Inst. Prozess- und Verfahrenstechnik

156 Items

Recent Submissions
Plastische Energiedissipation bei der Verarbeitung thermoplastischer Formmassen auf dem gleichläufigen Doppelschneckenextruder

Knieper, Alexander (2019)

Das initiale Aufschmelzen von thermoplastischen Polymeren durch plastische Energiedissipation ist nicht hinreichend verstanden und bildet noch heute eine entscheidende Wissenslücke bei der Prozessbeschreibung des gleichläufigen Doppelschneckenextruders. Es wird ein Testaufbau vorgestellt, bei dem das Fördern, die Kompression und die Deformation von Kunststoffgranulat im Querschnitt der Plastif...

Diffusion of methane in supercritical carbon dioxide across the Widom line

Guevara-Carrion, Gabriela ; Ancherbak, Sergiy ; Mialdun, Aliaksandr ; Vrabec, Jadran ; Shevtsova, Valentina (2019-06-11)

Diffusion of methane diluted in supercritical carbon dioxide is studied by experiment and molecular simulation in the temperature range from 292.55 to 332.85 K along the isobars 9.0, 12.5 and 14.7 MPa. Measurements of the Fick diffusion coefficient are carried out with the Taylor dispersion technique. Molecular dynamics simulation and the Green-Kubo formalism are employed to obtain Fick, Maxwel...

Systematische Analyse des Koaleszenzverhaltens von zweiphasigen Flüssigsystemen bei Ionenzugabe

Villwock, Jörn (2019)

Prozesse, in denen zwei nicht ineinander lösliche Flüssigkeiten verwendet werden, spielen eine wichtige Rolle in der industriellen Anwendung. Eine besonders wichtige die Prozesseffizienz bestimmende Größe ist dabei die Tropfengrößenverteilung, die sich aus den beiden simultan ablaufenden und sich überlagernden Phänomenen Tropfenbruch und -koaleszenz ergibt. Vor allem die Tropfenkoaleszenz ist a...

Extension and improvement of the coupled CFD-DEM approach to describe multidimensional heat transfer and non-spherical particle shape for fluidized systems

Oschmann, Tobias Sebastian (2019)

The design and improvement of industrial applications involving granular materials in the field of energy and thermal process engineering is often based on the results of numerical simulations as the experimental determination of the key process parameters of interest is frequently hard to conduct due to limited accessibility of the processes. Most used numerical frameworks for granular materia...

Composition dependent transport diffusion in non-ideal mixtures from spatially resolved nuclear magnetic resonance spectroscopy

Pantoja, Christian F. ; Muñoz-Muñoz, Y. Mauricio ; Guastar, Lorraine ; Vrabec, Jadran ; Wist, Julien (2018-10-16)

Nuclear magnetic resonance (NMR) spectroscopy is a well-established technique for the measurement of intra-diffusion coefficients. Recently, such information has been used as a basis of predictive models to extrapolate to the Fick diffusion coefficient of liquid mixtures. The present work presents a new approach to directly access the Fick diffusion coefficient by spatially resolved NMR experim...

Diffusion Coefficients of a Highly Nonideal Ternary Liquid Mixture: Cyclohexane–Toluene–Methanol

Janzen, Tatjana ; Vrabec, Jadran (2018-10-26)

To better understand diffusion phenomena in highly nonideal ternary liquid mixtures, cyclohexane–toluene–methanol is studied by equilibrium molecular dynamics (EMD) simulation. Intradiffusion and Maxwell–Stefan (MS) diffusion coefficients, being strictly kinetic properties, are predicted by EMD over the entire composition range at ambient conditions. The thermodynamic contribution to the Fick d...

Kirkwood-Buff integration: A promising route to entropic properties?

Fingerhut, Robin ; Vrabec, Jadran (2018-12-13)

Kirkwood-Buff integration (KBI) is implemented into the massively-parallel molecular simulation tool ms2 and assessed by molecular dynamics simulations of binary liquid mixtures. The formalism of Krüger et al. (P. Krüger et al., J. Phys. Chem. Lett. 4: 235–238, 2013) that adopts NVT ensemble data to the μVT ensemble is employed throughout. Taking advantage of its linear scaling with inverse sys...

Diffusion limited evaporation of a binary liquid film

Chatwell, René Spencer ; Heinen, Matthias ; Vrabec, Jadran (2018-12-21)

An analytical solution of a model fluid’s time behavior, known as the Stefan problem, is presented. A scenario is investigated in which a planar two-component liquid film is continuously evaporating into a thermodynamically non-ideal vapor phase. Evaporation is initiated and maintained by a spatial chemical potential gradient, while its rate is limited by the components’ diffusion fluxes across...

Do ternary liquid mixtures exhibit negative main Fick diffusion coefficients?

Kozlova, S. ; Mialdun, Aliaksandr ; Ryzhkov, I. ; Janzen, Tatjana ; Vrabec, Jadran ; Shevtsova, Valentina (2019-01-07)

Experimental data on Fick diffusion coefficients of ternary and higher mixtures depend on the reference frame; those which are in common use are associated with the average velocity either with respect to volume, mass or mole number. In this study, the dependence of diffusion coefficients on the reference frame is thoroughly analyzed for three ternary mixtures of different types. The first one,...

Digitalization in Thermodynamics

Forte, Esther ; Jirasek, Fabian ; Bortz, Michael ; Burger, Jakob ; Vrabec, Jadran ; Hasse, Hans (2019-01-08)

Digitalization is about data and how they are used. This has always been a key topic in applied thermodynamics. In the present work, the influence of the current wave of digitalization on thermodynamics is analyzed. Thermodynamic modeling and simulation is changing as large amounts of data of different nature and quality become easily available. The power and complexity of thermodynamic models ...

Thermodynamic Speed of Sound Data for Liquid and Supercritical Alcohols

Javed, Muhammad Ali ; Baumhögger, Elmar ; Vrabec, Jadran (2019-02-28)

Because of their caloric and thermal nature, speed of sound data are vital for the development of fundamental Helmholtz energy equations of state for fluids. The present work reports such data for methanol, 1-propanol, 2-propanol, and 1-butanol along seven isotherms in the temperature range from 220 to 500 K and a pressure of up to 125 MPa. The overall expanded uncertainty varies between 0.07% ...

Efficient implementation of advanced molecularly-based equation of state models out of the documentation level

Merchan Restrepo, Victor Alejandro (2019)

Considering the increasing number of modern thermodynamic models for engineering applications and their continuously growing algebraic complexity, in the chemical process industry and research there is a high demand for methods and mechanisms that enhance the dissemination and reuse of these models in an efficient way. Experience shows that the common practice of providing model equations as a...

Experimental and numerical analysis of non-spherical particles in fluidized process/energy technology systems

Vollmari, Kevin (2019)

Fluid flow through a packing of granular material is commonly encountered in natural processes such as deep percolation of water, in industrial processes such as the movement of petroleum/natural gas through sand/rock in oil and gas extraction as well as in fixed and fluidized beds. Fixed beds are used among others for applications such as catalytic reactions, heat transfer, filtering, adsorpti...

DEM-Simulation der Trennkurven in Siebung und Gegenstromsichtung bei geringen Gutbeladungen

Spötter, Christian ; Elskamp, Frederik ; Hennig, Manuel ; Teipel, Ulrich ; Weber, Alfred P. ; Kruggel-Emden, Harald (2017)

Zur Abtrennung von Partikeln mit unterschiedlicher Größe sind in der Feststoffverfahrenstechnik trockene Klassierprozesse zur Herstellung von engen Fraktionen von großer Bedeutung. Um das Trennverhalten von Strömungs- und Siebklassierprozessen genauer vorhersagen zu können, wurden experimentelle Resultate mit DEM-Simulationen verglichen. Bei der Siebklassierung wurde der Einfluss der Partikelfo...

Extension of process models to predict batch screening results under the influence of moisture based on DEM simulations

Elskamp, Frederik ; Kruggel-Emden, Harald (2018)

Screening is a technical simple but still not fully understood process step, which can be used in a wide field of applications to separate bulk materials according to their particle sizes. A severe issue in screening technologies is that particles frequently prevail in moist conditions, due to effects related to the environment, the material or the process. This is often not preventable, althou...

DEM simulations of screening processes under the influence of moisture

Elskamp, Frederik ; Kruggel-Emden, Harald (2018)

In a wide field of applications, screening is required to separate bulk materials according to their particle sizes. Due to environmental, material or process related effects, particles frequently prevail in moist conditions, which is not preferred due to attractive forces altering the screening efficiency, but often not preventable. As for the design of dry screening processes detailed particl...

A strategy to determine DEM parameters for spherical and non-spherical particles

Elskamp, Frederik ; Kruggel-Emden, Harald ; Hennig, Manuel ; Teipel, Ulrich (2017)

In Discrete element method (DEM) simulations the choice of appropriate contact parameters is significant to obtain reasonable results. Particularly, for the determination of DEM parameters for non-spherical particles a general straightforward procedure is not available. Therefore, in a first step of the investigation here, methods to obtain the friction and restitution coefficients experimental...

Dispersion and phase separation in liquid multiphase systems

Hohl, Lena Katharina (2019)

Microemulsion systems consisting of water, 1-dodecene and different non-ionic surfactants can develop up to three liquid phases as a function of composition and process conditions. These innovative solvent systems are promising reaction media for processes such as the hydroformylation of long-chained olefins. In this work, the influence of the third phase on the drop size distributions and the ...

Entwicklung von Fehlererkennungs-, Zustandsschätzungs-, Regelungs- und ganzzahligen Optimalsteuerungsmethoden für pulsierende, detonative Brennkammern anhand eines akustischen Ersatzsystems

Wolff, Sascha Dominik (2019)

Aktuelle Forschungsbestrebungen zur Effizienzsteigerung von Gasturbinen verfolgen häufig den Ansatz eines Wechsels des zugrundeliegenden Kreisprozesses weg vom Brayton- hin zum Humphrey-Kreisprozess. Eine vielversprechende Möglichkeit, diesen Kreisprozess technischzu realisieren, ist durch den Einsatz einer pulsierenden, druckerhöhenden Detonationsbrennkammer gegeben. Eine solche Brennkammer be...

A framework for the derivation of dynamic process models for sieving

Elskamp, Frederik (2018)

For a wide field of applications in mechanical process engineering and materials preparation technology, screening as technical simple but still not satisfactorily understood process step is well suited to separate bulk materials according to their particle sizes. Frequently, particles prevail in broad size distributions, highly non-spherical shape and under moist conditions, complicating the h...