). For horizontal shaking of a binary system the demixing of small and large particles is found to occur at the same critical particle density as the liquid-solid transition, which leads to the conclusion that both phenomena, segregation and phase transition, are closely related.
... Eva Maria Littringer 1 , Stephan Maas 2 , Axel Mescher 3 , Hartmuth Schroettner 4 , Peter Wal... more ... Eva Maria Littringer 1 , Stephan Maas 2 , Axel Mescher 3 , Hartmuth Schroettner 4 , Peter Walzel 4 , Nora Anne Urbanetz 1 ... EXPERIMANTAL METHODS Materials Mannitol (Pearlitol SD 200) was kindly provided by Roquette, F-Lestrem. ...
ABSTRACT Deposition of solids within porous materials from a drying solution is an important phen... more ABSTRACT Deposition of solids within porous materials from a drying solution is an important phenomenon in numerous natural and industrial processes. A profound knowledge about influences of different parameters on the solid distribution in the material is required for an effective targeted impregnation process. Experimental investigations and simulations are used to study the influence of pore structure, drying conditions, and solute concentration on the solid distribution in porous support materials after impregnation and drying. It is found that low drying rates lead to strong solid accumulation at the material surface, whereas high drying rates reduce the solute transport to the surface and result in more uniform solid distributions. A small pore diameter and distribution width reduce solute migration during drying and lead to uniform solid distributions without being influenced by the drying conditions. A higher initial concentration of the impregnation solution causes pronounced surface accumulation, while low initial solute concentrations result in more uniform distributions. Fundamental effects during drying are captured in an existing pore network model by adaption of experimental pore structures and impregnation–drying conditions, resulting in a good general agreement of experiments with simulations.
Particle size reduction down to the submicron range (0.1-1 μm) is an effective option to increase... more Particle size reduction down to the submicron range (0.1-1 μm) is an effective option to increase the bioavailability of low water soluble active pharmaceutical ingredients. According to the Nernst-Brunner equation, the preparation of submicron sized particles increases the specific surface area, thus increases the dissolution rate. Conventional spray drying devices for submicron particles show certain limitations. The main challenge is the preparation of small and uniform droplets during the atomisation step. In this work, fine droplets were generated combining a nozzle with a droplet separator. Therefore, the aerosol is generated with a pneumatic nozzle and is sprayed into a cyclone droplet separator. Depending on the characteristics of the cyclone, droplets larger than the cut-off-size were separated and returned into the liquid feed. The conditioned aerosol at the top of the cyclone separator can then be introduced into the drying chamber. With this concept the usable part is se...
The entrainment by pulsed or rather so-called synthetic wall jets can be used to sustain a pressu... more The entrainment by pulsed or rather so-called synthetic wall jets can be used to sustain a pressure-less transport of thin liquid layers along ducts. These jets exhibit zero-net-mass-flow conditions and lead to a break of symmetry in the flow pattern during one oscillation cycle. Therefore, only a net impulse is transferred in jet direction and induces a directed movement of the ambient liquid by entrainment according to the jet direction. The aim is to investigate the applicability of the principle to counter-current contactors as an alternative to pressure drop or gravity as driving forces typically applied e.g. in counter-current liquid-liquid contactors. Experiments are performed with an apparatus containing wall-jet flow drives with a multitude of narrow slit-openings (slit-width s = 190 μm) along a channel for synthetic wall jet generation. Firstly, one single wall-jet flow drive is investigated regarding its conveying performance at different related oscillation amplitudes (eslit/s = 7–25) and frequencies (f = 1–5 Hz). Subsequently, the apparatus is extended by a second identical device, arranged in parallel but above and oriented in the opposite conveying direction. This is to demonstrate the applicability of synthetic wall jets for counter-current operations.
A summary of results is presented from experiments in granular systems, which are excited by vert... more A summary of results is presented from experiments in granular systems, which are excited by vertical and/or horizontal vibrations. The transitions between different dynamic states depend on internal properties of the granular system like the density of particles as well as external parameters of the driving shakers. Characteristic for granular systems are counterintuitive phenomena like the crystallization by increasing the vibration amplitude and thereby the energy input, or the rise of large particles in a sea of smaller ones (Brazil-nut effect). For horizontal shaking of a binary system the demixing of small and large particles is found to occur at the same critical particle density as the liquid-solid transition, which leads to the conclusion that both phenomena, segregation and phase transition, are closely related.
... Eva Maria Littringer 1 , Stephan Maas 2 , Axel Mescher 3 , Hartmuth Schroettner 4 , Peter Wal... more ... Eva Maria Littringer 1 , Stephan Maas 2 , Axel Mescher 3 , Hartmuth Schroettner 4 , Peter Walzel 4 , Nora Anne Urbanetz 1 ... EXPERIMANTAL METHODS Materials Mannitol (Pearlitol SD 200) was kindly provided by Roquette, F-Lestrem. ...
ABSTRACT Deposition of solids within porous materials from a drying solution is an important phen... more ABSTRACT Deposition of solids within porous materials from a drying solution is an important phenomenon in numerous natural and industrial processes. A profound knowledge about influences of different parameters on the solid distribution in the material is required for an effective targeted impregnation process. Experimental investigations and simulations are used to study the influence of pore structure, drying conditions, and solute concentration on the solid distribution in porous support materials after impregnation and drying. It is found that low drying rates lead to strong solid accumulation at the material surface, whereas high drying rates reduce the solute transport to the surface and result in more uniform solid distributions. A small pore diameter and distribution width reduce solute migration during drying and lead to uniform solid distributions without being influenced by the drying conditions. A higher initial concentration of the impregnation solution causes pronounced surface accumulation, while low initial solute concentrations result in more uniform distributions. Fundamental effects during drying are captured in an existing pore network model by adaption of experimental pore structures and impregnation–drying conditions, resulting in a good general agreement of experiments with simulations.
Particle size reduction down to the submicron range (0.1-1 μm) is an effective option to increase... more Particle size reduction down to the submicron range (0.1-1 μm) is an effective option to increase the bioavailability of low water soluble active pharmaceutical ingredients. According to the Nernst-Brunner equation, the preparation of submicron sized particles increases the specific surface area, thus increases the dissolution rate. Conventional spray drying devices for submicron particles show certain limitations. The main challenge is the preparation of small and uniform droplets during the atomisation step. In this work, fine droplets were generated combining a nozzle with a droplet separator. Therefore, the aerosol is generated with a pneumatic nozzle and is sprayed into a cyclone droplet separator. Depending on the characteristics of the cyclone, droplets larger than the cut-off-size were separated and returned into the liquid feed. The conditioned aerosol at the top of the cyclone separator can then be introduced into the drying chamber. With this concept the usable part is se...
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