TY - JOUR A1 - Pollack, Moritz A1 - Lück, Andrea A1 - Wolf, Mario A1 - Kraft, Eckhard A1 - Völker, Conrad T1 - Energy and Business Synergy: Leveraging Biogenic Resources from Agriculture, Waste, and Wastewater in German Rural Areas JF - Sustainability N2 - The imperative to transform current energy provisions is widely acknowledged. However, scant attention has hitherto been directed toward rural municipalities and their innate resources, notably biogenic resources. In this paper, a methodological framework is developed to interconnect resources from waste, wastewater, and agricultural domains for energy utilization. This entails cataloging existing resources, delineating their potential via quantitative assessments utilizing diverse technologies, and encapsulating them in a conceptual model. The formulated models underwent iterative evaluation with engagement from diverse stakeholders. Consequently, 3 main concepts, complemented by 72 sub-concepts, were delineated, all fostering positive contributions to climate protection and providing heat supply in the rural study area. The outcomes’ replicability is underscored by the study area’s generic structure and the employed methodology. Through these inquiries, a framework for the requisite energy transition, with a pronounced emphasis on the coupling of waste, wastewater, and agriculture sectors in rural environments, is robustly analyzed. KW - Energiewende KW - Energieplanung KW - Abfallwirtschaft KW - organischer Abfall KW - Biomasse KW - Regionalentwicklung KW - biogene Abfallstoffe KW - Abwassermanagement KW - OA-Publikationsfonds2023 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20231222-65172 UR - https://www.mdpi.com/2071-1050/15/24/16573 VL - 2023 IS - volume 15, issue 24, article 16573 SP - 1 EP - 25 PB - MDPI CY - Basel ER - TY - CHAP A1 - Kiesel, Gerd A1 - Engels, Merit A1 - Völker, Conrad ED - Kornadt, Oliver ED - Carrigan, Svenja ED - Hofmann, Markus ED - Völker, Conrad T1 - Energetische Transformation im ländlichen Raum – Aufbau eines prozessorientierten Entwicklungs- und Moderationsmodells T2 - Schriftenreihe des Fachgebiets Bauphysik/Energetische Gebäudeoptimierung N2 - Kleine Kommunen im ländlichen Raum sind aufgrund ihrer oft eingeschränkten personellen und finanziellen Kapazitäten bisher eher sporadisch in den Themenfeldern Energieeffizienz und Erneuerbare Energien aktiv. Immer wieder stellt sich daher Frage, wie die Klimaschutzstrategien des Bundes und der Länder dort mit dem verfügbaren Personal kostengünstig realisierbar sind. Vor diesem Hintergrund wird ein Werkzeug entwickelt, mit dessen Hilfe der aktive Einstieg in diese Thematik mit geringen Aufwand und überwiegend barrierefrei möglich ist. Der Aufbau eines prozessorientierten Entwicklungs- und Moderationsmodells zur Erprobung und Umsetzung bezahlbarer Handlungsoptionen für Energieeinsparungen und effizienten Energieeinsatz im überwiegend ländlichen geprägten Raum ist der Schwerpunkt der Softwarelösung. Kommunen werden mit deren Hilfe in die Lage versetzt, in die notwendigen Prozesse der Energie- und Wärmewende einzusteigen. Dabei soll der modulare Aufbau die regulären Schritte notwendiger (integrierter) Planungsprozesse nicht vollständig ersetzen. Vielmehr können innerhalb der Online-Anwendung - überwiegend automatisiert - konkrete Maßnahmenvorschläge erstellt werden, die ein solides Fundament der künftigen energetischen Entwicklung der Kommunen darstellen. Für eine gezielte Validierung der Ergebnisse und der Ableitung potentieller Maßnahmen werden für die Erprobung Modellkommunen in Thüringen, Bayern und Hessen als Reallabore einbezogen. Das Tool steht bisher zunächst nur den beteiligten Modellkommunen zur Verfügung. Die entwickelte Softwarelösung soll künftig Schritt für Schritt allen interessierten Kommunen mit diversen Hilfsmitteln und einer Vielzahl anderer praktischer Bestandteile zur Verfügung gestellt werden. KW - Modellierung KW - Kommune KW - Energiewende KW - Transformation KW - ländlicher Raum Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220617-46566 SN - 978-3-95974-176-7 SN - 2363-8206 PB - Eigenverlag Technische Universität Kaiserslautern CY - Kaiserslautern ER - TY - CHAP A1 - Hartmann, Maria A1 - Alsaad, Hayder A1 - Völker, Conrad T1 - Das Potential von Fassadenbegrünungen zur Verringerung des Wärmeinseleffekts: Simulation eines Beispielquartiers T2 - Bauphysiktage Kaiserslautern 2022 N2 - Die Auswirkungen einer Fassadenbegrünung auf den Wärmeinseleffekt in Stuttgart wurde für eine Hitzeperiode numerisch simuliert und bewertet. Die Ergebnisse zeigten positive Auswirkungen innerhalb des Simulationsgebiets sowie eine geringe Fernwirkung auf benachbarte Stadtquartiere. Diese Änderungen können zur Verbesserung des thermischen Komforts im Außenraum beitragen. Eine reduzierte Temperatur der Außenoberfläche führt darüber hinaus auch zu einer geringeren Oberflächentemperatur der Wandinnenseite, welche die Innenraumtemperatur beeinflusst. Folglich kann die thermische Behaglichkeit auch im Innenraum erhöht werden. KW - Mikroklima KW - Envi-Met KW - Städtische Wärmeinsel KW - Fassadenbegrünung KW - Living-wall Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220713-46676 SN - 978-3-95974-176-7 SN - 2363-8206 CY - Kaiserslautern ER - TY - CHAP A1 - Geske, Mara A1 - Benz, Alexander A1 - Völker, Conrad ED - Kornadt, Oliver ED - Carrigan, Svenja ED - Hofmann, Markus ED - Völker, Conrad T1 - Anwendung georeferenzierter Bilddaten bei energetischen Quartiersanalysen T2 - Tagungsband Bauphysiktage Kaiserslautern 2022 N2 - Bei Analysen des Gebäudebestands im Quartierskontext werden zu Dokumentationszwecken viele Bilddaten erzeugt. Diese Daten sind im Nachhinein häufig keinen eindeutig genauen Standorten und Blickwinkeln auf das Bauwerk zuzuordnen. Insbesondere gilt dies für Ortsunkundige oder für Detailaufnahmen. Eine zusätzliche Herausforderung stellt die Aufnahme von Wärmebrücken- oder andersartigen Gebäudedetails durch Thermogramme dar. In der Praxis kommen hier oftmals analoge, fehleranfällige Lösungen zum Einsatz. Durch die Nutzung von Georeferenzierung kann diese Lücke geschlossen und eine eindeutige Kommunikation und Auswertung gewährleistet werden. Im Gegensatz zu den üblichen Kameras sind Smartphones nach Stand der Technik ausreichend ausgestattet, um neben Daten zu Standort auch die Orientierungswinkel einer Bildaufnahme zu dokumentieren. Die georefenzierten Bilder können auf Grundlage der in den sogenannten Exif-Daten mitgeschriebenen Informationen händisch in ein bestehendes Quartiersmodell integriert werden. Anhand eines universitären Musterquartiers wird die nutzerfreundliche Realisierung beispielhaft erprobt und auf ihre Potentiale zur Automatisierung in Python untersucht. Hierfür wurde ein bestehendes Quartiersmodell als geometrische Grundlage genutzt und um RGB-Bilder sowie Thermogramme erweitert. Das beschriebene Vorgehen wird im Rahmen der Anwendung auf seinen möglichen Einsatz im Rahmen einer energetischen Quartierserfassung sowie einer Bauschadensdokumentation untersucht. Mit dem vorliegenden Beitrag wird dem Nutzenden ein Werkzeug bereitgestellt, das die hochwertige Dokumentation einer Bestandserfassung, auch im Quartierskontext, ermöglicht. KW - Quartiersanalyse KW - Bilddaten KW - Bauphysik und Sanierung Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220617-46544 SN - 987-3-95974-176-7 SN - 2363-8206 PB - Eigenverlag der Technischen Universität Kaiserslautern CY - Kaiserslautern ER - TY - JOUR A1 - Alsaad, Hayder A1 - Hartmann, Maria A1 - Völker, Conrad T1 - Hygrothermal simulation data of a living wall system for decentralized greywater treatment JF - Data in Brief N2 - This dataset presents the numerical analysis of the heat and moisture transport through a facade equipped with a living wall system designated for greywater treatment. While such greening systems provide many environmental benefits, they involve pumping large quantities of water onto the wall assembly, which can increase the risk of moisture in the wall as well as impaired energetic performance due to increased thermal conductivity with increased moisture content in the building materials. This dataset was acquired through numerical simulation using the coupling of two simulation tools, namely Envi-Met and Delphin. This coupling was used to include the complex role the plants play in shaping the near-wall environmental parameters in the hygrothermal simulations. Four different wall assemblies were investigated, each assembly was assessed twice: with and without the living wall. The presented data include the input and output parameters of the simulations, which were presented in the co-submitted article [1]. KW - Kupplung KW - Feuchteleitung KW - Heat transport KW - Moisture transport KW - Living wall KW - Wärmeübertragung KW - coupling KW - ENVI-Met KW - Delphin KW - OA-Publikationsfonds2022 Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220106-45483 UR - https://www.sciencedirect.com/science/article/pii/S2352340921010167?via%3Dihub VL - 2022 IS - volume 40, article 107741 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Teitelbaum, Eric A1 - Alsaad, Hayder A1 - Aviv, Dorit A1 - Kim, Alexander A1 - Völker, Conrad A1 - Meggers, Forrest A1 - Pantelic, Jovan T1 - Addressing a systematic error correcting for free and mixed convection when measuring mean radiant temperature with globe thermometers JF - Scientific reports N2 - It is widely accepted that most people spend the majority of their lives indoors. Most individuals do not realize that while indoors, roughly half of heat exchange affecting their thermal comfort is in the form of thermal infrared radiation. We show that while researchers have been aware of its thermal comfort significance over the past century, systemic error has crept into the most common evaluation techniques, preventing adequate characterization of the radiant environment. Measuring and characterizing radiant heat transfer is a critical component of both building energy efficiency and occupant thermal comfort and productivity. Globe thermometers are typically used to measure mean radiant temperature (MRT), a commonly used metric for accounting for the radiant effects of an environment at a point in space. In this paper we extend previous field work to a controlled laboratory setting to (1) rigorously demonstrate that existing correction factors used in the American Society of Heating Ventilation and Air-conditioning Engineers (ASHRAE) Standard 55 or ISO7726 for using globe thermometers to quantify MRT are not sufficient; (2) develop a correction to improve the use of globe thermometers to address problems in the current standards; and (3) show that mean radiant temperature measured with ping-pong ball-sized globe thermometers is not reliable due to a stochastic convective bias. We also provide an analysis of the maximum precision of globe sensors themselves, a piece missing from the domain in contemporary literature. KW - Strahlungstemperatur KW - Mean radiant temperature KW - Globe thermometers KW - Indoor environment KW - Thermal comfort KW - Measurements KW - OA-Publikationsfonds2022 Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220509-46363 UR - https://www.nature.com/articles/s41598-022-10172-5#citeas VL - 2022 IS - Volume 12, article 6473 PB - Springer Nature CY - London ER - TY - JOUR A1 - Alsaad, Hayder A1 - Hartmann, Maria A1 - Hilbel, Rebecca A1 - Völker, Conrad T1 - ENVI-met validation data accompanied with simulation data of the impact of facade greening on the urban microclimate JF - Data in Brief N2 - This dataset consists mainly of two subsets. The first subset includes measurements and simulation data conducted to validate the simulation tool ENVI-met. The measurements were conducted at the campus of the Bauhaus-University Weimar in Weimar, Germany and consisted of recording exterior air temperature, globe temperature, relative humidity, and wind velocity at 1.5 m at four points on four different days. After the measurements, the geometry of the campus was modelled and meshed; the simulations were conducted using the weather data of the measurements days with the aim of investigating the accuracy of the model. The second data subset consists of ENVI-met simulation data of the potential of facade greening in improving the outdoor environment and the indoor air temperature during heatwaves in Central European cities. The data consist of the boundary conditions and the simulation output of two simulation models: with and without facade greening. The geometry of the models corresponded to a residential buildings district in Stuttgart, Germany. The simulation output consisted of exterior air temperature, mean radiant temperature, relative humidity, and wind velocity at 12 different probe points in the model in addition to the indoor air temperature of an exemplary building. The dataset presents both vertical profiles of the probed parameters as well as the time series output of the five-day simulation duration. Both data subsets correspond to the investigations presented in the co-submitted article [1]. KW - Messung KW - Measurements KW - Simulations KW - ENVI-met KW - Living wall KW - Green facade KW - Simulation KW - OA-Publikationsfonds2022 Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220511-46455 UR - https://www.sciencedirect.com/science/article/pii/S2352340922004048#! VL - 2022 IS - Volume 42, article 108200 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Alsaad, Hayder A1 - Völker, Conrad T1 - Qualitative evaluation of the flow supplied by personalized ventilation using schlieren imaging and thermography JF - Building and Environment N2 - Personalized ventilation (PV) is a mean of delivering conditioned outdoor air into the breathing zone of the occupants. This study aims to qualitatively investigate the personalized flows using two methods of visualization: (1) schlieren imaging using a large schlieren mirror and (2) thermography using an infrared camera. While the schlieren imaging was used to render the velocity and mass transport of the supplied flow, thermography was implemented to visualize the air temperature distribution induced by the PV. Both studies were conducted using a thermal manikin to simulate an occupant facing a PV outlet. As a reference, the flow supplied by an axial fan and a cased axial fan was visualized with the schlieren system as well and compared to the flow supplied by PV. Schlieren visualization results indicate that the steady, low-turbulence flow supplied by PV was able to penetrate the thermal convective boundary layer encasing the manikin's body, providing clean air for inhalation. Contrarily, the axial fan diffused the supplied air over a large target area with high turbulence intensity; it only disturbed the convective boundary layer rather than destroying it. The cased fan supplied a flow with a reduced target area which allowed supplying more air into the breathing zone compared to the fan. The results of thermography visualization showed that the supplied cool air from PV penetrated the corona-shaped thermal boundary layer. Furthermore, the supplied air cooled the surface temperature of the face, which indicates the large impact of PV on local thermal sensation and comfort. KW - Bildverarbeitung KW - Photothermische Methode KW - Visualisierung KW - Belüftung KW - Lüftungsanlage KW - Schlieren imaging KW - Thermography KW - Visualization KW - Personalized ventilation KW - Axial fan Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20211008-45117 UR - https://www.sciencedirect.com/science/article/abs/pii/S0360132319306602?via%3Dihub N1 - This is the accepted manuscript of the article published by Elsevier in Building and Environment 167 (2020) 106450, which can be found at https://doi.org/10.1016/j.buildenv.2019.106450. VL - 2020 IS - Volume 167, article 106450 PB - Elsevier CY - New York ER - TY - CHAP A1 - Alsaad, Hayder A1 - Völker, Conrad T1 - Measuring and visualizing the flow supplied by personalized ventilation T2 - Proceedings Book Roomvent 2020 N2 - This study investigates the flow supplied by personalized ventilation (PV) by means of anemometer measurements and schlieren visualization. The study was conducted using a thermal manikin to simulate a seated occupant facing a PV outlet. Air velocity was measured at multiple points in the flow field; the collected velocity values were used to calculate the turbulence intensity. Results indicated that PV was supplying air with low turbulence intensity that was able to penetrate the convective boundary layer of the manikin to supply clean air for inhalation. The convective boundary layer, however, obstructed the supplied flow and reduced its velocity by a total of 0.26 m/s. The PV flow preserved its value until about 10 cm from the face where velocity started to drop. Further investigations were conducted to test a PV diffuser with a relatively large outlet diameter (18 cm). This diffuser was developed using 3d-modelling and 3d-printing. The diffuser successfully distributed the flow over the larger outlet area. However, the supplied velocity and turbulence fields were not uniform across the section. KW - Belüftung KW - Luftqualität KW - Personalized ventilation KW - Schlieren imaging KW - Air quality KW - Thermal manikin Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220622-46573 CY - Turin, Italy ER - TY - JOUR A1 - Becher, Lia A1 - Gena, Amayu Wakoya A1 - Alsaad, Hayder A1 - Richter, Bernhard A1 - Spahn, Claudia A1 - Völker, Conrad T1 - The spread of breathing air from wind instruments and singers using schlieren techniques JF - Indoor Air N2 - The spread of breathing air when playing wind instruments and singing was investigated and visualized using two methods: (1) schlieren imaging with a schlieren mirror and (2) background-oriented schlieren (BOS). These methods visualize airflow by visualizing density gradients in transparent media. The playing of professional woodwind and brass instrument players, as well as professional classical trained singers were investigated to estimate the spread distances of the breathing air. For a better comparison and consistent measurement series, a single high note, a single low note, and an extract of a musical piece were investigated. Additionally, anemometry was used to determine the velocity of the spreading breathing air and the extent to which it was quantifiable. The results showed that the ejected airflow from the examined instruments and singers did not exceed a spreading range of 1.2 m into the room. However, differences in the various instruments have to be considered to assess properly the spread of the breathing air. The findings discussed below help to estimate the risk of cross-infection for wind instrument players and singers and to develop efficacious safety precautions, which is essential during critical health periods such as the current COVID-19 pandemic. KW - Covid-19 KW - Pandemie KW - Blasinstrument KW - Gesang KW - Schlierenmethode KW - airborne infection KW - background-oriented schlieren KW - schlieren imaging Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220209-45817 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12869 VL - 2021 IS - volume 31, issue 6 SP - 1798 EP - 1814 PB - Wiley Blackwell CY - Oxford ER - TY - JOUR A1 - Dokhanchi, Najmeh Sadat A1 - Arnold, Jörg A1 - Vogel, Albert A1 - Völker, Conrad T1 - Measurement of indoor air temperature distribution using acoustic travel-time tomography: Optimization of transducers location and sound-ray coverage of the room JF - Measurement N2 - Acoustic travel-time TOMography (ATOM) allows the measurement and reconstruction of air temperature distributions. Due to limiting factors, such as the challenge of travel-time estimation of the early reflections in the room impulse response, which heavily depends on the position of transducers inside the measurement area, ATOM is applied mainly outdoors. To apply ATOM in buildings, this paper presents a numerical solution to optimize the positions of transducers. This optimization avoids reflection overlaps, leading to distinguishable travel-times in the impulse response reflectogram. To increase the accuracy of the measured temperature within tomographic voxels, an additional function is employed to the proposed numerical method to minimize the number of sound-path-free voxels, ensuring the best sound-ray coverage of the room. Subsequently, an experimental set-up has been performed to verify the proposed numerical method. The results indicate the positive impact of the optimal positions of transducers on the distribution of ATOM-temperatures. KW - Bauphysik KW - Bauklimatik KW - Akustische Laufzeit-Tomographie Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220524-46473 UR - https://www.sciencedirect.com/science/article/abs/pii/S0263224120304723?via%3Dihub VL - 2020 IS - Volume 164, article 107934 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Becher, Lia A1 - Völker, Conrad A1 - Rodehorst, Volker A1 - Kuhne, Michael T1 - Background-oriented schlieren technique for two-dimensional visualization of convective indoor air flows JF - Optics and Lasers in Engineering N2 - This article focuses on further developments of the background-oriented schlieren (BOS) technique to visualize convective indoor air flow, which is usually defined by very small density gradients. Since the light rays deflect when passing through fluids with different densities, BOS can detect the resulting refractive index gradients as integration along a line of sight. In this paper, the BOS technique is used to yield a two-dimensional visualization of small density gradients. The novelty of the described method is the implementation of a highly sensitive BOS setup to visualize the ascending thermal plume from a heated thermal manikin with temperature differences of minimum 1 K. To guarantee steady boundary conditions, the thermal manikin was seated in a climate laboratory. For the experimental investigations, a high-resolution DLSR camera was used capturing a large field of view with sufficient detail accuracy. Several parameters such as various backgrounds, focal lengths, room air temperatures, and distances between the object of investigation, camera, and structured background were tested to find the most suitable parameters to visualize convective indoor air flow. Besides these measurements, this paper presents the analyzing method using cross-correlation algorithms and finally the results of visualizing the convective indoor air flow with BOS. The highly sensitive BOS setup presented in this article complements the commonly used invasive methods that highly influence weak air flows. KW - Raumklima KW - Raumluftströmungen KW - Flow visualization KW - Convective indoor air flow KW - Background-oriented schlieren KW - Human thermal plume KW - Cross-correlation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220810-46972 N1 - This article is published by Elsevier in Optics and Lasers in Engineering 134 (2020) 106282 and may be found at https://doi.org/10.1016/j.optlaseng.2020.106282 Copyright © 2020 Elsevier Ltd. All rights reserved. This article may be downloaded for personal use only. Any other use requires prior permission of the authors and Elsevier Ltd. VL - 2020 IS - Volume 134, article 106282 ER - TY - JOUR A1 - Alsaad, Hayder A1 - Völker, Conrad T1 - Der Kühlungseffekt der personalisierten Lüftung T1 - The cooling effect of personalized ventilation systems JF - Bauphysik N2 - Personalisierte Lüftung (PL) kann die thermische Behaglichkeit sowie die Qualität der eingeatmeten Atemluft verbessern, in dem jedem Arbeitsplatz Frischluft separat zugeführt wird. In diesem Beitrag wird die Wirkung der PL auf die thermische Behaglichkeit der Nutzer unter sommerlichen Randbedingungen untersucht. Hierfür wurden zwei Ansätze zur Bewertung des Kühlungseffekts der PL untersucht: basierend auf (1) der äquivalenten Temperatur und (2) dem thermischen Empfinden. Grundlage der Auswertung sind in einer Klimakammer gemessene sowie numerisch simulierte Daten. Vor der Durchführung der Simulationen wurde das numerische Modell zunächst anhand der gemessenen Daten validiert. Die Ergebnisse zeigen, dass der Ansatz basierend auf dem thermischen Empfinden zur Evaluierung des Kühlungseffekts der PL sinnvoller sein kann, da bei diesem die komplexen physiologischen Faktoren besser berücksichtigt werden. N2 - Personalized ventilation (PV) can improve thermal comfort and inhaled air quality by supplying air to each workstation separately. This study investigates the impact of PV on the thermal state of the users under summer boundary conditions. Two approaches to evaluating the cooling effect of PV were investigated, based on equivalent temperature and based on thermal sensation. Both approaches implemented measured and simulated values of the cooling effect of PV. Before conducting the simulations, the numerical model was first validated against measured data collected in a climate chamber equipped with a thermal manikin. Results indicated that the thermal sensation approach can be more suitable for evaluating the cooling effect of PV due to the complex physiological factors it considers. KW - Lüftung KW - Strömung KW - Raumklima KW - Temperatur KW - personalized ventilation KW - computational fluid dynamics KW - Simulation KW - personalisierte Lüftung KW - äquivalente Temperatur KW - thermisches Empfinden Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20201020-42723 UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/bapi.202000018 N1 - © 2020 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Dieser Artikel kann für den persönlichen Gebrauch heruntergeladen werden. Andere Verwendungen bedürfen der vorherigen Zustimmung der Autoren und des Verlags Ernst & Sohn. Der folgende Artikel erschien in der Bauphysik 42 (2020), Heft 5, 218-225, DOI: 10.1002/bapi.202000018 VL - 2020 IS - volume 42, issue 5 SP - 218 EP - 225 PB - Ernst & Sohn bei John Wiley & Sons CY - Hoboken ER - TY - JOUR A1 - Alsaad, Hayder A1 - Völker, Conrad T1 - Performance evaluation of ductless personalized ventilation in comparison with desk fans using numerical simulations JF - Indoor Air N2 - The performance of ductless personalized ventilation (DPV) was compared to the performance of a typical desk fan since they are both stand-alone systems that allow the users to personalize their indoor environment. The two systems were evaluated using a validated computational fluid dynamics (CFD) model of an office room occupied by two users. To investigate the impact of DPV and the fan on the inhaled air quality, two types of contamination sources were modelled in the domain: an active source and a passive source. Additionally, the influence of the compared systems on thermal comfort was assessed using the coupling of CFD with the comfort model developed by the University of California, Berkeley (UCB model). Results indicated that DPV performed generally better than the desk fan. It provided better thermal comfort and showed a superior performance in removing the exhaled contaminants. However, the desk fan performed better in removing the contaminants emitted from a passive source near the floor level. This indicates that the performance of DPV and desk fans depends highly on the location of the contamination source. Moreover, the simulations showed that both systems increased the spread of exhaled contamination when used by the source occupant. KW - Behaglichkeit KW - Raumklima KW - Strömungsmechanik KW - Fluid KW - computational fluid dynamics KW - desk fan KW - ductless personalized ventilation KW - IAQ KW - thermal comfort Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200422-41407 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12672 VL - 2020 PB - John Wiley & Sons Ltd ER - TY - JOUR A1 - Alsaad, Hayder A1 - Völker, Conrad T1 - Could the ductless personalized ventilation be an alternative to the regular ducted personalized ventilation? JF - Indoor Air N2 - This study investigates the performance of two systems: personalized ventilation (PV) and ductless personalized ventilation (DPV). Even though the literature indicates a compelling performance of PV, it is not often used in practice due to its impracticality. Therefore, the present study assesses the possibility of replacing the inflexible PV with DPV in office rooms equipped with displacement ventilation (DV) in the summer season. Numerical simulations were utilized to evaluate the inhaled concentration of pollutants when PV and DPV are used. The systems were compared in a simulated office with two occupants: a susceptible occupant and a source occupant. Three types of pollution were simulated: exhaled infectious air, dermally emitted contamination, and room contamination from a passive source. Results indicated that PV improved the inhaled air quality regardless of the location of the pollution source; a higher PV supply flow rate positively impacted the inhaled air quality. Contrarily, the performance of DPV was highly sensitive to the source location and the personalized flow rate. A higher DPV flow rate tends to decrease the inhaled air quality due to increased mixing of pollutants in the room. Moreover, both systems achieved better results when the personalized system of the source occupant was switched off. KW - Strömungsmechanik KW - Kontamination KW - Belüftung KW - Luftqualität KW - computational fluid dynamics KW - cross-contamination KW - ductless personalized ventilation KW - indoor air quality KW - tracer gas Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200805-42072 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12720 VL - 2020 PB - John Wiley & Sons Ltd ER - TY - JOUR A1 - Gena, Amayu Wakoya A1 - Völker, Conrad A1 - Settles, Gary T1 - Qualitative and quantitative schlieren optical measurement of the human thermal plume JF - Indoor Air N2 - A new large‐field, high‐sensitivity, single‐mirror coincident schlieren optical instrument has been installed at the Bauhaus‐Universität Weimar for the purpose of indoor air research. Its performance is assessed by the non‐intrusive measurement of the thermal plume of a heated manikin. The schlieren system produces excellent qualitative images of the manikin's thermal plume and also quantitative data, especially schlieren velocimetry of the plume's velocity field that is derived from the digital cross‐correlation analysis of a large time sequence of schlieren images. The quantitative results are compared with thermistor and hot‐wire anemometer data obtained at discrete points in the plume. Good agreement is obtained, once the differences between path‐averaged schlieren data and planar anemometry data are reconciled. KW - Raumklima KW - Behaglichkeit KW - Digital image correlation KW - human thermal plume KW - schlieren imaging KW - schlieren velocimetry KW - thermal comfort KW - Schlierenspiegel Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200709-41936 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12674 VL - 2020 IS - volume 30, issue 4 SP - 757 EP - 766 PB - John Wiley & Sons ER - TY - INPR A1 - Vogel, Albert A1 - Völker, Conrad A1 - Bode, Matthias A1 - Marx, Steffen T1 - Messung und Simulation der Erwärmung von ermüdungsbeanspruchten Betonprobekörpern T2 - Bauphysik N2 - Im vorliegenden Beitrag werden Messungen und Berechnungen vorgestellt, die die Temperaturentwicklung in Betonzylindern aufgrund zyklischer Beanspruchung genau beschreiben. Die Messungen wurden in einem Versuchsstand, die Berechnungen im FEM-Programm ANSYS durchgeführt. Mit Hilfe der Temperaturmessungen konnten die Simulationen für die Temperaturentwicklung der Betonzylinder mit der verwendeten Betonrezeptur validiert werden. Die Untersuchungen lassen den Schluss zu, dass bei zyklischer Probekörperbelastung und der einhergehenden Probekörperdehnung Energie dissipiert wird und diese maßgeblich für die Erwärmung der Probe verantwortlich ist. N2 - This paper presents measurements and simulations that describe the temperature development in concrete cylinders due to cyclic loading. The measurements were carried out in a test stand, the simulations in the FEM program ANSYS. The simulations of the temperature development in the concrete cylinders with the used concrete recipe were validated using the temperature measurements. The investigations lead to the conclusion that energy is dissipated during cyclic test specimen loading and the accompanying test specimen elongation and that this is mainly responsible for the heating of the specimen. KW - zyklische Beanspruchung KW - Ermüdung KW - Dissipation KW - zyklische Beanspruchung KW - Ermüdung KW - Dissipation KW - cyclic load KW - fatigue Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200425-41471 UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/bapi.201900031 N1 - This is the pre-peer reviewed version of the following article: hhttps://onlinelibrary.wiley.com/doi/abs/10.1002/bapi.201900031, which has been published in final form at https://doi.org/10.1002/bapi.201900031. VL - 2020 IS - Volume 42, Issue 2 SP - 86 EP - 93 PB - John Wiley and Sons ER - TY - INPR A1 - Vogel, Albert A1 - Benz, Alexander A1 - Völker, Conrad T1 - Untersuchung des Wärmeübergangs von zyklisch beanspruchten Betonzylindern N2 - Wiederkehrende Belastungen, wie sie beispielsweise an Brücken oder Windenergieanlagen auftreten, können innerhalb der Nutzungsdauer solcher Bauwerke bis zu 1.000.000.000 Lastwechsel erreichen. Um das dadurch eintretende Ermüdungsverhalten von Beton zu untersuchen, werden diese zyklischen Beanspruchungen in mechanischen Versuchen mit Prüfzylindern nachgestellt. Damit Versuche mit solch hohen Lastwechselzahlen in akzeptablen Zeitdauern durchgeführt werden können, wird die Belastungsfrequenz erhöht. Als Folge dieser erhöhten Belas-tungsfrequenz erwärmen sich allerdings die Betonprobekörper, was zu einem früheren, unrealistischen Versagenszeitpunkt führen kann, weshalb die Erwärmung begrenzt werden muss. Um die Wärmefreisetzung in der Probe zu untersuchen, wurden Versuche und Simulationen durchgeführt. Im Beitrag wird die analytische und messtechnische Analyse des Wärmeübergangs an erwärmten Betonzylindern vorgestellt. Resultierend daraus wird eine Möglichkeit zur Reduktion der Erwärmung an zyklisch beanspruchten Betonzylindern vorgestellt. N2 - Periodic load cycles, such as those that occur on bridges or wind turbines, are of great importance for dynamic long-term considerations of concrete. Within the life span of such structures, up to 1,000,000,000 load changes can be expected. To determine the fatigue strength, the resistance to periodic loads can be determined in a short time in laboratory tests by increasing the load frequency. As a result of this increased load frequency, however, the concrete test specimens heat up, which can lead to an earlier, unrealistic time of failure, which is why the heating must be limited. Therefore, tests and simulations were carried out to investigate the heat release in the sample. In this article, the analytical analysis and measurements of the heat release of heated concrete cylinders are presented. As a conclusion, a possibility of reducing the temperature of dynamically stressed concrete cylinders is introduced. KW - Zyklische Beanspruchung KW - Wärmeübergang KW - Wärmeübergangskoeffizient KW - Dissipation KW - Wärmeübergangskoeffizient an Zylinder KW - heat transfer coefficient for cylinders KW - cyclic load Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200619-41813 N1 - This is the pre-peer reviewed version of the following article: https://onlinelibrary.wiley.com/doi/abs/10.1002/bapi.202000004, which has been published in final form at https://doi.org/10.1002/bapi.202000004 VL - 2020 IS - Volume 42, Issue 3 SP - 131 EP - 138 PB - John Wiley and Sons ER - TY - CHAP A1 - Dokhanchi, Najmeh Sadat A1 - Arnold, Jörg A1 - Vogel, Albert A1 - Völker, Conrad T1 - Acoustic Travel-Time Tomography: Optimal Positioning of Transceiver and Maximal Sound-Ray Coverage of the Room T2 - Fortschritte der Akustik - DAGA 2019 N2 - Acoustic travel-time tomography (ATOM) determines the distribution of the temperature in a propagation medium by measuring the travel-time of acoustic signals between transmitters and receivers. To employ ATOM for indoor climate measurements, the impulse responses have been measured in the climate chamber lab of the Bauhaus-University Weimar and compared with the theoretical results of its image source model (ISM). A challenging task is distinguishing the reflections of interest in the reflectogram when the sound rays have similar travel-times. This paper presents a numerical method to address this problem by finding optimal positions of transmitter and receiver, since they have a direct impact on the distribution of travel times. These optimal positions have the minimum number of simultaneous arrival time within a threshold level. Moreover, for the tomographic reconstruction, when some of the voxels remain empty of sound-rays, it leads to inaccurate determination of the air temperature within those voxels. Based on the presented numerical method, the number of empty tomographic voxels are minimized to ensure the best sound-ray coverage of the room. Subsequently, a spatial temperature distribution is estimated by simultaneous iterative reconstruction technique (SIRT). The experimental set-up in the climate chamber verifies the simulation results. KW - Bauphysik KW - Acoustic Travel-Time Tomography KW - Bauklimatik KW - Akustische Tomographie Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20190408-38778 UR - https://www.dega-akustik.de/publikationen/online-proceedings/ N1 - This conference paper has been submitted to the DAGA 2019. Thus, the original paper first is published in the "Fortschritte der Akustik - DAGA 2019" ER - TY - INPR A1 - Bode, Matthias A1 - Marx, Steffen A1 - Vogel, Albert A1 - Völker, Conrad T1 - Dissipationsenergie bei Ermüdungsversuchen an Betonprobekörpern N2 - Aufgrund des visko-elastoplastischen Materialverhaltens von Beton wird Probekörpern und Bauteilen infolge zyklischer Beanspruchungen Energie zugeführt. Die entsprechenden Energiegrößen werden durch Hystereseflächen der Spannungs-Dehnungslinien beschrieben. In der Literatur finden sich dabei unterschiedliche Ansätze, wofür diese Energie verwendet wird. Erste Untersuchungen zeigen, dass zumindest ein Teil dieser dissipierten Energie in thermische Energie umgewandelt wird. Mithilfe der in diesem Beitrag beschriebenen Methodik lassen sich diese Energiegrößen für jeden Lastwechsel eines Ermüdungsversuches schnell und zuverlässig bestimmen. Anschließend wurden mit dem implementierten Algorithmus die dissipierten Energien von insgesamt 27 zyklischen Versuchen ausgewertet. Analog zu der Dehnungsentwicklung und der Steifigkeitsdegradation weisen auch die Verläufe der dissipierten Energie über die Lastwechselzahl einen dreiphasigen Verlauf auf. Die Auswertung zeigt außerdem eine Korrelation zwischen der Bruchlastwechselzahl und der dissipierten Energie. Auch der Zusammenhang zwischen Probekörpererwärmung und dissipierter Energie konnte bestätigt werden. KW - Ermüdung KW - Beton KW - Dissipationsenergie KW - Probekörpererwärmung Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20211012-44938 UR - https://onlinelibrary.wiley.com/doi/10.1002/best.201900004 N1 - This is the pre-peer reviewed version of the following article: https://onlinelibrary.wiley.com/doi/10.1002/best.201900004, which has been published in final form at https://doi.org/10.1002/best.201900004 VL - 2019 ER -