Title: Influence of depth dependence of the Earth's mantle properties on thermal-convection characteristics Author: Hana Šustková Department: Department of Geophysics Supervisor: doc. RNDr. Ctirad Matyska, DrSc. Abstract: This thesis concerns the study of convection in Cartesian models in two and three dimensions. Specifically, it deals with the systematic monitoring of critical Rayleigh numbers based on the geometry model, on the functional dependence of the viscosity or of other parameters. Models has been created with layered viscosity and constant or temperature- and depth- dependent parameters (thermal expansion and conductivity). The system has been described by conventional dimensionless Boussinesq approximation. Part of the work is devoted to the application of matrix method for solving the appropriate Stokes flow and use of Euler's method for solving the thermal equation. The actual calculations were then performed in an environment of commercial software Comsol and thus by using the finite element method. It was shown that the dominant influence on the critical Rayleigh numbers has a viscosity model (with increasing viscosity the critical Rayleigh numbers increase), other important parameter is system's geometry (larger size and dimension of the geometry reduce the critical Rayleigh number). The...

In this research, a temperature dependent tribological investigation of selected ternary oxides was undertaken. Based on the promising results of previous studies on silver based ternary oxides, copper based ternary oxides were selected to conduct a comparative study since both copper and silver are located in the same group in the periodic table of the elements. Two methods were used to create ternary oxides: (i) solid chemical synthesis to create powders and (ii) sputtering to produce thin films. X-ray diffraction was used to explore the evolution of phases, chemical properties, and structural properties of the coatings before and after tribotesting. Scanning electron microscopy, Auger scanning nanoprobe spectroscopy, and X-ray photoelectron spectroscopy were used to investigate the chemical and morphological properties of these materials after sliding tests. These techniques revealed that chameleon coatings of copper ternary oxides produce a friction coefficient of 0.23 when wear tested at 430 °C. The low friction is due to the formation of copper tantalate phase and copper in the coatings. All sputtering coatings showed similar tribological properties up to 430 °C.

In Canada 15% of greenhouse gas (GHG) emissions are produced by the residential sector’s energy demand. The majority of the energy demand is space heating which is primarily met with natural gas combustion. Motivation exists to reduce GHG emissions due to their contribution to climate change. Integrated Community Energy Harvesting (ICE-Harvest) systems seek to integrate thermal and electrical energy production, storage, redistribution, and consumption in a way that reduces GHG emissions. Borehole thermal energy storage (BTES) is implemented in ICE-Harvest systems as seasonal thermal energy storage. This thesis presents a novel model of BTES thermal response with reduced complexity to aid in early siting, design, optimization, and control systems development work for ICE-Harvest systems. The reduced model can be used to approximate periodic steady state BTES thermal response. The model provides information on average ground storage volume temperature, outlet fluid temperature, heat exchanger fluid to storage volume heat transfer rate, storage volume top loss heat transfer rate, storage volume side and bottom loss heat transfer rate, and annual thermal energy storage efficiency which aids system modelling efforts for BTES in solar thermal and ICE-Harvest systems. The reduced model is formed from a solution of the thermal energy balance equations for the BTES ground storage volume and heat exchanger fluid with simplified operating conditions for a yearly BTES charging and discharging cycle. Ground storage volume temperature is lumped as a single value. Heat transfer rates between the storage volume and the heat exchanger fluid and the storage volume and its surroundings are modelled with periodic steady state thermal resistance values for the charging and discharging timesteps. A TRNSYS DST simulation of BTES is validated against measurements from a BTES installation and TRNSYS DST is used to generate the periodic steady state thermal resistance values the reduced model requires. The periodic steady state thermal resistance values of BTES charging and discharging are dependent on BTES design parameters (spacing between boreholes, number of boreholes, borehole depth, and storage volume size) and ground thermal properties (thermal capacity and thermal conductivity) which is presented in a series of parameter sweeps with respect to a reference simulation. The reduced model predicts periodic steady state average storage volume temperature with a RMSD of 0.96°C for charging and 1.3°C for discharging when compared to the TRNSYS DST reference simulation. The reduced model predicts the periodic steady state heat exchanger total energy transfer within 1.8% for the charging timestep and 2.8% for the discharging timestep when compared to the TRNSYS DST reference simulation. The reduced model’s periodic steady state thermal resistance values are demonstrated to be independent of heat exchanger fluid inlet temperature except for the side and bottom loss thermal resistance during discharging. The reduced model cannot replicate the change in heat transfer direction that occurs during BTES discharging when the temperature of the storage volume decreases below the temperature of the surrounding ground, however, the magnitude of the energy transfer that would occur is negligible compared to the magnitude of the BTES heat exchanger total energy transfer. / Thesis / Master of Applied Science (MASc)

Microactuators are needed to convert energy into mechanical work at the microscale. Thermal microactuators can be used to produce this needed mechanical work. The purpose of this research was to design, fabricate, and test thermal microactuators for use at the microscale in microelectromechanical systems (MEMS). The microactuators developed were tested to determine the magnitude of their deflection and estimate their force. Five groups of thermal microactuators were designed and tested. All of the groups used the geometrically constrained expansion of various segments to produce their deflection. The first group, Thermal Expansion Devices (TEDs), produced a rotational displacement and had deflections up to 20 µm. The second group, Bi-directional Thermal Expansion Devices (Bi-TEDs) were similar to the TEDs. The difference, as the name implies, was that the Bi-TEDs deflected up to 6 µm in two directions. Thermomechanical In-plane Micromechanisms (TIMs) were the third group tested. They produced a linear motion up to 20 µm. The fourth group was the Rapid Expansion Bi-directional Actuators (REBAs). These microactuators were bi-directional and produced up to 12 µm deflection in each direction. The final group of thermal microactuators was the Joint Actuating Micro-mechanical Expansion Systems (JAMESs). These thermal microactuators rotated pin joints up to 8 degrees. The thermal microactuators studied can be used in a wide variety of applications. They can move ratchets, position valves, move switches, change devices, or make connections. The thermal microactuator groups have their own unique advantages. The TIMS can be tailored for the amount of deflection and output force they produce. This will allow them to replace some microactuator arrays and decrease the space used for actuation. The Bi-TEDs and REBAs are bi-directional and can possibly replace two single direction micro-actuators. The JAMESs can be attached directly to a pin joint of an existing mechanism. These advantages allow these thermal microactuator groups to be used for a wide variety of applications.

No description available.

In order to make gas chromatography (GC) more widely accessible, considerable effort has been made in developing miniaturized GC systems. Thermal gradient gas chromatograpy (TGGC), one of the heating methods used in GC, has recieved attention over the years due to it's ability to enhance analyte focusing. The present work seeks to develop high performance miniaturized GC systems by combining miniaturized GC technology with thermal gradient control methods, creating miniaturized thermal gradient gas chromatography (µTGGC) systems. To aid in this development a thermal control system was developed and shown to successfully control various µTGGC systems. DAQ functionality was also included which allowed for the recording of temperature and power data for use in modeling applications. Thermal models of the various µTGGC systems were developed and validated against the recorded experiemental data. Thermal models were also used to aid in decisions required for the development of new µTGGC system designs. The results from the thermal models were then used to calibrate and validate a stochastic GC transport model. This transport model was then used to evaluate the effect of thermal gradient shape on GC separation performance.

No description available.

The building construction industry has seen the emergence of Cross Laminated Timber (CLT) as a renewable replacement for structural application of steel, concrete, and masonry. However, CLT has not been researched extensively as a nonstructural component of the building envelope/facade. In the presented research, the application of CLT is introduced in the form of lightweight CLT (CLT-L) panels and presents a framework to evaluate the opportunities and application of CLT-L panels as an alternative construction method for non-load-bearing exterior wall systems. Since exterior walls as part of the enclosure system have a significant role in energy consumption and human comfort level, the research evaluates application opportunities of the CLT panels for US climates, by conducting a life cycle environmental analysis, and a thermal evaluation of CLT-L systems for Phoenix, Arizona, and Minneapolis, Minnesota. The life cycle analysis was conducted to assess the environmental impact of a typical CLT wall system as compared to three conventional panelized wall systems. The results of the analysis have shown that CLT wall systems exhibit the lowest cumulative life cycle environmental impact indicators, including acidification potential, fossil fuel consumption, global warming potential, and human health particulate when compared to other wall systems. These results suggest that CLT wall systems could be a viable alternative to conventional panelized exterior wall systems from an environmental impact perspective. In the next step, a parametric study was conducted to determine the optimal configuration of a CLT-L wall system for enhanced thermal performance. This was achieved through dynamic thermal simulations by employing the conduction transfer algorithm and analyzing various thicknesses and locations of the thermal insulation layer. Through analysis of the annual thermal transmission load and decrement factor, the optimum insulation thicknesses for CLT wall systems in two climate regions were determined. The results showed that the exterior insulation location yields better thermal efficiency. The results of this phase were employed in the development of the CLT wall system model and conduction of a comparative parametric study on the thermal mass behavior of CLT and CMU wall systems via finite difference algorithm. One significant outcome of the simulation data analysis was the heat transfer dynamics within the CLT and CMU wall system when exterior insulation is applied. The analysis revealed that in the presence of exterior insulation, the CLT layer continues to be the primary contributor to the reduced thermal transmission of the wall. However, in the CMU mass wall configuration, the insulation layer assumes a dominant role in the reduced thermal transmission of the wall. The findings of this research present CLT as a potential environmentally efficient envelope alternative for framed buildings and provide insights into the thermal performance of CLT wall systems, which can lead to the opening of a new market for CLT panel application in the U.S. / Doctor of Philosophy / The construction industry has witnessed a notable shift with the advent of Cross Laminated Timber (CLT), presenting itself as a renewable substitute for conventional materials like steel, concrete, and masonry in structural applications. However, the potential of CLT as a building component, particularly as a component of building exteriors wall, remains relatively underexplored. This research endeavors to fill this gap by introducing lightweight CLT (CLT-L) panels, which are three-layer CLT panels, and exploring their viability as an alternative construction method for non-load-bearing exterior wall systems. Non-load bearing exterior wall panels do not carry any structural support for the building. Recognizing the significant influence of exterior walls on both energy consumption and human comfort levels, the study assesses the applicability of CLT panels across diverse climates in the United States including states Minnesota and Arizona which show exterior temperature swings. The investigation began by conducting a comprehensive life cycle environmental analysis, comparing the environmental impact of a typical CLT wall system with three conventional panelized wall systems. Results revealed that CLT wall systems exhibit the lowest cumulative life cycle environmental impact indicators suggesting their potential as a sustainable alternative. The environmental indicators included acidification potential, fossil fuel consumption, global warming potential, and human health particulates. Subsequently, a parametric study delved into optimizing the thermal performance of CLT-L wall systems through dynamic thermal simulations. The dynamic simulation considered the exterior temperature changes during the day. By varying insulation thicknesses and locations, the study identifies optimal configurations for different climate regions. Notably, the analysis underscores the efficacy of exterior insulation placement in enhancing thermal efficiency. Furthermore, the study investigated the thermal mass behavior of CLT compared to concrete block (CMU) wall systems under different scenarios. Findings revealed that while CLT retains its significance as a primary contributor to thermal mass, particularly with exterior insulation, CMU configurations see a shift in thermal mass dynamics towards the insulation layer. These findings collectively underscored the potential of CLT as an environmentally efficient envelope alternative for framed buildings, shedding light on its thermal performance and paving the way for broader adoption in the US construction industry.

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Call number: LD2668 .T4 1952 K43 / Master of Science