Made available in DSpace on 2014-06-11T19:23:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-15Bitstream added on 2014-06-13T19:30:01Z : No. of bitstreams: 1 kinoshita_d_me_ilha.pdf: 2189895 bytes, checksum: 18c800e5f3dc7c91ac3187a97f2410b9 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho realizou-se um estudo numérico do escoamento em gabinetes de refrigeradores domésticos operando em regime de convecção natural, usando-se o Método de Volumes Finitos. No procedmento numérico, o problema do acoplamento pressão-velocidade foi resolvido pelo algoritmo SIMPLE - Semi Implicit Method for Pressure Linked Equations para malha desencontrada. O esquema Power-Law foi utilizado como função de interpolação para os termos convectivo-difusivos e o TDMA-Tri Diagonal Matrix Algorithm foi usado para resolver os sistemas de equações algébricas. O gabinete do refrigerador foi modelado como uma cavidade tridimensional vazia sem prateleiras e o evaporador foi modelado como uma placa plana vertical com temperatura uniforme prescrita. O código numérico foi verificado parcialmente para problemas clássicos de convecção natural encontrados na literatura. Resultados experimentais preliminares para um refrigerador doméstico comercial de 350 l também foram levantados para a validação do código numérico. Após a validação do código numérico, as influências do posicionamento e temperatura do evaporador nos campos de temperatura e velocidade foram analisadas para três configurações do gabinete: gabinete sem gaveta de verdura, gabinete com gaveta de verdura e gabinete com gaveta de verdura com aberturas laterais. O modelo de gabinete com gaveta de verdura com aberturas laterais mostrou-se o mais adequado para estudar o problema. Nove posições do evaporador foram avaliadas, mostrando que o posicionamento na direção horizontal praticamente não influencia o campo de temperatura e velocidade do escoamento, enquanto que o posicionamento na direção vertical tem uma influencia significativa. Os campos de velocidade e temperatura e a carga térmica do evaporador... / A numerical study of the flow inside cabinets of domestic refrigerators working on natural convection regime is performed in this work using the Finite Volume Method as numerical procedure for solving the governing equations. The pressure-velocity coupling was solved using the algorithm SIMPLE–Semi Implicit Method for Pressure Linked Equations applied to a staggered mesh. The Power-Law scheme was used as interpolation function for the convective-diffusive terms, and the algorithm TDMA-Tri Diagonal Matrix Algorithm was used to solve the systems of algebraic equations. The model was applied to static refrigerator working in steady state with constant and uniform evaporator temperature. The cabinet was considered as an empty three-dimensional cavity without shelves and the evaporator was modeled as a vertical flat plate with prescribed uniform temperature. The numerical code was partially verified for classical natural convection problems usually found in the literature. Preliminary experimental results for a 350 l commercial domestic refrigerator were also obtained for validating the numerical code. After validating the numerical code, the influence of the positioning and temperature of the evaporator on the temperature and velocity fields were analyzed for three cabinet configurations: cabinet without vegetable drawer, cabinet with vegetable drawer, and cabinet with vegetable drawer presenting lateral openings. The model including the vegetable drawer with lateral openings showed to be the best model to study the problem. Nine evaporator positions were evaluated, showing that the positioning in the horizontal direction practically does not affect the temperature and velocity fields of the flow, while the vertical positioning has a significant effect on the results. The temperature and velocity... (Complete abstract click electronic access below)

Orientador: José Luiz Gasche / Banca: Cassio Roberto Macedo Maia / Banca: Sidnei José de Oliveira / Resumo: Neste trabalho realizou-se um estudo numérico do escoamento em gabinetes de refrigeradores domésticos operando em regime de convecção natural, usando-se o Método de Volumes Finitos. No procedmento numérico, o problema do acoplamento pressão-velocidade foi resolvido pelo algoritmo SIMPLE - Semi Implicit Method for Pressure Linked Equations para malha desencontrada. O esquema Power-Law foi utilizado como função de interpolação para os termos convectivo-difusivos e o TDMA-Tri Diagonal Matrix Algorithm foi usado para resolver os sistemas de equações algébricas. O gabinete do refrigerador foi modelado como uma cavidade tridimensional vazia sem prateleiras e o evaporador foi modelado como uma placa plana vertical com temperatura uniforme prescrita. O código numérico foi verificado parcialmente para problemas clássicos de convecção natural encontrados na literatura. Resultados experimentais preliminares para um refrigerador doméstico comercial de 350 l também foram levantados para a validação do código numérico. Após a validação do código numérico, as influências do posicionamento e temperatura do evaporador nos campos de temperatura e velocidade foram analisadas para três configurações do gabinete: gabinete sem gaveta de verdura, gabinete com gaveta de verdura e gabinete com gaveta de verdura com aberturas laterais. O modelo de gabinete com gaveta de verdura com aberturas laterais mostrou-se o mais adequado para estudar o problema. Nove posições do evaporador foram avaliadas, mostrando que o posicionamento na direção horizontal praticamente não influencia o campo de temperatura e velocidade do escoamento, enquanto que o posicionamento na direção vertical tem uma influencia significativa. Os campos de velocidade e temperatura e a carga térmica do evaporador... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: A numerical study of the flow inside cabinets of domestic refrigerators working on natural convection regime is performed in this work using the Finite Volume Method as numerical procedure for solving the governing equations. The pressure-velocity coupling was solved using the algorithm SIMPLE-Semi Implicit Method for Pressure Linked Equations applied to a staggered mesh. The Power-Law scheme was used as interpolation function for the convective-diffusive terms, and the algorithm TDMA-Tri Diagonal Matrix Algorithm was used to solve the systems of algebraic equations. The model was applied to static refrigerator working in steady state with constant and uniform evaporator temperature. The cabinet was considered as an empty three-dimensional cavity without shelves and the evaporator was modeled as a vertical flat plate with prescribed uniform temperature. The numerical code was partially verified for classical natural convection problems usually found in the literature. Preliminary experimental results for a 350 l commercial domestic refrigerator were also obtained for validating the numerical code. After validating the numerical code, the influence of the positioning and temperature of the evaporator on the temperature and velocity fields were analyzed for three cabinet configurations: cabinet without vegetable drawer, cabinet with vegetable drawer, and cabinet with vegetable drawer presenting lateral openings. The model including the vegetable drawer with lateral openings showed to be the best model to study the problem. Nine evaporator positions were evaluated, showing that the positioning in the horizontal direction practically does not affect the temperature and velocity fields of the flow, while the vertical positioning has a significant effect on the results. The temperature and velocity... (Complete abstract click electronic access below) / Mestre

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-03-16T21:31:14Z No. of bitstreams: 2 Dissertação - Izabela Cruvinel Di Castro - 2017.pdf: 1347539 bytes, checksum: 8e1d1119fb0fa51eacb218ca02174a81 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-03-20T13:34:58Z (GMT) No. of bitstreams: 2 Dissertação - Izabela Cruvinel Di Castro - 2017.pdf: 1347539 bytes, checksum: 8e1d1119fb0fa51eacb218ca02174a81 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-03-20T13:34:58Z (GMT). No. of bitstreams: 2 Dissertação - Izabela Cruvinel Di Castro - 2017.pdf: 1347539 bytes, checksum: 8e1d1119fb0fa51eacb218ca02174a81 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Pig production starts on the farms until reaching the final product that is generated in the refrigerator. One of the impasses in the pig termination phase is the best shape and the ideal batch size to be taken to the transport truck for shipment in order to minimize or eliminate animal stress and factors detrimental to carcass and quality Of meat. When driving the pigs to the truck, it is necessary to use management methods that minimize stress. For the conduct of the animals it is necessary to determine the number of animals to be driven at a time since a very large group could be subject to greater stress and agitation which can interfere in the final quality of the meat. The objective was to evaluate the relationship between the size of the group of finished pigs driven to the truck, the influence on meat quality, number of lesions and parameters of animal welfare. The experiment was carried out in five pig growth and finishing farms in the western region of Santa Catarina. Were used 198 finishing pigs of both sexes (females and males), divided in three ways of conduction (lot of three, five and ten animals) were used. The experimental design was completely randomized, with 54 animals from one of the farms (corresponding to three replicates for each treatment) and 36 animals from each farm (representing eight replicates per treatment). The variables analyzed were number of lesions, aspects of meat quality, physiological parameters of stress. Measurements of lesions in the farm, slaughterhouse and slaughterhouse, injuries of the type of fight, density and management, lesions in the loin, palette, leg and total, meat quality parameters in the Longissimus dorsi and Semimembranosus muscle, meat classification in CSR, NFP And RFN, and physiological measures of cortisol and lactate. In all treatments the data were submitted to analysis of variance, through the SAS program, and the means were compared by the Tukey test at 5% of significance. There were no significant differences between batch sizes, for lesions caused on the farm, slaughterhouse, slaughterhouse and totals, as well as between carcass, loin, palette, shank and total cuts. There were differences (p <0.05) in loin lesions, caused by fights where the group of ten animals had a larger number. Density-type lesions were also found in batch treatments of three and five animals when compared to the batch of ten animals. For management-type lesions, there was a statistical difference in the loins of the animals from a group of three animals that had a lower number of lesions when compared to five and ten animals. In the Longissimus dorsi muscle, at 45 minutes post-mortem temperature, there was a significant difference between the treatment of five animals that had a lower temperature than the other treatments. In the Semimembranosus muscle, the temperature 45 minutes post-mortem obtained a difference (p <0.05) in treatments five and ten animals with lower temperatures, when compared to the treatment with three animals. The pH measured 24 hours post mortem in the treatment of five animals is inferior to the other treatments and in the driploss the treatment of five animals obtained greater loss of water. As for the sizes of finishing pig lots driven to the truck, the results indicate that batches of three, five and ten animals can be shipped without impairing the quality of meat and animal welfare. / A produção de suínos inicia-se nas granjas até o alcance do produto final que é gerado no frigorífico. Um dos impasses na fase de terminação de suínos é a melhor forma e qual o tamanho do lote ideal a ser conduzido para o caminhão de transporte para o embarque de modo a minimizar ou eliminar o estresse do animal e os fatores prejudiciais a carcaça e a qualidade de carne. Na condução dos suínos até o caminhão devem-se utilizar formas de manejo que minimizem o estresse. Para a condução dos animais é preciso determinar o número de animais a serem conduzidos por vez já que um grupo muito grande poderia estar sujeito a um maior estresse e agitação o que pode interferir na qualidade final da carne. O objetivo foi avaliar a relação entre o tamanho do grupo de suínos terminados conduzidos ao caminhão, à influência na qualidade de carne, número de lesões e parâmetros de bem-estar animal. O experimento foi conduzido em cinco granjas de crescimento e de terminação de suínos na região do oeste de Santa Catarina. Foram utilizados 198 suínos em fase de terminação de ambos os sexos (fêmeas e machos), divididos em três formas de condução (lote de três, cinco e dez animais). Utilizou-se o delineamento experimental inteiramente ao acaso, sendo 54 animais de uma das granjas (correspondendo a três repetições para cada tratamento) e 36 animais em cada uma das granjas (representando oito repetições por tratamento). As variáveis analisadas foram número de lesões, aspectos da qualidade de carne, parâmetros fisiológicos do estresse. Foram realizadas medidas de lesões na granja, frigorífico e abate, lesões do tipo briga, densidade e manejo, lesões no lombo, paleta, pernil e total, parâmetros de qualidade de carne no músculo Longissimus dorsi e Semimembranosus, classificação da carne em RSE, PFN e RFN e, medidas fisiológicas de cortisol e lactato. Em todos os tratamentos os dados foram submetidos a análise de variância, por meio do programa SAS, e as médias comparadas pelo teste de Tukey a 5% de significância. Não se observou diferenças entre os tamanhos de lote de condução, para lesões ocasionadas na granja, frigorífico, abate e totais, bem como entre os cortes da carcaça, lombo, paleta, pernil e total. Foram encontradas diferenças (p<0,05) de lesões no lombo, ocasionadas por brigas onde o grupo de dez animais tiveram maior número. Lesões do tipo densidade foram igualmente mais encontradas nos tratamentos de lotes de três e cinco animais, quando em relação ao lote de dez animais. Para lesões do tipo manejo, houve diferença significativa, no lombo dos animais de grupo de três animais que tiveram menor número de lesões, quando comparado aos de cinco e dez animais. No músculo Longissimus dorsi, a temperatura 45 minutos post-mortem, houve diferença significativa entre o tratamento de cinco animais que teve temperatura inferior aos demais tratamentos. No músculo Semimembranosus, a temperatura 45 minutos post-mortem obteve diferença (p<0,05) nos tratamentos cinco e dez animais com temperaturas menores, quando em relação ao tratamento com três animais. O pH medido 24 horas post- mortem no tratamento de cinco animais é inferior aos demais tratamentos e no driploss o tratamento de cinco animais obteve maior perda de água. Quanto aos tamanhos de lotes de suínos em fase de terminação, conduzidos até o caminhão, os resultados indicam que lotes de três, cinco e dez animais podem ser embarcados sem prejuízos à qualidade de carne e bem-estar dos animais.

The attention for materials displaying high magnetocaloric effect (MCE) has grown during the past 30 years. One of the most important properties of MCE is the adiabatic temperature change ( ). The main aim of this work was to develop a method to measure the temperature change ( ) for magnetocaloric materials in a changing magnetic field.  A technique was developed where maximum reached  for Gadolinium was 1.19 K in a changing magnetic field of 1.3 T, however, this is lower value in comparison with previous studies (3.3 K in a changing magnetic field of 1 T, Bjørk, et al., 2010) which makes the developed method not sufficient enough to measure . Furthermore, finding novel materials displaying high MCE is of great interest. MnFePSiB alloys display promising MCE properties but processing method is expensive and time consuming. Therefore, a MnFePSiB compound was simply remelted several times and heat treated to enhance its properties. The MnFePSiB alloy was remelted 1, 2 and 3 times after initial casting. Melting the material 3 times resulted improvement in both the magnetic and magnetocaloric properties due to enhanced homogeneity. The material melted 3 times was further heat treated to improve its magnetic magnetocaloric properties. Heat treating the material for 5 hours at 1373K improved the magnetic entropy change more than 10 times compared to the as cast sample,  was moved closer to room temperature and maximum  of 0.71 K was obtained.

El tubo capilar con intercambio de calor líquido-succión (CT-LSHX) es un componente ampliamente utilizado en refrigeradores domésticos. Trabajos recientes han indicado que la entrada del tubo capilar era bifásica, aunque condiciones subenfriadas estaban medidas a la salida del condensador. El objetivo de esta tesis doctoral es examinar las condiciones reales a la entrada del tubo capilar de un refrigerador doméstico mediante el uso de un banco de pruebas innovador. Se instalaron tubos transparentes a la salida del condensador y a la entrada del tubo capilar con el fin de visualizar el flujo. La campaña de visualización experimental revela que el flujo a la entrada del tubo capilar era bifásico a pesar de la medición de un cierto subenfriamiento, independientemente de la posición del filtro instalado a la entrada del capilar (horizontal o vertical), la dirección del flujo (hacia arriba o hacia abajo) y la carga de refrigerante. Este estudio demuestra también que el filtro no estaba actuando como un acumulador ya que el nivel de líquido del capilar siempre siguió la entrada del tubo capilar, independientemente de la longitud del tubo capilar dentro del filtro. Se plantearon dos hipótesis para explicar el fenómeno: una condición de no equilibrio del refrigerante y/o un desequilibrio entre el caudal másico del compresor y del capilar, es decir, el sistema estaría equipado con un capilar no bastante restrictivo en comparación con las necesidades del compresor. El condensador original refrigerante-aire fue reemplazado por un condensador refrigerante-agua para evaluar, a partir del balance de calor en el condensador de agua, las condiciones del refrigerante a la salida del condensador y, por lo tanto, a la entrada del tubo capilar. Las mediciones indican un flujo bifásico no equilibrado compuesto de vapor y líquido subenfriados a la entrada del tubo capilar. Para verificar si la presencia de flujo bifásico se debía a un desequilibrio entre el caudal másico del compresor y del capilar, el diseño del banco de prueba se modificó utilizando un diámetro de tubo capilar más pequeño y aumentando la velocidad del compresor. Con esta nueva configuración, se alcanzó a llenar de líquido el filtro y, por lo tanto, tener condiciones exclusivamente líquidas a la entrada del tubo capilar. Se realizó una comparación de prestaciones entre un flujo bifásico y un flujo únicamente líquido a la entrada del capilar. Los resultados revelan que el COP fue mayor cuando la entrada del capilar era sólo líquida. / El tub capil·lar amb intercanvi de calor líquid-succió (CT-LSHX) és un component àmpliament utilitzat en refrigeradors domèstics. Treballs recents han indicat que l'entrada del tub capil·lar era bifàsica, encara que condicions sub-refredades estaven mesurades a l'eixida del condensador. L'objectiu d'aquesta tesi doctoral és examinar les condicions reals a l'entrada del tub capil·lar d'un refrigerador domèstic mitjançant l'ús d'un banc de proves innovador. Es van instal·lar tubs transparents a l'eixida del condensador i a l'entrada del tub capil·lar amb la finalitat de visualitzar el flux. La campanya de visualització experimental revela que el flux a l'entrada del tub capil·lar era bifàsic malgrat el mesurament d'un cert sub-refredament, independentment de la posició del filtre instal·lat a l'entrada del capil·lar (horitzontal o vertical), la direcció del flux (cap amunt o cap avall) i la càrrega de refrigerant. Aquest estudi demostra també que el filtre no estava actuant com un acumulador ja que el nivell de líquid del capil·lar sempre va seguir l'entrada del tub capil·lar, independentment de la longitud del tub capil·lar dins del filtre. Es van plantejar dues hipòtesis per a explicar el fenomen: una condició de no equilibri del refrigerant i/o un desequilibri entre el cabal màssic del compressor i del capil·lar, és a dir, el sistema estaria equipat amb un capil·lar no bastant restrictiu en comparació amb les necessitats del compressor. El condensador original refrigerant-aire va ser reemplaçat per un condensador refrigerant-aigua per a avaluar, a partir del balanç de calor en el condensador d'aigua, les condicions del refrigerant a l'eixida del condensador i, per tant, a l'entrada del tub capil·lar. Els mesuraments indiquen un flux bifàsic no equilibrat compost de vapor i líquid sub-refredats a l'entrada del tub capil·lar. Per a verificar si la presència de flux bifàsic es devia a un desequilibri entre el cabal màssic del compressor i del capil·lar, el disseny del banc de prova es va modificar utilitzant un diàmetre de tub capil·lar més xicotet i augmentant la velocitat del compressor. Amb aquesta nova configuració, es va aconseguir omplir de líquid el filtre i, per tant, tindre condicions exclusivament líquides a l'entrada del tub capil·lar. Es va realitzar una comparació de prestacions entre un flux bifàsic i un flux únicament líquid a l'entrada del capil·lar. Els resultats revelen que el COP va ser major quan l'entrada del capil·lar era només líquida. / Capillary tube with liquid-to-suction heat exchanger (CT-LSHX) is a component widely used in household refrigerators. Recent works have indicated that even when measuring subcooled conditions at the condenser outlet, the actual capillary tube inlet is two phase-flow. The aim of this PhD thesis is to examine the actual conditions at the capillary tube inlet of a household refrigerator by using an innovative test bench. Transparent tubes were set up at the condenser outlet and capillary tube inlet. The experimental visualisation campaign reveals that the capillary tube inlet was two-phase flow despite the measurement of a certain subcooling, regardless of the filter position (horizontal or vertical), flow direction (upward or downward) and refrigerant charge. This study also demonstrates that the filter was not acting as an accumulator since the liquid level of the capillary always followed the capillary tube entrance, regardless of the capillary tube length inside the filter. Two hypotheses were then posed to explain the phenomenon: a non-equilibrium condition of the refrigerant and/or an unbalanced matching between compressor and capillary tube, that is, the system would be equipped with a capillary tube with a notably large expansion capacity compared to the needs of the compressor. The original refrigerant-to-air condenser was replaced by a refrigerant-to-water condenser to assess, from the heat balance at the water condenser, the refrigerant conditions at the condenser outlet and therefore, at the capillary tube inlet. Measurements indicate a non-equilibrium two-phase flow composed of subcooled vapour and liquid at the capillary tube inlet. To verify if the presence of two-phase flow was due to unbalanced matching between the capillary tube and compressor, the test bench design was modified by using a smaller capillary tube diameter and increasing compressor speed. Fully liquid conditions at the capillary tube inlet were reached with this new configuration. A performance analysis comparison between a capillary tube inlet composed of vapour and liquid and a capillary tube inlet composed of only liquid was also performed. Results reveal that COP were higher in cases of fully liquid conditions at the capillary tube inlet. / Bardoulet, LV. (2018). Non-adiabatic capillary tubes in high efficiency household refrigerator: an experimental study [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/113170

Yes / Thermoacoustic refrigeration is an evolving cooling technology in which the acoustic power is used to pump heat. The operating conditions and geometric parameters are important for the thermoacoustic refrigerator performance, as they affect both its performance and the temperature difference across the stack. This paper investigates the effect of the stack geometric parameters and operating conditions on the performance of a standing wave thermoacoustic refrigerator and the temperature difference across the stack. DeltaEC software is used to make the thermoacoustic refrigerator model. From the obtained results, normalised values for the operating conditions andgeometric parameters are collected to compromise both the performance and the temperature difference across the stack.

The performance evaluation and parametric studies of an Inertance Tube Pulse Tube Refrigerator (IPTR) are performed for different length-to-diameter ratios, with the Computational Fluid Dynamics (CFD) package FLUENT. The integrated model consists of individual models of the components, namely, the compressor, compressor cooler, regenerator, cold heat exchanger, pulse tube, warm heat exchanger, inertance tube and the reservoir. The formulation consists of the governing equations expressing the conservation of mass, momentum and energy with axi-symmetry assumption and relations for the variable thermophysical properties of the working medium and the regenerator matrix, and friction factor and heat transfer coefficients in oscillatory flows. The local thermal non-equilibrium of the gas and the matrix is taken into account for the modeling of heat exchangers and the regenerator which are treated as porous zones. In addition, the wall thickness of the components is also accounted for. Dynamic meshing is used to model the compressor zone. The heat interaction between pulse tube wall and the oscillating gas, leading to surface heat pumping, is quantified. The axial heat conduction is found to reduce the overall performance. The thermal non-equilibrium results in a higher cold heat exchanger temperature due to inefficiencies. The dynamic characteristics of pulse tube are analyzed by introducing a time constant. The study is extended to other types of PTRs, namely, the Orifice type Pulse Tube Refrigerator (OPTR), Double Inlet type Pulse Tube Refrigerator (DIPTR) and a PTR with parallel combination of inertance tube and orifice (OIPTR). The focus of the second phase of analysis is the pulse tube region. The oscillatory flow and temperature fields in an open-ended pipe driven by a time-wise sinusoidally varying pressure at one end and subjected to an ambient-to-cryogenic temperature difference across the ends, is numerically studied both with and without the inclusion of buoyancy effects. Conjugate effects arising out of the interaction of oscillatory flow with heat conduction in the pipe wall are taken into account by considering a finite thickness wall with an insulated exterior surface. Parametric studies are conducted with frequencies in the range 5-15 Hz for an end-to-end temperature difference of 200 K. As the pressure amplitude increases, the temperature difference between the wall and the fluid decreases due to mixing at the cold end. The pressure amplitude and the frequency have negligible effect on the time averaged Nusselt number. The effect of buoyancy is studied for hot side up and cold side up configurations. It is found that the time averaged Nusselt number does not change significantly with orientation or Rayleigh number. Sharp changes in Nusselt number and velocity profiles and an increase in energy transfer through solid and gas were observed when natural convection comes into play with hot end placed down. Cooldown experiments are conducted on a preliminary experimental setup. Comparison of the numerical and experimental cooldown curves disclosed a number of areas where improvement is required, primarily the leakage past the piston and the design of the heat exchangers. The setup is being improved to bring out a second and improved version for attaining the lower cold heat exchanger temperature.

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La réfrigération solaire est une alternative à la production de froid à partir de machines à compression mécanique de vapeur dont l’alimentation est électrique. Parmi les technologies envisageables, le couplage d’une machine de réfrigération thermoacoustique avec un concentrateur solaire et un stockage frigorifique par chaleur latente apparait comme une option intéressante. Cette thèse introduit la problématique du sujet et présente les différentes technologies envisageables pour la conception d’un réfrigérateur thermoacoustique solaire. Ensuite, pour répondre au problème, le prototype expérimental qui a été conçu et fabriqué est présenté. Une méthode de modélisation transitoire au niveau système du prototype est proposée. Enfin les résultats obtenus par les simulations dynamiques sont discutés à travers l’analyse du comportement transitoire de l’ensemble du procédé et des performances associées. / Solar refrigeration is an alternative to electrically driven vapor compression cycle for refrigeration. Among the solar refrigeration technologies, the coupling of a heat driven thermoacoustic refrigerator with a solar concentrator and a cold latent energy storage system seems to be a promising technology. This thesis introduces the issue of the subject and analyzes the different available technologies to design a solar driven thermoacoustic refrigerator. Then, to address the problem, the prototype that has been designed and built, is presented. A lumped model is introduced to describe the transient behavior of the prototype. Finally, simulation results are presented and discussed in terms of dynamic behavior and performance analysis.

A existência de ondas gravitacionais foi confirmada indiretamente pela observação astronômica de pulsares binários. Detectores de ondas gravitacionais tem sido desenvolvidos desde o trabalho pioneiro de Weber nos anos 60. Esforços estão sendo realizados no sentido de aumentar a sensibilidade dos detectores e realizar uma detecção direta, que ainda não foi confirmada. O Grupo GRAVITON está aperfeiçoando e melhorando a sensibilidade de um detector de ondas gravitacionais que se encontra no Laboratório de Estado Sólido e Baixas Temperaturas do Instituto de Física da Universidade de São Paulo (LESBT/IFUSP), na cidade de São Paulo com apoio da FAPESP (processo 2006/56041-3). Esse detector, denominado MARIO SCHENBERG, é composto por uma massa ressonante esférica de CuAl(6%) com 65 cm de diâmetro, com aproximadamente 1150 kg, que deverá atingir a sensibilidade h ~ 10-22 em uma banda passante de 50 Hz, em torno de 3200 Hz, quando estiver operando a temperaturas da ordem de 0,05 K. Atualmente o detector já tem toda a sua infraestrutura criogênica montada e testada para resfriamentos a 4 K e toda a suspensão da esfera bem como todo o sistema de filtragem mecânica construídos e montados. Já foram realizadas as primeiras corridas comissionadas em 2006, 2007 e 2008, quando foram realizados vários diagnósticos sobre o sistema e desde então vem sendo desenvolvidos os transdutores para colocar o detector novamente em operação com melhor sensibilidade. Paralelamente, foram realizadas melhorias no próprio detector em razão dos diagnósticos realizados. O trabalho aqui apresentado está associado ao projeto acima. O autor desenvolveu atividades associadas à construção e desenvolvimentos do detector, que podem ser divididas em três partes principais: na parte mecânica, foi desenvolvido, instalado e testado um novo sistema de isolamento vibracional da suspensão da esfera; na parte criogênica foram feitas novas conexões térmicas, cálculos de gastos de hélio líquido e feitos desenvolvimentos para o funcionamento do refrigerador por diluição; e na parte eletrônica foi feita a instalação da eletrônica responsável pela transdução do sinal, além do desenvolvimento de um novo par de antenas de microfita. / The existence of gravitational waves has been confirmed indirectly by astronomical observation of binary pulsars. Gravitational wave detectors have been developed since the pioneering work of Weber in the 60s. Efforts are being made to increase the sensitivity of the detectors and perform a direct detection, wich has not been confirmed yet. The GRAVITON Group is enhancing and improving the sensitivity of a gravitational wave detector which is at the Laboratório de Estado Sólido e Baixas Temperaturas of the Instituto de Física of the Universidade de São Paulo (LESBT / IFUSP), in São Paulo city and is supported by FAPESP (processo 2006/56041-3). This detector, called MARIO SCHENBERG, consists of a spherical resonant mass of CuAl (6%) with 65 cm in diameter, and approximately 1150 kg, which should reach the sensitivity of h ~ 10-22 in a bandwidth of 50 Hz around 3200 Hz, when operating at temperatures of 0.05 K. Currently the detector already has all its infrastructure assembled and tested for cryogenic cooling down to 4 K and the whole suspension of the sphere as well as all mechanical isolation system constructed and assembled. Commissioning runs have already been done in 2006, 2007 and 2008, when several diagnoses on the system were performed and since then there have been many developments on the transducers to put back the detector into operation with improved sensitivity. At the same time, improvements have been made within the detector itself due to the diagnoses. The work presented here is associated with the above project. The author has developed activities and developments associated with the detector construction, which can be divided into three main parts: the mechanical part, in which a new system of vibration isolation was designed for the sphere suspension, installed and tested; the cryogenic part, in which new connections and thermal calculations of liquid helium boil-off rate were made as well as other developments for the operation of a dilution refrigerator; and the electronic part, in which the installation of the electronic signal responsable for the transduction was made, besides the development of a new pair of micro-strip antenna.