La chimenea solar es un sistema pasivo de acondicionamiento climático. Al tener la capacidad de generar movimiento de aire al interior de una habitación mediante la captación de radiación solar, este flujo de aire amplifica la zona de confort incrementando las condiciones de habitabilidad para el ser humano en situaciones de temperatura de aire y humedad elevados, principales características del clima tropical cálido húmedo. A pesar de que este dispositivo presenta una difusión extensiva en bibliografía relacionada a la eficiencia energética y medio ambiente, su aplicación real en la arquitectura es limitada. Esta investigación plantea identificar los parámetros de diseño que inciden en el desempeño de la chimenea solar, mediante el estudio de la morfología del dispositivo y la posición de las aberturas que intervienen en la trayectoria del flujo de aire. La evaluación de dichos parámetros se realiza con la construcción de un modelo virtual en el programa informático DesignBuilder, donde se evalúan las variables de diseño estableciendo puntos de cálculo de velocidad de aire. Principalmente el punto denominado HAB (Centro de la Habitación), que emula la posición del usuario. Posteriormente, mediante la construcción de un modelo experimental, que recoge los resultados de la etapa de simulación, se evalúa el comportamiento de la chimenea solar en la generación de movimientos de aire al centro de la habitación y en el hueco de entrada de la chimenea solar durante un ciclo anual completo, lo cual permite evaluar su desempeño en diferentes escenarios climáticos. Por último, la comparación de los registros de velocidad para los puntos de cálculo del modelo experimental con los calculados por DesignBuilder para determinar el grado de aproximación de la herramienta informática.Palabras clave: Chimenea solar, ventilación natural, confort térmico, clima cálido húmedo, DesignBuilder, ventilación cruzada.
Industrial building rehabilitation is one the latest trends within the field of sustainable development. However, these interventions often disregard the issue of user comfort, despite being the most important factor of energy efficiency. This work deals with the assessment of the indoor thermal conditions of a restored industrial building, considering not only air temperature but also mean radiant interior temperature. The research focuses in the influence of the radiative performance of the saw tooth roof of this building regarding these conditions. Results show that the analysed thermal parameters depend directly on the roof thermal behaviour. In fact, the glazed area of this type of roof is responsible for the 60% of the increase of the mean radiant temperature over air temperature. This result is a consequence of the high interior temperature reached by the glass panels, 47°C max, despite their northern orientation. These temperatures are a result of the diffuse radiation action and, particularly, the heat flux emitted by the opaque part of the saw tooth-roof, which significantly reduces the radiative cooling capacity of the glazed surface.
El entorno visual en los países mediterráneos se caracteriza por un importante contraste lumínico. La verticalidad del sol y una elevada frecuencia de días con cielo despejado definen un entorno visual donde conviven superficies bañadas por el sol y otras en sombra. La mayor parte del tiempo, las condiciones atmosféricas propician esta condición dual que genera un elevado contraste entre sol y sombra así como entre espacios exteriores e interiores. Además, la sombra mediterránea tiene diferentes grados de luminosidad dependiendo del contexto. La forma de la ciudad, su arquitectura y las características de la luz, determinan el aspecto del entorno iluminado, entendido éste como una sucesión de escenas visuales compuestas básicamente por fachadas, pavimentos y cielo con diferentes valores de luminancia. Es paradójico que, en entornos como el Mediterráneo, donde la disponibilidad de luz natural está claramente por encima del mínimo necesario, se utilicen elevados niveles de luz artificial en los interiores para contrarrestar los efectos del contraste generado con el exterior. Un diseño de iluminación más eficiente debería incorporar criterios sostenibles que integren el conocimiento del entorno luminoso exterior y que permitan deducir el contraste esperado con el interior del edificio. Como aproximación a esta situación, se estableció una metodología de análisis del entorno luminoso mediterráneo, y se aplicó a un caso de estudio representativo de este exterior. Los resultados permitieron poner a prueba del método y aproximar la magnitud del contraste existente entre el interior y el exterior en un entorno mediterráneo concreto, apuntando resultados para posteriores
Visual environment in Mediterranean countries is full of contrasts. The vertical position of the sun as well as the frequent clear sky condition shape an urban environment defined by surfaces flooded by the sun and in the shade, which causes a high contrast, also between interior and exterior spaces. It is paradoxical that, in latitudes where the amount of natural light available is clearly over demand, the design of interior lighting has to cope with this situation using high levels of artificial light. If sustainable criteria are aimed to be introduced in lighting design, it is important to know the lit environment outside and the contrast with the interior of the building. With this aim, an analysis implemented in a specific case of study was outlined. The results highlight the existing contrast between inside and outside in a specific Mediterranean urban environment, and lay the foundations for further studies.
This work deals with daylighting for indoor quality atmospheres, considering building skins and side-views. We also tested the vision perception provided by highly glazed façades. Several Spanish restaurants were analyzed, and two were assessed and measured under outside midday high luminance. The selected pictures can be identified as restaurants via MIT Scene Recognition software and are used to demonstrate working, stressful, and socializing atmospheres. Light and vision detailed analysis was performed defining three workplanes—“table”, “person”, and “outside”—from the viewpoint of the user. The obtained DGP (daylight glare probability) for the first case (facing southeast) shows a higher glare probability than the second (facing north). In both restaurants, there is notable spatial contrast and high information content. If, in the overall perception, the adaptation from the intermediate workplane is considered, the DGP is lower than if only one workplane is considered. The conducted indicative survey shows that there is a high light contrast, and there are some undesirable visual elements. The studied fully glazed façades tend to provide fraught atmospheres. These would be useful for some stimulating activities; however, for calm restaurants that offer tasting menus with quality food, it seems that the studied fully glazed façades may not be suitable.
Natural resources such as daylight and sunlight are highly appreciated in countries with prevailing overcast skies. Taking advantage of this scarce resource contributes to saving energy on arti¿cial lighting. In contrast to northern, southern European cities are distinguished by a large number of days with direct sunlight caused by a propitious climate condition. While it is a positive issue in terms of energy availability, the abundance of it can be counterproductive if management measures are not taken. Apart from the thermal consequences, lighting penetration into buildings causes a great contrast between inside and outside. This is especially critical when the visual system does not have enough time to adapt, as happens at entrance areas. The aim of this study is to analyze the light contrast between these areas and the urban outside in sunny conditions. To attain this objective, light data from ¿ve entrance spaces and their contiguous streets were analyzed and measured. The results were divided into three zones in the visual scene, showing an increasing contrast from top to bottom of the visual ¿eld. It may be concluded that interventions applied to urban areas and building pavements can improve visual adaptation in the transition zone.
Energy is considered as a main influence on urban configurations. However, there is a difficulty on translating the city models based on theoretical renewable energy concepts into practical applications. This study considers the possibility of understanding this future model as a transformation of the existing urban centres. With this objective, a methodology to intervene in existing cities based on the study of solar access is developed. Therefore, an analysis of solar potential in relation with urban morphology is carried on through a simulation software in l’Eixample, a neighbourhood of Barcelona. The distribution of the sun factor in the different areas of the building blocks envelope displays possible morphological modifications that would facilitate solar energy collection. Consequently, the analytical method presented could be applied to regulate urban interventions with the aim of obtaining more solar energy based cities.
In regions where the roof surface is the most exposed to solar radiation, the reduction of the heat flux transmitted through this element has a great impact on the cooling demand of buildings. Studying the possibilities of reducing cooling loads can highly influence the environmental and carbon footprint of the building stock worldwide. Although the main strategy to prevent solar access would be implementing shading systems, another approach could be taking advantage of the radiative cooling effect of the roof itself. Its efficiency depends on the roof properties (color, mass, thermal transmittance, etc) and on climate conditions (radiation, wind, humidity, etc). This paper deals with a comparative assessment of the radiative performance of two roofs exposed to different amounts of solar radiation depending on their percentage of cloudiness, and the repercussions over its surface temperature. Its aims is to evaluate the effect of radiative cooling depending on the local climates. Temperatures of two similar roofs, in Terrassa 41°33´LN (Spain) and in Santa Rosa 3°27´LS (Ecuador), were measured. Their transmittance, optical and thermal mass properties were considered in the calculations. The results obtained indicate that the effect of using the sky as a heat sink has a higher impact on the roof located in Terrassa (Spain) than the one in Santa Rosa (Ecuador). The results support that this behavior responds to the influence of the high presence of cloudiness on equatorial climates, which reduces significantly the heat losses in long wave radiation. The heat mass storage capacity of the roof could hinder even more the radiative cooling effect of the roof.
This publication presents the importance that the embodied energy of the material of the support of a photovoltaic installation can have in relation to the energy produced and, therefore, in relation to other efficiency factors in the design of photovoltaic installations. The importance of these costs cannot be neglected in the overall of the system’s efficiency.
The monitoring of photovoltaic panels after a few years of operation under real conditions demonstrates that a good integration of photovoltaic systems in constructive elements, even if their inclination or orientation is not the recommended one, may be better than just overlapping them in an optimal position. The embodied energy of the added constructive materials used when the system is not integrated may be more than the loss of production as a result of a non optimal photovoltaic modules disposal.
This paper illustrates the potential that architectural design applied to photovoltaic modules integration could represent, based on the experience of the photovoltaic pergola built in 2004 at the Forum esplanade in Barcelona. The ultimate goal is to consider the architectural design as another and important parameter when sizing photovoltaic systems, together with the orientation, tilt, temperature and other parameters regularly used.
The appearance of the city is strongly linked to many aspects such as climate, culture and sociological background. In cities with a prevalence of clear skies, one of the determining aspects is the climatic condition, which defines a luminous context where all elements appear significantly bright. In order to establish the luminosity of the urban scene and its components, an analysis of pictures taken in real environments is proposed, carried out through a digital image processing software developed by the authors. The information contained in each pixel of a digital image is used to assess the distribution of light in the picture. The pictures selected for assessment represent an urban scene as seen by a standing observer. In this situation the scene can be divided in three zones with similar features: pavement, sky and façades. The developed software provides output information for the aforementioned zones and the whole image consisting on light data (average, maximum, minimum and standard deviation) convertible to luminance (cd/m2) if reference values are provided. The validity of the procedure is tested in this work and implemented in real pictures. After testing it, the software has proven to be easy to use and the results obtained in the examples have shown a trend in their values. The implementation of the software suggests that a wider number of cases of study would make possible to establish a pattern in the daylight distribution of urban scenes conceived as an addition of zones with different luminous appearance.
La apariencia de la ciudad está fuertemente ligada a muchos aspectos como el clima, la cultura y el trasfondo sociológico. En las ciudades con una prevalencia de cielo despejado, uno de los aspectos determinantes es la condición climática, que define un contexto luminoso donde todos los elementos aparecen significativamente brillantes. Para establecer la luminosidad de la escena urbana y sus componentes se propone un análisis de imágenes tomadas en entornos reales, realizado a través de un software de procesamiento digital de imágenes desarrollado por los autores. La información contenida en cada píxel de una imagen digital se utiliza para evaluar la distribución de luz en la imagen. Las imágenes seleccionadas para la evaluación representan una escena urbana vista por un observador permanente. En esta situación la escena se puede dividir en tres zonas con características similares: pavimento, cielo y fachadas. El software desarrollado proporciona información de salida para las zonas antes mencionadas y toda la imagen consiste en datos de luz (promedio, máximo, mínimo y desviación estándar) convertibles en luminancia (cd/m2) si se proporcionan valores de referencia. La validez del procedimiento se prueba en este trabajo y se implementa en imágenes reales. Después de probarlo, el software ha demostrado ser fácil de usar y los resultados obtenidos en los ejemplos han mostrado una tendencia en sus valores. La implementación del software sugiere que un mayor número de casos de estudio haría posible establecer un patrón en la distribución diurna de escenas urbanas concebidas como una adición de zonas con diferente aspecto luminoso.
L'aparença de la ciutat està fortament lligada a molts aspectes com el clima, la cultura i el rerefons sociològic. A les ciutats amb una prevalença de cel clar, un dels aspectes determinants és la condició climàtica, que defineix un context lluminós on tots els elements apareixen significativament brillants. Per establir la lluminositat de l'escena urbana i els seus components es proposa una anàlisi d'imatges preses en entorns reals, realitzat a través d'un programari de processament digital d'imatges desenvolupat pels autors. La informació continguda en cada píxel d'una imatge digital s'utilitza per avaluar la distribució de llum a la imatge. Les imatges seleccionades per a l'avaluació representen una escena urbana vista per un observador permanent. En aquesta situació l'escena es pot dividir en tres zones amb característiques similars: paviment, cel i façanes. El programari desenvolupat proporciona informació de sortida per a les zones abans esmentades i tota la imatge consisteix en dades de llum (mitjana, màxim, mínim i desviació estàndard) convertibles en luminància (cd/m2) si es proporcionen valors de referència. La validesa del procediment es prova en aquest treball i s'implementa en imatges reals. Després de provar-ho, el programari ha demostrat ser fàcil d'usar i els resultats obtinguts en els exemples han mostrat una tendència en els seus valors. La implementació del programari suggereix que un major nombre de casos d'estudi faria possible establir un patró en la distribució diürna d'escenes urbanes concebudes com una addició de zones amb diferent aspecte lluminós.
Functional fatigue affects NiTi wires as accumulation of residual strain and reduction of transformation stress. Here we investigate the effects of moderate temperature thermo-mechanical treatments to reduce the accumulated fatigue effects
In this work, we explore the consequences of strain aging NiTi wires (2.46 mm diameter) at moderate temperatures (100ºC). The changes of the stress-strain behaviour on aged, as compared with non-aged wires, with comparatively smaller changes in thermal transformation, indicate the existence of relevant strain fields on these wires. The fact that thinner wires perform differently on aging suggests the possibility of radial dependence of the strain fields. Measurements were performed at CELLS-ALBA synchrotron, BL04 Materials Science Powder Diffraction beam-line. X-ray micro-diffraction for near 10 (mm)2 (FWHM) zones on cross-sections of samples was done, aiming to detect residual strains as function of radial position on the wire. The results show very small changes of diffraction peaks position, with more relevant variations near the surface. This might be interpreted as a high sensitivity of the transformation on stresses enabling defined paths of transformation.
Functional fatigue affecting superelastic
behaviour of NiTi wires includes an accumulation of residual
strain and an uneven decrement of transformation stress on
cycling. Although this evolution is observed to diminish
asymptotically, it represents an important loss in the
maximum recoverable strain level and in the hysteretic
dissipative capacity. In this work, the effect of moderate
temperature aging treatment on the functionally degraded
material properties was studied with two experimental
setups. Wire samples of 0.5 and 2.46 mm diameter were
subjected to different cycling programs intercalated by
aging treatments of different durations up to 48 h at
100ºC. Results show that important levels of recovery on
the residual strains and the transformation stresses were
attained after the aging treatments. The analysis indicates
that the characteristic of the recovered cycle are rather
independent from the treatment duration and from the reached
condition before each treatment
Isalgue, A.; Auguet, C.; Grau, R.; Torra, V.; Cinca, N.; Fernández, J. Journal of materials engineering and performance Vol. 24, num. 9, p. 3323-3327 DOI: 10.1007/s11665-015-1607-x Data de publicació: 2015-09-01 Article en revista
Shape memory alloys are considered smart materials because of their singular thermo-mechanical properties, due to a thermoelastic martensitic transformation, enabling possible uses as actuators (because of mechanical recovery induced from temperature changes) and as dampers (because of hysteresis). NiTi wires for dampers in Civil Engineering had been characterized and tested in facilities. Guaranteed performance needs to know behavior during fatigue life and knowledge of effects in the event of extreme conditions, as eventual overstraining. In this work, we check the possibilities to absorb mechanical energy on the fatigue life depending on stress level and explore the consequences of overstraining the material during installation, the possibilities of partial healing by moderate heating, and some effects of over-stressing the wires. The mechanical energy absorbed by the unit weight of damper wire might be very high during its lifetime if maximum stresses remain relatively low allowing high fatigue life. We show also some results on NiTi wire working as an actuator. The lifetime mechanical work performed by an actuator wire can be very high if applied stresses are limited. The overstraining produces relevant "residual" deformation, which can be to some extent reversed by moderate heating at zero stress. The reason for the observed characteristics seems to be that when external high stresses are applied to an NiTi wire, it undergoes some plastic deformation, leaving a distribution of internal stresses that alter the shape and position of the macroscopic stress-strain transformation path.
Shape memory alloys are considered smart materials because of their singular thermo-mechanical properties, due to a thermoelastic martensitic transformation, enabling possible uses as actuators (because of mechanical recovery induced from temperature changes) and as dampers (because of hysteresis). NiTi wires for dampers in Civil Engineering had been characterized and tested in facilities. Guaranteed performance needs to know behavior during fatigue life and knowledge of effects in the event of extreme conditions, as eventual overstraining. In this work, we check the possibilities to absorb mechanical energy on the fatigue life depending on stress level and explore the consequences of overstraining the material during installation, the possibilities of partial healing by moderate heating, and some effects of over-stressing the wires. The mechanical energy absorbed by the unit weight of damper wire might be very high during its lifetime if maximum stresses remain relatively low allowing high fatigue life. We show also some results on NiTi wire working as an actuator. The lifetime mechanical work performed by an actuator wire can be very high if applied stresses are limited. The overstraining produces relevant
Isalgue, A.; Cinca, N.; Guilemany, J.M.; Concustell, A.; Garcia-Cano, I.; Auguet, C. Congress of the Spanish Synchrotron User Association (AUSE) and the ALBA User's Meeting p. 25-26 Data de presentació: 2015-06 Presentació treball a congrés
In this study, time resolved X-ray scattering using a synchrotron X-ray source has been used to gain insight of time-temperature atomic ordering of an intermetallic Fe40Al ball-milled powder with the aim to estrapolate these results as an explanation of rapid ordering processes occurring during thermal spray coating deposition.
Torra, V.; Isalgue, A.; Lovey, F.C.; Sade, M. Journal of thermal analysis and calorimetry Vol. 119, num. 3, p. 1475-1533 DOI: 10.1007/s10973-015-4405-7 Data de publicació: 2015-03-01 Article en revista
The SMA was studied for their macroscopic application in damping for civil engineering. The study is a synthesis and includes an outline of the models required for the SMA simulation and some case studies using the finite element analysis methods. This work is an overview that focuses in the mitigation of the oscillations in structures induced by earthquakes, and for a reduction of the oscillations amplitude in stayed cables under the action of rain, wind or traffic. The analysis needs the required conditions for each application determining the working conditions. The study includes the number of working cycles, the temperature effects and the cooling actions and, for instance, the action of the cycling frequency. The main target relates the appropriateness of the SMA for each purpose, and the suitability of the SMA device is always experimentally guaranteed. Furthermore, the applicability of the obtained results for SMA and the practical behavior of the SMA dampers were studied in international facilities. The paper includes appropriate suggestions for a correct preparation of the SMA dampers. This work outlines the effects of stress and temperature aging in NiTi, describes the particular structural effects between 18R and 6R, introduces a first attempt in the dynamic properties of the CuAlBe single crystals and summarizes some recent suggestions for damping using SMA
The absence of solar radiation at night gives good opportunities for passive cooling of buildings in hot climates with frequently clear sky. However the possibility of also taking advantage of a clear sky cooling potential during the day is seldom considered.
Thermal radiation to sky can be used to cool. A body surface emits thermal radiation (far IR) and if direct solar radiation (visible and near IR) and thermal radiation coming from other surfaces do not reach it, there would be a net heat flux out.
A previous prototype was done with a simple element. That experiment confirmed that was possible to reduce around two degrees the interior temperature of the test unit exposed to sun light in July.
In this work a new design based on the first one is developed to adapt it to architectonical needs in order to reduce interior spaces temperature in hot climates.
The aim of this design is focused to so an architectonical adaptation is needed. Modular and replicable units could be a solution that permits to fulfill large flat surfaces as roofs or other architectonic elements. In this occasion, measurements were taken from a modular model with a geometrical design that avoided de direct solar incidence. These measurements were taken by a pyrgeometer during two weeks of August and results were similar to the previous experiment.
Coch, H.; Pardal, C.; Pages-Ramon, A.; Isalgue, A.; Crespo, I. World Renewable Energy Congress / Network p. 569-579 DOI: 10.1007/s00484-015-1109-4 Data de presentació: 2014-08 Presentació treball a congrés
CuAlAg alloys were syntetized and thermal treatment was obtained to have martensitic transformation. Alloys with high transformation temperature were obtained, but the alloys showed precipitation and formation of equilibrium phases after few thermal cycles
Metallic glasses produced with very high quenching rates contain large amounts of free volume and frozen-in stresses. Physical aging or structural relaxation drives glassy systems towards more relaxed states, releasing free volume and internal local stresses . It is well-known that structural relaxation induces significant changes in metallic glass properties, for instance changes from ductile to brittle fracture behaviour or in the corrosion resistance . For many metallic glasses, structural relaxation well below the glass transition is negligible for laboratory experimental times but it is clearly noticed in the change of properties several months after production. Some strategies for ductilization of metallic glasses involve mechanical deformation, making the glass more prone to physical aging even at relatively low temperatures. It is then technologically important to control the effects and mechanisms of physical aging. The dynamics of the glass-forming alloys are generally understood as driven by an ¿-relaxation process with characteristic times of 100s near glass transition and faster secondary relaxations. Below glass transition the characteristic time of the ¿-relaxation increases orders of magnitude, and the structural changes at these temperatures are generally attributed to the presence of secondary processes. In the work presented here we induced physical aging by annealing and we studied its effect on the mechanical relaxation times of Mg65Cu25Y10, Cu46Zr46Al8, Pd77.5Cu16Si6.5 and Fe-based metallic glasses. The analysis was performed for different glassy states, more or less relaxed. Mechanical spectroscopy, calorimetry and resistivity measurements allowed us to determine the dynamics of the different states and the characteristic times of structural. At low temperatures the mechanical relaxation of the glass is affected by the physical aging, but the latter is governed by a much longer time-scale. At higher temperatures, the structural relaxation is coupled with the main mechanical relaxation process as already shown in previous works .
Se trata la cinética del ordenamiento del intermetalico FeAl por medio de difraccion de R-X a diversas temperaturas, en función del tiempo, con difractogramas resueltos temporalmente en el sincrotron ALBA
Today, the building sector is one of the greatest energy consumers of the world. Therefore, it is impor-tant that designers think about strategies to save energy at the different stages of the building process,including during its life. Considering that a great deal of energy will be spent in artificial lighting, animprovement in the performance in front of light of the architecture itself could lead to a better vision ofthe spaces, which depends on the quantity and quality of light available and on the architectural char-acteristics as well. One of the most influential aspects is the colour of the space. Here, a case study ispresented in which three coloured spaces were assessed by observers under different lighting condi-tions. Luminance and illuminance measurements were taken to compare these values with the votesgiven. The results query the correlation between measured values and luminosity of three-dimensionalspaces. As a consequence, the choice of a particular colour may increase the sensation of light in a spaceand, therefore, a reduction of energy use in artificial lighting is possible. In addition, architectural designcan take advantage of colour to improve the visual quality of indoor spaces.
Isalgue, A.; Fernandez, J.; Cinca, N.; Villa, M.; Guilemany, J. Journal of alloys and compounds Vol. 577, num. Supplement 1, p. S277-S281 DOI: 10.1016/j.jallcom.2012.05.033 Data de publicació: 2013-11-15 Article en revista
The nanoindentation behavior of wear resistant coatings containing TiC–NiTi is studied. The raw material contained 60%weight of TiC and 40%weight of near equiatomic NiTi. The powder was sprayed by
plasma and HVOF techniques. Higher temperatures in the plasma spraying produced better matrix melting but also more cracks on cooling. The presence of some amorphous or nanocrystalline phase occurs, at least in some coatings, being this related to the good wear behavior. The projection conditions play an important role on the partial transformation because ofthe decomposition and oxidation ofthe NiTi as a
consequence of the temperatures involved during the spray deposition. The nanoindentation measures
suggest that, even with the presence of hard TiC particles, partial oxidation and dissociation of NiTi, there
is some pseudoelasticity.
Visual comfort in indoor spaces depends on the amount and quality of light available and also on space characteristics. One of the most influential aspects is the colour of surfaces definint a space. Each colour has a reflectance coefficient resulting from how much light is reflected back from the coloured surface. However, from the observer’s point of view, there are other factors that may affect visual perception of a space painted with colours. Some of them are psychological and depend on the background of the observer while other factors are physiological and are strongly connected to the sense of sight. According to this theory, architectural spaces could take advantage of the benefits of colour to improve visual responses for users.
In this paper, we present a case study in which three coloured spaces with different lighting conditions were assessed by a sample of observers. At the same time, luminance and illuminance measurements were taken so as to compare these values with light perceived in the spaces. The results of this field work show the influence that colour has on the perception of light in three-dimensional spaces and contribute to the study of colour in architecture.
The link between urban form and building energy demand is a complex balance of morphological, constructive, utilization and climatic factor. Especially in European compact city where existing areas prevail on much more energy-efficient new settlements, it is evident that operative ways to transform efficiently the building stock have to be found. Moreover, it is now widely accepted that urban scale has a first rate importance in the building design process and its correlated energy performance. It has been observed that scaling laws are useful in describing the complex structure of urban systems: modern cities have a “metabòlic rate” that approximately follows the living organism scaling laws. Nevertheless, it has not been entirely verified that this connection remains the same while studying the phenomena at the urban and building scale and what kind of relationship between mass and power exists (i.e. energy) depending on typologies and urban form. This study suggests an approach for using mass parameter - representative of built-form - as energy performance evaluation tools on a homogeneous urban texture. Mass is connected to both built-form and technology and these determine, to a great extent, the energy use. In Mediterranean climate, it has been observed that mass has strong relevance on energy demand playing an important role in reducing heating and cooling consumptions. Our work aims at validating this relationship, focusing on widespread urban fabrics of the Mediterranean compact city. Tests on diferent case studies from Barcelona and Rome (analyzed independently in terms of their energy demands and their masses) are carried out. Mass evaluation is based on calculation of effective mass of built elements. Building energy demand is assessed by modelling on multi space dynamic thermal analysis tool. Results presented and discussed point out that heating and cooling energy demand are related to urban fabrics mass and, starting from typological based analysis, it’s possible to estimate it. This work is a broader treatment of a research study about one possible way to comprehend “metabolic rate” scaling law concerning urban fabric. Such knowledge-base could giving hints to conscious and effective built environament transformations towards more efficient conditions.
This paper deals with both physical and psychological dimensions of visual and acoustic adaptability in architecture. Studies revealed that thermal comfort at one point in a transitional space is determined by the relative temperature at the location compared to the average temperatures the subjects had previously been exposed to. The objective of this study is to investigate whether these results can be extrapolated to visual and acoustic perception. The proposed methodology is based on observing individual behaviour with a sequenced exposure to different controlled visual and acoustic conditions. The results, which will be discussed, can be applied not only to general change in environmental conditions but also while walking through transitional spaces, where a weII-designed gradient of environmental conditions could imply energy savings.
Auguet, C.; Isalgue, A.; Torra, V.; Carreras, G.; Lovey, F.C. Materials science forum Vol. 730-732, p. 853-858 DOI: 10.4028/www.scientific.net/MSF.730-732.853 Data de publicació: 2013-06-01 Article en revista
The main interest focuses in the necessary tools for accurate simulation of the damper behavior in their application. It’s essential a well determined knowledge of the dissipated energy and of the hysteresis cycle shape for a correct simulation. The self-heating effects and the coupling between hysteresis and the relevant temperature effects associated to continuous cycling were studied. In particular, the experimental analysis concentrates in the action of cycling frequency on the hysteresis width and on the dissipated energy. The external and the self-heating temperature effects were studied. In particular, the convective actions of cooling in the conditioned air were visualized. The study of self-heating actions at extremely slow cycles, built by strain steps, shows minor latent heat dissipations in the entire sample. For trained samples, the temperature measurements establish that the transformation is “distributed” not “localized” in the complete sample.
Isalgue, A.; Auguet, C.; Cinca, N.; Fernandez, J.; Cano, I.G.; Guilemany, J.M. International Conference on Shape Memory and Superelastic Technologies p. 78 Data de presentació: 2013-05-22 Presentació treball a congrés
Isalgue, A.; Auguet, C.; Grau, R.; Torra, V.; Cinca, N.; Fernandez, J. International Conference on Shape Memory and Superelastic Technologies p. 452-453 Data de presentació: 2013-05-22 Presentació treball a congrés
Isalgue, A.; Auguet, C.; Cinca, N.; Fernandez, J.; Cano, I.G.; Guilemany, J.M.; Sampath, S. International Conference on Shape Memory and Superelastic Technologies p. 261-262 Data de presentació: 2013-05-20 Presentació treball a congrés
Shape Memory Alloys (SMAs) are good candidates for solid-state dampers appropriate for the oscillations of bridge stay cables because of their large recoverable strain, hysteresis and reasonable fatigue-life. This work experimentally analyzes the relevant properties of NiTi SMA and conducts facility measurements, frequency analyzes and simulations of the effects of SMA on stay cables. Appropriate phenomenological SMA models were developed and included in a Finite Element (FE) simulation environment. A complete damping solution for bridge stay cables was developed from these experimental analyzes. This paper detail the required properties for a NiTi SMA and analyzes their performance. For instance, the fatigue-life and several of the thermo-mechanical effects influencing the application of NiTi SMAs are outlined. The damping effect of the SMA was studied in two facilities. The first series of measurements was performed using cable 1 of the ELSA facility (JRC-EU, Ispra, Italy). The second was completed in two campaigns at IFSTTAR (Bouguenais, near Nantes in France). The numeric analyzes and simulated results were completely coherent with these experiments: the SMA dampers also drastically reduce the maximum oscillation amplitude induced by the simulated action. The frequency evolution of the damped cable was studied using direct calculations on the signals, the windowed Fourier transform and Morlet wavelets.
Torra, V.; Auguet, C.; Isalgue, A.; Lovey, F.C.; Carreras, G. Journal of thermal analysis and calorimetry Vol. 112, num. 2, p. 777-780 DOI: 10.1007/s10973-012-2585-y Data de publicació: 2013-04 Article en revista
The NiTi SMA was studied by temperature (mainly at 373 K) and by stress–temperature aging. The temperature induces monotonic changes in Rs transformation temperature near 10–20 K/year. The simultaneous stress/temperature aging produced strong changes in the stress–strain cycles and in the necessary stress to continue transforming with an increase of maximal stress near 45 MPa/month at 373 K.
Following years of research and design in architecture under bio-climatic, sustainable and passive-energy concepts, today’s buildings are often well designed and constructed, responding to determined climate conditions and the user’s requirements for comfort and, in some cases, they are integrated into the urban environment. However, the lifetime of a building can be over 100 years and the climate is changing rapidly. This work investigates the impact of climate change future (2040 and 2070) on the energy consumption of residential buildings recently constructed, under three possible scenarios. The scenarios are created considering a low, medium or strong effect of global warming. Two types of buildings, with comparable consumption results of today, are investigated in three different cities around the world with a multi-zone type 56 of Trnsys simulation tool. At the end of the work, the concepts of energy robustness and global thermal effusivity of buildings are discussed as important strategies to reduce the possible impact of climate change on the built environment. The use of simulation tools to estimate the sensitivity of buildings is also analyzed, taking into consideration the recent goals of applying uncertainty and sensitivity analysis to building performance simulation science.
Torra, V.; Isalgue, A.; Auguet, C.; Casciati, F.; Casciati, S.; Terriault, P. Advances in science and technology Vol. 78, p. 92-102 DOI: 10.4028/www.scientific.net/AST.78.92 Data de publicació: 2013-01-06 Article en revista
The wind, rain and traffic induce oscillations in the stayed cables for bridges. One eventual solution relates the use of semi-active devices as the magneto-rheologic fluids. These devices need guaranteed electrical power and computing and, also, technical attention. The Shape Memory Alloys (SMA) has been studied for their application as passive elements. The study is focused in the required properties of SMA for appropriate reliability of the SMA dampers. The fatigue/fracture life, the thermal effects induced by external temperature and by self-heating wires were studied. The SMA dampers were applied to cables in "facilities": the 45 m cable No 1 in the ELSA-JRC in Ispra, Italy, the 50 m cable of IFSTTAR near Nantes, France. The experimental results establish a reduction of the oscillation amplitude to a half of less. The action of SMA increases the cable frequency, and the use of WFT or WT shows a change of frequency associate to the evolution of the amplitude. The change of amplitude produces a change of stiffness in the SMA. A phenomenological model of the hysteresis cycle permits appropriate simulation by standard Finite Elements Analysis as, for instance, ANSYS.
Isalgue, A.; Fernandez, J.; Cinca, N.; Cano, I.G.; Torra, V.; Grau, R.; Auguet, C. Materials science forum Vol. 738-739, p. 311-315 DOI: 10.4028/www.scientific.net/MSF.738-739 Data de publicació: 2013 Article en revista
Torra, V.; Isalgue, A.; Auguet, C.; Carreras, G.; Lovey, F.C.; Terriault, P. Canadian metallurgical quarterly Vol. 52, num. 1, p. 81-89 DOI: 10.1179/1879139512Y.0000000036 Data de publicació: 2013-01-01 Article en revista
The link between urban form and building energy demand is a complex balance of morphological, constructive, utilization and climatic factor. Especially in the European compact city, where existing areas prevail on much more energy-efficient new settlements, it is evident that operative ways to transform efficiently the building stock have to be found. This paper explores the existence of a relation between built mass and energy demand depending on urban form. Focusing on the compact city of Mediterranean climate, tests on different case studies simulations are carried out. Results presented and discussed, point out that mass has strong relevance on energy demand and plays an important role in reducing energy consumptions. This paper is a preliminary report of an ongoing research study about one possible way to comprehend “metabolic rate” scaling law - the relationship between power and mass of a complex system in its process - concerning urban fabric. This knowledge-base could help verify the accordance with this rule on urban scale and give hints to conscious and effective built environment transformations towards more efficient conditions.