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Institute
- Fachbereich Energietechnik (1104) (remove)
For typical cases of non-isolated lightning
protection systems (LPS) the impulse currents are investigated which may flow through a human body directly touching a structural part of the LPS. Based on a basic LPS model with conventional down-conductors especially the cases of external and internal steel columns and metal façades are considered and compared. Numerical simulations of the line quantities voltages and currents in the time domain are performed with an equivalent circuit of the entire LPS.
As a result it can be stated that by increasing the number of conventional down-conductors and external steel columns the threat for a human being can indeed be reduced, but not down to an acceptable limit. In case of internal steel columns used as natural down-conductors the threat can be reduced sufficiently, depending on the low-resistive connection of the steel columns to the lightning equipotential bonding or the earth termination system, resp. If a metal façade is used the threat for human beings touching is usually very low, if the façade is sufficiently interconnected and multiply connected to the lightning equipotential bonding or the earth termination system, resp.
Theoretische und experimentelle Untersuchung der Erwärmung von Metallblechen bei Blitzeinschlag
(1990)
The longitudinal voltage of cable tubes with a screening mesh caused by partial lightning currents
(1989)
The proposed Den Haag Zuidwest district heating system of the city of The Hague consists of a deep doublet in a Jurassic sandstone layer that is designed for a production temperature of 75 °C and a reinjection temperature of 40 °C at a flow rate of 150 m3 h−1. The prediction of reservoir temperature and production behavior is crucial for success of the proposed geothermal doublet. This work presents the results of a study of the important geothermal and geohydrological issues for the doublet design. In the first phase of the study, the influences of the three-dimensional (3D) structures of anticlines and synclines on the temperature field were examined. A comprehensive petrophysical investigation was performed to build a large scale 3D-model of the reservoir. Several bottomhole temperatures (BHTs), as well as petrophysical logs were used to calibrate the model using thermal conductivity measurements on 50 samples from boreholes in different lithological units in the study area. Profiles and cross sections extracted from the calculated temperature field were used to study the temperature in the surrounding areas of the planned doublet. In the second phase of the project, a detailed 3D numerical reservoir model was set up, with the aim of predicting the evolution of the producer and injector temperatures, and the extent of the cooled area around the injector. The temperature model from the first phase provided the boundary conditions for the reservoir model. Hydraulic parameters for the target horizons, such as porosity and permeability, were taken from data available from the nearby exploration wells. The simulation results are encouraging as no significant thermal breakthrough is predicted. For the originally planned location of the producer, the extracted water temperature is predicted to be around 79 °C, with an almost negligible cooling in the first 50 years of production. When the producer is located shallower parts of the reservoir, the yield water temperatures is lower, starting at ≈76 °C and decreasing to ≈74 °C after 50 years of operation. This comparatively larger decrease in temperature with time is caused by the structural feature of the reservoir, namely a higher dip causes the cooler water to easily move downward. In view of the poor reservoir data, the reservoir simulation model is constructed to allow iterative updates using data assimilation during planned drilling, testing, and production phases. Measurements during an 8 h pumping test carried out in late 2010 suggest that a flow rate of 150 m3 h−1 is achievable. Fluid temperatures of 76.5 °C were measured, which is very close to the predicted value.
The Effect of Openings on Out-of-Plane Capacity of Masonry Infilled Reinforced Concrete Frames
(2018)
Cryopumps without liquid nitrogen shielding are used to provide a vacuum of 10−6 torr in the spectrometer. The vacuum system is subdivided in three sections that can be separated by valves.
The first section (scattering chamber) has a volume of 60 l, two rotation transmissions with 35 cm dia and a sliding seal that allows a rotation of 160° without deteriorating the vacuum. The second section includes the vacuum chambers inside the magnets with 6 × 80 cm cross-section and a length of 1200 cm. The third section (detector box) has a volume of 4300 l and contains a moveable detector system. The gas inside the detector with a pressure of 760 torr is separated from the vacuum by a 15 μm mylar foil with an area of 300 cm2. The detector box can be valved off by a valve with the dimension of 10 × 100 cm.
The layout of system is given. The instrumentation and the interlock system are described. First experiences with this system are presented.
With proven impact of statistical fracture analysis on fracture classifications, it is desirable to minimize the manual work and to maximize repeatability of this approach. We address this with an algorithm that reduces the manual effort to segmentation, fragment identification and reduction. The fracture edge detection and heat map generation are performed automatically. With the same input, the algorithm always delivers the same output. The tool transforms one intact template consecutively onto each fractured specimen by linear least square optimization, detects the fragment edges in the template and then superimposes them to generate a fracture probability heat map.
We hypothesized that the algorithm runs faster than the manual evaluation and with low (< 5 mm) deviation. We tested the hypothesis in 10 fractured proximal humeri and found that it performs with good accuracy (2.5 mm ± 2.4 mm averaged Euclidean distance) and speed (23 times faster). When applied to a distal humerus, a tibia plateau, and a scaphoid fracture, the run times were low (1–2 min), and the detected edges correct by visual judgement. In the geometrically complex acetabulum, at a run time of 78 min some outliers were considered acceptable. An automatically generated fracture probability heat map based on 50 proximal humerus fractures matches the areas of high risk of fracture reported in medical literature.
Such automation of the fracture analysis method is advantageous and could be extended to reduce the manual effort even further.
The adsorption of fluor-carbon complexes on GaAs(110) studied by electron energy loss spectroscopy
(1986)
Textile reinforced concrete. Part I: Process model for collaborative research and development
(2003)
One of the most important parameters in a burning chamber - in power stations, in waste to energy plants - is the temperature. This temperature is in the range of 700-1500 °C - one of the most advanced measuring methods being the acoustic pyrometry with the possibility of producing temperature mapping in one level of the burning chamber - comparable to computer tomography. The results of these measurements discussed in the presentation can be used - to fulfil the legal requirements in the FRG or in the EU - to equalise the temperature in one level of the burning chamber to optimise the steam production (better efficiency of the plant) and to minimise the production of temperature controlled flue gas components (NO, CO a. o.) - to control the SNCR-process if used.
Technisches Zeichnen : Lösungsvorschläge für das Selbststudium. (Berichte aus dem Maschinenbau)
(2012)
Technical assessment of Brayton cycle heat pumps for the integration in hybrid PV-CSP power plants
(2022)
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).
This paper describes two courses on
simulation methods for graduate students:
“Simulation Methods” and “Simulation and
Optimization in Virtual Engineering” The
courses were planned to teach young engineers
how to work with simulation software as well as
to understand the necessary mathematical background.
As simulation software COMSOL is
used. The main philosophy was to combine
theory and praxis in a way that motivates the
students. In addition “soft skills” should be
improved. This was achieved by project work as
final examination. As underlying didactical principle
the ideas of Bloom’s revised taxonomy
were followed. The paper basically focusses on
educational aspects, e.g. how to structure the
course, plan the exercises, organize the project
work and include practical COMSOL examples.
Surgical clip applicator
(1996)
Wind loads have great impact on many engineering structures. Wind storms often cause irreparable damage to the buildings which are exposed to it. Along with the earthquakes, wind represents one of the most common environmental load on structures and is relevant for limit state design. Modern wind codes indicate calculation procedures allowing engineers to deal with structural systems, which are susceptible to conduct wind-excited oscillations. In the codes approximate formulas for wind buffeting are specified which relate the dynamic problem to rather abstract parameter functions. The complete theory behind is not visible in order to simplify the applicability of the procedures. This chapter derives the underlying basic relations of the spectral method for wind buffeting and explains the main important applications of it in order to elucidate part of the theoretical background of computations after the new codes. The stochasticity of the wind processes is addressed, and the analysis of analytical as well as measurement based power spectra is outlined. Short MATLAB codes are added to the Appendix 3 which carry out the computation of a single sided auto-spectrum from a statistically stationary, discrete stochastic process. Two examples are presented.
Die PIA GmbH prüft seit fast 8 Jahren die Standsicherheit von Behältern für Kleinkläranlagen. Diese bestehen in der Regel aus Kunststoff oder Beton und müssen über ihre gesamte Lebensdauer den Beanspruchungen aus Handhabung, Einbau und Betrieb standhalten. Die Standsicherheit kann nach EN 12566 wahlweise durch einen rechnerischen Nachweis oder durch einen praktischen Nachweis wie die Bruchlastprüfung oder die Prüfung in der Grube erfolgen.
Eine seismische Anregung verursacht in einem Flüssigkeitstank einen kombinierten Spannungszustand, was zu einem Stabilitätsversagen der häufig sehr dünnwandigen Konstruktionen führen kann. Für die Durchführung von Stabilitätsnachweisen stehen verschiedene Verfahren zur Verfügung. Üblicherweise werden aus Gründen der Einfachheit spannungsbasierte Verfahren angewendet. Diese sind für Einheitslastfälle experimentell abgesichert, wobei eine Übertragung auf kombinierte Spannungszustände wie im Erdbebenfall nur begrenzt möglich ist. Alternativ kann ein globales, numerisches Konzept, das LBA/MNA-Verfahren, angewendet werden. Das Verfahren kombiniert eine materiell nichtlineare Berechnung (MNA) mit einer linearen Beulanalyse (LBA) und erfasst die Interaktion verschiedener gleichzeitig auftretender Beanspruchungen implizit im Nachweis. Dieser Beitrag demonstriert die Anwendung der Verfahren am Beispiel verschiedener Tankgeometrien mit Höhe/Radius-Verhältnissen zwischen 1 ≤ H/R ≤ 2 und Radius/Tankwand-Verhältnissen zwischen 500 ≤ R/t ≤ 1000 und diskutiert zusätzlich die Defizite der spannungsbasierten Nachweisverfahren.
Speicheroptimierung
(2011)
In dieser Lektion wurden beginnend mit der Darstellung des fundamentalen Wandels
des Gasmarktes die daraus folgenden Implikationen für die Einsatzweise von
Gasspeichern abgeleitet. Anschließend wurden zwei Bewertungs- und Steuerungsverfahren für einen Gasspeicher an den beiden Marktstufen Termin- und Spotmarkt methodisch vorgestellt und anhand von Beispielrechnungen illustriert.
Das Verfahren zur Bewertung und Steuerung im Terminmarkt stellt ein sehr
robustes und methodisch einfaches Verfahren dar. Hierbei wird die Saisonalität
der Forwardkurve bzw. deren Veränderungen arbitragefrei mithilfe des Speichers
ausgenutzt. Dieses Verfahren kann nicht den gesamten Zeitwert des Speichers
ausweisen. Es zieht in jedem Zeitpunkt nur die aktuellen Informationen der Forwardkurve zur Entscheidung heran. Es bildet aber keine bedingte Erwartung über
zukünftige Erträge und deren Beeinflussung durch die aktuelle Speicherfahrweise,
um hieraus eine optimale Entscheidung zu formulieren.
Bei der Bewertung gegenüber dem Spotmarkt mithilfe der Least-Squares-Monte-
Carlo-Simulation wird in einer stochastischen Optimierung dagegen der volle Zeitwert des Speichers und damit der gesamte Zusatznutzen der Flexibilität ermittelt. Hierdurch leiten sich auch wesentlich andere Hedging-Empfehlungen als im ersten Verfahren ab, um diesen zu sichern. Der Einsatz der beiden Verfahren im Alltag zur Bewirtschaftung des Speichers hängt insbesondere vom Know-how, den Speicherparametern und der Risikobereitschaft des Handels ab. Beide Strategien liefern hierzu Hedging-Empfehlungen ab, mit welchem der zugrunde liegende Wert gesichert werden kann. Risikoaverse Händler, die einen Großteil des inneren Wertes sichern wollen, könnten im Terminmarkt einen Großteil des Speichers mithilfe des „Intrinsic Rolling“-Verfahrens bewirtschaften. Sie würden hierdurch den saisonalen Spread in der Forwardkurve rollierend sichern. Gleichzeitig kann ein kleinerer Anteil mithilfe der stochastischen Optimierung und den damit verbundenen Ausübungsgrenzen gegenüber dem Spotmarkt bewirtschaftet werden.
In einem liquiden vollständigen Markt wird eine Steuerung des Speichers allein
gegenüber den vorhandenen Marktstufen vorgenommen und der Wert für alle
Marktteilnehmer objektiv messbar. Für den Fall, dass der Markt illiquide ist und
hierdurch z. B. eine Kundenlast nicht allein am Termin- und Spotmarkt jederzeit
gedeckt werden kann, erscheint es notwendig, den Speicher im Kontext einer Portfoliooptimierung zu bewerten. Dies wird in der nächsten Lektion vorgenommen.
Hierbei ist aber zu beachten, dass der Speicher dadurch eine individualisierte Wertkomponente erhält, die von der konkreten Ausgestaltung des jeweiligen Portfolios abhängt.
Speicher statt Kohle. Integration thermischer Stromspeicher in vorhandene Kraftwerksstandorte
(2019)
Solares Kochen
(1990)