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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Compact safety system for automatic flagpole : Flow sensor anemometer / Kompakt säkerhetssystem för automatisk flaggstång : Flow sensor anemometer

Ström, David, Jensen, Carl January 2019 (has links)
Automating tasks and processes are becoming more and more common in both corporate and everyday life. The aim of this project is to assist the company Hotswap in the development of a safety system for an existing automatic flagpole. The safety system should be able to monitor wind velocity and, optionally, wind direction as well as communicate the data to the flagpole’s main control unit. The thesis describes and discusses the different possible mechanisms, solutions for measuring wind, and a possible implementation. A method for measuring wind velocity by utilizing an FS5 thermal mass flow sensor was selected and a prototype was developed for testing the performance of the implementation. The tests showed that the thermal mass flow sensor fulfilled the requirements regarding wind velocity measurement and accuracy with an average deviation of 0.19 m/s from the reference value. The solution was then discussed and compared with Hotswap’s existing prototype. The comparison showed that the prototype was a viable alternative. Finally, some suggestions for further development were presented along with the conclusion that the prototype provides a proof of concept for a fully realizable solution. / Automatisering av arbetsuppgifter och processer blir mer och mer vanligt både på företag och i vardagslivet. Detta projekt hade som mål att bistå företaget Hotswap med utvecklingen av ett säkerhetssystem för en befintlig automatisk flaggstång. Säkerhetssystemet ska kunna mäta vindstyrka och vindriktning och kommunicera den uppmätta datan till flaggstångens kontrollenhet. Rapporten beskriver och diskuterar de olika möjliga mekanismer och lösningar som finns för att mäta vindhastighet samt en möjlig implementering. En metod för mätning av vindhastighet där en hot-wire flödessensor valdes och en prototyp utvecklades sedan för att testa den implementerade metodens prestanda. Testen visade att användning av flödessensorn tillfredsställde de ställda kraven på prototypen gällande vindhastighetsmätning och mätprecision med en medelavvikelse på 0.19 m/s från referensvärdet. Lösningen diskuterades och jämfördes sedan med Hotswaps befintliga prototyp. Jämförelsen visade att prototypen var ett rimligt alternativ. Slutligen presenterades några förslag på vidareutveckling tillsammans med slutsatsen att prototypen är en konceptvalidering för en fullt realiserbar lösning.
22

Väderprognosstyrda värmesystem i byggnader : En jämförelse mot traditionell styrning / Weather-forecast controlled heating systems in buildings : A comparison with traditional control systems

Andersson, Victor January 2019 (has links)
The aim of this essay is to investigate how forecast control can affect the energy consumption and the top effects for heating compared to the traditional control system in facilities with different building structures. In 2013 were the energy consumption 80 TWh for the heating and domestic hot water in resident buildings and facilities. This corresponds to 55 % of the total energy consumption within the building sector and facilities represent 28 % of the buildings. This indicates that there is room for efficiency for the heating systems in facilities.Demands from new directives for stricter energy consumptions for buildings are going to be established in the Swedish regulations and 19:th of June 2018 were the new amending directives published which need to be established in the Swedish regulations latest 10 March 2020. The demands on the buildings is pushed further and further. It is getting more difficult to reach the requirements from BBR and even more difficult to reach the requirements from environmental certifications like Miljöbyggnad. Therefore, it is important with detailed solutions that is able to lower the energy consumptions for the heating systems.A reference building has been used and created in the simulation software IDA ICE with three different building constructions to compare forecast control against the traditional control system. One with a large U-value and low amount of thermal mass, one with a smaller U-value and a low amount of thermal mass and one with a smaller U-value and a high amount of thermal mass.The centrally controlled forecast control is tested against the traditional controlled system for each building structure. Traditional controlled systems in facilities is normally using thermostatic valves, due to the lack of sustainability and the lack of maintenance the control systems are also tested without the thermostatic valves.The results for the forecast control indicate on an increase for the energy saving by 3.4 % without the thermostatic valves and an increase by 2.7 % with the thermostatic valves. The top effects can be improved with forecast control by 33 % without thermostatic valves and by 15 % with thermostatic valves. These improvements were made for the building construction with high amount of thermal mass. It is possible to argue for benefits with forecast control if it is installed in a heavy constructed building with regard to the decreased top effects. It is more difficult to argue for the benefits with regard to the energy consumption. Large benefits were found with in local control, especially for buildings with large U-value and low amount of thermal mass. The result indicated on an improvement of 30 % for the traditional control with thermostatic valves and of 28 % for the forecast control with thermostatic valves compared to the scenario without the thermostatic valves.Knowledge about the building characteristics has a significance for the choice of control system. According to the results forecast control may be a benefit with regard to the top effects if it is a heavy building construction. Regarding the energy consumption is the best strategy to carefully adjust and maintain the current traditional control system. / Denna rapport har i avsikt att undersöka hur energianvändningen och värmeeffekterna för uppvärmning påverkas med prognosstyrning i jämförelse med traditionell styrning av värmesystem i lokaler av olika byggnadskonstruktioner. 2013 var energianvändningen 80 TWh för uppvärmning och tappvarmvatten i hushåll och lokalbyggnader. Detta motsvarade då 55 % av den totala energianvändningen inom sektorn där lokaler representerar 28 % av byggnaderna. Med andra ord finns det utrymme för effektivisering av uppvärmningen i lokaler.Krav från direktiv om skärpt energianvändning av byggnader måste införas i svenska regler. Den 19 juni 2018 publicerades nya ändringsdirektiv som måste vara införda i svenska regler senast den 10 mars 2020. Kraven på byggnader blir allt hårdare för att uppnå kraven som ställs från BBR och så även för att uppnå miljöcertifieringar som miljöbyggnad. Det blir alltså allt viktigare att hitta detaljlösningar som kan minska på energianvändningen på byggnader.För att ställa prognosstyrning mot traditionell styrning har en referensbyggnad använts. Den har byggts upp i simuleringsverktyget IDA ICE med tre olika byggnadskonstruktioner. Ett med både högt U-värde och liten termisk massa (originalkonstruktion), en med lägre U-värde men fortfarande liten termisk massa (lätt konstruktion) och en med lägre U-värde och mycket termisk massa (tung konstruktion).Den centralt styrda prognosstyrningen prövades sedan mot den traditionella styrningen för respektive byggnadskonstruktion. Med traditionell styrning används vanligtvis termosstatventiler i lokaler men då hållbarheten på dessa är låg vilket också underhållet av dessa kan vara, prövas även båda strategierna utan termostatventiler också.Resultatet visar att prognosstyrningen förbättrar energianvändningen som mest med 3.4 % i det fallet termostatventiler inte används och 2.7 % i det fallet termostatventiler används. Effekttopparna kan förbättras med 33 % utan termostatventiler och 15 % med termostatventiler. Dessa förbättringar genererades med den tunga konstruktionen. En tung konstruktion kan visa på fördelar med prognosstyrning med avseende på lägre effekttoppar. Utifrån resultaten går det däremot inte att se några fördelar med avseende på energianvändningen.Stora fördelar kunde däremot gå att se med lokal reglering med termostatventiler, vilket var särskilt gynnsamt för byggnader med högt U-värde och låg termisk massa. Resultatet visade då på en förbättring med 30 % för den traditionella styrningen och 28 % för prognosstyrningen när jämförelse med om de inte användes.En god förståelse av byggnadsstommens karaktär har en betydande roll för valet av reglersystem. Prognosstyrning kan vara fördelaktigt med avseende på toppeffekterna, framför allt med den tunga konstruktionen i resultatet. För att minska på energianvändningen är det dock troligtvis viktigast att se över och injustera det befintliga systemet på både central som lokal nivå.
23

Microchip Thermal Gradient Gas Chromatography

Wang, Anzi 01 December 2014 (has links) (PDF)
Although the airbath oven is a reliable heating method for gas chromatography (GC), resistive heating is needed for higher analytical throughput and on-site chemical analysis because of size, heating rate and power requirements. In the last thirty years, a variety of resistive heating methods were developed and implemented for both benchtop and portable GC systems. Although fast heating rates and low power consumption have been achieved, losses in column efficiency and resolution, complex construction processes and difficulties experienced in recovering damaged columns have also become problematic for routine use of resistively heated columns. To solve these problems, a new resistively heated column technique, which uses metal columns and self-insulated heating wires, was developed for capillary gas chromatography. With this method, the total thermal mass was significantly less than in commercial column assemblies. Temperature-programming using resistive heating was at least 10 times faster than with a conventional oven, while only consuming 1—5% of the power that an oven would use. Cooling a column from 350 °C to 25 °C with an air fan only required 1.5 min. Losses in column efficiency and peak capacity were negligible when compared to oven heating. The major trade-off was slightly worse run-to-run retention time deviations, which were still acceptable for most GC analyses. The resistively heated column bundle is highly suitable for fast GC separations and portable GC instruments. Fabrication technologies for microelectromechanical systems (MEMS) allow miniaturization of conventional benchtop GC to portable, microfabricated GC (µGC) devices, which have great potential for on-site chemical analysis and remote sensing. The separation performance of µGC systems, however, has not been on par with conventional GC. Column efficiency, peak symmetry and resolution are often compromised by column defects and non-ideal injections. The relatively low performance of µGC devices has impeded their further commercialization and broader application. This problem can be resolved by incorporating thermal gradient GC (TGGC) into microcolumns. Negative thermal gradients reduce the on-column peak width when compared to temperature-programmed GC (TPGC) separations. This unique focusing effect can overcome many of the shortcomings inherent in µGC analyses. In this dissertation research, the separation performance of µGC columns was improved by using thermal gradient heating with simple set-ups. The analysis time was ~20% shorter for TGGC separations than for TPGC when wide injections were performed. Up to 50% reduction in peak tailing was observed for polar analytes, which significantly improved their resolution. The signal-to-noise ratios (S/N) of late-eluting peaks were increased by 3 to 4 fold. These results indicate that TGGC is a useful tool for bridging the performance gap between µGC and benchtop GC.
24

Thermal mass applications in the hot‐humid region of Austin, TX

Kerbacher, Mariel Elizabeth 17 February 2011 (has links)
Thermal mass can be successfully implemented in the hot‐humid region of Austin, TX especially when well designed and with supplementary aids like nightcooling and day‐lighting. This study shows that in some situations thermal mass can be actually more beneficial at reducing electricity demands in hot‐humid regions than in the hot‐dry regions that are so emphasized in the literature. / text
25

Comparative assessment of two structural materials from a life-cycle point of view : Using dynamic and LCA calculation units from LESOSAI

Matricon, Geoffrey January 2015 (has links)
Life-cycle assessment is being applied to an increasing number of building projects from one side while the usual dynamic thermal simulations are being conducted from the other side on the same projects. However, there are few observations in the literature linking these two types of calculations: embodied and operating energies are rarely directly compared. This paper compares those energies for some case studies. The challenge is to quantify to what extent chosen structural materials can change their global life-cycle energy balance. This question is raised by the different dynamic thermal behavior of materials. Consequently, the case studies focus on the influence of materials’ thermal mass on the operating energy consumptions.Nonetheless, few software programs can conduct both these calculations (LCA and dynamic thermal modeling). The Swiss regulatory tool LESOSAI has been implemented and offers now these two possibilities. However, its LCA database is arcane, this paper will first assess the LCA results of LESOSAI by comparing it with the French tool ELODIE developed by the CSTB. Measuring the reproducibility of their results provides boundaries to the LCA calculations that LESOSAI can perform. These identified limits enable to set the starting assumptions of the case studies. Two raw materials are compared: wood and concrete structures. Considering thermal mass as a dynamic property, different typologies of building usages and climates have been investigated for the materials comparisons. Finally, the conclusion emphasizes the material that permits the lowest life-cycle impact for each typology and climate.
26

Heating system performance and thermal mass evaluation of a former military building in mid-Sweden

Ruiz Pacheco, Javier January 2023 (has links)
The concern about global warming is gaining momentum. So, many initiatives, such as the Green European pact, which aims to reach to zero greenhouses emissions in 2050, are emerging to halt it. The aim of this study is to evaluate the energy usage, thermal mass and thermal comfort of a past-military building, now part of Gävle’s University Campus. For this purpose, changes in the heating schedule and location of the building, have been made. The results are based on theorical knowledge and computer simulations using IDA-ICE software. For the modeling of the building, a large number of parameters have been taken into consideration, such as climate values, the walls, windows and roof materials, room occupancy, etc. The results have proven that the current heating schedule of the university (24h working) is the most suitable schedule showing the best results on peak power demand and thermal comfort. Compared to constant heating regulation, turning off heating completely during weekends resulted in 10% energy saving, but 369% higher peaking power and discomfort increasing from 18 to 21 Predicted Percentage Dissatisfied (PPD). Same constant heating regulation compared with 8:00 to 18:00 heating regulation shows 18.7% energy saving, but 451% higher peaking power and discomfort increasing from 18 to 36 Predicted Percentage Dissatisfied (PPD), with the greatest discomfort feeling between 8:00 to 9:00. Finally, when comparing the current heating schedule with one on where the heating is shut off on the DH peak moments, results show 3% energy saving, but 152% higher peaking power and discomfort increasing from 18 to 27 PPD. Regarding thermal mass behavior, promising comfort results have been seen for warm indoor environments where cooling would be needed, simulations have shown 30.9% higher discomfort when in this environments there is not heavy walls. Moreover, for situations where heating is needed, the heating storage capacity of the heavy walls shows some advantages slowing temperature drops during heating reduction and therefore lowering the peak power demanded.
27

Thermal storage solutions for a building in a 4th generation district heating system : Development of a dynamic building model in Modelica

Eriksson, Rickard, Andersson, Pontus January 2018 (has links)
The world is constantly striving towards a more sustainable living, where every part of contribution is greatly appreciated. When it comes to heating of buildings, district heating is often the main source of heat. During specific times, peak demands are created by the tenants who are demanding a lot of heat at the same time. This demand peak puts a high load on the piping system as well as the need for certain peak boilers that run on non-environmental friendly peak fuel. One solution that is presented in this degree project that solves the time difference between production and demand is by utilizing thermal storage solutions. A dynamic district heated building model is developed with proper heat propagation in the pipelines, thermal inertia in the building and heat losses through the walls of the building. This is all done utilizing 4th generation district heating temperatures. Modelica is the tool that was used to simulate different scenarios, where the preheating of indoor temperature is done to mitigate the possibility for demand peaks. Using an already existing model, implementation and adjustments are done to simulate thermal storage and investigate its effectiveness in a 4th generation district heating system. The results show that short-term energy storage is a viable solution in concrete buildings due to high building mass. However, combining both 4th generation district heating with storage in thermal mass is shown not to be suitable due to low temperatures of supply water, which is not able to increase the temperature of the building’s mass enough.
28

Étude de l'influence de l'inertie thermique sur les performances énergétiques des bâtiments / Study of the impact of thermal mass on the energy performance of buildings

Munaretto, Fabio 07 February 2014 (has links)
Étant de plus en plus isolés, les bâtiments très performants sont très sensibles aux apports solaires transmis par les vitrages ainsi qu'aux apports internes. Dans ce contexte, l'inertie thermique peut être utile en stockant l'énergie excédentaire et en réduisant les variations de température, améliorant ainsi le confort thermique.Évaluer la performance énergétique, environnementale et le confort thermique des bâtiments nécessite des outils de simulation thermique dynamique (STD) fiables. Historiquement, les modélisateurs ont essayé de trouver un compromis approprié entre précision et efficacité. Des hypothèses simplificatrices ont alors été intégrées dans les outils STD et ont un lien étroit avec l'inertie thermique. La validité de telles hypothèses, notamment la globalisation des échanges convectifs et radiatifs GLO intérieurs, ou la distribution forfaitaire des apports solaires transmis par les vitrages nécessitent particulièrement d'être remises en questions dans le contexte des bâtiments très isolés.Ainsi, un modèle découplant les échanges convectifs et radiatifs GLO ainsi qu'un modèle de suivi de la tache solaire (modèles détaillés) ont été implémentés dans une plateforme de simulation mettant en œuvre l'analyse modale et une discrétisation par volumes finis.Une première comparaison entre les modèles détaillés et simplifiés a été réalisée sur des cas d'études du "BESTEST", intégrant aussi des résultats d'outils STD de référence au niveau international (EnergyPlus, ESP-r, TRNSYS). Un travail similaire a été réalisé sur le cas d'une maison passive instrumentée (plateforme INCAS à Chambéry) en utilisant des techniques d'analyses d'incertitudes et de sensibilité.Les résultats montrent qu'une tendance à la baisse concernant les besoins de chauffage et de refroidissement existe en ce qui concerne les modèles détaillés considérés ici. D'autre part, il semble que ces modèles détaillés ne contribuent pas à diminuer significativement les écarts entre les simulations et les mesures. / Being highly insulated, low energy buildings are very sensitive to variable solar and internal gains. In this context, thermal mass is useful by storing surplus energy and reducing temperature variation, thus improving thermal comfort.Assessing energy, environmental and thermal comfort performances requires reliable building dynamic thermal simulation (DTS) tools. Historically, model developers have tried to find a fair-trade between accuracy and simulation efficiency within a fit-to-purpose philosophy. Simplifying assumptions have therefore been integrated into DTS tools and have a close relation with thermal mass. The validity of such assumptions, for instance constant interior convective and infrared radiative superficial exchange coefficients, or fixed distribution of solar gains transmitted through windows, particularly need to be reassessed in the case of high performance buildings.A first comparison between detailed and simplified models has been performed according to the "BESTEST", integrating also international DTS reference tools (EnergyPlus, ESP-r, TRNSYS). Similar work, but using uncertainty and sensivitivity methods has been carried out using experimental measurements on a passive building (INCAS platform in Chambéry). The results show a trend for the detailed models studied here to estimate lower heating and cooling loads. Furthermore, it seems that these detailed models don't contribute to reduce significantly discrepancies between simulations and measurements.
29

Modélisation dynamique tridimensionnelle avec tache solaire pour la simulation du comportement thermique d’un bâtiment basse consommation / A three dimensional thermal room and sun patch model to simulate the transient behaviour of an energy efficient building

Rodler, Auline 25 November 2014 (has links)
Cette thèse s’inscrit dans le contexte du développement de Bâtiments Basse Consommation. La conception de telles constructions les rend sensibles aux sollicitations internes. Aussi, les outils de thermique du bâtiment existants ne sont pas adaptés pour simuler assez fidèlement ce type de bâtiments, si bien qu’un modèle tridimensionnel et dynamique a été développé ici. Celui-ci présente plusieurs particularités : il s’appuie sur une discrétisation spatiale optimisée des parois, la tache solaire y est localisée et l’intégration des dynamiques des conditions environnementales est assurée par un solveur numérique à pas de temps adaptatif et un seul nœud d’air est considéré. La validation du modèle s’est suivant une confrontation avec des mesures en conditions réelles réalisées dans une cellule de BESTlab d’EDF R&D. Un suivi visuel de la tache solaire a permis de confirmer sa bonne localisation par notre modèle. Des mesures de température en surface complétées par des cartographies thermographiques ont été comparées aux champs de températures simulés, montrant une bonne concordance. Les comparaisons de températures d’air mesurées et simulées ont montré des résidus ne dépassant pas 1,5 ˚C, pour des erreurs moyennes de 0,5 ˚C. La pertinence des deux principales innovations du modèle a été ensuite démontrée : l’utilisation d’entrées échantillonnées à la minute associées à un solveur à pas de temps adaptatif permet de minimiser les erreurs de simulation : en mi-saison, les résidus maximaux sont respectivement de 1 ˚C et 2 ˚C pour des entrées à la minute et à l’heure. En hiver, les températures d’air simulées tendent à plus osciller autour de la consigne quand le pas d’échantillonnage des entrées s’allonge. Deux modèles unidimensionnels, représentatifs de modèles courants, M1D,sol diluant le rayonnement solaire sur le sol seul et M1D,parois le distribuant de façon homogène sur les parois au prorata de la taille de la tache solaire censée les frappées, ne dégradent que légèrement la précision des calculs de température d’air. Cependant, ces modèles 1D ne permettent pas de calcul des champs de températures sur les parois si bien qu’ils présentent des erreurs locales dépassant 20 ˚C aux endroits touchés par la tache solaire. Enfin en hiver, le modèle 3D permet de prédire des consommations de chauffage surestimées de 6,5 % quand M 1D,parois les surestime de 11 % et M1D,sol de 22 %. Les améliorations apportées par notre modèle ont été confirmées pour d’autres types de cellules. D’ailleurs des écarts plus importants entre M1D,sol et le modèle 3D ont été observés pour une cellule dont parois et sol ont des compositions très différentes, alors que l’orientation a aussi un impact. Ce travail confirme la nécessité de représenter plus finement les phénomènes physiques pour des locaux fortement isolés. Des améliorations sont à intégrer, comme la description de l’anisothermie de l’air. / Low energy building constructions become sensitive to internal gains : any internal heating source has an impact on the envelope. Therefore, it is important to evaluate the performance of current transient thermal models when adapted to low energy buildings. This work describes a numerical model to simulate a single room, using a refined spatial three-dimensional description of heat conduction in the envelope but a single air node is considered. The model has been developed for environmental conditions that vary over short time-steps and has integrated the projection of solar radiation through a window onto interior walls : the sun patch. The validation of the model has been done through a detailed comparison between model and measurements. The in situ experiment has been carried out in one of the BESTlab cells (EDF R&D). The sun patch has been followed by a camera to validate its calculated position and surface. Temperature measurements by thermocouples and by thermal cameras have been compared to the models outputs. Differences between air and surface temperatures measured and simulated were never above 1.5 ˚C and mean errors reached 0.5 ˚C. The two innovations of the model have then be proven. Using minute wise weather data and inputs associated to an adaptative solver, enabled to pull down simulation errors : in May maximal differences rised from 1 ˚C to 2 ˚C for respectivelly one minute and hourly wise inputs. More important errors are seen in summer whereas in winter, air temperatures simulated tend to more fluctuate around the set up temperature when the sampling step gets longer. Two one dimensional models, close to traditional taken simulation tools, were used. Model M 1D,sol supposed the incoming radiation to reach only the floor. A 1D model with sun patch movement, called 1D,parois , was also used. These two models evaluated the air temperature with an acceptable error. However, their surface temperatures were still subject to important errors. Thus, for temperature surfaces evaluation, both 1D model presented differences up to 20 ˚C for surfaces touched by the sun patch. In winter, the 3D model can predict heating energy consumptions overestimated by 6.5 % when M 1D,parois overestimated them by 11 % and M1D,sol by 22 %. The improvements brought by our model have been proven also for other cells with different thermal masses. For these cells, differences between M1D,sol and the 3D model could reach 4.5 ˚C. Differences seemed to be more important for low thermal mass cells, and the orientation of the building had a strong impact. This work has confirmed the necessity of representing more accuratelly the descriptions of the enveloppe for strongly insulated rooms. To improve the model, the anisothermal hypotheses of the air should be considered.
30

Systémy energeticky úsporných budov / Systems of energy efficient buildings

Šlampová, Kateřina Unknown Date (has links)
The topic of this diploma thesis is systems of energy efficient buildings with a focus on the building envelope. The first theoretical part describes the quantities that we consider when designing the building envelope. The second half of the theoretical part is with reference to the experimental part of the thesis focused on a special type of vertical perimeter structure, namely walls with live vegetation installed from the outside of the structure. The second, practical part of this work, deals with the design of heating and hot water supply for a multifunctional building. The design is elaborated in two variants - heating by means of radiators in the first variant and in the second variant by means of floor heating for residential units of the solved building. The third part define an experiment, which had the task of comparing the measured quantities on two types of vertical perimeter structures, namely a structure with growing greenery from the outside and an identical structure only without a layer of greenery. At the same time, the task was to check the possible influence of the applied greenery on heat losses, and thus the design of the heating system.

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