TY - CHAP A1 - Rödder, Maximilian A1 - Frank, Lena A1 - Kirschner, Daniel A1 - Neef, Matthias A1 - Adam, Mario ED - The International Centre for Sustainable Development of Energy, Water and Environment Systems, T1 - EnergiBUS4home – Sustainable energy resourcing in low-energy buildings T2 - 12th Conference on Sustainable Development of Energy, Water and Environment Systems, 04.-08.10.2017, Dubrovnik KW - energiBUS4home Y1 - 2017 ER - TY - CHAP A1 - Dubberke, Frithjof H. A1 - Priebe, Klaus-Peter A1 - Vrabec, Jadran A1 - Neef, Matthias A1 - Rödder, Maximilian T1 - Thermodynamic simulation and experimental validation of a cascaded two-stage organic Rankine cycle T2 - ASME ORC 2015, Brussels KW - simulation Y1 - 2015 CY - Brussels ER - TY - CHAP A1 - Rödder, Maximilian A1 - Neef, Matthias A1 - Laux, Christoph A1 - Priebe, Klaus-P. T1 - Systematic Fluid Selection for Organic Rankine Cycles (ORC) and Performance Analysis for a Combined High and Low Temperature Cycle T2 - Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration N2 - The organic Rankine cycle (ORC) is an established thermodynamic process that converts waste heat to electric energy. Due to the wide range of organic working fluids available the fluid selection adds an additional degree of freedom to the early design phase of an ORC process. Despite thermodynamic aspects such as the temperature level of the heat source, other technical, economic and safety aspects have to be considered. For the fluid selection process in this paper, 22 criteria were identified in six main categories while distinguishing between elimination and tolerance criteria. For an ORC design, the suggested method follows a practical engineering approach and can be used as a structured way to limit the number of interesting working fluids before starting a detailed performance analysis of the most promising candidates. For the first time the selection process is applied to a two-stage reference cycle which uses the waste heat of a large reciprocating engine for cogeneration power plants. It consists of a high temperature and a low temperature cycle in which the condensation heat of the high temperature (HT) cycle provides the heat input of the low temperature (LT) cycle. After the fluid selection process the detailed thermodynamic cycle design is carried out with a thermodynamic design tool that also includes a database for organic working fluids. The investigated ORC cycle shows a net thermal efficiency of about 17,4% in the high temperature cycle with Toluene as the working fluid and 6,2% in low temperature cycle with iso-Butane as the working fluid. The electric efficiency of the cogeneration plant increases from 40,4% to 46,97% with the both stages of the two-stage ORC in operation. Y1 - 2015 UR - https://asmedigitalcollection.asme.org/GT/proceedings/GT2015/56673/Montreal, Quebec, Canada/236733 SN - 978-0-7918-5667-3 U6 - https://doi.org/10.1115/GT2015-42432 PB - American Society of Mechanical Engineers ER - TY - CHAP A1 - Helm, Peter A1 - Spliethoff, Hartmut A1 - Neef, Matthias T1 - Closing the Gap: Measuring Bristle Blow Down of Brush Seals T2 - 19 th International Conference on Fluid Sealing, Poitiers Y1 - 2007 CY - Poitiers ER - TY - CHAP A1 - Neef, Matthias A1 - Hepermann, Florian A1 - Sürken, Norbert A1 - Schettel, Joachim T1 - Brush Seal Porosity Modeling: Applicability and Limitations T2 - ETC7 – 7th Conference on Turbomachinery, Athens Y1 - 2007 CY - Athens ER - TY - CHAP A1 - Neef, Matthias A1 - Hummel, Dietrich T1 - Euler solutions for a finite-span flapping wing T2 - "Fixed, flapping and rotary wing vehicles at very low Reynolds numbers, Notre Dame, Indiana, USA Y1 - 2000 ER - TY - CHAP A1 - Neef, Matthias A1 - Fussenecker, Claudia A1 - Niemann, Jörg A1 - Zielke, Thomas ED - Clark, Robin ED - Munkebo Hussmann, Peter ED - Järvinen, Hannu-Matti T1 - Publish your undergraduate research! A mandatory course for master students in engineering T2 - Creativity, innovation and entrepreneurship for engineering education excellence : proceedings of the 46th SEFI Annual Conference 2018, Copenhagen, Denmark N2 - Undergraduate students in engineering often have little exposure to the world of scientific publishing and the culture of sharing research work. While the beneficial exchange between research and teaching is well promoted, while the benefits of conference participation for students have already been surveyed and while courses on scientific writing are readily available, the concept of mini-conferences as part of the curriculum combines all three aspects into one. Therefore, the course "Engineering Conferences" was developed and installed as a mandatory part of a master program for engineering students. The idea is to go beyond simply teaching the standards of academic writing and skills for using scientific publications. By using a learner-centered approach, the students are engaged in typical activities around an active attendance of a real conference. Based on their bachelor thesis, they write a paper complying with common academic standards, submit the paper and review submissions of their fellow students. They also produce a poster and defend their work in a poster session held publicly on campus. This contribution is based on the experience from the first four terms teaching the course. It explains the didactic rationale behind the concept and individual teaching modules, it comprises the collection of useful resources for teaching and organizing scientific publishing and it includes the consequences drawn from course evaluation results. Y1 - 2018 SN - 978-2-87352-016-8 PB - SEFI - Société Européenne pour la Formation des Ingénieurs CY - Brussels ER - TY - CHAP A1 - Neef, Matthias T1 - Innerstädtische Nutzung von Kleinwindkraftanlagen: Potentiale und Hürden T2 - Mülheimer Initiative für Klimaschutz, 06.05.2013 Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-21017 CY - Mülheim an der Ruhr ER - TY - CHAP A1 - Helm, Peter A1 - Pugachev, Alexander A1 - Neef, Matthias T1 - Breaking the Swirl With Brush Seals: Numerical Modeling and Experimental Evidence T2 - Proceedings of the ASME Turbo Expo 2008 : presented at the 2008 ASME Turbo Expo, June 9 - 13, 2008, Berlin, Germany N2 - Striving for smaller losses in turbomachinery has led to many advancements in the design of seals. Modern sealing concepts such as brush seals hold a great potential to increase the efficiency of both flight engines and stationary turbines. At the same time, in order to maintain stable operating conditions of the rotor, swirl-induced forces must be kept at a minimum in the sealing channels. Therefore, the influence of the permeable and flexible bristle pack of brush seals on the flow around the rotor surface must be known. In this paper the swirl flow in the cavities of two different seal geometries is studied experimentally and numerically. A conventional three-tooth labyrinth serves as a reference. A second seal arrangement with a bristle pack upstream of two teeth is compared with the reference labyrinth. The swirl is evaluated experimentally from total and static pressure measurements in various axial and circumferential positions. Additionally, the axial swirl distribution is calculated using computational fluid dynamics (CFD). Here, the numerical model of the brush seal is based on the porous medium approach and is calibrated using the experimental values of the leakage and the bristle clearance by adjusting the thickness of the bristle pack. The calibrated CFD model is then used to study the impact of the brush seal on the swirl component of the sealing flow. The observed significant decrease of the swirl by the brush seal shows good agreement with the experimental data. The impact of changes in bristle pack clearance on the swirl is also investigated and compared with experimental evidence. The aim is to show that the brush seals have a natural tendency to interrupt seal swirl. They can therefore be used for swirl control in order to create a beneficial impact on the dynamic stability of turbomachines. Y1 - 2008 SN - 978-0-7918-4314-7 U6 - https://doi.org/10.1115/GT2008-50257 VL - 4 SP - 1387 EP - 1396 PB - ASME CY - New York ER - TY - CHAP A1 - Neef, Matthias A1 - Sulda, Erik A1 - Sürken, Norbert A1 - Walkenhorst, Jan T1 - Design Features and Performance Details of Brush Seals for Turbine Applications T2 - Proceedings of the ASME Turbo Expo 2006 : presented at the 2006 ASME Turbo Expo, May 6 - 11, 2006, Barcelona, Spain N2 - Adaptive and contacting seals such as brush seals have been successfully applied to turbomachinery for several years. In large steam turbine applications, however, various challenges still persist. Special focus is directed at the long-term performance and longevity of brushes on conventional spring-backed seal segments in steam turbines. This issue is particularly related to wear during startup conditions. This paper discusses the results of wear tests, derived from simulated transient turbine behavior, where the resultant seal leakage under steady state conditions is monitored. It is shown that the brush seal is significantly capable of adapting to varying operating conditions, but exhibits a degree of performance degradation during the initial startups. Together with previously reported mid-term wear data and an experience based long-term phenomenological approach a general model for brush seal performance degradation is developed. This model can be used for performance prediction and exerts influence on brush seal design. Y1 - 2006 SN - 0-7918-4238-X U6 - https://doi.org/10.1115/GT2006-90404 VL - 3 SP - 1385 EP - 1392 PB - ASME CY - New York ER -