@article{BecherGenaAlsaadetal., author = {Becher, Lia and Gena, Amayu Wakoya and Alsaad, Hayder and Richter, Bernhard and Spahn, Claudia and V{\"o}lker, Conrad}, title = {The spread of breathing air from wind instruments and singers using schlieren techniques}, series = {Indoor Air}, volume = {2021}, journal = {Indoor Air}, number = {volume 31, issue 6}, publisher = {Wiley Blackwell}, address = {Oxford}, doi = {10.1111/ina.12869}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220209-45817}, pages = {1798 -- 1814}, abstract = {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.}, subject = {Covid-19}, language = {en} } @article{DokhanchiArnoldVogeletal.2020, author = {Dokhanchi, Najmeh Sadat and Arnold, J{\"o}rg and Vogel, Albert and V{\"o}lker, Conrad}, title = {Measurement of indoor air temperature distribution using acoustic travel-time tomography: Optimization of transducers location and sound-ray coverage of the room}, series = {Measurement}, volume = {2020}, journal = {Measurement}, number = {Volume 164, article 107934}, publisher = {Elsevier}, address = {Amsterdam}, doi = {10.1016/j.measurement.2020.107934}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220524-46473}, year = {2020}, abstract = {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.}, subject = {Bauphysik}, language = {en} } @article{BecherVoelkerRodehorstetal., author = {Becher, Lia and V{\"o}lker, Conrad and Rodehorst, Volker and Kuhne, Michael}, title = {Background-oriented schlieren technique for two-dimensional visualization of convective indoor air flows}, series = {Optics and Lasers in Engineering}, volume = {2020}, journal = {Optics and Lasers in Engineering}, number = {Volume 134, article 106282}, doi = {https://doi.org/10.1016/j.optlaseng.2020.106282}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220810-46972}, pages = {9}, abstract = {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.}, subject = {Raumklima}, language = {en} } @article{AlsaadVoelker, author = {Alsaad, Hayder and V{\"o}lker, Conrad}, title = {Der K{\"u}hlungseffekt der personalisierten L{\"u}ftung}, series = {Bauphysik}, volume = {2020}, journal = {Bauphysik}, number = {volume 42, issue 5}, publisher = {Ernst \& Sohn bei John Wiley \& Sons}, address = {Hoboken}, doi = {10.25643/bauhaus-universitaet.4272}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20201020-42723}, pages = {218 -- 225}, abstract = {Personalisierte L{\"u}ftung (PL) kann die thermische Behaglichkeit sowie die Qualit{\"a}t der eingeatmeten Atemluft verbessern, in dem jedem Arbeitsplatz Frischluft separat zugef{\"u}hrt wird. In diesem Beitrag wird die Wirkung der PL auf die thermische Behaglichkeit der Nutzer unter sommerlichen Randbedingungen untersucht. Hierf{\"u}r wurden zwei Ans{\"a}tze zur Bewertung des K{\"u}hlungseffekts der PL untersucht: basierend auf (1) der {\"a}quivalenten Temperatur und (2) dem thermischen Empfinden. Grundlage der Auswertung sind in einer Klimakammer gemessene sowie numerisch simulierte Daten. Vor der Durchf{\"u}hrung der Simulationen wurde das numerische Modell zun{\"a}chst anhand der gemessenen Daten validiert. Die Ergebnisse zeigen, dass der Ansatz basierend auf dem thermischen Empfinden zur Evaluierung des K{\"u}hlungseffekts der PL sinnvoller sein kann, da bei diesem die komplexen physiologischen Faktoren besser ber{\"u}cksichtigt werden.}, subject = {L{\"u}ftung}, language = {de} } @article{AlsaadVoelker, author = {Alsaad, Hayder and V{\"o}lker, Conrad}, title = {Performance evaluation of ductless personalized ventilation in comparison with desk fans using numerical simulations}, series = {Indoor Air}, volume = {2020}, journal = {Indoor Air}, publisher = {John Wiley \& Sons Ltd}, doi = {10.1111/ina.12672}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200422-41407}, pages = {14}, abstract = {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.}, subject = {Behaglichkeit}, language = {en} } @article{AlsaadVoelker, author = {Alsaad, Hayder and V{\"o}lker, Conrad}, title = {Could the ductless personalized ventilation be an alternative to the regular ducted personalized ventilation?}, series = {Indoor Air}, volume = {2020}, journal = {Indoor Air}, publisher = {John Wiley \& Sons Ltd}, doi = {10.1111/ina.12720}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200805-42072}, pages = {13}, abstract = {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.}, subject = {Str{\"o}mungsmechanik}, language = {en} } @article{PollackLueckWolfetal., author = {Pollack, Moritz and L{\"u}ck, Andrea and Wolf, Mario and Kraft, Eckhard and V{\"o}lker, Conrad}, title = {Energy and Business Synergy: Leveraging Biogenic Resources from Agriculture, Waste, and Wastewater in German Rural Areas}, series = {Sustainability}, volume = {2023}, journal = {Sustainability}, number = {volume 15, issue 24, article 16573}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/su152416573}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20231222-65172}, pages = {1 -- 25}, abstract = {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.}, subject = {Energiewende}, language = {en} } @article{GenaVoelkerSettles, author = {Gena, Amayu Wakoya and V{\"o}lker, Conrad and Settles, Gary}, title = {Qualitative and quantitative schlieren optical measurement of the human thermal plume}, series = {Indoor Air}, volume = {2020}, journal = {Indoor Air}, number = {volume 30, issue 4}, publisher = {John Wiley \& Sons}, doi = {10.1111/ina.12674}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200709-41936}, pages = {757 -- 766}, abstract = {A new large-field, high-sensitivity, single-mirror coincident schlieren optical instrument has been installed at the Bauhaus-Universit{\"a}t 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.}, subject = {Raumklima}, language = {en} } @article{BenzTarabenLichtenheldetal., author = {Benz, Alexander and Taraben, Jakob and Lichtenheld, Thomas and Morgenthal, Guido and V{\"o}lker, Conrad}, title = {Thermisch-energetische Geb{\"a}udesimulation auf Basis eines Bauwerksinformationsmodells}, series = {Bauphysik}, journal = {Bauphysik}, number = {40, Heft 2}, doi = {10.25643/bauhaus-universitaet.3819}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181102-38190}, pages = {61 -- 67}, abstract = {F{\"u}r eine Absch{\"a}tzung des Heizw{\"a}rmebedarfs von Geb{\"a}uden und Quartieren k{\"o}nnen thermisch-energetische Simulationen eingesetzt werden. Grundlage dieser Simulationen sind geometrische und physikalische Geb{\"a}udemodelle. Die Erstellung des geometrischen Modells erfolgt in der Regel auf Basis von Baupl{\"a}nen oder Vor-Ort-Begehungen, was mit einem großen Recherche- und Modellierungsaufwand verbunden ist. Sp{\"a}tere bauliche Ver{\"a}nderungen des Geb{\"a}udes m{\"u}ssen h{\"a}ufig manuell in das Modell eingearbeitet werden, was den Arbeitsaufwand zus{\"a}tzlich erh{\"o}ht. Das physikalische Modell stellt die Menge an Parametern und Randbedingungen dar, welche durch Materialeigenschaften, Lage und Umgebungs-einfl{\"u}sse gegeben sind. Die Verkn{\"u}pfung beider Modelle wird innerhalb der entsprechenden Simulations-software realisiert und ist meist nicht in andere Softwareprodukte {\"u}berf{\"u}hrbar. Mithilfe des Building Information Modeling (BIM) k{\"o}nnen Simulationsdaten sowohl konsistent gespeichert als auch {\"u}ber Schnittstellen mit entsprechenden Anwendungen ausgetauscht werden. Hierf{\"u}r wird eine Methode vorgestellt, die thermisch-energetische Simulationen auf Basis des standardisierten {\"U}bergabe-formats Industry Foundation Classes (IFC) inklusive anschließender Auswertungen erm{\"o}glicht. Dabei werden geometrische und physikalische Parameter direkt aus einem {\"u}ber den gesamten Lebenszyklus aktuellen Geb{\"a}udemodell extrahiert und an die Simulation {\"u}bergeben. Dies beschleunigt den Simulations-prozess hinsichtlich der Geb{\"a}udemodellierung und nach sp{\"a}teren baulichen Ver{\"a}nderungen. Die erarbeite-te Methode beruht hierbei auf einfachen Modellierungskonventionen bei der Erstellung des Bauwerksinformationsmodells und stellt eine vollst{\"a}ndige {\"U}bertragbarkeit der Eingangs- und Ausgangswerte sicher. Thermal building simulation based on BIM-models. Thermal energetic simulations are used for the estimation of the heating demand of buildings and districts. These simulations are based on building models containing geometrical and physical information. The creation of geometrical models is usually based on existing construction plans or in situ assessments which demand a comparatively big effort of investigation and modeling. Alterations, which are later applied to the structure, request manual changes of the related model, which increases the effort additionally. The physical model represents the total amount of parameters and boundary conditions that are influenced by material properties, location and environmental influences on the building. The link between both models is realized within the correspondent simulation soft-ware and is usually not transferable to other software products. By Applying Building Information Modeling (BIM) simulation data is stored consistently and an exchange to other software is enabled. Therefore, a method which allows a thermal energetic simulation based on the exchange format Industry Foundation Classes (IFC) including an evaluation is presented. All geometrical and physical information are extracted directly from the building model that is kept up-to-date during its life cycle and transferred to the simulation. This accelerates the simulation process regarding the geometrical modeling and adjustments after later changes of the building. The developed method is based on simple conventions for the creation of the building model and ensures a complete transfer of all simulation data.}, subject = {Geb{\"a}udeh{\"u}lle}, language = {de} }