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Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (December 20, 2006) Includes bibliographical references.

Este trabalho apresenta o desenvolvimento do protótipo em escala reduzida de um sistema de refrigeração de ambientes baseado no efeito Peltier, para aplicação análoga aos condicionadores de ar comercializados atualmente, utilizando módulos termoelétricos. A pesquisa é motivada pela possibilidade de concepção de um equipamento de refrigeração para obtenção de conforto térmico, sem algumas desvantagens dos condicionadores de ar comerciais como por exemplo a vibração, ruído além das grandes dimensões como na atualidade pode ser visto. Através da pesquisa exploratório busca-se detalhar o fenômeno térmico conhecido como efeito Peltier, suas características, materiais além da revisão do estado da arte afim de encontrar estudos correlatos a proposta apresentada. Apresentam-se as etapas e detalha-se o desenvolvimento do protótipo compreendendo a parte mecânica, elétrica e térmica. Em um segundo momento, o protótipo desenvolvido é submetido a testes de validação que demonstram a real funcionalidade conforme previsto, porém, com baixo rendimento em comparação aos equipamentos existentes de refrigeração. Realiza-se ainda, uma análise comparativa por extrapolação entre o protótipo desenvolvido e condicionadores de ar comercializados permitindo a avaliação de possibilidade e implementação em escala real de aplicação. Conclui-se sugerindo melhorias e novos estudos para otimização e ajustes nas dinâmicas térmicas podem obter um produto tecnicamente viável e comercialmente apropriado. / This work describes the development of a prototype for a cooling system for environments with base on the Peltier effect, for application analogous to air conditioners currently marketed, using thermoelectric modules. The search is motivated by the possibility of conception of a cooling device to obtain a thermal comfort without some disadvantages of commercial air conditioners such as vibration, noise beyond large as can be seen today. Through exploratory research seeks to detail the thermal phenomenon known as the Peltier effect, their characteristics, materials beyond the state of the art review in order to find related studies the proposal. Presents the steps and prototype development details related the mechanics part, electrical and thermal. In a second moment, the prototype is submitted to validation tests that demonstrate the functioning as planned however, with low performance compared with commercial refrigeration equipment. It presents also a comparative analysis through extrapolation between the prototype and air conditioners commercialized allowing the evaluation of possibility and implementation in full-scale application. It concluded that the proposed improvements and new studies for optimization and adjustments in the thermal dynamics can obtain a product technically viable and commercially appropriate.

Este trabalho apresenta o desenvolvimento do protótipo em escala reduzida de um sistema de refrigeração de ambientes baseado no efeito Peltier, para aplicação análoga aos condicionadores de ar comercializados atualmente, utilizando módulos termoelétricos. A pesquisa é motivada pela possibilidade de concepção de um equipamento de refrigeração para obtenção de conforto térmico, sem algumas desvantagens dos condicionadores de ar comerciais como por exemplo a vibração, ruído além das grandes dimensões como na atualidade pode ser visto. Através da pesquisa exploratório busca-se detalhar o fenômeno térmico conhecido como efeito Peltier, suas características, materiais além da revisão do estado da arte afim de encontrar estudos correlatos a proposta apresentada. Apresentam-se as etapas e detalha-se o desenvolvimento do protótipo compreendendo a parte mecânica, elétrica e térmica. Em um segundo momento, o protótipo desenvolvido é submetido a testes de validação que demonstram a real funcionalidade conforme previsto, porém, com baixo rendimento em comparação aos equipamentos existentes de refrigeração. Realiza-se ainda, uma análise comparativa por extrapolação entre o protótipo desenvolvido e condicionadores de ar comercializados permitindo a avaliação de possibilidade e implementação em escala real de aplicação. Conclui-se sugerindo melhorias e novos estudos para otimização e ajustes nas dinâmicas térmicas podem obter um produto tecnicamente viável e comercialmente apropriado. / This work describes the development of a prototype for a cooling system for environments with base on the Peltier effect, for application analogous to air conditioners currently marketed, using thermoelectric modules. The search is motivated by the possibility of conception of a cooling device to obtain a thermal comfort without some disadvantages of commercial air conditioners such as vibration, noise beyond large as can be seen today. Through exploratory research seeks to detail the thermal phenomenon known as the Peltier effect, their characteristics, materials beyond the state of the art review in order to find related studies the proposal. Presents the steps and prototype development details related the mechanics part, electrical and thermal. In a second moment, the prototype is submitted to validation tests that demonstrate the functioning as planned however, with low performance compared with commercial refrigeration equipment. It presents also a comparative analysis through extrapolation between the prototype and air conditioners commercialized allowing the evaluation of possibility and implementation in full-scale application. It concluded that the proposed improvements and new studies for optimization and adjustments in the thermal dynamics can obtain a product technically viable and commercially appropriate.

Este trabalho apresenta o desenvolvimento do protótipo em escala reduzida de um sistema de refrigeração de ambientes baseado no efeito Peltier, para aplicação análoga aos condicionadores de ar comercializados atualmente, utilizando módulos termoelétricos. A pesquisa é motivada pela possibilidade de concepção de um equipamento de refrigeração para obtenção de conforto térmico, sem algumas desvantagens dos condicionadores de ar comerciais como por exemplo a vibração, ruído além das grandes dimensões como na atualidade pode ser visto. Através da pesquisa exploratório busca-se detalhar o fenômeno térmico conhecido como efeito Peltier, suas características, materiais além da revisão do estado da arte afim de encontrar estudos correlatos a proposta apresentada. Apresentam-se as etapas e detalha-se o desenvolvimento do protótipo compreendendo a parte mecânica, elétrica e térmica. Em um segundo momento, o protótipo desenvolvido é submetido a testes de validação que demonstram a real funcionalidade conforme previsto, porém, com baixo rendimento em comparação aos equipamentos existentes de refrigeração. Realiza-se ainda, uma análise comparativa por extrapolação entre o protótipo desenvolvido e condicionadores de ar comercializados permitindo a avaliação de possibilidade e implementação em escala real de aplicação. Conclui-se sugerindo melhorias e novos estudos para otimização e ajustes nas dinâmicas térmicas podem obter um produto tecnicamente viável e comercialmente apropriado. / This work describes the development of a prototype for a cooling system for environments with base on the Peltier effect, for application analogous to air conditioners currently marketed, using thermoelectric modules. The search is motivated by the possibility of conception of a cooling device to obtain a thermal comfort without some disadvantages of commercial air conditioners such as vibration, noise beyond large as can be seen today. Through exploratory research seeks to detail the thermal phenomenon known as the Peltier effect, their characteristics, materials beyond the state of the art review in order to find related studies the proposal. Presents the steps and prototype development details related the mechanics part, electrical and thermal. In a second moment, the prototype is submitted to validation tests that demonstrate the functioning as planned however, with low performance compared with commercial refrigeration equipment. It presents also a comparative analysis through extrapolation between the prototype and air conditioners commercialized allowing the evaluation of possibility and implementation in full-scale application. It concluded that the proposed improvements and new studies for optimization and adjustments in the thermal dynamics can obtain a product technically viable and commercially appropriate.

The thermoelectric properties of lanthanum-doped strontium titanate (LSTO) were investigated for high temperature applications. Ceramics with the formulation La(2x/3)Sr(1-x)TiO(3-delta) (x = 0.1, 0.3, 0.5, 0.7, 0.9) were produced using the conventional mixed oxide route. After 18 hours of milling the powders were calcined at 1373 K for 4 hours and sintered at 1733 K (± 180 K/hour) for 4 hours in air. SEM, XRD, and TEM techniques were employed to characterise the microstructure of the ceramics as well as density measurements. Subsequently the electrical conductivity, Seebeck coefficient, and thermal conductivity in order to determine the thermoelectric figure of merit of the ceramics. Key thermal conductivity results were further investigated using a computational approach. This production method resulted in high quality, high density (> 97 %) ceramics that were mostly single phase determined by XRD with a Pm3m space group, with the exception of the x = 0.9 ceramic that had a Cmmm space group. SEM imaging confirmed this finding and revealed a core-shell structure in x = 0.1 and x = 0.3 ceramics whereby the core was La-rich/Sr-deficient. Thermal conductivity of the ceramics decreased with increasing La content. This was investigated further computationally employing the Green-Kubo method. It was established that the decrease in thermal conductivity was due to phonon-scattering from A-site vacancies, and not from the stabilisation of oxygen vacancies as suggested elsewhere. The electrical properties were dramatically improved through sintering the LSTO ceramics in a 5 % H2 95 % Ar atmosphere. This led to a reduction of Ti4+ to Ti3+. The maximum electrical conductivity increased to 789 S.cm-1 resulting in a power factor of 0.0013 W.m-1 K-2 at 477 K for x = 0.3. A zT of 0.27 at 870 K for x = 0.5 was obtained due to a lower thermal conductivity. The ceramic LSTO x50H was subsequently doped with excess lanthanum; A maximum of 3 % excess was able to be fully incorporated into the lattice. This resulted in a further increase of the electrical conductivity to 875 S.cm-1 at 377 K. A decrease in the lattice thermal conductivity of ∼ 1 W.m-1 K-1 was also achieved due to the oxygen vacancies that were introduced as a result of the reducing sintering conditions. Overall a zT 0.27 at 1016 K was obtained for 3 % excess lanthanum. The ceramic LSTO x50H was also doped with niobium and vanadium. Reduction in the lattice parameter from the La substitution inhibited the niobium from fullyincorporating into the matrix. This was not the case for vanadium that resulted in an electrical conductivity of 144 S.cm-1 , Seebeck coefficient of -106 µV.K-1 , and thermal conductivity of 2.08 W.m-1 K-1 at 308 K, resulting in an overall maximum zT of 0.08 at 1070 K.

Title from PDF of title page. / Document formatted into pages; contains 43 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Skutterudites have been of great interest for thermoelectric applications over the last ten years. Scientific interest has focused on the unique transport properties Skutterudites possess due to the unique crystal structure. Technical interest has grown since it was discovered that some compounds rival the current best thermoelectric materials. To further the understanding of this material system, and optimize its thermoelectric properties, the synthesis and characterization of polycrystalline n- and p-type CoGe&esc;b1&esc;s&&dotb;esc;b5&esc;sSe&esc;b1&esc;s&&dotb;esc;b5&esc;s was undertaken. Structural, morphological, chemical, electrical, thermal and magnetic properties were studied. These data are compared to those of the binary Skutterudite CoSb3. The results of this study show a very sensitive dependence of the physical properties on stoichiometry. / ABSTRACT: While the thermoelectric figure of merit is low in these materials, it is apparent that optimization via doping and "void filling" will lead to improved thermoelectric properties. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Thermal transport in nanowires and nanotubes has attached much attention due to their use in various functional devices and their use as a model system for low dimensional transport phenomena. The precise control of the crystal structure, defects, characteristic size, and electronic properties of nanowires has allowed for fundamental studies of phonon and electron transport in a variety of nanoscale systems. The thermal conductivity in nanostructured materials can vary greatly compared to bulk values owing to classical and quantum size effects. In this work, two model systems for investigating fundamental phonon transport were investigated for potential use in thermoelectric and thermal management applications. The thermoelectric properties of twin defect indium arsenide nanowires and the thermal conductivity of polythiophene nanofibers with improved polymer chain crystallinity were measured with a microfabricated measurement device. The effects of twin planes on reducing the mean free path of phonons in indium arsenide and the effects of improved chain alignment in increasing the thermal conductivity in polymer fibers is discussed. / text

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