@article{26154, abstract = {{A high-temperature short residence time flow reactor system has been realized for the investigation of the gas phase sintering kinetics of nanoparticles separated from all other synthesis mechanisms, e.g., chemical reaction, nucleation, coagulation and condensation. Major components are a hot-wall tubular reactor for the production of unsintered aggregates consisting of spherical primary particles in the size range 10–80 nm and a sintering reactor for the investigation of the sintering kinetics at well-defined temperature and residence time history. Therefore, rapid heating and quenching of the particles at the beginning and at the end of the reaction zone, respectively, is maintained. Main parameters in the sintering reactor are: temperatures up to 1873 K and residence times in the range 8–1000 ms. The reactor conditions are characterized by temperature profile measurements with a newly constructed suction thermocouple probe and by computational fluid dynamics simulations of the residence time distributions. Exemplary results of the sintering of silica nanoparticles obtained by transmission electron microscopy analysis are presented.}}, author = {{Kirchhof, Martin J. and Schmid, Hans-Joachim and Peukert, Wolfgang}}, issn = {{0034-6748}}, journal = {{Review of Scientific Instruments}}, number = {{11}}, pages = {{4833--4840}}, title = {{{Reactor system for the study of high-temperature short-time sintering of nanoparticles}}}, doi = {{10.1063/1.1809258}}, volume = {{75}}, year = {{2004}}, } @article{26155, author = {{Messerer, A. and Schmid, Hans-Joachim and Knab, C. and Pöschl, U. and Nießner, R.}}, issn = {{0009-286X}}, journal = {{Chemie Ingenieur Technik}}, number = {{8}}, pages = {{1092--1096}}, title = {{{Erhöhung der Abscheidung ultrafeiner Dieselrußpartikeln durch Mikrokugelbeschichtung auf metallträgerbasierten Katalysatorstrukturen}}}, doi = {{10.1002/cite.200403418}}, volume = {{76}}, year = {{2004}}, } @article{26156, abstract = {{Electro-hydrodynamic two-phase flows are encountered in various applications, e.g. electrically enhanced coating, electrostatic precipitation or toner application. In all cases there is a complex interaction between a turbulent flow field, a strong electric field, a corona discharge and the particle motion. This paper starts with an overview and classification of possible modelling approaches for all major phenomena. Afterwards the manuscript focuses on the modelling of particle dynamics: A Lagrangian, continuous random walk model is compared with an Eulerian approach for a number of test cases. The study is mostly focused on fine particles, i.e. roughly smaller than 100 μm in diameter for the Lagrangian approach and smaller than about 10 μm in the case of Eulerian modelling. It is shown that a local turbulent dispersion coefficient may be derived based on flow field calculations with a constant of proportionality identical to the Lagrangian random walk model. In this case the turbulent dispersion is equally described by both models even for inhomogeneous turbulence. For a superimposed particle drift velocity a model equation introduced by Csanady gives a reasonable agreement. Finally it is shown that modelling of the charging kinetics is a very crucial point in Eulerian modelling. This is demonstrated for the example of electrostatic precipitation where good agreement between Lagrangian and Eulerian modelling is achieved only if local particle charging kinetics is accounted for. Even though Lagrangian particle tracking is still superior in terms of physical modelling of electro-hydrodynamic particulate flows, it is shown that an Eulerian approach may lead to reasonable results with substantially reduced numerical effort.}}, author = {{Schmid, Hans-Joachim and Vogel, Lutz}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{118--135}}, title = {{{On the modelling of the particle dynamics in electro-hydrodynamic flow-fields: I. Comparison of Eulerian and Lagrangian modelling approach}}}, doi = {{10.1016/j.powtec.2003.08.009}}, volume = {{135/136}}, year = {{2003}}, } @article{26157, abstract = {{A simulation method is applied to calculate particle dynamics in electrostatic precipitators as characterised by particle flux density and concentration profiles in arbitrary channel cross-sections and flux density profiles of dust precipitated at the collecting electrodes (CEs). A simple statistical model allows the determination of confidence intervals for flux profiles. First, a ‘standard case’ considering full coupling of all physical phenomena occurring in this problem, i.e., electric field, flow field and particle dynamics is simulated. Subsequently, this standard case is compared to simulations with one quantity (e.g., electric field strength, turbulence intensity) substituted by a mean value which is homogeneously distributed in the precipitation zone. This reveals the relevance of the various physical phenomena: It turned out that the secondary flows had only a minor influence on the overall particle precipitation although they cause some ‘patterning’ of local precipitation. Turbulence inhomogeneity shows a stronger effect on particle dynamics. However, the electric field appears to be by far the most important quantity in simulating particle dynamics. Consequently, in order to achieve most reasonable simulation results for a given numerical effort most attention has to be devoted to field calculations, including correct boundary conditions.}}, author = {{Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{136--149}}, title = {{{On the modelling of the particle dynamics in electro-hydrodynamic flow fields: II. Influences of inhomogeneities on electrostatic precipitation}}}, doi = {{10.1016/j.powtec.2003.08.010}}, volume = {{135/136}}, year = {{2003}}, } @article{26158, abstract = {{Rasche technologische Entwicklungen haben für Chemieingenieure bzw. Verfahrenstechniker neue Beschäftigungsmöglichkeiten eröffnet, wodurch sich zusätzliche Anforderungen an die Ausbildung ergeben. Der vorliegende Beitrag beschreibt die Lösungsansätze im Fachgebiet der Partikeltechnik: Es findet eine noch stärkere Betonung der Grundlagen statt, wobei Beispiele aus klassischen und neuen Anwendungen exemplarisch vertieft werden. Kernpunkt des Curriculums sind die Produkteigenschaften. Besonderes Gewicht wird außerdem auf die Betrachtung ganzer Prozesse gelegt. Die Vorlesungen sind in drei Ebenen strukturiert: Grundlagen, Grundoperationen und Prozesse/Anwendungen. Methodisch wird ein zweifacher Ansatz verfolgt: Die Lehre der grundlegenden Fakten wird ergänzt durch eine aktive Teilnahme der Studenten, insbesondere bei der Erarbeitung von Beispielen und in Labor- bzw. Rechnerpraktika. Durch eine ganzheitliche Sicht der Universitätsausbildung sollen auch „soft skills“ gefördert werden.}}, author = {{Peukert, W. and Schmid, Hans-Joachim}}, issn = {{0009-286X}}, journal = {{Chemie Ingenieur Technik}}, number = {{3}}, pages = {{177--183}}, title = {{{Herausforderungen für die Lehre am Beispiel der mechanischen Verfahrenstechnik}}}, doi = {{10.1002/cite.200390035}}, volume = {{75}}, year = {{2003}}, } @article{26159, abstract = {{A population balance model is presented, which tracks particle growth in the gas phase and accounts for simultaneous agglomeration and sintering: Simulations reveal the evolution of the full distribution of a volume equivalent diameter and, amongst others, the evolution of the agglomerate collision diameter, a mean primary particle size and the number of primary particles per agglomerate. Furthermore, assuming fractal behaviour of the growing agglomerate particles—for the first time—a model for the evolution of a mean value of the fractal dimension based on physical and process parameters is proposed and incorporated into the simulation model. PARSIVAL, a commercial solver for integro-differential equations is employed to solve the equations involved. It is based on a generalised finite-element scheme with self-adaptive grid- and order construction. Calculations are performed to validate the model against monodisperse and sectional models published in literature for the exemplary case of Si production. The results are in good agreement if the same simplifying assumptions are made. However, results obtained from the new model for both—isothermal and non-isothermal process conditions—clearly show that it is important to consider the changing fractal dimension in many cases.}}, author = {{Artelt, C. and Schmid, Hans-Joachim and Peukert, W.}}, issn = {{0021-8502}}, journal = {{Journal of Aerosol Science}}, number = {{5}}, pages = {{511--534}}, title = {{{On the relevance of accounting for the evolution of the fractal dimension in aerosol process simulations}}}, doi = {{10.1016/s0021-8502(03)00005-3}}, volume = {{34}}, year = {{2003}}, } @article{26160, abstract = {{Thermal charging of submicron and nanometer particles has been studied for model aerosols of TiO2 and SiO2 as well as Al-Si (aluminosilicate) at 1 000 °C with a new quasi in-situ technique. The size dependence of the particle separation efficiency for electrostatic precipitation was determined. The charging state of the particles was obtained from evaluating the global Deutsch number for precipitation in an electric field applied to a laminar flow based on particle trajectory considerations.}}, author = {{Schiel, Annette and Weber, Alfred P. and Kasper, Gerhard and Schmid, Hans-Joachim}}, issn = {{0934-0866}}, journal = {{Particle & Particle Systems Characterization}}, number = {{6}}, pages = {{410--418}}, title = {{{In-Situ Determination of the Charging of Nanometer and Submicron Particles at High Temperatures}}}, doi = {{10.1002/ppsc.200290004}}, volume = {{19}}, year = {{2002}}, } @article{26161, abstract = {{An optical measuring technique is presented allowing the exact in-situ measurement of local particle flux densities in a confined channel flow by counting single particles penetrating an optically well defined measuring volume. This enables a precise flux determination up to the direct vicinity of planar walls. The measurement set-up and its calibration as well as the whole test facility are described in detail. This measurement technique is used to study the particle transport in electrostatic precipitators. Exemplarily, results of particle flux profiles as well as precipitation, as gained from balances of parts of the precipitator channel, are presented. Furthermore, the possibility to determine particle velocity fluctuations is demonstrated.}}, author = {{Schmid, Hans-Joachim and Veith, Susanne and Umhauer, Heinz}}, issn = {{0934-0866}}, journal = {{Particle & Particle Systems Characterization}}, number = {{3}}, title = {{{In-Situ Measurement of Local Particle Flux Densities in a Complex Two-Phase Flow}}}, doi = {{10.1002/1521-4117(200207)19:3<203::aid-ppsc203>3.0.co;2-7}}, volume = {{19}}, year = {{2002}}, } @inbook{26169, abstract = {{Summary Elektrische Staubabscheidung Wirkprinzip Mikroprozesse und Grundvorgänge Sekundäreinflüsse auf die Partikelabscheidung Wichtige Bestandteile und verschiedene Bauformen Auslegung von Abscheidern }}, author = {{Schmid, Hans-Joachim}}, booktitle = {{Handbuch der Mechanischen Verfahrenstechnik}}, title = {{{Trennprozesse: Abschnitt 7.5.3}}}, doi = {{10.1002/3527603352.ch7r}}, year = {{2002}}, } @article{29826, author = {{Schmid, Hans-Joachim and Peukert, Wolfgang}}, journal = {{chemical engineering education}}, number = {{4}}, title = {{{Novel Concepts for Teaching Particle Technology }}}, volume = {{36}}, year = {{2002}}, } @article{29484, abstract = {{Electro-hydrodynamic (EHD) flows are investigated theoretically and numerically in this paper and results are presented for the flow field in model electrostatic precipitators (EPs). The resulting flow fields are shown in various representations and explained qualitatively. Numerical calculations with different flow models (non-turbulent and RANS) were conducted to investigate the influence of the flow model on the resulting secondary flows. Furthermore, a perturbation analysis is presented, leading to a simple differential equation of the Helmholtz type. This allows a more detailed view of the important mechanisms forming the secondary flows as well as being able to obtain a very fast estimation of the resulting flow field. The calculations reveal a strong influence of a vortex formation at the beginning of the precipitation zone on the whole flow field. Furthermore, a strong effect of the boundary conditions of the electric field and the operating parameters is shown.}}, author = {{Schmid, Hans-Joachim}}, journal = {{Flow, Turbulence and Combustion}}, pages = {{63--89}}, publisher = {{Springer}}, title = {{{On the Modelling of the Electro-Hydrodynamic Flow Field in Electrostatic Precipitators}}}, doi = {{10.1023/A:1015666116174}}, volume = {{68}}, year = {{2002}}, } @phdthesis{29825, author = {{Schmid, Hans-Joachim}}, isbn = {{978-3-8265-4850-5}}, pages = {{242}}, publisher = {{Shaker Verlag}}, title = {{{Zum Partikeltransport in Elektrischen Abscheidern}}}, year = {{1998}}, }