TY - JOUR A1 - Betzold, Christina A1 - Dentel, Arno T1 - Smart integration of heat pumps by predictive controls JF - Heat Pumping Technologies Magazine N2 - The integration of heat pumps into a PV and battery system faces the challenge of sharing the available PV power among the actors. In order to coordinate this competition, a suitable energy concept, as well as the control, must match. In a cluster of eight terraced houses, an energy system has been implemented, which should represent a smart integration of heat pumps. To coordinate the interaction of the components, model predictive controls are used. The simulation shows very good results for the predictive controls, but the results cannot be replicated in total practice. Y1 - 2022 U6 - https://doi.org/https://doi.org/10.23697/7mmf-3f37 VL - 40 IS - 3 SP - 25 EP - 27 ER - TY - JOUR A1 - Scheffler, Holger A1 - Moder, Michael A1 - Schrage, Nico A1 - Lippert, Kaj A1 - Heß, Max A1 - Rostan, Fabian A1 - Carstensen, Dirk A1 - Köhler, Albrecht A1 - Schaarschmidt, Lars T1 - Zusammenwirken von Planung und hydraulischer Untersuchung am HRB Weilers/Bracht JF - WASSERWIRTSCHAFT N2 - Der Neubau eines Hochwasserrückhaltebeckens (HRB) erfordert umfangreiche hydraulische Untersuchungen. Möglichkeiten zur Überprüfung und Optimierung einer wasserbaulichen Planung sind sowohl der physikalische Modellversuch als auch eine hydrodynamisch-numerische Strömungsmodellierung. Fragestellungen zur Wirkungsweise und zu den Wechselwirkungen der Betriebseinrichtung eines HRB können so beantwortet werden. Der vorliegende Beitrag beschreibt das Zusammenwirken von Planung und hydraulischen Untersuchungen am Neubauprojekt HRB Weilers/Bracht in Hessen. KW - Physikalische Modellierung KW - 3D hydrodynamisch-numerische Simulation KW - 2D hydrodynamisch-numerische Simulation KW - 3D-Druck Y1 - 2023 U6 - https://doi.org/10.1007/s35147-023-1833-3 SN - 0043-0978 VL - 113 IS - 6 SP - 44 EP - 47 PB - Springer Science and Business Media LLC ER - TY - RPRT A1 - Roy, Alastair A1 - Fahnøe, Kristian A1 - Farrier, Alan A1 - Heinrich, Marco A1 - Kronbæk, Mette A1 - Sowa, Frank T1 - How the COVID-19 pandemic has affected the lives of homeless young people and welfare services in three European cities BT - A qualitative study N2 - At the beginning of the year 2020, the pandemic caused by COVID-19 reached Europe. European countries implemented restrictions on movement and public life in order to contain its spread. The pandemic, as well as these policy responses, altered everyday lives for people all over Europe. This research explores effects of the pandemic on the everyday lives and lived realities of homeless young people in three cities in different countries: Nuremberg (Germany), Copenhagen (Denmark) and Manchester (United Kingdom). We focus on young people between the ages of 18 and 29 who have experienced homelessness. In addition, we explore how three different social welfare organisations worked to provide practical and emotional support to homeless young people during the pandemic. KW - covid-19 ; homeless young people Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:92-opus4-18477 SP - 3 EP - 98 CY - Nuremberg/Copenhagen/Preston ER - TY - JOUR A1 - Gundermann, Michael A1 - Raab, Florian A1 - Raab, Daniel A1 - Botsch, Tilman T1 - Investigation of the heat transfer coefficient during the condensation of small quantities of water vapour from a mixture with a high proportion of non-condensable gas in a horizontal smooth tube JF - International Journal of Heat and Mass Transfer N2 - During heat recovery of exhaust gas energy in a shell and tube heat exchanger, the exhaust gas is cooled down and the water vapour content may condense when the corresponding temperature is reached. In this case, a condensation heat exchanger allows recovering the latent heat in addition to the sensible heat and is therefore beneficial for a preferably high heat recovery. The database and algorithms for the design of this kind of apparatus are still nowadays quite week because only little experimental work is realized with condensation of water vapour from a mixture with a very high proportion of non-condensable gas in horizontal tubes. The actual research work improves this database with a considerable amount of experimental data and proposes a correlation for the prediction of the heat transfer coefficient in an exhaust gas heat exchanger in which parts of the gas humidity condense. All experiments were carried out under conditions, which are typical for this kind of heat exchangers, hence the presented results can be used for the design of condensation heat exchangers in industrial heat transfer systems. A gas inlet temperature of 120 °C, a range of the air-steam mixture Reynolds number 11,000 Re 31,000, three tube lengths between 1.87 m and 3.04 m, water vapour volume fractions of 7 % to 14.5 % as well as tube diameters of 22 mm and 28 mm were selected to derive the correlation. Furthermore, additional tube lengths (0.574 m, 0.973 m, 1.373 m) were investigated to determine the parameters influencing the condensation rate and comprehensive location profiles over the tube length. A correlation for a correction factor is derived, which enables to calculate the increase of the heat transfer coefficient due to condensation from the dry heat transfer coefficient without condensation. This dry heat transfer coefficient is calculated by the measured values in the inlet and outlet for a purely dry air-steam mixture cooling without condensation. The correction factor depend on the water vapour volume fraction, the Reynolds number and the geometry ratio between the inner diameter and the tube length. KW - Condensation ; Non-condensable gas ; Heat transfer correlation ; Inside horizontal tube ; Heat exchangers ; Flue gas Y1 - 2021 U6 - https://doi.org/10.1016/j.ijheatmasstransfer.2021.121016 SN - 0017-9310 VL - 170 PB - Elsevier BV ER - TY - JOUR A1 - Botsch, T. A1 - Goldsteinas, A. T1 - Unterdruckaufkohlung - Modellierung und Simulation der Eindringtiefe verschiedener Aufkohlungsgase in Sacklochbohrungen JF - HTM Journal of Heat Treatment and Materials N2 - Es wird ein Modell vorgestellt, mit dem für den Unterdruckaufkoh­lungsprozess die Eindringtiefe von Propan und Ethin in Sackloch­bohrungen vorhergesagt werden kann. Das Modell basiert auf Men­genbilanzen überdas Gasvolumen in der Bohrung. Testrechnungenergaben eine gute Übereinstimmung zwischen dem berechneten Ver­lauf der Konzentration des Aufkohlungsgases in der Bohrung undder aus Härtemessungen bestimmten Eindringtiefe. Die in demModell verwendeten Werte für die Aufkohlungswirkung bei der in derBohrung vorherrschenden geringen Propan- bzw. Ethinkonzentra­tion wurden gemessen und werden dargestellt. Aus den Messergeb­nissen wird deutlich, dass sich die Aufkohlungs wirkung von Propannur unwesentlich von der von Ethin unterscheidet und dass bereitsab einem Propan- oder Ethinanteil im Gas von ca. 20% eine zufrie­denstellende Aufkohlung möglich ist. Für die industrielle Anwen­dung bedeutet dies, dass auch große und dicht gepackte Chargenmit Propan aufgekohlt werden können. Durch einen entsprechendgroßen Volumenstrom des zuströmenden Gases muss lediglich dafürgesorgt werden, dass der Propangehalt im Zentrum der Chargegrößer als 20 % ist. Modellrechnungen zeigen, dass sich Ethin vorallem deshalb besser zur Aufkohlung von Sackloch-bohrungen eignetals Propan, da der Diffusionswiderstand des bei der Aufkohlungs­reaktion entstehenden Zerfallsproduktes Wasserstoff sehr klein ist.Da die Verwendung von Ethin als Aufkohlungsgas aber aufwändigerund teurer ist als die von Propan, sollte Ethin nur eingesetzt werden,wenn dies unbedingt erforderlich ist. Das vorgestellte Modell kannhelfen, bereits vor den ersten Versuchen die maximale Bohrungs­tiefe bzw. den minimalen Bohrungsdurchmesser abzuschätzen, dermit Propan bzw. Ethin noch aufgekohlt werden kann. Y1 - 2001 U6 - https://doi.org/10.1515/htm-2002-570507 SN - 2194-1831 VL - 57 IS - 5 ER - TY - CHAP A1 - Lemouedda, A. A1 - Breuer, Michael A1 - Franz, E. T1 - Pareto optimization of heat transfer enhancement of finned-tube heat exchangers with delta-winglet vor-tex generators T2 - Turbulence, heat and mass transfer 6 : proceedings of the Sixth International Symposium on Turbulence, Heat and Mass Transfer Rome, Italy, 14 - 18 September, 2009 N2 - For circular finned tubes often used in heat exchangers, the wake regions behind the tubes are regions with low heat transfer coefficient. Delta-winglet vortex generators on the fin surfaces reduce the width of the wake regions and improve the overall heat transfer rate. The present work studies numerically the effect of enhancing the performance of the finned-tubes using delta-winglets. Simulations were carried out on a model of three circular tube rows with circular fins for Reynolds numbers of 500, 700, and 900 (based on the inlet velocity and the hydraulic diameter of unit cell). Eighteen basic configurations with different number and positions of delta-winglets were investigated. The flow and heat transfer behaviors are analyzed for certain configurations. Finally, the optimal configurations are presented based on the Pareto optimality strategy. Y1 - 2009 SN - 978–1–56700–262–1 U6 - https://doi.org/10.1615/ICHMT.2009.TurbulHeatMassTransf.1860 SN - 2377-2816 SP - 1015 EP - 1018 ER - TY - CHAP A1 - Krippner, Roland A1 - Flade, Fabian T1 - Building Integrated Solar Technology BT - valuating 20 Years of Experience with Solar Buildings from an International Competition Y1 - 2021 U6 - https://doi.org/10.18086/swc.2021.09.01 PB - International Solar Energy Society CY - Freiburg, Germany ER - TY - JOUR A1 - Möldner, Fabian A1 - Hentschel, Bernd A1 - Carstensen, Dirk T1 - Ice-Jam Investigations along the Oder River Based on Satellite and UAV Data JF - Water N2 - The Oder River, situated along the border between Poland and Germany, is regularly affected by ice-jam events and their associated hazards, such as a sudden rise in water level and the endangerment to flood-protection infrastructure. The existing databases on past ice-jam events lack substantial information considering ice formation, blockage origins or the spatiotemporal evolution of the ice cover needed for a comprehensive understanding of relevant ice processes. Within this study, the evaluation of satellite and Uncrewed Aerial Vehicle (UAV) data was carried out in order to analyze the capabilities of enhancing river ice information in the study area. Satellite imagery was proven to be a valuable source of investigating ice-jam phenomena on all scales, leading to the identification of initial ice-jam locations, surveying spatiotemporal ice cover evolution or monitoring the maximum ice-cover extent. A simplified approach for river ice classification of satellite radar data using the K-Means Cluster Analysis is introduced, enabling the differentiation between river ice formations. Based on UAV data taken in this study, workflows were presented, allowing for measurements of ice floe velocities and the localization of flooded and ice-covered flow control structures. KW - river ice monitoring KW - ice-jam flooding KW - ice detection and characterization KW - space-borne remote sensing KW - Sentinel-1 KW - uncrewed aerial vehicles KW - Oder River Y1 - 2024 U6 - https://doi.org/10.3390/w16101323 SN - 2073-4441 VL - 16 IS - 10 PB - MDPI AG ER - TY - JOUR A1 - Birkner, Lena A1 - Foreta, Michael A1 - Rinaldi, Ali A1 - Orekhov, Anton A1 - Willinger, Marc-Georg A1 - Eichelbaum, Maik T1 - Dynamic accelerated stress test and coupled on-line analysis program to elucidate aging processes in proton exchange membrane fuel cells JF - Scientific Reports N2 - AbstractThe application of hydrogen proton exchange membrane fuel cells (PEMFC) in greenhouse gas emission free heavy-duty vehicles requires extremely durable PEMFC components with service lives in the range of 30,000 h. Hence suitable test and analysis methods are required that reflect realistic operation scenarios, but significantly accelerate aging. For this purpose, a dynamic accelerated stress test was developed, which is coupled with a comprehensive in-depth in-situ and ex-situ analysis program to determine the aging processes of a PEMFC membrane electrode assembly (MEA). The test comprehends dynamic cycling between low, moderate and high load, different temperature and humidity conditions as well as recovery sequences to distinguish between reversible and irreversible failure modes. All phases of the PEMFC system (i.e. solid, liquid and gaseous) are monitored on-line during aging by sophisticated electrochemical, mass spectrometric and ion chromatographic analytical methods. The structural and elemental composition of the MEA before and after the aging program (post-mortem) are investigated by X-ray fluorescence, scanning and transmission electron microscopy. This program was able to age a commercial PEMFC to end-of-life in 1000 h, while providing an accurate picture of the aging processes involved. Y1 - 2024 U6 - https://doi.org/10.1038/s41598-024-54258-8 SN - 2045-2322 VL - 14 IS - 1 PB - Springer Science and Business Media LLC ER - TY - JOUR A1 - Feix, Tobias A1 - Fadhil, Aseel Ali A1 - Troegel, Dennis T1 - Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents JF - Hydrometallurgy N2 - Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly C=C, but also C=O or C=N double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study. KW - Silicone elastomer KW - Platinum KW - Catalyst KW - Leaching KW - Recovery Y1 - 2024 U6 - https://doi.org/10.1016/j.hydromet.2024.106283 SN - 0304-386X VL - 225 SP - 1 EP - 9 PB - Elsevier BV ER -