04 Fakultät Energie-, Verfahrens- und Biotechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5
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Item Open Access Analysis and extension of Wertheim's thermodynamic perturbation theory(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2019) Zmpitas, Wasilios; Groß, Joachim (Prof. Dr.-Ing.)Item Open Access Atomistic simulation of fluid structure and diffusion in functionalized mesoporous silica(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2023) Kraus, Hamzeh; Hansen, Niels (Prof. Dr.-Ing.)Despite the importance of supported catalysts in industrial applications a rational design based on an understanding of molecular-level processes is still a challenging endeavor, in particular for liquid phase reactions. Ordered mesoporous silicas are common support materials for hosting organometallic catalysts and provide a tailored microenvironment that may lead to enhanced selectivities, productivities and activities. In the present work a computational tool box was developed that facilitates rapid model building of functionalized silica pores and, together with pre- and post-analysis tools, allows for systematic molecular simulation studies of confinement effects in various applications. The tool box was subsequently applied to different research questions including modelling of the uptake of aromatic compounds from the aqueous phase on cyclodextrin-functionalized silica and a detailed investigation of diffusion in cylindrical mesopores allowing to assess the discrepancy among recent experimental diffusion measurements.Item Open Access Berechnung von Grenzflächeneigenschaften mithilfe der klassischen Dichtefunktionaltheorie mit einem Funktional auf Grundlage der PCP-SAFT Zustandsgleichung(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2018) Klink, Christoph; Groß, Joachim (Prof. Dr.-Ing.)Die Arbeit beschreibt die Weiterentwicklung eines Dichtefunktionaltheorie-Formalismus zur Berechnung von Grenzflächeneigenschaften von polaren Reinstoffen und nicht- bzw, schwach polaren Mischungen. Als Zustandsgleichung kommt die perturbed chain polar statistical associating fluid thoery (PCP-SAFT) zur Anwendung.Item Open Access Biomolecular force fields probed by free energies of binding and solvation(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2021) Gebhardt, Julia; Hansen, Niels (apl. Prof. Dr.-Ing.)Item Open Access Calculation of pure substance and mixture viscosities using PCP-SAFT and entropy scaling(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2020) Lötgering-Lin, Oliver; Gross, Joachim (Prof. Dr.-Ing.)Item Open Access Correlating and predicting thermal conductivity and self-diffusion from entropy scaling using PCP-SAFT(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2022) Hopp, Madlen; Groß, Joachim (Prof. Dr.-Ing.)For a complete description and design of thermodynamic processes, knowledge of the properties of all substances involved is absolutely necessary. While the equilibrium properties are already well understood, there is still a lack of a handy description of the transport properties. Entropy scaling is an intriguingly simple approach for correlating and predicting transport properties of real substances and mixtures. As convincingly documented in the literature entropy scaling is indeed a firm concept for the shear viscosity of real substances, including hydrogen-bonding species and strongly non-spherical species and for mixtures. In this thesis, we investigate whether the entropy scaling approach is applicable for the thermal conductivity as well as the self-diffusion coefficients of pure substances. In accordance with the entropy scaling approach proposed by Y. Rosenfeld [Phys. Rev. A 1977, 15, 2545-2549], we observe that the thermal conductivity and the self-diffusion coefficient of real substances, once made dimensionless with an appropriate reference expression, only depend on residual entropy. We propose suitable reference expressions for both properties, to calculate the coefficients of pure substances from entropy scaling using the Perturbed-Chain Polar Statistical Associating Fluid Theory (PCP-SAFT) equation of state. Good entropy scaling behavior is found for the entire fluid region for water and more than 130 organic substances from various chemical families: linear and branched alkanes, alkenes, aldehydes, aromatics, ethers, esters, ketones, alcohols and acids. Models for both, thermal conductivity and self-diffusion coefficient, show satisfying robustness for extrapolating the coefficients to conditions rather distant from state points where experimental data is available. Additionally, a predictive group-contribution method for thermal conductivity based on entropy scaling is derived. The excess entropy for this approach is calculated using the group-contribution PCP-SAFT equation of state. The model is applicable for gaseous phases and for liquid-phase conditions covering wide ranges of temperature and pressure.Item Open Access Development of a polarizable transferable force field for vapor-liquid equilibria calculations(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2019) Waibel, Christian; Groß, Joachim (Prof. Dr.-Ing.)Item Open Access Development of hydrodynamic density functional theory for mixtures and application to droplet coalescence(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2021) Stierle, Rolf; Groß, Joachim (Prof. Dr.-Ing.)Predicting accurately coalescence phenomena is critical to the accurate description of the hydrodynamics of fluids and their mixtures. A promising framework for the development of models for such phenomena is dynamic density functional theory. Dynamic density functional theory enables the analysis of dynamical processes in inhomogeneous systems of pure fluids and fluid mixtures at the molecular level. In this work, a hydrodynamic density functional theory model for mixtures in conjunction with Helmholtz energy functionals based on the PC-SAFT equation of state is proposed, that obeys the first and second law of thermodynamics and simplifies to the isothermal Navier-Stokes equation for homogeneous systems. The hydrodynamic density functional theory model is derived from a variational principle and accounts for both viscous forces and diffusive molecular transport. A Maxwell-Stefan model is applied for molecular transport. This work identifies a suitable expression for the driving force for molecular diffusion of inhomogeneous systems that captures the effect of interfacial tension. The proposed hydrodynamic density functional theory is a non-local theory that requires the computation of weighted (spatial averaged) densities around each considered spatial coordinate by convolution, which is computationally expensive. This work uses Fourier-type transforms to determine the weighted densities. A pedagogical derivation is presented for the efficient computation of the convolution integrals occurring in the Helmholtz energy functionals in Cartesian, cylindrical, and spherical coordinates on equidistant grids using fast Fourier and similar transforms. The applied off-the-shelf algorithms allow to reduce dimensionality and complexity of many practical problems. Furthermore, an algorithm for a fast first-order Hankel transform is proposed, allowing fast and easy density functional theory calculations in rotationally symmetric systems. Application of the hydrodynamic density functional theory model using a well-balanced finite-volume scheme to one-dimensional droplet and bubble coalescence of pure fluids and binary mixtures is presented. The required transport coefficients, shear viscosity and Maxwell-Stefan diffusion coefficients, are obtained by applying entropy scaling to inhomogeneous fluids. The considered systems show a qualitative difference in the coalescence characteristics of droplets compared to bubbles. This constitutes a first step towards predicting the phase rupture leading to coalescence using dynamic density functional theory.Item Open Access Disentangling force field and sampling issues in biomolecular systems(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2020) Markthaler, Daniel; Hansen, Niels (apl. Prof. Dr.-Ing.)Item Open Access Dynamic properties of fluids from molecular simulations and entropy scaling(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2022) Fischer, Matthias; Groß, Joachim (Prof. Dr.-Ing.)The design of most processes in chemical industry depends on reliable estimates of the transport properties of fluids. Various approaches exist for the prediction of these quantities, which can be used to compensate for insufficient experimental data. The present work deals with two of the approaches: Molecular simulations and entropy scaling. According to the latter approach, transport coefficients, such as shear viscosity, thermal conductivity or self diffusion coefficients, defined as dimensionless quantities using a suitable reference, are univariant functions of only the residual entropy of the fluid. The two methods, molecular simulations and entropy scaling are used jointly in order to achieve synergistic effects. A suitable mixture-model for entropy scaling models was investigated in molecular simulations as part of this work. Mixtures of simple model fluids, namely Lennard-Jones mixtures, are regarded and it is found that the principle of entropy scaling holds also for mixtures, to excellent approximation. Entropy scaling, in turn, is used to more efficiently design and evaluate molecular simulations. In this context, the TAMie force field developed in Stuttgart is assessed with respect to the accuracy of predicted transport coefficients. The TAMie model, like many other force fields developed for thermodynamic properties, uses rigid bond lengths between interaction sites within a molecule. In order to ensure a meaningful assessment of transport coefficients in Molecular Dynamic simulations, an analysis of bond-length models is conducted: what is the influence of the model for intramolecular atomic bonds on the predicted static and dynamic fluid properties? It is shown that it is possible to obtain the same results for transport coefficients with flexible atomic bonds, within statistical accuracy, as with the same force field but using a rigid description of the bonds. Within the context of the simulation studies carried out in this thesis, a workflow has been developed that enables efficient evaluation of simulations for determining transport properties. In combination with entropy scaling, this work presents a methodology that can be used to efficiently determine transport quantities from molecular simulations, thus enabling extensive simulation studies for either predicting fluid properties or to enable force field development where transport coefficients are considered in the objective function.Item Open Access Entwicklung eines übertragbaren Kraftfeldes (TAMie) für Phasengleichgewichte mit Monte Carlo Simulationen im großkanonischen Ensemble(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2019) Hemmen, Andrea; Groß, Joachim (Prof. Dr.-Ing)Item Open Access Interfacial properties using classical density functional theory : curved interfaces and surfactants(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2021) Rehner, Philipp; Groß, Joachim (Prof. Dr.-Ing.)Interfaces play an important role in natural and industrial processes. Classical density functional theory (DFT) has been established as a tool capable of predicting interfacial properties, but also of providing insight in the structure of fluids at interfaces. Compared to other statistical mechanical methods, particularly molecular simulation, an efficient implementation of DFT offers a significant reduction in computation time. This advantage comes with the cost of an increased modeling effort. In this work, the calculation of interfacial properties using DFT is discussed and applied to different aspects of interfaces. First, the properties of highly curved interfaces, as they appear in nucleation processes, are studied. This is done first by directly calculating the properties of nanodroplets using DFT in spherical coordinates and afterwards in an expansion around a flat interface. Because for some applications, the calculation time of DFT is a limiting factor, a new method to predict surface tensions from equation of state parameters is introduced. This is achieved by using a Taylor expansion of the full DFT Helmholtz energy functional around a local density. The resulting functional is identical to that used in density gradient theory except for an explicit, temperature and density dependent expression for the influence matrix. The method is subsequently used to examine in detail the parametrization of associating components, particularly water and alcohols, that pose difficulties with respect to the simultaneous description of bulk phase equilibria and interfacial properties. A multiobjective optimization approach is used to assess different models and to quantify their capabilities and limitations. The so obtained water model presents the foundation for the last segment of this work, that studies the interfacial properties of water/surfactant and water/alkane/surfactant systems. The amphiphilic surfactant molecules are modeled using a heteronuclear DFT approach that resolves the distributions of individual segments. The parameters of this group contribution method are obtained by fitting to properties of small surfactant molecules and can then be used to predict properties of larger molecules for which less or no experimental data is available. The model is used to study the adsorption and orientation of surfactant molecules at interfaces and the corresponding reduction in interfacial tension.Item Open Access Molecular dynamics study of interactions between nano crystals and solid-liquid phase equilibria(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2020) Bauer, Gernot; Groß, Joachim (Prof. Dr.-Ing.)Item Open Access A new approach to optimize the transferable anisotropic Mie force field (TAMie) for mixtures(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2021) Weidler, Dominik; Groß, Joachim (Prof. Dr.-Ing.)In this thesis the development of a molecular force field is presented, which allows an application focus on the calculation of phase equilibria. Based on the ”Transferable Anisotropic Mie (TAMie)” force field by Hemmen et al. the parameter set of the force field is extended to small cyclic molecules and polar groups of substances such as esters and ketones. It is a classical atomistic force field, but hydrogen atoms are often effectively considered together with neighbouring larger atoms. The force field parameters are transferable, i.e. they can be used for all substances within a group of substances. Although the phase equilibrium results obtained are very good, the transferable model with simple point charges reaches some limitations. This is shown in deviations of the saturation vapor pressure from the simulations compared to experimental data. However, it is desirable to describe the vapor pressure as accurately as possible in order to be able to predict mixture properties with good agreement to experimental data. In order not to destroy the transferable character of the force field and at the same time ensure the accuracy of the vapor pressure for individual substances, the individualized TAMie force field is introduced. With the help of a correction parameter ψ all energetic interactions of a pure substance are scaled in order to increase the accuracy for experimentally well measured substances. It is shown that this concept leads to significantly improved correlations and predictions of mixture properties. Using various binary mixtures, the transferability of cross-interaction parameters that correct van der Waals interactions between two pure substances is also demonstrated. Further investigations and experiments are recommended for validation.Item Open Access A new dispersion contribution based on the PCP-SAFT equation of state in the framework of classical density functional theory(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2019) Sauer, Elmar; Groß, Joachim (Prof. Dr.-Ing.)This dissertation presents the development and evaluation of a dispersion contribution model of a Helmholtz energy functional in the framework of classical density functional theory. The model is based on the PCP-SAFT equation of state and was applied to fluid-liquid interfaces, confined systems, and sessile droplet systems.Item Open Access On the prediction of thermodynamic properties by atomistic simulation : from vapor-liquid equilibrium of alcohols to self-assembly in mixed solvents(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2020) Baz, Jörg; Hansen, Niels (apl. Prof. Dr.-Ing. habil.)This dissertation presents the results of atomistic molecular simulations. Therefor systems of varying complexity with relevance in materials science, biotechnology and chemical engineering have been considered.Item Open Access PC-SAFT density functional theory in 3 dimensions : adsorption in ordered porous media and solvation free energies in non-polar solvents(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2023) Eller, Johannes; Groß, Joachim (Prof. Dr.-Ing.)Item Open Access Perturbation theory and molecular simulation of nonprimitive model electrolyte solutions(Stuttgart : Universität Stuttgart, Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, 2021) Drunsel, Florian; Groß, Joachim (Prof. Dr.-Ing.)