TY - CHAP A1 - Helsper, Christoph A1 - Dressler, Jörg ED - Gail, Lothar ED - Gommel, Udo ED - Hortig, Hans-Peter T1 - Partikelmesstechnik T2 - Reinraumtechnik N2 - Der Schutz von Produkten vor der Kontamination durch Partikel gilt als eine zentrale Aufgabe der Reinraumtechnik. Da es dabei um Kontaminationseffekte weit unterhalb der visuellen Wahrnehmbarkeit geht, braucht es leistungsfähige Verfahren, um die Messgröße „Partikelkontamination“ über den gesamten Bereich, den Anwender fordern, präzise zu bestimmen. Neben der Partikelhäufigkeit ist dabei die Größe der Partikel, die sowohl das Transportverhalten wie auch die mögliche Wirkung auf das Produkt beeinflusst, von entscheidender Bedeutung. Ferner kann es für die Ermittlung von Kontaminationsquellen von Interesse sein, die Form und die chemische Natur der Partikel zu bestimmen (z. B. textile Fasern, Metallabrieb, flüssige Tröpfchen). Die Partikelhäufigkeit wird üblicherweise als Konzentration, d. h. bezogen auf das analysierte Gasvolumen angegeben. Bei den in reinen Technologien üblichen niedrigen Konzentrationen dient als Häufigkeitsmaß die Partikelanzahlkonzentration, also die Partikelanzahl pro Volumeneinheit des Trägermediums. Y1 - 2012 SN - 978-3-642-19435-1 U6 - http://dx.doi.org/10.1007/978-3-642-19435-1_3 VL - 2012 SP - 69 EP - 95 PB - Springer CY - Berlin ET - 3 ER - TY - JOUR A1 - Pieper, Martin A1 - Klein, Peter T1 - A simple and accurate numerical network flow model for bionic micro heat exchangers JF - Heat mass transfer Y1 - 2011 SN - 0947-7411 VL - 47 IS - 5 SP - 491 EP - 503 PB - Springer CY - Berlin ER - TY - JOUR A1 - Pieper, Martin A1 - Klein, Peter T1 - Application of simple, periodic homogenization techniques to non-linear heat conduction problems in non-periodic, porous media JF - Heat mass transfer N2 - Often, detailed simulations of heat conduction in complicated, porous media have large runtimes. Then homogenization is a powerful tool to speed up the calculations by preserving accurate solutions at the same time. Unfortunately real structures are generally non-periodic, which requires unpractical, complicated homogenization techniques. We demonstrate in this paper, that the application of simple, periodic techniques to realistic media, that are just close to periodic, gives accurate, approximative solutions. In order to obtain effective parameters for the homogenized heat equation, we have to solve a so called “cell problem”. In contrast to periodic structures it is not trivial to determine a suitable unit cell, which represents a non-periodic media. To overcome this problem, we give a rule of thumb on how to choose a good cell. Finally we demonstrate the efficiency of our method for virtually generated foams as well as real foams and compare these results to periodic structures. Y1 - 2012 U6 - http://dx.doi.org/10.1007/s00231-011-0879-4 SN - 0947-7411 VL - 48 IS - 2 SP - 291 EP - 300 PB - Springer CY - Berlin ER - TY - CHAP A1 - Cresser, J. D. A1 - Häger, J. A1 - Leuchs, G. A1 - Rateike, Franz-Matthias A1 - Walther, H. T1 - Resonance fluorescence of atoms in strong monochromatic laser fields T2 - Dissipative systems in quantum optics. Ed. by Rodolfo Bonifacio. Topics in current physics. Vol. 27 N2 - The investigation of atomic resonance fluorescence has always been of special interest as a means for the determination of atomic parameters. In addition, information on the interaction mechanism between atoms and radiation can be obtained. In the standard fluorescence experiment the frequency distribution of the incident photons is larger than the natural width of the respective transition; as a consequence the correlation time in the photon-atom interaction is determined by the lifetime of the atoms in the excited state. With the development of lasers and especially of tunable dye lasers in recent years it became possible to study the case where the incident radiation has a spectral distribution which is narrower than the natural width. This corresponds to a correlation time of the incoming light wave which is much longer than the excited-state lifetime. In this chapter a survey of experiments on the resonance fluorescence of atoms in monochromatic laser fields will be given. Y1 - 1982 SN - 978-3-642-81719-9 U6 - http://dx.doi.org/10.1007/978-3-642-81717-5_3 SP - 21 EP - 59 PB - Springer CY - Berlin ER - TY - JOUR A1 - Alebouyeh Samami, Behzad A1 - Pieper, Martin A1 - Breitbach, Gerd A1 - Hodapp, Josef T1 - Heat production in the windings of the stators of electric machines under stationary condition JF - Heat and mass transfer N2 - In electric machines due to high currents and resistive losses (joule heating) heat is produced. To avoid damages by overheating the design of effective cooling systems is required. Therefore the knowledge of heat sources and heat transfer processes is necessary. The purpose of this paper is to illustrate a good and effective calculation method for the temperature analysis based on homogenization techniques. These methods have been applied for the stator windings in a slot of an electric machine consisting of copper wires and resin. The key quantity here is an effective thermal conductivity, which characterizes the heterogeneous wire resin-arrangement inside the stator slot. To illustrate the applicability of the method, the analysis of a simplified, homogenized model is compared with the detailed analysis of temperature behavior inside a slot of an electric machine according to the heat generation. We considered here only the stationary situation. The achieved numerical results are accurate and show that the applied homogenization technique works in practice. Finally the results of simulations for the two cases, the original model of the slot and the homogenized model chosen for the slot (unit cell), are compared to experimental results. Y1 - 2014 U6 - http://dx.doi.org/10.1007/s00231-014-1371-8 SN - 0947-7411 (Print) ; 1432-1181 (E-Journal) VL - 50 SP - 1707 EP - 1716 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Borchert, Jörg A1 - Hasenbeck, Marc A1 - Jungbluth, Christian A1 - Schemm, Ralf T1 - Bewertung und Steuerung von Gasspeichern bzw. Gasspeicherscheiben JF - Zeitschrift für Energiewirtschaft N2 - In diesem Artikel werden zunächst einleitend der Gasmarkt Deutschland und der sich daraus ergebende Speicherbedarf skizziert. Folgend wird auf verschiedene Speichernutzen aus betriebswirtschaftlicher Perspektive eingegangen und die in diesem Artikel vorgestellten Bewertungsverfahren einleitend beschrieben. In diesem Artikel werden stochastische Optimierungsmethoden aufgegriffen, die sowohl eine Bewertung der Speicher gegenüber einem Spotpreis, als auch gegenüber einer gesamten Forwardcurve ermöglichen. Hierzu werden zunächst Modelle zur Beschreibung der Marktpreise vorgestellt und anhand empirischer Daten kalibriert. Dann wird eine beispielhafte Speicherscheibe zunächst auf Basis der LeastSquareMonteCarloTechnik gegenüber dem stochastischen mehrfaktoriellen Spotpreismodell bewertet. Hieran schließt sich die Vorstellung der Bewertung sowie des Hedgings gegenüber der Forwardcurve an. Abschließend erfolgt eine vergleichende Gegenüberstellung beider Verfahren. Y1 - 2009 U6 - http://dx.doi.org/10.1007/s12398-009-0033-x SN - 1866-2765 VL - 33 IS - 4 SP - 279 EP - 293 PB - Springer CY - Berlin ER - TY - CHAP A1 - Srivastava, Alok A1 - Knolle, Friedhart A1 - Hoyler, Friedrich A1 - Scherer, Ulrich W. A1 - Schnug, Ewald T1 - Uranium Toxicity in the State of Punjab in North-Western India T2 - Management of Natural Resources in a Changing Environment N2 - Lately there has been an increasing concern about uranium toxicity in some districts of Punjab State located in the North Western part of India after the publication of a report (Blaurock-Busch et al. 2010) which showed that the concentration of uranium in hair and urine of children suffering from physical deformities, neurological and mental disorder from Malwa region (Fig. 1) of Punjab State was manifold higher than the reference ranges. A train which connects the affected region with the nearby city of Bikaner which has a Cancer Hospital has been nicknamed as Cancer Express due to the frenzy generated on account of uranium related toxicity. Y1 - 2015 SN - 978-3-319-12559-6 U6 - http://dx.doi.org/10.1007/978-3-319-12559-6_21 SP - 271 EP - 275 PB - Springer CY - Cham ER - TY - JOUR A1 - Kürten, Sylvia A1 - Mottaghy, Darius A1 - Ziegler, Martin T1 - A new model for the description of the heat transfer for plane thermo-active geotechnical systems based on thermal resistances JF - Acta Geotechnica Y1 - 2015 U6 - http://dx.doi.org/10.1007/s11440-014-0311-6 SN - 1861-1133 VL - 10 IS - 2 SP - 219 EP - 229 PB - Springer CY - Berlin ER - TY - CHAP A1 - Altay, Okyay A1 - Taddei, Francesca A1 - Butenweg, Christoph A1 - Klinkel, Sven T1 - Vibration mitigation of wind turbine towers with tuned mass dampers T2 - Wind turbine control and monitoring. (Advances in industrial control) N2 - Because of its minor environmental impact, electricity generation using wind power is getting remarkable. The further growth of the wind industry depends on technological solutions to the challenges in production and construction of the turbines. Wind turbine tower vibrations, which limit power generation efficiency and cause fatigue problems with high maintenance costs, count as one of the main structural difficulties in the wind energy sector. To mitigate tower vibrations auxiliary measures are necessary. The effectiveness of tuned mass damper is verified by means of a numeric study on a 5 MW onshore reference wind turbine. Hereby, also seismic-induced vibrations and soil–structure interaction are considered. Acquired results show that tuned mass damper can effectively reduce resonant tower vibrations and improve the fatigue life of wind turbines. This chapter is also concerned with tuned liquid column damper and a semiactive application of it. Due to its geometric versatility and low prime costs, tuned liquid column dampers are a good alternative to other damping measures, in particular for slender structures like wind turbines. Y1 - 2014 SN - 978-3-319-08412-1 (Print) ; 978-3-319-08413-8 (E-Book) U6 - http://dx.doi.org/10.1007/978-3-319-08413-8_12 SP - 337 EP - 373 PB - Springer CY - Cham ; Heidelberg ; New York ; Dordrecht ; London ER - TY - JOUR A1 - Srivastava, A. A1 - Chahar, V. A1 - Sharma, V. A1 - Sun, Y. A1 - Bol, R. A1 - Knolle, F. A1 - Schnug, E. A1 - Hoyler, Friedrich A1 - Naskar, N. A1 - Lahiri, S. A1 - Patnaik, R. T1 - Study of uranium toxicity using low-background gamma-ray spectrometry JF - Journal of Radioanalytical and Nuclear Chemistry Y1 - 2017 U6 - http://dx.doi.org/10.1007/s10967-017-5466-9 SN - 1588-2780 IS - Online first SP - 1 EP - 7 PB - Springer CY - Berlin ER - TY - CHAP A1 - Meskouris, Konstantin A1 - Butenweg, Christoph A1 - Hinzen, Klaus-G. A1 - Höffer, Rüdiger T1 - Stochasticity of Wind Processes and Spectral Analysis of Structural Gust Response T2 - Structural Dynamics with Applications in Earthquake and Wind Engineering N2 - 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. KW - Wind turbulence KW - Gust wind response KW - Spectral analysis Y1 - 2019 SN - 978-3-662-57550-5 (Online) SN - 978-3-662-57548-2 (Print) U6 - http://dx.doi.org/10.1007/978-3-662-57550-5_3 SP - 153 EP - 196 PB - Springer CY - Berlin ER - TY - JOUR A1 - Cheenakula, Dheeraja A1 - Hoffstadt, Kevin A1 - Krafft, Simone A1 - Reinecke, Diana A1 - Klose, Holger A1 - Kuperjans, Isabel A1 - Grömping, Markus T1 - Anaerobic digestion of algal–bacterial biomass of an Algal Turf Scrubber system JF - Biomass Conversion and Biorefinery N2 - This study investigated the anaerobic digestion of an algal–bacterial biofilm grown in artificial wastewater in an Algal Turf Scrubber (ATS). The ATS system was located in a greenhouse (50°54′19ʺN, 6°24′55ʺE, Germany) and was exposed to seasonal conditions during the experiment period. The methane (CH4) potential of untreated algal–bacterial biofilm (UAB) and thermally pretreated biofilm (PAB) using different microbial inocula was determined by anaerobic batch fermentation. Methane productivity of UAB differed significantly between microbial inocula of digested wastepaper, a mixture of manure and maize silage, anaerobic sewage sludge, and percolated green waste. UAB using sewage sludge as inoculum showed the highest methane productivity. The share of methane in biogas was dependent on inoculum. Using PAB, a strong positive impact on methane productivity was identified for the digested wastepaper (116.4%) and a mixture of manure and maize silage (107.4%) inocula. By contrast, the methane yield was significantly reduced for the digested anaerobic sewage sludge (50.6%) and percolated green waste (43.5%) inocula. To further evaluate the potential of algal–bacterial biofilm for biogas production in wastewater treatment and biogas plants in a circular bioeconomy, scale-up calculations were conducted. It was found that a 0.116 km2 ATS would be required in an average municipal wastewater treatment plant which can be viewed as problematic in terms of space consumption. However, a substantial amount of energy surplus (4.7–12.5 MWh a−1) can be gained through the addition of algal–bacterial biomass to the anaerobic digester of a municipal wastewater treatment plant. Wastewater treatment and subsequent energy production through algae show dominancy over conventional technologies. KW - Biogas KW - Methane KW - Algal Turf Scrubber KW - Algal–bacterial bioflm KW - Circular bioeconomy Y1 - 2022 U6 - http://dx.doi.org/10.1007/s13399-022-03236-z SN - 2190-6823 N1 - Corresponding author: Dheeraja Cheenakula VL - 13 SP - 15 Seiten PB - Springer CY - Berlin ER - TY - CHAP A1 - Leicht-Scholten, Carmen A1 - Steuer-Dankert, Linda T1 - Educating engineers for socially responsible solutions through design thinking T2 - Design thinking in higher education: interdisciplinary encounters N2 - There is a broad international discussion about rethinking engineering education in order to educate engineers to cope with future challenges, and particularly the sustainable development goals. In this context, there is a consensus about the need to shift from a mostly technical paradigm to a more holistic problem-based approach, which can address the social embeddedness of technology in society. Among the strategies suggested to address this social embeddedness, design thinking has been proposed as an essential complement to engineering precisely for this purpose. This chapter describes the requirements for integrating the design thinking approach in engineering education. We exemplify the requirements and challenges by presenting our approach based on our course experiences at RWTH Aachen University. The chapter first describes the development of our approach of integrating design thinking in engineering curricula, how we combine it with the Sustainable Development Goals (SDG) as well as the role of sustainability and social responsibility in engineering. Secondly, we present the course “Expanding Engineering Limits: Culture, Diversity, and Gender” at RWTH Aachen University. We describe the necessity to theoretically embed the method in social and cultural context, giving students the opportunity to reflect on cultural, national, or individual “engineering limits,” and to be able to overcome them using design thinking as a next step for collaborative project work. The paper will suggest that the successful implementation of design thinking as a method in engineering education needs to be framed and contextualized within Science and Technology Studies (STS). Y1 - 2020 SN - 978-981-15-5780-4 U6 - http://dx.doi.org/10.1007/978-981-15-5780-4 SP - 229 EP - 246 PB - Springer CY - Singapore ER - TY - CHAP A1 - Brauner, Philipp A1 - Vervier, Luisa A1 - Brillowski, Florian A1 - Dammers, Hannah A1 - Steuer-Dankert, Linda A1 - Schneider, Sebastian A1 - Baier, Ralph A1 - Ziefle, Martina A1 - Gries, Thomas A1 - Leicht-Scholten, Carmen A1 - Mertens, Alexander A1 - Nagel, Saskia K. T1 - Organization Routines in Next Generation Manufacturing T2 - Forecasting Next Generation Manufacturing N2 - Next Generation Manufacturing promises significant improvements in performance, productivity, and value creation. In addition to the desired and projected improvements regarding the planning, production, and usage cycles of products, this digital transformation will have a huge impact on work, workers, and workplace design. Given the high uncertainty in the likelihood of occurrence and the technical, economic, and societal impacts of these changes, we conducted a technology foresight study, in the form of a real-time Delphi analysis, to derive reliable future scenarios featuring the next generation of manufacturing systems. This chapter presents the organization dimension and describes each projection in detail, offering current case study examples and discussing related research, as well as implications for policy makers and firms. Specifically, we highlight seven areas in which the digital transformation of production will change how we work, how we organize the work within a company, how we evaluate these changes, and how employment and labor rights will be affected across company boundaries. The experts are unsure whether the use of collaborative robots in factories will replace traditional robots by 2030. They believe that the use of hybrid intelligence will supplement human decision-making processes in production environments. Furthermore, they predict that artificial intelligence will lead to changes in management processes, leadership, and the elimination of hierarchies. However, to ensure that social and normative aspects are incorporated into the AI algorithms, restricting measurement of individual performance will be necessary. Additionally, AI-based decision support can significantly contribute toward new, socially accepted modes of leadership. Finally, the experts believe that there will be a reduction in the workforce by the year 2030. Y1 - 2022 SN - 978-3-031-07734-0 U6 - http://dx.doi.org/10.1007/978-3-031-07734-0_5 SP - 75 EP - 94 PB - Springer CY - Cham ER - TY - CHAP A1 - Hinke, Christian A1 - Vervier, Luisa A1 - Brauner, Philipp A1 - Schneider, Sebastian A1 - Steuer-Dankert, Linda A1 - Ziefle, Martina A1 - Leicht-Scholten, Carmen T1 - Capability configuration in next generation manufacturing T2 - Forecasting next generation manufacturing : digital shadows, human-machine collaboration, and data-driven business models N2 - Industrial production systems are facing radical change in multiple dimensions. This change is caused by technological developments and the digital transformation of production, as well as the call for political and social change to facilitate a transformation toward sustainability. These changes affect both the capabilities of production systems and companies and the design of higher education and educational programs. Given the high uncertainty in the likelihood of occurrence and the technical, economic, and societal impacts of these concepts, we conducted a technology foresight study, in the form of a real-time Delphi analysis, to derive reliable future scenarios featuring the next generation of manufacturing systems. This chapter presents the capabilities dimension and describes each projection in detail, offering current case study examples and discussing related research, as well as implications for policy makers and firms. Specifically, we discuss the benefits of capturing expert knowledge and making it accessible to newcomers, especially in highly specialized industries. The experts argue that in order to cope with the challenges and circumstances of today’s world, students must already during their education at university learn how to work with AI and other technologies. This means that study programs must change and that universities must adapt their structural aspects to meet the needs of the students. Y1 - 2022 SN - 978-3-031-07733-3 U6 - http://dx.doi.org/10.1007/978-3-031-07734-0_6 SP - 95 EP - 106 PB - Springer CY - Cham ER - TY - CHAP A1 - Butenweg, Christoph A1 - Holtschoppen, Britta T1 - Seismic design of structures and components in industrial units T2 - Structural Dynamics with Applications in Earthquake and Wind Engineering N2 - Industrial units consist of the primary load-carrying structure and various process engineering components, the latter being by far the most important in financial terms. In addition, supply structures such as free-standing tanks and silos are usually required for each plant to ensure the supply of material and product storage. Thus, for the earthquake-proof design of industrial plants, design and construction rules are required for the primary structures, the secondary structures and the supply structures. Within the framework of these rules, possible interactions of primary and secondary structures must also be taken into account. Importance factors are used in seismic design in order to take into account the usually higher risk potential of an industrial unit compared to conventional building structures. Industrial facilities must be able to withstand seismic actions because of possibly wide-ranging damage consequences in addition to losses due to production standstill and the destruction of valuable equipment. The chapter presents an integrated concept for the seismic design of industrial units based on current seismic standards and the latest research results. Special attention is devoted to the seismic design of steel thin-walled silos and tank structures. KW - Industrial units KW - Seismic design KW - Tanks KW - Silos KW - Components Y1 - 2019 SN - 978-3-662-57550-5 U6 - http://dx.doi.org/10.1007/978-3-662-57550-5_5 SP - 359 EP - 481 PB - Springer CY - Berlin ER - TY - CHAP A1 - Giresini, Linda A1 - Butenweg, Christoph T1 - Earthquake resistant design of structures according to Eurocode 8 T2 - Structural Dynamics with Applications in Earthquake and Wind Engineering N2 - The chapter initially provides a summary of the contents of Eurocode 8, its aim being to offer both to the students and to practising engineers an easy introduction into the calculation and dimensioning procedures of this earthquake code. Specifically, the general rules for earthquake-resistant structures, the definition of design response spectra taking behaviour and importance factors into account, the application of linear and non-linear calculation methods and the structural safety verifications at the serviceability and ultimate limit state are presented. The application of linear and non-linear calculation methods and corresponding seismic design rules is demonstrated on practical examples for reinforced concrete, steel and masonry buildings. Furthermore, the seismic assessment of existing buildings is discussed and illustrated on the example of a typical historical masonry building in Italy. The examples are worked out in detail and each step of the design process, from the preliminary analysis to the final design, is explained in detail. KW - Seismic design KW - Eurocode 8 KW - Design examples KW - Response spectrum KW - Pushover analysis Y1 - 2019 SN - 978-3-662-57550-5 (Online) SN - 978-3-662-57548-2 (Print) U6 - http://dx.doi.org/10.1007/978-3-662-57550-5_4 SP - 197 EP - 358 PB - Springer CY - Berlin ER - TY - JOUR A1 - Rossi, Leonardo A1 - Holtschoppen, Britta A1 - Butenweg, Christoph T1 - Official data on the economic consequences of the 2012 Emilia-Romagna earthquake: a first analysis of database SFINGE JF - Bulletin of Earthquake Engineering Y1 - 2019 U6 - http://dx.doi.org/10.1007%2Fs10518-019-00655-8 VL - 17 IS - 9 SP - 4855 EP - 4884 PB - Springer CY - Berlin ER - TY - JOUR A1 - Butenweg, Christoph A1 - Marinkovic, Marko A1 - Salatic, Ratko T1 - Experimental results of reinforced concrete frames with masonry infills under combined quasi-static in-plane and out-of-plane seismic loading JF - Bulletin of Earthquake Engineering Y1 - 2019 U6 - http://dx.doi.org/10.1007/s10518-019-00602-7 SN - 1573-1456 VL - 17 SP - 3397 EP - 3422 PB - Springer CY - Berlin ER - TY - JOUR A1 - Blanke, Tobias A1 - Hagenkamp, Markus A1 - Döring, Bernd A1 - Göttsche, Joachim A1 - Reger, Vitali A1 - Kuhnhenne, Markus T1 - Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates JF - Geothermal Energy N2 - Previous studies optimized the dimensions of coaxial heat exchangers using constant mass fow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar fow types. In contrast, in this study, fow conditions in the circular ring are kept constant (a set of fxed Reynolds numbers) during optimization. This approach ensures fxed fow conditions and prevents inappropriately high or low mass fow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic efort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass fow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefcients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy diference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy fux and hydraulic efort. The Reynolds number in the circular ring is instead of the mass fow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar fow and 60% for turbulent fow scenarios. Net-exergetic optimization shows a predominant infuence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the fow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics. Y1 - 2021 U6 - http://dx.doi.org/10.1186/s40517-021-00201-3 SN - 2195-9706 N1 - Corresponding author: Tobias Blanke VL - 9 IS - Article number: 19 PB - Springer CY - Berlin ER -