In Sweden the industries releases about 50 TWh / year of low temperature waste heat[1], often in the form of humid air flows. Today, conventional flue gas condensation is only exploiting a minor part of the energy from these flows. It is a well-established and profit­able way of improving the efficiency of district heating plants and other boilers for wet fuels. How­ever, the condensation is only applicable when the dew point of the flue gas is above the temperature demand for the heating net. The paper industry gives a good illustration of the limitations for conventional condensation: several MW of wet air streams with dew points of 60-65 ̊ C are released but cannot be recovered since the tempe­ra­ture demand is 70-80 ̊ C for the heating net. Different technologies for more advanced waste heat recovery are developing and this report is evaluating a demonstration plant for “hygro­scopic condenser”, which uses a hygroscopic solution that allows condensation above the dew point. The hygro­scopic solution is potassium formate, which enables condensation to start about 20 ̊ C above the dew point and is sufficiently non-toxic and non-corrosive. The objective of this work is to evaluate both the equipment and the process during some initial tests at the paper mill at Holmen, Braviken. The aim is also to suggest improvements of the process, the components and the additional equipment for future continuous operation.  The equipment consists of two main parts:  a hygroscopic absorption stage and a regene­ration stage. The major part of the humid air is led into an absorption column where vapor is absorbed by the formate solution and rises its temperature. This recovered waste heat is transferred to the heating net by a plate heat exchanger. The regeneration unit is used to maintain the hygroscopic concentrations by evaporation of vapor from the formate solution (amount of absorbed vapor = amount of evaporated vapor). The regene­rator is driven by process steam from the existing 3.5 bar net. The evaporated vapor is led to a conventional condenser where the regeneration energy can be recovered and the condensate is bled off.  The recovered heat from the process (hygroscopic absorber + regeneration condenser) is used in the heating net at Holmen, Braviken (VVG-net).    The initial tests have been made during 15 hours of initial operation, when the equipment has delivered about 3 MWh in total. The tests show a good temperature performance since the dew point of the humid air has been lowered from about 60oC to 47oC. The reco­vered heat was used for heating from 65oC to about 80oC. During the initial tests the capacity has not yet reached the design values. As an example the delivered heat was measured to 280 kW where­of 46kW from absorbed vapor, 129 kW from the sensible heat in the incoming humid air and 105 kW from the regeneration. The bottle-neck parts of the equipment have been localized and will be overseen during the summer of 2011 and the process is planned to be in use during the autumn with an output capacity of 500kW. The coefficient of performance (COP) is calculated to just below 2 during normal operation but was about 2.7 in the test runs due to the high portion of sensible heat. [1]Förekomst av industriellt spillvärme vid låga temperaturer,  Ingrid Nyström, Per-Åke Franck, Industriell Energianalys AB, 2002-04-15

No description available.

Zeolithgranulate sind etablierte Materialien für die Speicherung von Wärme mittels Wassersorption. Eine Erhöhung der Wärmespeicherdichte des Granulats ist durch Kombination mit hygroskopischen Salzen wie Calciumchlorid, Magnesiumchlorid oder Magnesiumsulfat möglich. In der vorliegenden Dissertation wird gezeigt, dass die Wär-mespeichereigenschaften derartiger Komposite von der Deliqueszenzluftfeuchte des Salzes, von der Salzbeladung und von der Luftfeuchte bei der Wassersorption abhängen. Liegt die Luftfeuchte unterhalb der Deliqueszenzluftfeuchte des Salzes, so nehmen Was-serbeladungshub, Wärmespeicherdichte und thermische Leistung mit steigender Salz-beladung um bis zu 71 % ab. Dies wird darauf zurückgeführt, dass Salzionen in die Mik-roporen des Zeoliths inkludiert werden und das für die Wassersorption zur Verfügung stehende Volumen verringern. Unterhalb der Deliqueszenzluftfeuchte ist das einge-brachte Salz daher thermochemisch inaktiv. Oberhalb der Deliqueszenzluftfeuchte und oberhalb einer salz- und luftfeuchteabhängigen Mindestsalzbeladung kommt es zur Ausbildung einer Salzlösung im Sekundärporensystem des Granulats. Die Absorption von Wasserdampf in der Salzlösung führt gegenüber dem salzfreien Granulat zu einer Steigerung von Wasserbeladungshub und Wärmespeicherdichte um bis zu 53 %. Dies geht jedoch einher mit einer Verringerung der thermischen Leistung um bis zu 50 %. Die Hydratation von kristallinem Salz im Granulat spielt gegenüber Salzinklusion und Ausbildung der Salzlösung nur eine untergeordnete Rolle. Die aus den experimentellen Befunden abgeleiteten Erkenntnisse konnten in ein semiempirisches mathematisches Modell überführt werden, welches den Wasserbeladungshub der Komposite quantitativ beschreibt. / Zeolite beads are established materials for the storage of heat by water sorption. An increase of the heat storage density of the beads is possible via the combination with hygroscopic salts. In this thesis it is shown, that the heat storage properties of compo-sites of this kind depend in a complex manner on the deliquescence humidity of the salt, on the salt loading, and on the humidity during water sorption. When the humidity is below the deliquescence humidity of the salt, water loading lift, heat storage density, and thermal power are reduced by up to 71 % with increasing salt content. This is at-tributed to the inclusion of salt into the micropores of the zeolite and the reduction of the volume available for the sorption of water. Thus, below the deliquescence humidity, the salt is thermochemically inactive. Above the deliquescence humidity and above a salt- and humidity-dependend minimum salt loading, a salt solution is formed in the secondary pore system of the beads. The absorption of water vapor in the salt solution gives rise to an increase of the water loading lift and of the heat storage density by up to 53 %, compared to the salt-free zeolite beads. However, this is accompanied by a reduc-tion of the thermal power output by up to 50 %. The hydration of crystalline salt in the beads is only of minor importance for the composites. The findings from the experi-mental work were transferred into a semi-empirical mathematical model, which de-scribes the water loading lift of the composites.

Many studies have previously been done on moisture-induced strains in wood. An in- finitesimal/engineering strain model has been used for most of these studies, which is often an accurate approximation for small rotations. However, if large deformations oc- cur, then fictive strains are obtained resulting from the simplified engineering strain.  This work aims to develop a finite element formulation for problems of moisture- induced strains in orthotropic materials based on the total Lagrangian approach, where large displacements and rotations are considered. This model is then used to examine static drying deformations and their effect on dynamic vibrations. A dynamic vibration test was also done to estimate the modulus of elasticity in the fibre direction. The pur- pose is to increase the understanding of moisture-induced strains in wood and also to emphasize the advantages of using a large deformation model.  To facilitate the understanding of large deformation theory, the implementation is first done for a 2D isotropic beam where static and dynamic simulations are made. Re- sults will be compared with a standard model based on engineering strains. For the static part, two types of wooden species are studied, radiata pine and Norway spruce, and com- pared with a previous research study [32] where engineering strain theory is used. The dynamical considerations are divided into a theoretical and an experimental part. The theoretical part analyzes the vibration of radiata pine and Norway spruce samples from a study by Cown and Ormarsson 2005 [32]. In the experimental part, three Norway spruce boards were analyzed.  The results from the numerical implementation showed, among other things, that by taking moisture-induced strains into account two additional properties, the matrix Gm and the vector Emf appear in the finite element formulation. It was concluded that by using a large deformation model the accuracy will increase without causing any extra computational costs.  The transient numerical mass flow analysis showed reasonable results although the sorption exchange rate has to be slightly higher than indicated by comparable measure- ments. For the dynamic part, the performed experiment showed a difference in response between the three Norway spruce species. It was shown that the frequency increases with distance from the pith and also with lower moisture content. The difference in vibration response between Norway spruce and radiata pine was analyzed based on boards from a study by Cown and Ormarsson 2005 [32]. The response for Norway spruce tends to show a higher frequency compared to radiata pine for the test performed in this investigation. This is mainly due to a higher modulus of elasticity and lower density for Norway spruce compared to radiata pine.

No description available.

Die Samenausbreitung ist eine entscheidende Phase im Lebenszyklus von Pflanzen. Verschiedene Mechanismen haben sich entwickelt, um eine erfolgreiche Keimung zukünftiger Generationen sicherzustellen. Diese schließen die Selbstverbreitung von Samen durch hygroskopische Bewegung von Grannen neben der Verbreitung durch Wind, Wasser oder Tiere ein. Das Verständnis der Struktur-Funktions-Beziehung ist sowohl für das Verstehen, wie sich Pflanzen an spezifische Umweltbedingungen anpassen können, als auch für die potenzielle Entwicklung biomimetischer Anwendungen wichtig. Diese Dissertation konzentriert sich auf die Ausbreitung von Taubem Hafer (Avena sterilis) und zielt darauf ab, die komplexe Bewegung der Grannen zu charakterisieren. Dies wird erreicht, indem die Zellwandstruktur und -zusammensetzung, welche die Bewegung antreiben, mit einer Reihe von komplementären mikroskopischen und spektroskopischen Methoden analysiert werden. / Seed dispersal is a crucial stage in the life cycle of plants. Different mechanisms have evolved to ensure successful germination of future generations. This includes the self-dispersal of seeds by hygroscopic movement of awns among dispersal by wind, water, or animals. Understanding the structure-function relationship is important to comprehend how plants can adapt to specific environmental conditions and also for potential development of biomimetic applications. This thesis focuses on the dispersal of wild oats (Avena sterilis) and aims to characterize the complex movement of the awns by analyzing the cell wall structure and composition that drives the motion with a range of complementary microscopic and spectroscopic methods.

Les matériaux hygroscopiques, et tout particulièrement le bois et ses dérivés possèdent des propriétés complexes rendant difficile la modélisation des transferts couplés de chaleur et de masse dans les parois incluant ces matériaux. De ce fait, très peu d'outils numériques sont aujourd'hui capables de prédire correctement la performance hygrothermique de l'habitat bois. L'objectif de ce travail est de caractériser expérimentalement les transferts chaleur-masse dans les parois des constructions bois afin de valider un outil numérique destiné à simuler le comportement hygrothermique des parois comportant des matériaux hygroscopiques. Dans un premier temps, les notions théoriques et les études antérieures sur les transferts couplés chaleur - masse sont présentés. Ensuite, nous donnons un descriptif détaillé du dispositif expérimental conçu pour caractériser les transferts couplés chaleur-masse dans les parois. Les expériences de caractérisation des performances hygrothermiques des parois fournies par les industriels partenaires du projet TRANSBATIBOIS dans lequel s'inscrit cette thèse sont également abordées. Nous détaillons par la suite les expériences réalisées ainsi que la phase de confrontation des résultats expérimentaux avec les résultats prédits par le code numérique BuildingPore et l'outil commercial WUFI. La troisième partie de ce travail est consacrée aux expérimentations à l'échelle de l'enveloppe. Nous y présentons une analyse de la performance hygrothermique et des consommations énergétiques des constructions bois à travers le suivi de modules-test exposés au climat extérieur. La dernière partie du travail est consacrée aux dispositifs de suivi de bâtiments. / Coupled heat and moisture transfer through hygroscopic materials, particularly wood and wood-based products are difficult to model. This is partly due to some specific and complex properties of these materials that are often not included in numerical models. Currently, only a few numerical models are able to predict accurately the hygrothermal performance of wooden building envelope. The aim of this work is to assess the heat and moisture transfer in wooden building envelope through experiments and validate the prediction capacity of a numerical model developed to simulate hygrothermal behavior of envelope including wooden materials. After giving a theoretical reminder of the coupled heat and moisture transfer through building envelope and reporting the results of previous studies in this field, we will give details of the experimental investigation on heat and moisture transfer through timber walls. Firstly, the experimental apparatus used for the wall tests is presented. Then, we will analysis the hygrothermal performance of wooden walls provided by the partners of the TRANSBATIBOIS project in which this work was achieved. Experimental works achieved for Buildingpore model validation and results of the comparisons between experimental assessment and numerical predictions with Buildingpore and WUFI are also reported. The third part of this study deals with the experimental assessment of wooden building envelopes exposed to climatic conditions. An analysis of the hygrothermal performance and the energy consumption of wooden test-cells is performed and reported in this part. The latest part concerns experimental works on buildings.

La connaissance de l'impact des aérosols sur le climat, au cours de leur cycle de vie, est aujourd'hui un enjeu majeur de la communauté scientifique. En particulier, les aérosols organiques secondaires (AOS) constituent une part importante de la fraction fine des aérosols et pourtant leurs propriétés optiques et hygroscopiques présentent encore des fortes incertitudes. Cette étude avait pour objectif de comprendre et d'évaluer l'évolution des propriétés optiques et hygroscopiques de l'AOS produit dans la chambre de simulation atmosphérique CESAM à partir de l'ozonolyse de l'α-pinène au cours de sa formation et de son vieillissement dans l'atmosphère. Afin de mener à bien ce projet, un HTDMA a été développé et validé. Cette approche a été complétée en mesurant les propriétés hygroscopiques de l'ensemble de la population polydispersé d'aérosols par humidification au sein de la chambre de simulation. Afin de mettre en évidence des modifications de propriétés optiques, l'évolution temporelle de l'indice complexe de réfraction a été déterminée. La méthodologie a été validée et l'effet du temps de contact des particules avec la vapeur d'eau a été investigué. Cette méthodologie a ensuite été appliquée à l'étude des propriétés optiques et hygroscopiques de l'AOS généré par ozonolyse de l'α-pinène au cours de sa formation et du vieillissement par différents processus: dans le noir, en présence d'un excès d'ozone et par photolyse. Les liens avec des modifications possibles de la composition chimique ont été investigués par des observations et par modélisation / The impact of aerosols on climate represents a major challenge in atmospheric science. This is particularly true for secondary organic aerosols, representing a major fraction of the fine aerosols. However, their optical and hygroscopic properties are poorly understood. The present work investigates the optical and hygroscopic properties of SOA generated from the ozonolysis of α-pinene at first and after having undergone atmospheric ageing reactions using the laboratory smog chamber CESAM. For that purpose, an HTDMA has been built and a new approach has been developed to measure hygroscopic properties of polydispersed aerosols by humidifying them directly in the smog chamber. The refractive index has been calculated to investigate the optical properties changes. The methodology has been validated and the residence time of particles with water vapor has been investigated. Then, it has been applied to study the optical and hygroscopic properties of α-pinene SOA during its formation and during ageing by various processes: reaction in the dark, with ozone, and photolysis. The link with changes in the composition has been investigated by measurements and modeling

<div> <p><a>Polymer nanocomposites are envisioned for use in many advanced applications, such as structural industries, aerospace, automotive technology and electronic materials, due to the improved properties like mechanical strengthening, thermal and chemical stability, easy bulk processing, and/or light-weight instigated by the filler-matrix combination compared to the neat matrix. In recent years, due to increasing environmental concerns, many industries are inclining towards developing sustainable and renewable polymer nanocomposites. Cellulose nanomaterials (CNs), including cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), have gained popularity due to their excellent mechanical properties and eco-friendliness (extracted from trees, algae, plants etc.). However, to develop CN-reinforced nanocomposites with industrial applications it is necessary to understand impact of hygroscopic swelling (which has very limited </a>quantitative study at present), aspect ratio, orientation, and content of CNs on the overall performance of nanocomposites; and overcome the low dispersibility of CNs and improve their compatibility with hydrophobic matrix. In this work, we attempt to understand the influence of single nanocrystals in the hygroscopic and optical response exhibited by nanostructured films; effect of CNCs on the properties of PVA/CNC fibers by experimental evidence with mathematical modeling predictions; and hydrophobized CNFs using a facile, aqueous surface modification to improve interfacial compatibility with epoxy. </p><p><br></p> <p>To evaluate the effect of CNC alignment in the bulk response to hygroscopic expansion, self-organized and shear-oriented CNC films were prepared under two different mechanisms. The coefficient of hygroscopic swelling (CHS) of these films was determined by using a new contact-free method of Contrast Enhanced Microscopy Digital Image Correlation (CEMDIC) that enabled the characterization of dimensional changes induced by hygroscopic swelling of the films. This method can be readily used for other soft materials to accurately measure hygroscopic strain in a non-destructive way. By calculating the CHS values of CNC films, it was determined that hygroscopic swelling is highly dependent on the alignment of nanocrystals within the films, with aligned CNC films showing dramatically reduced hygroscopic expansion than randomly oriented films. Finite element analysis was used to simulate moisture sorption and kinetics profile which further predicted moisture diffusion as the predominant mechanism for swelling of CNC films. </p> <p><br></p><p>To study the effects of different types and aspect ratios of CNCs on mechanical, thermal and morphological properties of polyvinyl alcohol (PVA) composite <a>fibers, CNCs extracted from wood pulp and cotton were reinforced into PVA to produce fibers by dry-jet-wet spinning. The fibers were collected as-spun and with first stage drawing up to draw ratio 2. </a>The elastic modulus and tensile strength of the fibers improved with increasing CNC content (5 – 15 wt. %) at the expense of their strain-to-failure. The mechanical properties of fibers with cotton CNC were higher than the fibers with wood CNC when the same amount of CNCs were added due to their higher aspect ratio. The degree of orientation along the spun fiber axis was quantified by 2D X-ray diffraction. As expected, the CNC orientation correlates to the mechanical properties of the composite fibers. Micromechanical models were used to predict the fiber performance and compare with experimental results. Finally, surface and cross-sectional morphologies of fibers were analyzed by scanning electron microscopy and optical microscopy.</p><p><br></p> <p>To improve the dispersibility and compatibility of CNFs with epoxy, CNFs were modified by using a two-step water-based method where tannic acid (TA) acts as a primer with CNF suspension and reacts with hexadecylamine (HDA), forming the modified product as CNF-TA-HDA. The modified (-m) and unmodified (-um) CNFs were filled into hydrophobic epoxy resin with a co-solvent (acetone), which was subsequently removed to form a solvent-free two component epoxy system, followed by addition of hardener to cure the resin. Better dispersion and stronger adhesion between fillers and epoxy were obtained for m-CNF than the um-CNF, resulting in better mechanical properties of nanocomposites at the same loading. Thermal stability and the degradation temperature of m-CNF/epoxy improved when compared to neat epoxy. </p> </div> <br>

Silicon magnetic sensors based on the Hall effect have proven to be an excellent sensor choice for many applications, such as position sensing, gear-tooth sensing, contact-less switching and linear sensing. Although a sensor can be trimmed over temperature before it is shipped to the customer, little can be done about the sensitivity's stability once the sensor has been installed in its final application. The goal of this project is to propose and implement mechanisms to stabilize the Hall sensor's sensitivity through the use of mechanical stress feedback and magnetic feedback.