34 research outputs found
Acoustics in Sports halls
No full textProblem statement Sports teachers (and other users) often suffer from bad acoustics in sports halls. A survey revealed that most complaints are about tiredness, throat problems and hearing problems. Bad acoustics in sports halls are mainly caused by an uneven distribution of the sound absorbing material in a hall. Often, the roof absorbs most of the sound where the floor and walls up to 3 meter reflect most of the sound. This lower part of the walls needs to be strong, flat and hard to rebound balls. In this way, vertically reflected sound is being absorbed faster than horizontally reflected sound. This difference causes sagging Schroeder curves and therefore long reverberation times. Dutch standards for acoustics are mainly based on reverberation times, so sagging curves are unwanted. Besides the problem of the long reverberation times, another problem is found. Measurements show that sports halls constructed with stone-like materials absorb sound according to the expectations of the material properties. Sports halls constructed with perforated steel sound absorbing panels give different results. These panels seem to behave differently on sound absorption than expected. Especially low frequencies seem to be absorbed extremely well by the panels. The research question therefore is: ‘Why do perforated steel sound absorbing panels seem to behave differently in absorption coefficient in sports halls than expected from laboratory test results?’ Because this question is part of the larger subject ‘acoustics in sports halls’, it is necessary to investigate the acoustical behaviour of perforated steel panels for a broad demarcation of the subject. Approach In order to find an answer to the research question, two hypotheses are tested by measurements. The measurements are done in a laboratory and in a scale model. The results are analysed. The conclusions give insight in the sound absorbing behaviour of perforated steel sound absorbing panels. Besides that, the conclusions give guidelines to the design phase of this graduation project. Hypotheses: 1. A perforated steel panel behaves differently in practice than in a laboratory situation on absorption coefficient because the shape of the panels causes sound absorption of parallel striking sound based on a phase shift principle. 2. A perforated steel panel behaves differently in practice than in a laboratory situation on absorption coefficient because the backing construction has influence on the result. Laboratory measurements Absorption coefficient measurements are done in the reverberation room of the acoustical laboratory. Different samples of the roof structure are tested. By comparing the results, we get insight in the influence of different parts of the roof structure. Besides that, hypothesis one can be tested: the influence of the backing construction will become clear. Scale model measurements The scale model makes it possible to test the influence of different shaped roof structures in a small model. By using the same, reflecting material for all walls, we get insight in the influence of changes in roof shapes. Some of the roof structures are (partly) covered with a sound absorbing material to compare the results of those to the other variations. This research should give an answer to hypothesis two. Results The scale model measurement results show that profiled structures cause a considerable decrease in local sound pressure compared to a hard, flat surface. This decrease is largest for low frequencies. The surface with sound absorbing material on top causes the biggest decrease, which is caused by the sound absorption of the facing material. The ‘sound absorption by shape’ is caused by the phenomena of diffusion and interference. It is not visible in reverberation times (T20), just in histograms and Schroeder curves. The laboratory measurements show that the influence of the thermal insulation layer; a part of the backing construction, is large on (low frequent) sound absorption. The rock wool panels give a high peak in the sound absorption graph for 100 Hz. This very good sound absorption is probably caused by the panel being its own panel-resonator and porous absorber in one. The influence of the ‘cannelurevulling’ is small, like the influence of the vapour barrier and different perforation degrees. Conclusions Perforated steel sound absorbing panels absorb more low frequent sound than expected. This good sound absorption is probably achieved by the profiled shape of the steel panels in combination with the backing thermal insulation. The profiled shape causes the effect of sound absorption caused by the effects of diffusion and interference. The backing construction absorbs a large part of the low frequent sound because the hard, stiff and heavy rock wool panels are probably a porous material and panel resonator in one. The research does not give strong guidelines to improve the roof structure. The gained knowledge is used in the design of a wall panel. The walls up to three meters are still the weakest link when talking about acoustics in sports halls. The designed panel should improve this situation.Green Building InnovationBuilding TechnologyArchitectur
Renewed Trombe wall passively reduces energy consumption
No full textIn order to reduce the energy demand of households, a new type of Trombe wall is being designed during a ‘research through design project’ called ‘Double Face 2.0’. A Trombe wall is a passive system that reduces the energy demand of a building. In winter, it captures the heat from the sun during the day and releases this heat into the building at night. In summer, it captures the heat from internal sources during the day and releases that heat at night towards outdoors. First simulations showed that our prototype of a lightweight, translucent, adjustable Trombe wall reduces the energy demand for heating of a typical Dutch household by 25-30%. Instead of stone-like materials, the new type of Trombe wall will consist of translucent materials: phase change material (pcm) and insulating aerogel. The insulation gives the opportunity to direct the thermal mass of the pcm. In this way, the system is adjustable for cooling and heating purposes. A selection of the design concepts is described in this paper, explaining the design choices and method of validation. Depending on the level of detail, different simulation software has been used. This paper describes the comparison and the experiences of using it.Accepted Author ManuscriptBuilding PhysicsDesign Informatic
Double Face 2.0: An adjustable, translucent, PCM-based Trombe wall
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Building PhysicsDesign Informatic
The influence of profiled ceilings on sports hall acoustics: Ground effect predictions and scale model measurements
No full textOver the last few years, reverberation times and sound pressure levels have been measured in many sports halls. Most of these halls, for instance those made from stony materials, perform as predicted. However, sports halls constructed with profiled perforated steel roof panels have an unexpected very low reverberation time in the 125 and 250 Hz octave bands. The aim of this study was to provide an explanation for this low-frequency anomaly. A 1:20 scale model of a sports hall was constructed and placed in a small anechoic chamber. The roof could be equipped with differing ceiling types: a flat non-absorbing ceiling, a flat absorbing ceiling, two different profiled non-absorbing ceilings and a profiled absorbing ceiling. With a spark sound source and a small microphone, the impulse-response of the scale model could be registered and analysed. Moreover, a Matlab model was constructed to simulate the acoustic behaviour of the sports hall. This model included the ‘ground effect’ of the roof surface, an effect typically not included in commercial ray-tracing programs. The measurements and the simulations showed that the high sound absorption values of a perforated panel roof structure at 125 and 250 Hz can be (partly) explained by its shape. The diffusing properties of the corrugated roof have an effect similar to sound absorption. Because the roof is the largest absorbing surface in a sports hall, this effect can have a significant effect on the low-frequency reverberation time.Accepted Author ManuscriptBuilding Physic
Integrating technical performances within design exploration: The case of an innovative Trombe wall
No full textThe Double Face 2.0 research project aims at developing a novel type of an adaptive translucent Trombe wall. The novelty of the proposed system is based on the integration of new lightweight and translucent materials, used both forlatent heat storage and insulation, advanced computational design processes, used to identify the relationship between variations in geometry and their effect in terms of overall performance, as well as proposed fabrication methods basedon Fused Deposition Modelling. Various concepts and geometric configurations are explored and improved via a computational design workflow. The exploration is deeply rooted in performance simulations manufacturing constraints and measurements of prototypes. The paper presents the workflow of the overall on-going research project, with specific emphasis on the incorporation of a omputational assessment and optimization process. Moreover, it presents the preliminary set of measurements and simulations for thermal performances, their results and related conclusions.Design InformaticsBuilding Physic
CD39 and immune regulation in a chronic helminth infection: The puzzling case of Mansonella ozzardi
No full textHost-parasite interactio
Temperature Control in (Translucent) Phase Change Materials Applied in Facades: A Numerical Study
No full textPhase change materials (PCMs) are materials that can store large amounts of heat during their phase transition from solid to liquid without a significant increase in temperature. While going from liquid to solid this heat is again released. As such, these materials can play an important role in future energy-efficient buildings. If applied in facades as part of a thermal buffer strategy, e.g., capturing and temporarily storing solar energy in so-called Trombe walls, the PCMs are exposed to high solar radiation intensities, which may easily lead to issues of overheating. This paper therefore investigates the melting process of PCM and arrives at potential solutions for countering this overheating phenomenon. This study uses the simulation program Comsol to investigate the heat transfer through, melting of and fluid flow inside a block of PCM (3 × 20 cm2) with a melting temperature of around 25 °C. The density, specific heat and dynamic viscosity of the PCM are modeled as a temperature dependent variable. The latent heat of the PCM is modeled as part of the specific heat. One side of the block of PCM is exposed to a heat flux of 300 W/m2. The simulations show that once part of the PCM has melted convection arises transporting heat from the bottom of the block to its top. As a result, the top heats up faster than the bottom speeding up the melting process there. Furthermore, in high columns of PCM a large temperature gradient may arise due to this phenomenon. Segmenting a large volume of PCM into smaller volumes in height limits this convection thereby reducing the temperature gradient along the height of the block. Moreover, using PCMs with different melting temperature along the height of a block of PCM allows for controlling the speed with which a certain part of the PCM block starts melting. Segmenting the block of PCM using PCMs with different melting temperature along its height was found to give the most promising results for minimizing this overheating effect. Selecting the optimal phase change temperatures however is critical in that case
Double Face 2.0: A lightweight translucent adaptable Trombe wall
No full textDouble Face 2.0 is a novel solar wall, joining a strong design identity and high technical performances. In response to the need for energy saving, new high-performance building elements are shape-optimised for passive climate design and to increase user engagement. Given a design concept, computational approaches help to optimise and to customise high-performance building elements for any environment. Double Face 2.0 has been developed by research through design involving designing, 3D modelling, robotic FDM printing, prototyping, experimenting, simulating, and simulation-based optimising. An adjustable, lightweight, translucent Trombe wall has been developed, using an insulator (aerogel) and heat storage (phase change material) encapsulated in optimised and customizable shapes. In winter, it captures, stores, and re-radiates heat from the sun (heating); in summer, it captures internal heat (cooling).Building PhysicsDesign Informatic
Association of In Utero Sensitization to Schistosoma haematobium with Enhanced Cord Blood IgE and Increased Frequencies of CD5-B Cells in African Newborns
No full textHost-parasite interactio
