@article{VoelkerMaempelKornadt, author = {V{\"o}lker, Conrad and M{\"a}mpel, Silvio and Kornadt, Oliver}, title = {Measuring the human body's micro-climate using a thermal manikin}, series = {Indoor Air}, journal = {Indoor Air}, number = {24, 6}, doi = {10.25643/bauhaus-universitaet.3815}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181025-38153}, pages = {567 -- 579}, abstract = {The human body is surrounded by a micro-climate which results from its convective release of heat. In this study, the air temperature and flow velocity of this micro-climate were measured in a climate chamber at various room temperatures, using a thermal manikin simulating the heat release of the human being. Different techniques (Particle Streak Tracking, thermography, anemometry, and thermistors) were used for measurement and visualization. The manikin surface temperature was adjusted to the particular indoor climate based on simulations with a thermoregulation model (UCBerkeley Thermal Comfort Model). We found that generally, the micro-climate is thinner at the lower part of the torso, but expands going up. At the head, there is a relatively thick thermal layer, which results in an ascending plume above the head. However, the micro-climate shape strongly depends not only on the body segment, but also on boundary conditions: the higher the temperature difference between the surface temperature of the manikin and the air temperature, the faster the air flow in the micro-climate. Finally, convective heat transfer coefficients strongly increase with falling room temperature, while radiative heat transfer coefficients decrease. The type of body segment strongly influences the convective heat transfer coefficient, while only minimally influencing the radiative heat transfer coefficient.}, subject = {Raumklima}, language = {en} } @article{VoelkerKornadtOstry, author = {V{\"o}lker, Conrad and Kornadt, Oliver and Ostry, Milan}, title = {Temperature reduction due to the application of phase change materials}, series = {Energy and Buildings}, journal = {Energy and Buildings}, number = {40, 5}, doi = {10.25643/bauhaus-universitaet.3816}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181025-38166}, pages = {937 -- 944}, abstract = {Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model.}, subject = {Raumklima}, language = {en} } @article{VoelkerBeckmannKoehlmannetal., author = {V{\"o}lker, Conrad and Beckmann, Julia and Koehlmann, Sandra and Kornadt, Oliver}, title = {Occupant requirements in residential buildings - an empirical study and a theoretical model}, series = {Advances in Building Energy Research}, journal = {Advances in Building Energy Research}, number = {7 (1)}, doi = {10.25643/bauhaus-universitaet.3813}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181015-38137}, pages = {35 -- 50}, abstract = {Occupant needs with regard to residential buildings are not well known due to a lack of representative scientific studies. To improve the lack of data, a large scale study was carried out using a Post Occupancy Evaluation of 1,416 building occupants. Several criteria describing the needs of occupants were evaluated with regard to their subjective level of relevance. Additionally, we investigated the degree to which deficiencies subjectively exist, and the degree to which occupants were able to accept them. From the data obtained, a hierarchy of criteria was created. It was found that building occupants ranked the physiological needs of air quality and thermal comfort the highest. Health hazards such as mould and contaminated building materials were unacceptable for occupants, while other deficiencies were more likely to be tolerated. Occupant satisfaction was also investigated. We found that most occupants can be classified as satisfied, although some differences do exist between different populations. To explain the relationship between the constructs of what we call relevance, acceptance, deficiency and satisfaction, we then created an explanatory model. Using correlation and regression analysis, the validity of the model was then confirmed by applying the collected data. The results of the study are both relevant in shaping further research and in providing guidance on how to maximize tenant satisfaction in real estate management.}, subject = {Post Occupancy Evaluation}, language = {en} } @article{VoelkerAlsaad, author = {V{\"o}lker, Conrad and Alsaad, Hayder}, title = {Simulating the human body's microclimate using automatic coupling of CFD and an advanced thermoregulation model}, series = {Indoor Air}, volume = {2018}, journal = {Indoor Air}, number = {28, Heft 3}, doi = {10.25643/bauhaus-universitaet.3851}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20190218-38517}, pages = {415 -- 425}, abstract = {This study aims to develop an approach to couple a computational fluid dynamics (CFD) solver to the University of California, Berkeley (UCB) thermal comfort model to accurately evaluate thermal comfort. The coupling was made using an iterative JavaScript to automatically transfer data for each individual segment of the human body back and forth between the CFD solver and the UCB model until reaching convergence defined by a stopping criterion. The location from which data are transferred to the UCB model was determined using a new approach based on the temperature difference between subsequent points on the temperature profile curve in the vicinity of the body surface. This approach was used because the microclimate surrounding the human body differs in thickness depending on the body segment and the surrounding environment. To accurately simulate the thermal environment, the numerical model was validated beforehand using experimental data collected in a climate chamber equipped with a thermal manikin. Furthermore, an example of the practical implementations of this coupling is reported in this paper through radiant floor cooling simulation cases, in which overall and local thermal sensation and comfort were investigated using the coupled UCB model.}, subject = {Numerische Str{\"o}mungssimulation}, language = {en} } @article{TeitelbaumAlsaadAvivetal., author = {Teitelbaum, Eric and Alsaad, Hayder and Aviv, Dorit and Kim, Alexander and V{\"o}lker, Conrad and Meggers, Forrest and Pantelic, Jovan}, title = {Addressing a systematic error correcting for free and mixed convection when measuring mean radiant temperature with globe thermometers}, series = {Scientific reports}, volume = {2022}, journal = {Scientific reports}, number = {Volume 12, article 6473}, publisher = {Springer Nature}, address = {London}, doi = {10.1038/s41598-022-10172-5}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220509-46363}, pages = {18}, abstract = {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.}, subject = {Strahlungstemperatur}, 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{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{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.3835}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181221-38354}, 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 = {Building Information Modeling}, language = {de} } @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} }