Inst. Prozess- und Verfahrenstechnik

165 Items

Recent Submissions
On diffusion coefficients of multicomponent liquid mixtures predicted by equilibrium molecular dynamics simulation

Janzen, Tatjana (2019)

In the present thesis equilibrium molecular dynamics simulation and the Green-Kubo formalism were employed for the investigation of diffusion coefficients of liquid mixtures. The capability of the utilized simulation method and molecular models to predict composition dependent transport properties was tested by examining 20 binary mixtures composed of methanol, ethanol, acetone, benzene, cycloh...

Comparison of energy stable simulation of moving contact line problems using a thermodynamically consistent Cahn–Hilliard Navier–Stokes model

Bonart, Henning ; Kahle, Christian ; Repke, Jens-Uwe (2019-09-19)

Liquid droplets sliding along solid surfaces are a frequently observed phenomenon in nature, e.g., raindrops on a leaf, and in everyday situations, e.g., drops of water in a drinking glass. To model this situation, we use a phase field approach. The bulk model is given by the thermodynamically consistent Cahn– Hilliard Navier–Stokes model from [Abels et al., Math. Mod. Meth. Appl. Sc., 22(3), 2...

Direct Numerical Simulations of Liquids on Microstructured Surfaces: Analysing the Fluid Dynamics on Packing

Bonart, Henning ; Repke, Jens-Uwe (2018)

Structured high performance packing for packing columns have macrostructures, e.g., corrugated or folded sheets, and in many cases microstructures or surface topographies with geometrical dimensions in the same order of magnitude as the film thicknesses. For an optimal design of microstructured surfaces and for the development of novel methodologies to predict the mass transfer, a reliable desc...

Influence of Liquid Density and Surface Tension on the Pinning of Sliding Droplets on a Triangular Microstructure

Bonart, Henning ; Jung, Johannes ; Kahle, Christian ; Repke, Jens-Uwe (2019-06-11)

Sliding droplets are crucial in many industrial applications. Examples are coating and separation processes involving multiple phases and liquid films. Often one can observe how a sliding droplet halts midstream on a solid surface. Wetting defects such as topographic structures can lead to a pinning of sliding droplets. In order to assess the influence of liquid density and surface tension on t...

Experimental characterization of stable liquid rivulets on inclined surfaces: Influence of surface tension, viscosity and inclination angle on the interfacial area

Bonart, Henning ; Marek, André ; Repke, Jens-Uwe (2017-07-22)

In this work, liquid rivulets on inclined, smooth surfaces were examined experimentally using light-induced fluorescence. The influence of viscosity, surface tension and inclination angle was studied in terms of the Reynolds and Kapitza numbers. Detailed results on the interfacial area of the rivulets were obtained. Based on the experimental results, a correlation of the interfacial area in dep...

Untersuchung der Mechanismen zur Wärmeübertragung in Direktkontaktlatentwärmespeichern

Kunkel, Sven (2019)

Die Energiewende in Deutschland ist in vollem Gange. Durch den gezielten Ausbau der erneuerbaren Energien steigt gleichzeitig der Anteil der fluktuierenden Energiequellen entsprechend an. Dies erfordert effiziente und wirtschaftliche Speichertechnologien zum Ausgleich der Diskrepanz zwischen Energieangebot und -nachfrage. Ebenfalls wird eine solche Speichertechnologie zur effizienten Nutzung vo...

Dynamic Model of Chloralkali Membrane Process

Budiarto, Thomas ; Esche, Erik ; Repke, Jens-Uwe ; Leksono, Edi (2017)

Chloralkali is one of the most important and energy intensive processes in the chemical industry. The process produces chlorine through electrochemical conversion. The process's energy consumption is a major production cost for the chloralkali industry. Since the demand for energy efficiency and environmentally friendly processes in industry increases, ion exchange membranes are used intensivel...

Growth Behavior of Human Adipose Tissue-Derived Stromal/Stem Cells at Small Scale: Numerical and Experimental Investigations

Jossen, Valentin ; Eibl, Regine ; Kraume, Matthias ; Eibl, Dieter (2018-12-04)

Human adipose tissue-derived stromal/stem cells (hASCs) are a valuable source of cells for clinical applications, especially in the field of regenerative medicine. Therefore, it comes as no surprise that the interest in hASCs has greatly increased over the last decade. However, in order to use hASCs in clinically relevant numbers, in vitro expansion is required. Single-use stirred bioreactors i...

Beitrag zur Bindemittelbrikettierung von Steinkohlenabrieb für dessen Einsatz im COREX®-Einschmelzvergaser

Lohmeier, Reinhard (2019)

Das COREX®-Verfahren ist ein Schmelzreduktionsprozess zur Herstellung von flüssigem Roheisen aus Eisenerz. Das Verfahren ist eine Alternative zum konventionellen Hochofenprozess. Ein wesentlicher Unterschied zwischen beiden Verfahren ist die Möglichkeit des direkten Einsatzes von stückigen Kraftwerkssteinkohlen (x > 8 mm) im COREX®-Einschmelzvergaser, ohne die Kohle vorab zu Hochofenkoks verede...

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% ...