@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{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{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 = {Performance assessment of a ductless personalized ventilation system using a validated CFD model}, series = {Journal of Building Performance Simulation}, volume = {2018}, journal = {Journal of Building Performance Simulation}, number = {11, Heft 6}, doi = {10.25643/bauhaus-universitaet.3850}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20190218-38500}, pages = {689 -- 704}, abstract = {The aim of this study is twofold: to validate a computational fluid dynamics (CFD) model, and then to use the validated model to evaluate the performance of a ductless personalized ventilation (DPV) system. To validate the numerical model, a series of measurements was conducted in a climate chamber equipped with a thermal manikin. Various turbulence models, settings, and options were tested; simulation results were compared to the measured data to determine the turbulence model and solver settings that achieve the best agreement between the measured and simulated values. Subsequently, the validated CFD model was then used to evaluate the thermal environment and indoor air quality in a room equipped with a DPV system combined with displacement ventilation. Results from the numerical model were then used to quantify thermal sensation and comfort using the UC Berkeley thermal comfort model.}, subject = {Ventilation}, 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{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{JentschKulleBodeetal., author = {Jentsch, Mark F. and Kulle, Christoph and Bode, Tobias and Pauer, Toni and Osburg, Andrea and Namgyel, Karma and Euthra, Karma and Dukjey, Jamyang and Tenzin, Karma}, title = {Field study of the building physics properties of common building types in the Inner Himalayan valleys of Bhutan}, series = {Energy for Sustainable Development 38}, journal = {Energy for Sustainable Development 38}, doi = {10.25643/bauhaus-universitaet.3139}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170419-31393}, pages = {48 -- 66}, abstract = {Traditionally, buildings in the Inner Himalayan valleys of Bhutan were constructed from rammed earth in the western regions and quarry stone in the central and eastern regions. Whilst basic architectural design elements have been retained, the construction methods have however changed over recent decades alongside expectations for indoor thermal comfort. Nevertheless, despite the need for space heating, thermal building performance remains largely unknown. Furthermore, no dedicated climate data is available for building performance assessments. This paper establishes such climatological information for the capital Thimphu and presents an investigation of building physics properties of traditional and contemporary building types. In a one month field study 10 buildings were surveyed, looking at building air tightness, indoor climate, wall U-values and water absorption of typical wall construction materials. The findings highlight comparably high wall U-values of 1.0 to 1.5 W/m²K for both current and historic constructions. Furthermore, air tightness tests show that, due to poorly sealed joints between construction elements, windows and doors, many buildings have high infiltration rates, reaching up to 5 air changes per hour. However, the results also indicate an indoor climate moderating effect of more traditional earth construction techniques. Based on these survey findings basic improvements are being suggested.}, subject = {Luftdichtheit}, language = {en} } @misc{Jahn, type = {Master Thesis}, author = {Jahn, Rosa}, title = {Evaluation von Nutzerbed{\"u}rfnissen in Wohngeb{\"a}uden unter Ber{\"u}cksichtigung hygrothermischer Messdaten}, doi = {10.25643/bauhaus-universitaet.1875}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20130320-18758}, school = {Bauhaus-Universit{\"a}t Weimar}, abstract = {Evaluation von Nutzerbed{\"u}rfnissen in Wohngeb{\"a}uden unter Ber{\"u}cksichtigung hygrothermischer Messdaten}, subject = {Raumklima}, language = {de} } @article{Gallo1990, author = {Gallo, Emmanuelle}, title = {R{\"a}umliche und soziale Strategie zur Sicherung des W{\"a}rmekomforts}, doi = {10.25643/bauhaus-universitaet.1074}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-10740}, year = {1990}, abstract = {Wissenschaftliches Kolloquium vom 27. bis 30. Juni 1989 in Weimar an der Hochschule f{\"u}r Architektur und Bauwesen zum Thema: ‚Produktivkraftentwicklung und Umweltgestaltung. Sozialer und wissenschaftlich-technischer Fortschritt in ihren Auswirkungen auf Architektur und industrielle Formgestaltung in unserer Zeit. Zum 100. Geburtstag von Hannes Meyer'}, subject = {Raumklima}, language = {de} }