This thesis is based on eight articles all related to the characteristics of the cooling system and plate evaporator of a household refrigerator. Through these articles, knowledge is provided that can be used to increase the operational efficiency in household refrigeration. Papers A, B and C focus on heat transfer and pressure drop in a commonly used free convection evaporator – the plate evaporator. Applicable correlations are suggested on how to estimate the air side heat transfer, the refrigerant side pressure drop and the refrigerant side heat transfer. Papers D, E and F hold a unique experimental study of the refrigerant charge distribution in the cooling system at transient and steady state conditions. From this cyclic losses are identified and estimated and ways to overcome them are suggested. In paper G the topic “charging and throttling” is investigated in an unparalleled experimental study based on more than 600 data points at different quantities of charge and expansions device capacities. It results in recommendations on how to optimize the capillary tube length and the quantity of refrigerant charge. Finally, Paper H holds a thermographic study of the overall cooling system operating at transient conditions. Overall, a potential to lower the energy use by as much as 25 % was identified in the refrigerator studied. About 10 % was found on the evaporator’s air side. 1-2 % was identified as losses related to the edge effect of the evaporator plate. About 8 % was estimated to be cyclic losses. About 5 % was found in cycle length optimization.  It is believed that most of these findings are of general interest for the whole field of household refrigeration even though the results come from one type of refrigerator. Suggestions of simple means to reduce the losses without increasing the unit price are provided within the thesis / <p>QC 20120411</p>

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-02-03Bitstream added on 2014-06-13T19:12:11Z : No. of bitstreams: 1 bagagli_rp_me_bauru.pdf: 1886943 bytes, checksum: a693fc27655c63ad68c8b6f960ca899f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Com a crise energética recente, houve uma nova conscientização da necessidade de utilização mais racional da energia. Desta feita, uma série de pesquisas com fontes alternativas de energia, que vinham sendo preteridos em função da impressão que a crise energética do início da década de 1970 havia passado, tem ganho nova força. Dentre todas as alternativas para aproveitamento de energia solar, uma das mais utilizadas são os chamados sistemas domésticos de aquecimento de água. Este tipo de sistema, entretanto, ainda é complexo, constituído de uma série de dutos e conexões entre coletor e tanque armazenador, que contribuem para o elevado custo destes dispositivos. Uma alternativa para otimizar o custo final é o uso dos sistemas solar integrados coletor-tanque (ICS). Neste trabalho, foi avaliado o processo de movimentação natural do fluido em uma das geometrias mais comuns de sistemas deste tipo: a trapezoidal. Foi aplicada a condição de fluxo de calor constante na face inclinada para avaliação... / The recent energy crisis has developed a new conscience for necessity of rational energy use. Several works treating about renewable energy was stopped in past based in a false idea that the 1970's energy crisis was finished. Nowadays, these works have been retaken with the large use of solar energy in the Solar Domestic Hot Water Systems. However, this device is quite complex and has several components like pipes and fittings coupling solar collectors and storage tanks. This characteristic makes it an expensive system and bring difficulties for his large use. An alternative to turn it cheaper is the construction of a device with solar collector and storage tank integrated in one single component (ICS). In this work was done an evaluation of free convection process in a common geometry of this device: the trapezoidal shape. For this analysis, a constant heat flux condition was applied to the inclined face for evaluation of free convection process. Numerical results... (Complete abstract click electronic access below)

Made available in DSpace on 2014-12-17T14:58:19Z (GMT). No. of bitstreams: 1 HugoSMO_DISSERT.pdf: 2443429 bytes, checksum: f4aa985ea6a69a950cd97df70afeffe5 (MD5) Previous issue date: 2012-11-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Experiments were performed to study the effect of surface properties of a vertical channel heated by a source of thermal radiation to induce air flow through convection. Two channels (solar chimney prototype) were built with glass plates, forming a structure of truncated pyramidal geometry. We considered two surface finishes: transparent and opaque. Each stack was mounted on a base of thermal energy absorber with a central opening for passage of air, and subjected to heating by a radiant source comprises a bank of incandescent bulbs and were performed field tests. Thermocouples were fixed on the bases and on the walls of chimneys and then connected to a data acquisition system in computer. The air flow within the chimney, the speed and temperature were measured using a hot wire anemometer. Five experiments were performed for each stack in which convective flows were recorded with values ranging from 17 m? / h and 22 m? / h and air flow velocities ranging from 0.38 m / s and 0.56 m / s for the laboratory tests and air velocities between 0.6 m/s and 1.1m/s and convective airflows between 650 m?/h and 1150 m?/h for the field tests. The test data were compared to those obtained by semi-empirical equations, which are valid for air flow induced into channels and simulated data from 1st Thermodynamics equation. It was found that the chimney with transparent walls induced more intense convective flows than the chimney with matte finish. Based on the results obtained can be proposed for the implementation of prototype to exhaust fumes, mists, gases, vapors, mists and dusts in industrial environments, to help promote ventilation and air renewal in built environments and for drying materials, fruits and seeds / Estudou-se o efeito do acabamento da superf?cie de um canal vertical aquecido por uma fonte de radia??o t?rmica na indu??o de fluxo de ar por convec??o livre. Dois canais (prot?tipos de chamin? solar) foram constru?dos com placas de vidro, compondo uma estrutura de geometria tronco-piramidal. Consideraram-se dois acabamentos de superf?cie: transparente e opaco. Cada chamin? foi montada sobre uma base absorvedora de energia t?rmica, com uma abertura central para passagem de ar, e submetidas a aquecimento por meio de uma fonte radiante composta por um banco de l?mpadas incandescentes e foram feitos ensaios em campo. Termopares foram fixados nas bases absorvedoras e nas paredes das chamin?s e, em seguida, conectados a um sistema de aquisi??o de dados por computador. O fluxo de ar no interior da chamin?, sua velocidade e temperatura foram medidos utilizando-se um anem?metro de fio quente. Realizaram-se cinco ensaios para cada chamin?, nos quais foram registrados fluxos convectivos com valores variando entre 17 m?/h e 22 m?/h e velocidades de escoamento de ar variando entre 0,38 m/s e 0,56 m/s para os ensaios em laborat?rio e velocidades entre 0,6 m/s e 1,1 m/s e fluxos de ar variando entre 650 m?/h e 1150 m?/h para os ensaios em campo. Os dados dos ensaios foram comparados ?queles obtidos por meio de equa??es semi-emp?ricas, v?lidas para escoamento de ar induzido em canais e com dados obtidos atrav?s da 1? lei da Termodin?mica. Constatou-se que a chamin? com paredes transparentes induziu fluxos convectivos mais intensos que a chamin? com acabamento opaco. Com base nos resultados obtidos pode-se propor a aplica??o do prot?tipo para exaust?o de fumos, n?voas, gases, vapores, poeiras e neblinas em ambientes industriais, para auxiliar na promo??o de ventila??o e renova??o de ar em ambientes constru?dos e para secagem de materiais, frutas e sementes

Диссертация посвящена исследованию проблемы нерационального использования теплоизоляционного слоя при канальной прокладке трубопроводов в непроходных каналах. Определены все термические сопротивления тепловому потоку различных составляющих теплотрассы. Спрогнозированна примерная окупаемость теплоизолируещих слоев различной толщины. Выявлена наиболее оптимальная толщина теплоизолируещего слоя. Для более точного определения теплопотерь трубопроводов в непроходном канале, в программном коплексе ANSYS® построена модель поперечного сечения теплотрассы. Выявлен режим свободной конвекции внутри канала. Смоделированы поля распределения скорости и температуры для сеток различного качества при различных моделях турбулентности. / The thesis is devoted to the study of the problem of the irrational use of the heat-insulating layer in the channel laying of pipelines in impassable channels. All thermal resistance to the heat flux of various components of the heating main are determined. The estimated payback of heat-insulating layers of various thicknesses is predicted. The most optimal thickness of the insulating layer was revealed. To more accurately determine the heat loss of pipelines in a non-passage channel, a cross-sectional model of a heating main has been built in ANSYS®. The mode of free convection inside the channel is revealed. The velocity and temperature distribution fields are simulated for grids of various quality with various turbulence models.