Thesis (M.Arch.)--University of Hong Kong, 2002. / Includes bibliographical references. Also available in print.

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Orientador: Kamal A. R. Ismail / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-22T01:57:32Z (GMT). No. of bitstreams: 1 MicaroniNeto_Franco_M.pdf: 5213508 bytes, checksum: e8c2adb85dc9e1a8f2d71ce32a728400 (MD5) Previous issue date: 1996 / Resumo: Diversas formas construtivas são empregadas na construção de armazenadores de calor latente. Em sistema de ar condicionado é muito comum o emprego de armazenadores do tipo gelo-sobre-serpentinas. Esses armazenadores apresentam algumas características próprias e são poucos os estudos encontrados na literatura sobre esse tipo de armazenador. A condução de calor axial no material de mudança de fase e no fluido de transferência de calor foi desprezada. A temperatura de entrada do FTC é considerada constante. O acoplamento do problema de mudança de fase com a transferência de calor para o FTC é obtido fazendo-se um balanço de energia em um elemento do fluido. O coeficiente convectivo do FTC é calculado através de fórmulas que aproximam resultados numéricos para fluxo em tubos curvos. A convecção natural no MMF é desprezada. O modelo numérico é obtido através da formulação por diferenças finitas com esquema de três-niveis-tempo para o incremento de tempo. No modelo bidimensionalo coeficiente convectivo é função da direção periférica. No modelo unidimensionala parede da serpentina é substituída por uma resistência equivalente e o coeficiente convectivo é constante na direção periférica. O modelo foi considerado bom para simular o processo de carregamento do armazenador. Os resultados mostram a influência da condutividade da parede, número de Biot, natureza do FTC, temperatura de entrada do FTC, e parâmetros próprios desse tipo de armazenador como o número de Nusselt médio axial e o número de Nusselt periférico. Os resultados desse trabalho são importantes porque mesmo não solucionando totalmente o problema devido a sua complexidade fornece as informações necessárias para que soluções numéricas e analíticas mais simples sejam aplicadas com bons resultados / Abstract: Several constructive form are used to build latent heat storages. In air conditioning systems, the use of ice-on-coil type storage is very common. These storages have some particular characteristics and few studies are found in literature on this type of storages. Heat conduction parallel to the tube axes and the effects ofaxial changes in the temperature of the heat transfer fluid (HTF) was neglected. The HFT input temperature is considered constant. The coupling of the problem of phase change with heat transfer to the HFT is achieved by performing an energy balance in a fluid elemento The HFT convective coefficient is calculated by formulas which approximate the numerical results for flow in curved pipes. Natural convection in PCM is neglected. The numerical model is obtained by the formulation by finite-differences with a three-time-Ievel scheme for the time increment. In the two-dimensional model, the convective coefficient is a function of the peripheral coordinate. In the one-dimensional model, the coil wall is replaced by an equivalent thermal resistance and the convective coefficient is constant in the peripheral direction. The model was considered adequate to simulate the charging period of the storage. The results show the influence of the conductivity of the wall, Biot number, nature of HFT, input temperature of HFT, and specific parameters of this type of storage with the mean axial Nusselt number and the peripheral Nusselt number. The results of this work are important because, although they do not solve the problem thoroughly due to its complexity, they provide the information required for simpler numeric and analytical solutions can be applied with good results / Mestrado / Mestre em Engenharia Mecânica

The development of energy storage and conversion techniques with high efficiency and power density is of great importance for the sustainable development of our green world. Li-O₂ batteries with high theoretical energy density has attracted extensive attention. However there are still many issues waiting to be solved, such as low stability of cathode catalyst, as well as the deactivation of cathode by H₂O and CO₂ from air. Reversible solid oxide fuel cells can be used for electricity production by SOFCs and fuel production (H₂ and O₂) by SOECs. Thus, oxygen storage materials can bridge Li-O₂ batteries and reversible SOFCs with the purpose of increasing the whole efficiency of the system. The discovery of oxygen storage materials with reversible oxygen release/storage behaviours and high oxygen storage capacities dependent on temperature or oxygen partial pressures (e.g., inert and oxidation gases) still needs further research. The work in this thesis mainly focuses on the preparation of transition-metal based oxides (such as perovskite oxides, brownmillerite-type oxides, layered-perovskite oxides, coated β-MnO₂ nanorods, transition-metal doped CeO₂ nanocrystals) as oxygen storage materials and their energy-related applications, seeking to discover the principles for oxygen storage/release properties and their performance in energy conversion and storage applications. The prepared materials included nanostructured and bulk materials via various synthesis methods, including citrate-modified evaporation-induced self-assembly method, hydrothermal method, pechini method, as well as solid state method. This work investigated the oxygen storage capacities of several crystal structure types oxides based on transition-metals. Nanostructured La₀.₆Ca₀.₄Fe₁₋ₓCoₓO[sub](3-δ) and La₀.₆Ca₀.₄Mn₁₋ₓFeₓO[sub](3-δ) exhibit high oxygen storage capacities and stability under reductive 5%H₂/Ar, but the oxygen-storage content under inert argon is low, just about 0.2 wt%. Brownmillerite-type Ca₂AlMnO₅ is demonstrated to possess a large amount of oxygen release/storage capacities depending on temperature even under flowing oxygen, as well as high oxygen storage/release properties and reversibility under alternating inert and oxygen gases at 500 °C. Substituting Ga on the Al-site would reduce the oxygen storage capacities, even though these substituted samples still posses good reversibility. The effect of A-site species (Mg, Ca, Sr) have been also investigated and demonstrated. It can't obtain pure brownmillerite-type crystal structure when Ca is partially or totally substituted by Mg or Sr, resulting in poor reversibility and low oxygen storage capacities. Nanostructured layered-perovskite La₁.₇Ca₀.₃M₁₋ₓCuₓO[sub](4-δ) (M = Fe, Co, Ni, Cu) have also been investigated for oxygen storage and as potential cathodes for IT-SOFCs. Even though the as-prepared layered-perovskite oxides have been demonstrated to be good candidates as cathode materials for IT-SOFCs with high performance, they do not possess high amount of oxygen storage/release ability under inert atmospheres because of the robust phase stability. β-MnO₂ nanorods can release large amount of oxygen (ca. 9.2 wt%) with increasing temperature at about 560 °C under various gases (air, N₂). Coating β-MnO₂ nanorods with CeO₂ nanocrystals could result in lower temperatures for oxygen mobility and removal under N₂ because of the enhanced oxygen mobility between CeO₂₋ₓ and β-MnO₂, while coating β-MnO₂ nanorods with SnO₂ nanocrystals have no enhanced oxygen mobility behaviours. The results demonstrate the positive and negative synergetic effect between other metal oxides and β-MnO₂ on the oxygen migration. Cr- and Cu-doped CeO₂ nanocrystals (i.e. nanorods, nanocubes and nanoparticles) were chosen to investigate the effect of transition-metal doping on CeO₂ and their valence changes with temperature and various atmospheres, as well as their oxygen storage capacities. The effect of Cr- or Cu- doping on CeO₂ nanocrystal morphology and oxygen storage capacities have been investigated and demonstrated. This provides some basic information for transition-metals doped CeO₂ nanocrystal evolution and stability, as well as further applications in energy-related fields, such as three-way catalysts, electrode materials in solid oxide fuel cells and Li-air batteries.

Storage is a central part of computing. Driven by exponentially increasing content generation rate and a widening performance gap between memory and secondary storage, researchers are in the perennial quest to push for further innovation. This has resulted in novel ways to “squeeze” more capacity and performance out of current and emerging storage technology. Adding intelligence and leveraging new types of storage devices has opened the door to a whole new class of optimizations to save cost, improve performance, and reduce energy consumption. In this dissertation, we first develop, analyze, and evaluate three storage exten- sions. Our first extension tracks application access patterns and writes data in the way individual applications most commonly access it to benefit from the sequential throughput of disks. Our second extension uses a lower power flash device as a cache to save energy and turn off the disk during idle periods. Our third extension is designed to leverage the characteristics of both disks and solid state devices by placing data in the most appropriate device to improve performance and save power. In developing these systems, we learned that extending the storage stack is a complex process. Implementing new ideas incurs a prolonged and cumbersome de- velopment process and requires developers to have advanced knowledge of the entire system to ensure that extensions accomplish their goal without compromising data recoverability. Futhermore, storage administrators are often reluctant to deploy specific storage extensions without understanding how they interact with other ex- tensions and if the extension ultimately achieves the intended goal. We address these challenges by using a combination of approaches. First, we simplify the stor- age extension development process with system-level infrastructure that implements core functionality commonly needed for storage extension development. Second, we develop a formal theory to assist administrators deploy storage extensions while guaranteeing that the given high level goals are satisfied. There are, however, some cases for which our theory is inconclusive. For such scenarios we present an experi- mental methodology that allows administrators to pick an extension that performs best for a given workload. Our evaluation demostrates the benefits of both the infrastructure and the formal theory.

Total produced energy in the world is mostly consumed as thermal energy which is used for space or water heating. Currently, more than 85% of total thermal energy consumption is supplied from fossil fuels. This high consumption rate increases the depletion risk of fossil fuels as well as causing a tremendous release of hazardous gases such as carbon dioxide, carbon monoxide, sulfur oxides, nitrogen oxides and particulate matter that effects both environment and human health. Those drawbacks force humankind to search for new technologies, like renewables, to reduce fossil fuel dependency on thermal energy production. Thermal energy storage in adsorbent beds is one of the resulting technologies. Adsorption is an exothermic process in which a fluid (adsorbate) diffuses into the pores of a porous solid material (adsorbent) and trapped into the crystal lattice. In this system, exothermic adsorption of water vapor from air is carried out by using hybrid adsorbent of activated alumina and zeolite. In previous studies, through literature review, this adsorbent was selected to be the most efficient adsorbent for this process due to its high water adsorption capacity, high heat of adsorption, and stability [Dicaire and Tezel, 2011]. In this study, previous studies started on this project was confirmed and pursued by trying to increase the efficiency of the process and confirm the feasibility and applicability of this system in larger scales. In this thesis, various zeolite and activated alumina hybrid adsorbents with varying zeolite compositions were screened to find the most efficient adsorbent for thermal energy storage process that gives the highest energy density. Then, existing small column was replaced with a new one, which is 16 times bigger in volume, in order to confirm the feasibility of this process at larger scales. Applicability of on-off heat release in adsorption process was also investigated by conducting several on-off experiments at different on-off time periods. Moreover, exothermic adsorption process was modeled by doing mass and energy balances in the column, water accumulation balance in the pellets, and energy balance in the column wall. Validity of this model was confirmed by comparing it with experimental results at different column volumes, and at different volumetric flow rates. Finally, an overall plant design, capital cost and thermal energy price estimations were done for adsorption thermal energy storage plants for different storage capacities and payback periods.

Modified atmosphere packaging storage combines an atmosphere of higher carbon dioxide and lower oxygen levels than air, with chilling temperatures to extend shelf-life of fresh fruits. In three modified atmosphere packaging storage trials, blueberries were packaged in film bags with different gas permeabilities, and stored at about 4°C. Storage of blueberries in packages of a film with intermediate gas permeability produced an aerobic atmosphere and a relatively low carbon dioxide level, resulting in rapid growth of yeast and molds on blueberries. Packaging blueberries in a film with very low gas permeability created a high carbon dioxide almost anaerobic atmosphere, which successfully inhibited yeast and mold growth on blueberries for up to eight weeks. The possibility of yeast inhibition by antifungal compounds accumulated in blueberries stored under modified atmosphere packaging conditions was investigated by using the disk diffusion assay. The results of these assays showed the absence of antifungal activity against two Rhodotorula species, a Zygosaccharomyces species, a Cryptococcus species, a Debaryomyces species, and indicated that the inhibition of yeast growth was due to low temperature, high carbon dioxide level and anaerobic conditions. The effects of temperature and atmosphere composition were investigated by using natural flora of blueberry juice and two yeast isolates grown in sterilized juice. At 21°C, yeast growth was slow in the presence of carbon dioxide and absence of oxygen. At low temperature, yeast growth was slow in the presence of oxygen, but was inhibited in the anaerobic, high carbon dioxide environment. It is proposed that the micro-aerobic environment of modified atmosphere packaging storage might have allowed slow desaturation of yeast membrane fatty acids which enabled yeasts to maintain membrane fluidity and function at low .temperature. Furthermore, yeast growth during storage of modified atmosphere packaged blueberries may be affected by low temperature and high carbon dioxide conditions. / Land and Food Systems, Faculty of / Graduate

<p>Hop (<i>Humulus lupulus</i> L) belongs to the Cannabaceae family and is well-known to be a dioecious, perennial climbing plant. The common hop is native to temperate climates, but due to its widespread commercial use in the brewing industry, hop plants are grown worldwide. The bittering components in hops, especially the a-acids, provide a pleasant bitterness and characteristic flavors to beer. On their own, a-acids do not contribute much to beer bitterness but do so after they are converted to iso-a-acids during the kettle boil step in brewing. b-acids in hops are not as important as a-acids, since they only supply about a third of the bittering power as a-acids but are mostly responsible for hops’ antimicrobial properties. The goal of this study was to investigate the effects of storage conditions on the degradation rate of hop constituents. Pelletized hops from two varieties grown in Knightstown, IN were studied: Cascade (typically used as aroma hops) and Chinook (mostly used as bittering hops). The impact of storage conditions on hop chemical constituents, hop storage index (HSI), and color parameters was evaluated at three storage temperatures (4℃, 25℃, 35^oC) with hop pellets exposed to two different gases in headspace (nitrogen or air) for a duration of up to 168 days (4℃ and 25℃) and 70 days (35℃). Hop acids content was determined by UV/Vis spectrophotometry and HPLC-DAD. Results showed that increased storage temperature decreased the a-acid concentration in hops. At 4°C and 25°C the loss in a-acids was (14.5 – 23.4%) whereas at 35°C there was a greater loss in a-acids. The a-acid loss between nitrogen flushed and air exposed pellets was not significantly different (p>0.05) except for Chinook pellets stored at 35°C. b-acids remained mostly stable for the duration of the study; however, at 35℃ the loss of b-acids over time became significant for both varieties. HIS values increased over time for both varieties at 4 and 25^oC, however, those values remained below the recommended 0.40 value. At 35^oC, the HSI values indicated unsuitable hops for brewing at the end of the study for both varieties. The color parameters L* and b* remained constant after 168 days at 4 and 25^oC, while the a* value and the hue angle showed a significant decrease with time and increasing temperature. At the conclusion of the study it was demonstrated that the loss in a-acids from Cascade pellets at 35℃ was lower than the loss in Chinook, suggesting that at high temperature the a-acids in cascade were more stable than those in Chinook.</p>

Includes bibliography. / The Institute for Medical Literature (IML) provides an online bibliographic service to the biomedical community in South Africa. The requirements of the users of the services of IML were evaluated in respect of needs and satisfaction of these needs. A non-user population was also identified and evaluated. The research study was undertaken by (a) conducting a review of the literature; and (b) conducting an empirical study of users and non-users of IML to construct both a "personal" and "information behaviour" profile of both the user and non-user groups. The literature was studied to provide (i) a conceptual framework for the field of research, (ii) a compilation of findings in studies related to this study and (iii) a basis for the selection of the methodology employed in the study. The "personal" profile comprised details of age, rank and work activity type and the "information behaviour" profile comprised details of use of information channels. The needs of the users, as measured by various criteria for satisfaction of these needs, were also measured. The reasons for the non-use of the service were also investigated. The principal conclusions reached were: (a) The expressed information need of the users of IML were satisfied; (b) the majority of non-users had not heard of IML; (c) there was a difference between the information seeking behaviour of users and non-users of IML; and (d) age, rank and work activity type influenced the use or non-use of IML.

This bachelor thesis investigates the implementation of a solar panel and battery storage system in a Swedish church that is intermittently heated focusing on its economic effect and its environmental impact in terms of CO2 emissions. The models are developed to evaluate the costs and CO2 emissions associated with power production, storage, usage and installation of the implemented system. The thesis examines two cases: Case 1, where all the energy is bought from the grid, representing the current energy usage in many churches, and Case 2 which assumes the integration of a solar panel and battery storage system. In terms of economic effects, the thesis reveals that the solar panel and battery storage system results in a negative impact on the church’s costs regarding energy usage. Over a period of 25 years, the church is projected to incur a loss of 956 400 SEK. However, it is worth noting that the direct energy costs when having an implemented solar panel and battery storage system are reduced by 33%, and the sale of surplus solar power generates an income of 1 816 100 SEK. Regarding the environmental impact, the implementation of the solar panel and battery storage system results in increased emissions compared to when only consuming the Swedish electricity mix. This is mainly due to the emissions regarding manufacturing of the solar panel and battery storage system. However, it is visible that the implementation of solely solar panels would lower the system’s total CO2 emissions. The sensitivity analysis demonstrates that replacing the Swedish electricity mix with the EU electricity mix for sold solar energy results in a positive environmental impact. This since the power generated from the solar panels replaces the European electricity mix which has a higher CO2- emission equivalent. This is important to consider since it is impossible to determine which electricity mix the sold PV energy will replace. In conclusion, while the implementation of a solar panel and battery storage system negatively affects the church’s energy costs and leads to increased CO2 emissions in the examined case, there are certain benefits to consider. The reduced energy bought from the grid and lowered direct energy costs, as well as the revenue from selling surplus solar power establishes the potential for the system to provide a positive impact. However, there is a need for advancements in battery technology for this to be a possibility.