No description available.

No description available.

Sensors with the capability of multi-signal acquisition at the “same” site and “same” time draw abundant attention throughout the academic society. However, designing of multi-signal sensors is a challenging process. The goal of the study is to explore the design theories and methodologies for multi-signal sensors with current device manufacturing technologies. To achieve this goal, this study strives to meet the following two objectives: (1) define general design principles for such sensors, and (2) develop demonstration prototypes to prove the effectiveness of the design principle. The study takes two signals acquisition as a vehicle without loss of generality. For Objective 1, this study proposes three general design principles for multi-signal sensors. The first design principle is to acquire multiple signals through a stem signal. The second principle is to design the structure so that one signal can be accurately inferred while another signal can be directly measured. The third principle is to design an integral structure that inherently acquires two signals. For objective 2, prototypes for the second and third principles were built to demonstrate the effectiveness of the design principles. Contributions of this study to the field of composite materials and sensor design include: (1) findings of the three design principles for multi-signal acquisition, (2) proof-of-concept construction/application of two prototype multi-signal devices (one for temperature and pressure, and the other for temperature and pH), and (3) discovery of the highly linear relationship between the temperature and electrical resistivity with a carbon nanotube and polymer composite within the temperature range from room temperature to approximately 70 Celsius degrees.

The structure of old monumental churches differs a lot from contemporary buildings. The structural materials were wood, brick and stone. In order to construct high buildings with huge spans, thick massive walls and many massive columns were needed. Originally these buildings had no heating and for centuries the outdoor temperature determined the indoor climate. As churches are considered historical heritage buildings their renovation should be thoroughly studied.               In this thesis the transmission losses of Hamrånge church will be analysed. Hence, the transmission trough walls and windows as well as the heat buffering of materials will be examined. In addition, the effect of possible reformation measurements will be concluded.               Finally, this project belongs to a complete study of the church, were not only transmission losses are considered but also air infiltration losses and solar heat gain. That way, a comparison between them will be carried out in order to contribute to attain the objective of the project: possible restoration for church heating system with respect to preservation, energy requirements, thermal comfort and aesthetics. / Church project

No description available.

No description available.

No description available.

Due to rising energy prices as well as supply and ecological concerns, there is a strong interest in reducing the energy used in buildings. As such, it is desirable to model the operation of a building and predict its future energy use. In predicting the energy use of a building, the heat gain/loss through windows is an important factor. In order to accurately model this heat gain/loss, the convective heat transfer coefficient of any insect screens mounted adjacent to the windows needs to be known. This thesis describes an investigation into the heat transfer from insect screens mounted towards the indoor side of a window. The convective heat transfer coefficient of an insect screen varies based on several parameters. For implementation in building energy modelling software, it is desirable to be able to predict the convective heat transfer coefficient for an arbitrary insect screen. Due to the number of variables and the large dynamic range of the details required for modelling, direct simulation of a range of whole insect screens was not completed. Instead, a range of numerical models representing small sections of an insect screen were created. By comparing results from these to available correlations for simpler geometries, such as cylinders and flat plates, estimates for the heat transfer coefficient of a screen can be obtained. The results were non-dimensionalized for analysis and different methodologies for the prediction of heat transfer from an indoor window insect screen are described.

No description available.

Gas turbines are used to convert thermal energy into mechanical energy. The thermal efficiency of the gas turbine is directly related to the turbine inlet temperature. The combustion and turbine technology has improved to such an extent that the operating temperature in the turbine inlet is higher than the melting temperature of the turbine material. Different techniques are used to cope with this problem. One of the most commonly used methods is internal cooling of the turbine blades. Conventionally air from the compressor is used for this purpose but due to higher heat capacity, steam can be used as coolant. This opens up the possibility to increase the gas temperature. In the case of a combined cycle power plant, its availability provides a good opportunity to be used as a coolant. The trailing edge of the gas turbine blades is an important region as it affects the aerodynamics of the flow. The aerodynamics demands a sharp and thin trailing edge to reduce profile losses. The conventional method is the release of a lot of cooling air though a slot along the airfoil trailing edge. However in the case of internal only cooling designs, the coolant is not allowed to leave the channel except from the root section to avoid mixing of the gas in the main flow path with the coolant and loss of cooling medium. The challenge is to design an inner cooling channel, with the cooling medium entering and leaving the blade at the root section, which reduces the metal temperatures to the required values without an increase of the profile losses and at acceptable cooling flow rate and pressure drop. This thesis presents Computational Fluid Dynamic (CFD) based numerical work concentrated firstly on the flow and heat transfer in two-pass rectangular channels with and without turbulator ribs. The aspect ratio of the inlet pass was reduced to accommodate more channels in the blade profile in chord-wise direction. Additionally, the divider-to-tip wall distance was varied for these channels. Their effect on heat transfer and pressure drop was studied for smooth as well as ribbed channels.  It was followed by a numerical heat transfer study in the trapezoidal channel. Different RANS based turbulence models were used to compare the numerical results with the experimental results. Further, new designs to enhance heat transfer in the channel’s side walls (named as trailing edge wall) were studied. These include the provision of ribs at the trailing edge wall only, inline arrangement of ribs at the bottom as well as at the trailing edge wall and a staggered arrangement of these ribs. The final study was a conjugate heat transfer problem with an aim to propose the best internal cooling channel design to reduce the metal temperature of the trailing edge surface for the given thermal and flow conditions. A number of different options were studied and changes were made to get the best possible channel design. The results show that for a two-pass rectangular channel (both smooth and ribbed), the reduction in inlet channel aspect ratio reduces the pressure drop. For a smooth channel the reduction in the width of the inlet pass does not affect the heat transfer enhancement at the inlet pass and outlet pass regions. In case of ribbed channels, heat transfer decreases at the tip and bend bottom with decrease in the width of the inlet pass. Among different turbulence models used to validate numerical results against experimental results for case of trapezoidal channel, the low-Re k-epsilon model is found to be the most appropriate. Using the turbulence model that yields results that are closest to the experimental data, the staggered arrangement of ribs at the trailing edge wall is found to have maximum thermal performance. The results from the conjugate heat transfer problem suggest using steam as coolant if it is available as it requires less mass flow rate to get similar wall temperature values as compared to air at similar thermal and flow conditions. It is also found that staggered arrangement of ribs is the best option compared to others to enhance heat transfer in trailing edge of the gas turbine blade with the pressure drop in the cooling duct in the acceptable range. / Gasturbiner används för att omvandla värmeenergi till mekanisk energi. Den termiska verkningsgraden för en gasturbin är direkt relaterad till turbinen inloppstemperatur. Förbrännings- och turbintekniken har förbättrats så mycket att gastemperaturen i turbininloppet är högre än smälttemperaturen för turbinmaterialet. Olika tekniker används för att hantera detta problem. En av de vanligaste metoderna är intern kylningen av turbinbladen. Konventionellt luft från kompressorn används för detta ändamål, men på grund av högre värmekapacitet kan ånga användas som kylmedel. Detta öppnar för möjligheten att höja gasens temperatur. Vid ett kombikraftverk, ger dess tillgänglighet ett bra tillfälle att användas som kylmedel.   Den bakre delen av turbinbladen är ett viktigt område eftersom geometrin påverkar strömningen. Aerodynamiken kräver en skarp och tunn bakkant för att minska profilförlusterna. Den konventionella metoden för kylning av denna är att släppa ut en stor mängd kylluft genom en spalt längs bakkanten. Men i fallet med enbart inre kylning får kylmediet inte lämna skovelprofilen i strömningskanalen utan endast genom rotsektionen för att undvika blandning av förbränningsluften i turbinens strömningskanal med kylmediet och förlust av kylmedium.   Utmaningen är att utforma en inre kylkanal, i vilken kylmediet kommer in och lämnar bladet i rotsnittet som är tillräckligt bra för att hålla metalltemperaturen på normala värden utan att öka profilförlusterna och med acceptabla kylluftflöden och tryckfall.   Denna avhandling består av ett Computational Fluid Dynamics (CFD) baserat numeriskt arbetet koncentrerat på strömning och värmeöverföring först i två-pass rektangulära kanaler med och utan turbulensalstrande ribbor. Geometrin för inloppspassagen reducerades för att ge utrymme för fler kylkanaler inom bladets profil i kordans riktning. Dessutom varierades mellanväggens avstånd till toppväggen. Effekten på värmeöverföring och tryckfall studerades för båda kanalerna. Därefter följde en numerisk studie av värmeöverföringen i liknande men trapetsformade kanaler. Olika RANS baserade turbulensmodeller användes för att jämföra numeriska och experimentella resultat. Vidare har nya konstruktioner för att förbättra värmeöverföringen i kanalens sidoväggar och bakkant studeras. Dessa inkluderar turbulensribbor på enbart bakkantsväggen samt ribbor på såväl sidoväggar som på bakkantsväggen i linje med och förskjutna mot varandra. Den slutliga studien var ett sammansatt värmeöverföringsproblem bakkantens yta för ett visst angivet tillstånd i form av värmebelastning, tryck, temperatur och flöden. Ett antal olika alternativ har studerats och modifierats för att bästa möjliga kanalutformningen.   Resultaten visar att för en två-pass rektangulär kanal (både släta och ribbade), minskar tryckfallet när inloppskanalens geometri reducerades. För en slät kanal påverkar inte den minskade bredden på inloppskanalen värmeöverförning i inlopps- och utloppskanalerna. Vid ribbade kanaler minskar värmeöverföring vid toppen och på toppväggen med minskad bredd på inloppskanalen. Av de olika turbulensmodeller som används för att validera numeriska resultat mot experimentella för fallet med trapetsformad kanal visade sig låg-Re k-epsilon modellen den mest lämpliga. Genom att använda den turbulensmodell som är närmast experimentella data visar det att geometrin med förskjutna ribbor på bakkantsväggen har maximal termiska prestanda. Resultaten från det sammansatta värmeöverföringsproblemet framhåller användning av ånga som kylmedium om den finns tillgänglig eftersom den kräver mindre massflöde för att få samma värden på väggtemperaturerna jämfört med luft vid samma termiska tillstånd. Det kunde också visas att förskjutna turbulensribbor är det bästa alternativet jämfört med andra för att öka värmeöverföringen i bakkanten av ett gasturbinblad med acceptabelt tryckfall i kylkanalen. / QC 20111108