Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Bemerkung Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Zugriffsart Link Abteilungen OPUS4-11092 Arbeitspapier Drescher, Hans Paul, hanspaul.drescher@budi.de Critical review of the 1. Stokes' problem and consequences for mixed turbulent/laminar flow The "1. Stokes' problem", the "suddenly accelerated flat wall", is the oldest application of the Navier-Stokes equations. Stokes' solution of the "problem" does not comply with the mathematical theorem of Cauchy and Kowalewskaya on the "Uniqueness and Existence" of solutions of partial differential equations and violates the physical theorem of minimum entropy production/dissipation of the Thermodynamics of Irreversible Processes. The result includes very high local shear stresses and dissipation rates. That is of special interest for the theory of turbulent and mixed turbulent/laminar flow. A textbook solution of the "1. Stokes Problem" is the Couette flow, which has a constant sheer stress along a linear profile. A consequence is that the Navier-Stokes equations do not describe any S-shaped part of a turbulent profile found in any turbulent Couette experiment. The paper surveys arguments referring to that statement, concerning the history of >150 years. Contrary to this there is always a Navier-Stokes solution near the wall, observed by a linear part of the Couette profile. There a turbulent description (e.g. by the logarithmic law-of-the-wall) fails completely. That is explained by the minimum dissipation requirement together with the Couette feature τ = const. The local co-existence of a turbulent zone and a laminar zone near the wall is stable and observed also at high Reynolds-Numbers. 2024 27 Seiten weltweit OPUS4-11088 misc Hüning, Felix, huening@fh-aachen.de Positionssensorvorrichtung [Offenlegungsschrift] Die Erfindung betrifft eine Positionssensorvorrichtung zur Bestimmung einer Absolutposition eines beweglichen ersten Teils relativ zu einem ortsfesten zweiten Teil mit einem mit dem beweglichen ersten Teil gekoppelter Codekörper, der dazu eingerichtet ist, eine Codespur mit einer Mehrzahl von in Spurrichtung aufeinanderfolgenden Codeelementen zu enthalten zur Bildung eines Codewortes, mit einer magnetischen Detektionseinrichtung zur Detektion der Codespur, wobei die Detektionseinrichtung zum einen an dem Codekörper befestigte und entlang der Spurrichtung in einem solchen Abstand gegenpolig zueinander angeordnete Permanentmagneten aufweist, dass der Abstand mit einer vorgegebenen Länge der jeweiligen Codeelemente übereinstimmt, und zum anderen eine Anzahl von ortsfest und quer zu dem Codekörper versetzt angeordnete Wiegandsensoren aufweist, wobei der Abstand des Wiegandsensors zu einer Erstreckungsebene der Permanentmagneten derart gewählt ist, dass bei Überdeckung des Wiegandsensors durch den Permanentmagneten ein Wiegandpuls in dem Wiegandsensor induziert wird. 2024 Offenlegungsschrift zu DE102022124159A1 2024.03.21 weltweit Patent ansehen bei DPMA Fachbereich Elektrotechnik und Informationstechnik OPUS4-11087 Konferenzveröffentlichung Neumann, Hannah, ; Adam, Mario, ; Backes, Klaus, ; Börner, Martin, ; Clees, Tanja, ; Doetsch, Christian, ; Glaeser, Susanne, ; Herrmann, Ulf, ulf.herrmann@sij.fh-aachen.de; May, Johanna, ; Rosenthal, Florian, rosenthal@fh-aachen.de; Sauer, Dirk Uwe, ; Stadler, Ingo, Development of open educational resources for renewable energy and the energy transition process The dissemination of knowledge about renewable energies is understood as a social task with the highest topicality. The transfer of teaching content on renewable energies into digital open educational resources offers the opportunity to significantly accelerate the implementation of the energy transition. Thus, in the here presented project six German universities create open educational resources for the energy transition. These materials are available to the public on the internet under a free license. So far there has been no publicly accessible, editable media that cover entire learning units about renewable energies extensively and in high technical quality. Thus, in this project, the content that remains up-to-date for a longer period is appropriately prepared in terms of media didactics. The materials enable lecturers to provide students with in-depth training about technologies for the energy transition. In a particular way, the created material is also suitable for making the general public knowledgeable about the energy transition with scientifically based material. Freiburg International Solar Energy Society 2021 6 Seiten ISES SWC 2021 ISES Solar World Congress, virtual conference 25-29 October 2021 10.18086/swc.2021.47.03 https://doi.org/10.18086/swc.2021.47.03 Fachbereich Energietechnik OPUS4-11086 Konferenzveröffentlichung Niederwestberg, Stefan, ; Schneider, Falko, f.schneider@sij.fh-aachen.de; Teixeira Boura, Cristiano José, boura@sij.fh-aachen.de; Herrmann, Ulf, ulf.herrmann@sij.fh-aachen.de Introduction to a direct irradiated transparent tube particle receiver New materials often lead to innovations and advantages in technical applications. This also applies to the particle receiver proposed in this work that deploys high-temperature and scratch resistant transparent ceramics. With this receiver design, particles are heated through direct-contact concentrated solar irradiance while flowing downwards through tubular transparent ceramics from top to bottom. In this paper, the developed particle receiver as well as advantages and disadvantages are described. Investigations on the particle heat-up characteristics from solar irradiance were carried out with DEM simulations which indicate that particle temperatures can reach up to 1200 K. Additionally, a simulation model was set up for investigating the dynamic behavior. A test receiver at laboratory scale has been designed and is currently being built. In upcoming tests, the receiver test rig will be used to validate the simulation results. The design and the measurement equipment is described in this work. Melville, NY AIP conference proceedings / American Institute of Physics 2022 9 Seiten SOLARPACES 2020 978-0-7354-4195-8 26th International Conference on Concentrating Solar Power and Chemical Energy Systems 28 September-2 October 2020 Freiburg, Germany 2445 / 1 10.1063/5.0086735 https://doi.org/10.1063/5.0086735 Fachbereich Energietechnik OPUS4-11085 Konferenzveröffentlichung Caminos, Ricardo Alexander Chico, ; Schmitz, Pascal, schmitz@sij.fh-aachen.de; Atti, Vikrama, ; Mahdi, Zahra, ; Teixeira Boura, Cristiano José, boura@sij.fh-aachen.de; Sattler, Johannes Christoph, sattler@sij.fh-aachen.de; Herrmann, Ulf, ulf.herrmann@sij.fh-aachen.de; Hilger, Patrick, ; Dieckmann, Simon, Development of a micro heliostat and optical qualification assessment with a 3D laser scanning method The Solar-Institut Jülich (SIJ) and the companies Hilger GmbH and Heliokon GmbH from Germany have developed a small-scale cost-effective heliostat, called "micro heliostat". Micro heliostats can be deployed in small-scale concentrated solar power (CSP) plants to concentrate the sun's radiation for electricity generation, space or domestic water heating or industrial process heat. In contrast to conventional heliostats, the special feature of a micro heliostat is that it consists of dozens of parallel-moving, interconnected, rotatable mirror facets. The mirror facets array is fixed inside a box-shaped module and is protected from weathering and wind forces by a transparent glass cover. The choice of the building materials for the box, tracking mechanism and mirrors is largely dependent on the selected production process and the intended application of the micro heliostat. Special attention was paid to the material of the tracking mechanism as this has a direct influence on the accuracy of the micro heliostat. The choice of materials for the mirror support structure and the tracking mechanism is made in favor of plastic molded parts. A qualification assessment method has been developed by the SIJ in which a 3D laser scanner is used in combination with a coordinate measuring machine (CMM). For the validation of this assessment method, a single mirror facet was scanned and the slope deviation was computed. Melville, NY AIP conference proceedings / American Institute of Physics 2022 8 Seiten SOLARPACES 2020 978-0-7354-4195-8 26th International Conference on Concentrating Solar Power and Chemical Energy Systems 28 September-2 October 2020 Freiburg, Germany 2445 / 1 10.1063/5.0086262 https://doi.org/10.1063/5.0086262 Fachbereich Energietechnik OPUS4-11084 Konferenzveröffentlichung Zahra, Mahdi, ; Phani Srujan, Merige, ; Caminos, Ricardo Alexander Chico, ; Schmitz, Pascal, schmitz@sij.fh-aachen.de; Herrmann, Ulf, ulf.herrmann@sij.fh-aachen.de; Teixeira Boura, Cristiano José, boura@sij.fh-aachen.de; Schmitz, Mark, ; Gielen, Hans, ; Gedle, Yibekal, ; Dersch, Jürgen, Modeling the thermal behavior of solar salt in electrical resistance heaters for the application in PV-CSP hybrid power plants Concentrated Solar Power (CSP) systems are able to store energy cost-effectively in their integrated thermal energy storage (TES). By intelligently combining Photovoltaics (PV) systems with CSP, a further cost reduction of solar power plants is expected, as well as an increase in dispatchability and flexibility of power generation. PV-powered Resistance Heaters (RH) can be deployed to raise the temperature of the molten salt hot storage from 385 °C up to 565 °C in a Parabolic Trough Collector (PTC) plant. To avoid freezing and decomposition of molten salt, the temperature distribution in the electrical resistance heater is investigated in the present study. For this purpose, a RH has been modeled and CFD simulations have been performed. The simulation results show that the hottest regions occur on the electric rod surface behind the last baffle. A technical optimization was performed by adjusting three parameters: Shell-baffle clearance, electric rod-baffle clearance and number of baffles. After the technical optimization was carried out, the temperature difference between the maximum temperature and the average outlet temperature of the salt is within the acceptable limits, thus critical salt decomposition has been avoided. Additionally, the CFD simulations results were analyzed and compared with results obtained with a one-dimensional model in Modelica. Melville, NY AIP conference proceedings / American Institute of Physics 2022 9 Seiten SOLARPACES 2020 978-0-7354-4195-8 26th International Conference on Concentrating Solar Power and Chemical Energy Systems 28 September-2 October 2020 Freiburg, Germany 2445 / 1 10.1063/5.0086268 https://doi.org/10.1063/5.0086268 Fachbereich Energietechnik OPUS4-11083 Wissenschaftlicher Artikel Zhen, Manghao, ; Liang, Yunpei, ; Staat, Manfred, m.staat@fh-aachen.de; Li, Quanqui, ; Li, Jianbo, Discontinuous fracture behaviors and constitutive model of sandstone specimens containing non-parallel prefabricated fissures under uniaxial compression The deformation and damage laws of non-homogeneous irregular structural planes in rocks are the basis for studying the stability of rock engineering. To investigate the damage characteristics of rock containing non-parallel fissures, uniaxial compression tests and numerical simulations were conducted on sandstone specimens containing three non-parallel fissures inclined at 0°, 45° and 90° in this study. The characteristics of crack initiation and crack evolution of fissures with different inclinations were analyzed. A constitutive model for the discontinuous fractures of fissured sandstone was proposed. The results show that the fracture behaviors of fissured sandstone specimens are discontinuous. The stress-strain curves are non-smooth and can be divided into nonlinear crack closure stage, linear elastic stage, plastic stage and brittle failure stage, of which the plastic stage contains discontinuous stress drops. During the uniaxial compression test, the middle or ends of 0° fissures were the first to crack compared to 45° and 90° fissures. The end with small distance between 0° and 45° fissures cracked first, and the end with large distance cracked later. After the final failure, 0° fissures in all specimens were fractured, while 45° and 90° fissures were not necessarily fractured. Numerical simulation results show that the concentration of compressive stress at the tips of 0°, 45° and 90° fissures, as well as the concentration of tensile stress on both sides, decreased with the increase of the inclination angle. A constitutive model for the discontinuous fractures of fissured sandstone specimens was derived by combining the logistic model and damage mechanic theory. This model can well describe the discontinuous drops of stress and agrees well with the whole processes of the stress-strain curves of the fissured sandstone specimens. Amsterdam Elsevier 2024 13 Seiten Theoretical and Applied Fracture Mechanics 131 Art. No. 104373 10.1016/j.tafmec.2024.104373 campus https://doi.org/10.1016/j.tafmec.2024.104373 Fachbereich Medizintechnik und Technomathematik OPUS4-11082 Wissenschaftlicher Artikel Engelmann, Ulrich M., engelmann@fh-aachen.de; Simsek, Beril, ; Shalaby, Ahmed, ; Krause, Hans-Joachim, h.krause@fh-aachen.de Key contributors to signal generation in frequency mixing magnetic detection (FMMD): an in silico study Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled Néel-Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dc > 25 nm nm with narrow size distributions (σ < 0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays. Basel MDPI 2024 Artikel 1945 Sensors 24 This article belongs to the Special Issue "Advances in Magnetic Sensors and Their Applications" 6 10.3390/s24061945 weltweit https://doi.org/10.3390/s24061945 Fachbereich Medizintechnik und Technomathematik OPUS4-11081 Buch (Monographie) Elsaesser, Evelyn, ; Klebinggat, Michael, ; Kuhn, Wilfried, ; Michielsens, Constant, ; Pauels, Willibert, ; Popkes, Enno E., ; Schneider, Elke, ; Laack, Walter van, Dr.vanLaack@web.de; Warven, Rinus van, Laack, Walter van Schnittstelle Tod - Ist die Menschheit zu retten ohne Vertrauen auf ein Danach Aachen van Laack Buchverlag 2024 156 Seiten 978-3-936624-58-8 8. Tagungsband zum NTE-Seminar in Aachen am, 11.11.2023 https://www.vanlaack-buch.de/buecher-d/schnittstelle-tod-ist-die-menschheit-zu-retten-ohne-vertrauen-auf-ein-danach/ Fachbereich Medizintechnik und Technomathematik OPUS4-11080 Konferenzveröffentlichung Mahdi, Zahra, ; Dersch, Jürgen, ; Schmitz, Pascal, schmitz@sij.fh-aachen.de; Dieckmann, Simon, ; Caminos, Ricardo Alexander Chico, ; Teixeira Boura, Cristiano José, boura@sij.fh-aachen.de; Herrmann, Ulf, ulf.herrmann@sij.fh-aachen.de; Schwager, Christian, ; Schmitz, Mark, ; Gielen, Hans, ; Gedle, Yibekal, ; Büscher, Rauno, Technical assessment of Brayton cycle heat pumps for the integration in hybrid PV-CSP power plants The hybridization of Concentrated Solar Power (CSP) and Photovoltaics (PV) systems is a promising approach to reduce costs of solar power plants, while increasing dispatchability and flexibility of power generation. High temperature heat pumps (HT HP) can be utilized to boost the salt temperature in the thermal energy storage (TES) of a Parabolic Trough Collector (PTC) system from 385 °C up to 565 °C. A PV field can supply the power for the HT HP, thus effectively storing the PV power as thermal energy. Besides cost-efficiently storing energy from the PV field, the power block efficiency of the overall system is improved due to the higher steam parameters. This paper presents a technical assessment of Brayton cycle heat pumps to be integrated in hybrid PV-CSP power plants. As a first step, a theoretical analysis was carried out to find the most suitable working fluid. The analysis included the fluids Air, Argon (Ar), Nitrogen (N2) and Carbon dioxide (CO2). N2 has been chosen as the optimal working fluid for the system. After the selection of the ideal working medium, different concepts for the arrangement of a HT HP in a PV-CSP hybrid power plant were developed and simulated in EBSILON®Professional. The concepts were evaluated technically by comparing the number of components required, pressure losses and coefficient of performance (COP). Melville, NY AIP conference proceedings / American Institute of Physics 2022 11 Seiten SOLARPACES 2020 978-0-7354-4195-8 26th International Conference on Concentrating Solar Power and Chemical Energy Systems 28 September-2 October 2020 Freiburg, Germany 2445 / 1 10.1063/5.0086269 https://doi.org/10.1063/5.0086269 Fachbereich Energietechnik