@article{DubberkeLinnemannAbbasetal.2018, author = {Dubberke, Frithjof H. and Linnemann, Matthias and Abbas, Wameedh Khider and Baumh{\"o}gger, Elmar and Priebe, Klaus-Peter and Roedder, Maximilian and Neef, Matthias and Vrabec, Jadran}, title = {Experimental setup of a cascaded two-stage organic Rankine cycle}, series = {Applied Thermal Engineering}, volume = {131}, journal = {Applied Thermal Engineering}, publisher = {Elsevier}, doi = {10.1016/j.applthermaleng.2017.11.137}, pages = {958 -- 964}, year = {2018}, abstract = {In combination with a bottoming cycle, operated with a pure fluid in transcritical mode, the usage of a zeotropic mixture as a working fluid appears to be exergetically favorable for power cycle efficiency in cascaded two-stage organic Rankine cycles (CORC). A CORC is set up and initially tested with cyclopentane and propane as working fluids in its high temperature and low temperature cycle, respectively. A thermal oil cycle serves as the heat source and is powered electrically with a maximum heat flow of 158 kW. The design of this experimental setup allows for a rapid replacement of individual components and for a wide range of conditions in terms of fluids and thermodynamic states. The components of all cycles and the measurement and control technology are described in detail. A testing procedure is presented, followed by a discussion of the measurement results, where it is shown that the intended concept of two cascaded organic Rankine cycles is operational and that the measured data are consistent.}, language = {en} } @techreport{AdamDreherEblingetal.2017, author = {Adam, Mario and Dreher, Martina and Ebling, Dirk and Knopp, Reinhold and Neef, Matthias and Niess, Robert and Pohl, Tobias and Stahl, Wilhelm and van Rießen, Anne and Waldow, Friederike and Weber, Konradin and Weis, Stephanie}, title = {LUST Forschungsprojekt - lebenswerte und umweltgerechte Stadt}, address = {D{\"u}sseldorf}, organization = {Hochschule D{\"u}sseldorf}, isbn = {978-3-941334-43-4}, doi = {10.20385/978-3-941334-43-4}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-11458}, year = {2017}, abstract = {LUST (lebenswerte und umweltgerechte Stadt) ist ein interdisziplin{\"a}res Projekt der Fachbereiche Architektur, Maschinenbau und Verfahrenstechnik sowie Kultur- und Sozialwissenschaften der Hochschule D{\"u}sseldorf. Mittelpunkt des Projektes ist die fach{\"u}bergreifende Entwicklung neuer Konzepte f{\"u}r eine lebenswerte und umweltgerechte Stadt. Es wurde gef{\"o}rdert vom Land Nordrhein-Westfalen im Rahmen des Programms „FH Struktur".}, language = {de} } @article{FrankRoedderNeefetal.2021, author = {Frank, Lena and R{\"o}dder, Maximilian and Neef, Matthias and Adam, Mario}, title = {Heating, Ventilation, Domestic Appliances - an Energy Integrated System Concept for the Household of the Future}, series = {Energy}, volume = {234}, journal = {Energy}, publisher = {Elsevier}, issn = {0360-5442}, doi = {10.1016/j.energy.2021.121303}, year = {2021}, language = {en} } @inproceedings{DubberkePriebeVrabecetal.2015, author = {Dubberke, Frithjof and Priebe, Klaus-Peter and Vrabec, Jadran and Neef, Matthias and R{\"o}dder, Maximilian}, title = {Thermodynamic simulation and experimental validation of a cascaded two-stage organic Rankine cycle}, series = {ASME ORC 2015, Brussels}, booktitle = {ASME ORC 2015, Brussels}, address = {Brussels}, year = {2015}, language = {en} } @inproceedings{RoedderNeefLauxetal.2015, author = {R{\"o}dder, Maximilian and Neef, Matthias and Laux, Christoph and Priebe, Klaus-P.}, title = {Systematic Fluid Selection for Organic Rankine Cycles (ORC) and Performance Analysis for a Combined High and Low Temperature Cycle}, series = {Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration}, booktitle = {Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration}, publisher = {American Society of Mechanical Engineers}, organization = {International Gas Turbine Institute}, isbn = {978-0-7918-5667-3}, doi = {10.1115/GT2015-42432}, year = {2015}, abstract = {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.}, language = {en} } @inproceedings{HelmSpliethoffNeef2007, author = {Helm, Peter and Spliethoff, Hartmut and Neef, Matthias}, title = {Closing the Gap: Measuring Bristle Blow Down of Brush Seals}, series = {19 th International Conference on Fluid Sealing, Poitiers}, booktitle = {19 th International Conference on Fluid Sealing, Poitiers}, address = {Poitiers}, year = {2007}, language = {en} } @inproceedings{NeefHepermannSuerkenetal.2007, author = {Neef, Matthias and Hepermann, Florian and S{\"u}rken, Norbert and Schettel, Joachim}, title = {Brush Seal Porosity Modeling: Applicability and Limitations}, series = {ETC7 - 7th Conference on Turbomachinery, Athens}, booktitle = {ETC7 - 7th Conference on Turbomachinery, Athens}, address = {Athens}, year = {2007}, language = {en} } @inproceedings{NeefHummel2000, author = {Neef, Matthias and Hummel, Dietrich}, title = {Euler solutions for a finite-span flapping wing}, series = {"Fixed, flapping and rotary wing vehicles at very low Reynolds numbers, Notre Dame, Indiana, USA}, booktitle = {"Fixed, flapping and rotary wing vehicles at very low Reynolds numbers, Notre Dame, Indiana, USA}, year = {2000}, language = {en} } @article{BaierNeef2019, author = {Baier, Andr{\´e} and Neef, Matthias}, title = {Studierende lehren und lernen sozial-{\"o}kologische Verantwortung}, series = {Die Neue Hochschule}, volume = {60}, journal = {Die Neue Hochschule}, number = {5}, organization = {Hochschullehrerbund - Bundesvereinigung - e.V. (hlb)}, pages = {8 -- 11}, year = {2019}, language = {de} } @inproceedings{Neef2013, author = {Neef, Matthias}, title = {Innerst{\"a}dtische Nutzung von Kleinwindkraftanlagen: Potentiale und H{\"u}rden}, series = {M{\"u}lheimer Initiative f{\"u}r Klimaschutz, 06.05.2013}, booktitle = {M{\"u}lheimer Initiative f{\"u}r Klimaschutz, 06.05.2013}, address = {M{\"u}lheim an der Ruhr}, organization = {M{\"u}lheimer Initiative f{\"u}r Klimaschutz e.V.}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-21017}, year = {2013}, language = {de} } @phdthesis{Neef2002, author = {Neef, Matthias}, title = {Analyse des Schlagfluges durch numerische Str{\"o}mungsberechnung}, volume = {ZLR-Forschungsbericht, 2}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:084-14501}, pages = {245}, year = {2002}, abstract = {Mit Hilfe eines Finite-Volumen-Verfahrens wird die dreidimensionale reibungsbehaftete Stroemung um einen schlagenden Fluegel berechnet. Die Bewegungsparamter sind dabei vergleichbar mit den Bedingungen im Reiseflug grosser Voegel. Das numerische Verfahren wird fuer den gezeigten Anwendungsfall, indem eine Methode zur Realisierung von beliebigen periodischen Bewegungen implemetiert wird. Eine Verifizierung erfolgt durch den Vergleich mit analytischen, numerischen und experimentellen Ergebnissen aus der Literatur. Mit dem verifizierten Verfahren werden die instationaeren Groessen wie Druck und Geschwindigkeiten in der Umgebung des bewegten Fluegels berechnet. Daraus ergeben sich ferner die zeitlich gemittelten Groessen wie Schub und Wirkungsgrad des Schlagfluges. Ausserdem wird die Interaktion von Laengs- und Querwirbeln im Nachlauf des schlagenden Fluegels untersucht. Es zeigt sich ein dominanter Einfluss der pulsierenden Randwirbel aufgrund der endlichen Spannweite, waehrend die Anfahr- und Stoppwirbel, verursacht durch die Fluegelbewegung, im Reiseflug grosser Voegel nahezu vernachlaessigbar erscheinen.}, language = {de} } @inproceedings{NeefFusseneckerNiemannetal.2018, author = {Neef, Matthias and Fussenecker, Claudia and Niemann, J{\"o}rg and Zielke, Thomas}, title = {Publish your undergraduate research! A mandatory course for master students in engineering}, series = {Creativity, innovation and entrepreneurship for engineering education excellence : proceedings of the 46th SEFI Annual Conference 2018, Copenhagen, Denmark}, booktitle = {Creativity, innovation and entrepreneurship for engineering education excellence : proceedings of the 46th SEFI Annual Conference 2018, Copenhagen, Denmark}, editor = {Clark, Robin and Munkebo Hussmann, Peter and J{\"a}rvinen, Hannu-Matti}, publisher = {SEFI - Soci{\´e}t{\´e} Europ{\´e}enne pour la Formation des Ing{\´e}nieurs}, address = {Brussels}, organization = {European Society for Engineering Education SEFI}, isbn = {978-2-87352-016-8}, year = {2018}, abstract = {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.}, language = {en} } @article{FesekerKinellNeef2018, author = {Feseker, Daniel and Kinell, Mats and Neef, Matthias}, title = {Experimental Study on Pressure Losses in Circular Orifices With Inlet Cross Flow}, series = {Journal of Turbomachinery}, volume = {140}, journal = {Journal of Turbomachinery}, number = {7}, address = {ASME}, doi = {10.1115/1.4039842}, pages = {210}, year = {2018}, abstract = {The ability to understand and predict the pressure losses of orifices is important in order to improve the air flow within the secondary air system. This experimental study investigates the behavior of the discharge coefficient for circular orifices with inlet cross flow which is a common flow case in gas turbines. Examples of this are at the inlet of a film cooling hole or the feeding of air to a blade through an orifice in a rotor disk. Measurements were conducted for a total number of 38 orifices, covering a wide range of length-to-diameter ratios, including short and long orifices with varying inlet geometries. Up to five different chamfer-to-diameter and radius-to-diameter ratios were tested per orifice length. Furthermore, the static pressure ratio across the orifice was varied between 1.05 and 1.6 for all examined orifices. The results of this comprehensive investigation demonstrate the beneficial influence of rounded inlet geometries and the ability to decrease pressure losses, which is especially true for higher cross flow ratios where the reduction of the pressure loss in comparison to sharp-edged holes can be as high as 54\%. With some exceptions, the chamfered orifices show a similar behavior as the rounded ones but with generally lower discharge coefficients. Nevertheless, a chamfered inlet yields lower pressure losses than a sharp-edged inlet. The obtained experimental data were used to develop two correlations for the discharge coefficient as a function of geometrical as well as flow properties.}, language = {en} } @misc{FrankRoedderNeefetal.2018, author = {Frank, Lena and R{\"o}dder, Maximilian and Neef, Matthias and Adam, Mario}, title = {Heizung, L{\"u}ftung, Weiße Ware - Ein integriertes Systemkonzept f{\"u}r das Haus der Zukunft}, series = {KI K{\"a}lte Luft Klimatechnik}, volume = {54}, journal = {KI K{\"a}lte Luft Klimatechnik}, number = {11}, publisher = {H{\"u}thig}, issn = {1865-5432}, pages = {50 -- 56}, year = {2018}, abstract = {In energieeffizienten Geb{\"a}uden spielt der Bedarf an Energie f{\"u}r die Raumheizung gegen{\"u}ber der ben{\"o}tigten Energie f{\"u}r Warmwasser und zum Antrieb elektrischer Ger{\"a}te eine zusehends untergeordnete Rolle. Die thermische Energie f{\"u}r elektrische Haushalts­ger{\"a}te, wie Waschmaschine, K{\"u}hlschrank etc., wird f{\"u}r gew{\"o}hnlich dezentral im Ger{\"a}t erzeugt. Vor diesem Hintergrund ist das Ziel eines Forschungsprojekts der Bau und der Test eines Funktionsmusters zur funktionalen und energetischen Kopplung der Haushaltsger{\"a}te und der Heizungs- und L{\"u}ftungstechnik des Geb{\"a}udes. Grundgedanke dabei ist die Nutzung von Synergien bei Komponenten und W{\"a}rmestr{\"o}men, wie der W{\"a}rmepumpe als K{\"a}lteaggregat f{\"u}r den K{\"u}hlschrank, und die effiziente Nutzung von Abw{\"a}rme der Haushaltsger{\"a}te f{\"u}r die Warmwasserbereitung und Raumheizung.}, language = {de} } @article{BonkLauxRoedderetal.2017, author = {Bonk, Christian Dirk and Laux, Christoph and R{\"o}dder, Maximilian and Neef, Matthias}, title = {Design of a 1 KW Organic Rankine Cycle for Teaching and Research Issues}, series = {Energy Procedia}, volume = {129}, journal = {Energy Procedia}, publisher = {Elsevier}, doi = {10.1016/j.egypro.2017.09.117}, pages = {931 -- 938}, year = {2017}, abstract = {This paper deals with the design of a micro-scale ORC plant for teaching and research including the development of an automated control concept. The aim is to provide a safe and environmentally acceptable micro-scale heat engine, which can be developed, implemented and used in university labs for the education of students as well as for small research projects. The test rig allows the support of several learning outcomes on a multi-disciplinary level particularly for the implementation and simulation of small power systems. Special attention was given to the organic working fluid characteristics and its selection process. In addition to the above-mentioned performance goals, favourable safety properties and low global warming potential were decisive in the selection of the novel organic fluid called 3M™ Novec™ 649. The performance and the fluid behaviour of Novec 649 in a micro-scale power cycle are of major interest and the research goal for the test rig presented in this paper. Due to the expected power output of 1 kW, a scroll expander was chosen as the generator drive for the micro plant. In order to design the major parts of the ORC, the thermodynamic simulation software EBSILON®Professional was used. The supply temperature was set to 140 °C. As a result of the simulation, feasible expander inlet pressures spread from 5.5 bar to 8.5 bar. This leads to thermal efficiencies of the ORC in the order of 5 \%. Adding a recuperator to the cycle system decreases the operating pressure range but in the end, the thermal efficiency can be increased by 1.5 \%-points up to 6.2 \%. Finally, an automated control concept is introduced, where the pump is controlled via the fill level measurement system.}, language = {en} } @article{NeefZielkeFussenecker2017, author = {Neef, Matthias and Zielke, Thomas and Fussenecker, Claudia}, title = {„Engineering Conferences": Wissenschaftlich Kommunizieren im Master}, series = {Die Neue Hochschule}, volume = {58}, journal = {Die Neue Hochschule}, number = {3}, pages = {4}, year = {2017}, language = {de} } @article{RoedderNeefLauxetal.2016, author = {Roedder, Maximilian and Neef, Matthias and Laux, Christoph and Priebe, Klaus-P.}, title = {Systematic Fluid Selection for Organic Rankine Cycles and Performance Analysis for a Combined High and Low Temperature Cycle}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {138}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {031701}, publisher = {ASME}, doi = {10.1115/1.4031361}, pages = {168}, year = {2016}, abstract = {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 (EC) and tolerance criteria (TC). 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 (HT) and a low temperature (LT) cycle in which the condensation heat of the HT cycle provides the heat input of the 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 HT cycle with toluene as the working fluid and 6.2\% in LT cycle with isobutane 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.}, language = {en} } @article{WolterZekornNeef2016, author = {Wolter, Nina and Zekorn, Thomas and Neef, Matthias}, title = {Station{\"a}re thermodynamische Prozesssimulationen am Beispiel eines Industriekraftwerks}, series = {BWK: das Energie-Fachmagazin}, volume = {68}, journal = {BWK: das Energie-Fachmagazin}, number = {6}, pages = {6 -- 10}, year = {2016}, abstract = {Um bauliche Ver{\"a}nderungen in bestehenden Kraftwerksprozessen auf ihre Wirkungsweise untersuchen und thermodynamisch beziehungsweise wirtschaftlich bewerten zu k{\"o}nnen, werden thermische Kraftwerksprozesse mit geeigneter Simulationssoftware abgebildet und in verschiedenen Detaillierungsstufen ausgelegt oder nachgerechnet. Im Folgenden wird ein Weg aufgezeigt, wie mit Hilfe einer station{\"a}ren Simulationssoftware die Gesamtjahresbilanz eines Kraftwerks vorausberechnet werden kann. Mit Hilfe von Prozessdaten aus Vorjahren wird nachgewiesen, dass das Berechnungsmodell das bestehende Kraftwerk mit einer Abweichung von weniger als drei Prozent bez{\"u}glich erzeugter elektrischer Leistung und Brennstoffeinsatz und bei bekannter Dampfproduktion abbilden kann. Das so verifizierte Modell kann zur Untersuchung von Zubaumaßnahmen oder Ver{\"a}nderungen im Kraftwerksprozess eingesetzt werden.}, language = {de} } @inproceedings{LauxGotterNeef2019, author = {Laux, Christoph and Gotter, Andreas and Neef, Matthias}, title = {Experimental investigation of a low pressure steam Rankine cycle for waste heat utilization of internal combustion engines}, series = {Proceedings of the 5th International Seminar on ORC Power Systems}, booktitle = {Proceedings of the 5th International Seminar on ORC Power Systems}, publisher = {The National Technical University of Athens (NTUA)}, address = {Athens}, isbn = {978-90-9032038-0}, year = {2019}, abstract = {High heat losses via exhaust gas and coolant in internal combustion engines (ICE) are the basis for numerous investigations regarding downstream processes for power generation. The most promising concepts are Organic Rankine Cycles (ORC) and Steam Rankine Cycles (SRC). In previous work of the Center of Innovative Energy Systems, D{\"u}sseldorf (Germany), the technical and economic feasibility of a low pressure SRC has been investigated and the advantages in comparison to organic Rankine cycles are highlighted. A distinctive feature of the cycle is the use of the ICE coolant heat for evaporation, which limits the cycles maximum steam pressure to values below atmospheric pressure. This work presents first results of a test rig with data reconciliation according to DIN 2048 to validate the simulation results and design calculations. As a basis for the experimental investigations, a gas fired CHP plant was selected. The design of the test rig is optimized for the operation in the laboratory, where the coolant heat is emulated by a tempering device and the exhaust heat of the CHP plant is emulated by a gas burner. With the designed test rig, it is possible to control the volume flow and the temperatures of the coolant and exhaust gas, so that different load conditions of the gas fired CHP plant can be investigated. For initial tests, the turbine in the SRC is replaced by a throttle to achieve the pressure drop of the turbine. The experimental results show, that the exhaust and coolant heat of a 36 kWel CHP plant can be emulated and the performance expectations of the cycle can be met in stable steady-state conditions. Based on the measurement results and the turbine design calculations an electric power output of the cycle of 3.8 kW will be possible, which results in a cycle efficiency of about 6.5 \% and an increase of the electrical power output of the CHP plant of about 10 \%. The results show that the plant concept is technically feasible and, with further optimization, also represents an alternative to ORC plants in terms of increasing the efficiency of a cogeneration plant.}, language = {en} } @inproceedings{KramerLernerSacheretal.2018, author = {Kramer, Tim and Lerner, Igor and Sacher, Patrick and Neef, Matthias and Baier, Andr{\´e}}, title = {Blue Engineering: Was ist das und wie gelingt die Implementierung an meiner Hochschule?}, series = {Diversit{\"a}t und Kulturelle Vielfalt - Differenzieren, Individualisieren - oder Integrieren? Wege zu technischer Bildung : Referate der 13. Ingenieurp{\"a}dagogischen Regionaltagung 2018 and der Hochschule Bochum vom 7.-9. Juni 2018}, booktitle = {Diversit{\"a}t und Kulturelle Vielfalt - Differenzieren, Individualisieren - oder Integrieren? Wege zu technischer Bildung : Referate der 13. Ingenieurp{\"a}dagogischen Regionaltagung 2018 and der Hochschule Bochum vom 7.-9. Juni 2018}, editor = {Dederichs-Koch, Andrea and Mohnert, Andrea and Kammasch, Gudrun}, publisher = {Ingenieur-P{\"a}dagogische Wissensgesellschaft (IPW)}, address = {Berlin}, isbn = {978-3-9818728-2-8}, year = {2018}, language = {de} }