Latent heat during recalesence and nucleation and post-recalesence temperature was analysed for refractory metals. An effect on latent heat was found by alloying the pure elements with other refractories. Latent heat was found to be 15-65% of tabulated values. Interface energy was evaluated from undercooling experiments. It was found that the dimensionless numbers β (σLs/ σLv) and α can be used to classify elements into distinctive groups and crystallographic structure. The phase diagrams for Al-Ti, Al-Ti-B and Al-Ti-C as well as inoculation were analysed. It was found that Al nucleates on Al3Ti which nucleates on TiB2. TiC was found to decompose into Al4C3 and Al3Ti. The inoculation of nodular cast iron with Mg, Ce; Ca and the formation of sulphides and oxides was analysed. The formation of new inclusions during the solidification as well as the formation of graphite is discussed. / QC 20100602

Information from the TRMM-CSH and TRMM-2A12 datasets is used to examine the four-dimensional latent heating (LH) structures over the Asian monsoon region between 1998 and 2006. High sea surface temperatures, ocean-land contrasts and complex terrain produce large precipitation and atmospheric heating rates whose spatial and temporal characteristics are relatively undocumented. Analyses identify interannual and intraseasonal LH variations, with a large fraction of the interannual variability induced by internal intraseasonal variability. Also, the analyses identify a spatial dipole of LH anomalies between the equatorial Indian Ocean and the Bay of Bengal regions occurring during the summer active and suppressed phases of the monsoon intraseasonal oscillation. Comparisons made between the TRMM-CSH and TRMM-2A12 datasets indicate significant differences in the shape of the vertical profile of LH. Comparison of TRMM-LH retrievals with sounding budget observations made during the South China Sea Monsoon experiment shows a high correspondence in the timing of positive LH episodes during rainy periods. Negative values of LH, associated with radiative cooling and with higher troposphere cooling from non-precipitating clouds, are not captured by any of the TRMM datasets. In summary, LH algorithms based on satellite information are capable of representing the spatial and temporal characteristics of the vertically integrated heating in the Asian monsoon region. The TRMM-CSH presents better performance than TRMM-2A12. However, the vertical distribution of atmospheric heating is not captured accurately throughout all different convective phases. It is suggested that satellite derived radiative heating/cooling products are needed to supplement the LH products in order to give an overall better depiction of atmospheric heating.

Thermal energy storage is a major contributor to bridge the gap between energy demand (consumption) and energy production (supply) by concentrating solar power. The utilization of high latent heat storage capability of phase change materials is one of the keys to an efficient way to store thermal energy. However, some of the limitations of the existing technology are the high volumetric expansion and low thermal conductivity of phase change materials (PCMs), low energy density, low operation temperatures and high cost. The present work deals with encapsulated PCM system, which operates at temperatures above 500°C and takes advantage of the heat transfer modes at such high temperatures to overcome the aforementioned limitations of PCMs. Encapsulation with sodium silicate coating on preformed PCM pellets were investigated. A low cost, high temperature metal, carbon steel has been used as a capsule for PCMs with a melting point above 500° C. Sodium silicate and high temperature paints were used for oxidation protection of steel at high temperatures. The emissivity of the coatings to enhance heat transfer was investigated.

Using techniques of remote detection, this work aimed to obtain the energy balance in the Basin of Low Jaguaribe, Perimeter irrigated Tabuleiro de Russas and dam Santo Antônio de Russas. Two images of sensor TM of the satellite Landsat 5 obtained together DGI (Department of Generation of Images) of INPE, composed by six bands, (1,2,3,4,5,7) of the spectrum of the visible and a thermal band, (6) dated of 13/08/2007 and 28/09/2008, were used for this. After, I linked the variations of the obtained results, with the indexes of rain observed in four pluviometers, belonging to FUNCEME, entered in the study area. There was not rain registration during the five previous days the image of 2007, already in 2008, three pluviometers registered 14 mm, 15 mm and 3,2 mm.The processing of the images, the Software ERDAS 8.7 was used, being used for the estimate of the energy balance, the method proposed by the algorithm SEBAL (Surface Energy Balancy Algorithm Land). This algorithm calculated: reflectance, vegetation indexes, temperature of the surface, radiation balance, flow of sensitive heat, flow of latent heat among others. For the obtaining of some of those parameters was used surface data obtained in the automatic station of the municipal district of Russas. The medium reflectance, in 2008, was of 0,249. and in 2007, it was of 0,236, being verified a small increase in 2008. The Index of Vegetation of the normalized difference presented average of 0,376 in 2008, and 0,162 in 2007, being verified a strong influence of the rains in that parameter. The radiation balance in 2007, 570 W/m², was higher than 2008, 522 W/m². I concluded that this increase is related with smaller reflectance index and larger incidence of the radiation of short waves in 2007. The flow of sensitive heat in 2007 was of 303 W/m² and, in 2008, it was of 185 W/m², observed that the rains, in 2008, will reduce the flow of sensitive heat. The flow of latent heat presented opposite values to the flow of sensitive heat as expected. In 2007 the obtained average was 162 W/m², and in 2008, it increased due ace rains, for 272 W/m². / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Utilizando técnicas de sensoriamento remoto, o presente trabalho teve como objetivo a obtenção do balanço de energia à superfície na Bacia do Baixo Jaguaribe, no perímetro irrigado Tabuleiro de Russas e no açude Santo Antônio de Russas. Foram utilizadas para isso, duas imagens do sensor TM do satélite Landsat 5 obtidas junto ao DGI (Departamento de Geração de Imagens) do INPE compostas por seis bandas, (1,2,3,4,5,7) do espectro do visível e de uma banda do termal, (6), datadas de 28/09/2007 e 13/08/2008. Após, relacionou-se as variações dos resultados obtidos, com os índices de chuva observados em quatro pluviômetros, pertencentes à FUNCEME, inseridos na área de estudo. Não houve registro de chuva durante os cinco dias anteriores à imagem de 2007. Já em 2008, três pluviômetros registraram chuvas de 14 mm, 15 mm e 3,2 mm. Para o processamento das imagens, usou-se o Software ERDAS 8.7, utilizando-se para a estimativa do balanço de energia, o método proposto pelo algoritmo SEBAL (Surface Energy Balancy Algorithm Land). Através desse algoritmo estimou-se: albedo, índices de vegetação, temperatura da superfície, saldo de radiação, fluxo de calor sensível, fluxo de calor latente, entre outros. Para a obtenção de alguns desses parâmetros utilizou-se dados meteorológicos de superfície, obtidos na estação automática do município de Russas. O albedo médio, em 2008, foi de 0,249, e em 2007, de 0,236, constatandose um pequeno aumento em 2008. O Índice de Vegetação da Diferença Normalizada apresentou média de 0,376 em 2008 e 0,162 em 2007, verificando-se uma forte influência das chuvas nesse parâmetro. O saldo de radiação em 2007, 570 W/m², foi superior ao de 2008, 522 W/m². Concluí-se que, esse aumento está relacionado com menor índice de albedo e maior incidência da radiação de ondas curtas em 2007. O fluxo de calor sensível em 2007 foi de 303 W/m² e, em 2008, de 185 W/m², observando-se, dessa forma, que as chuvas, em 2008, diminuíram significativamente o fluxo de calor sensível. O fluxo de calor latente apresentou valores opostos ao fluxo de calor sensível, como se esperava. Em 2007, a média obtida foi de 162 W/m², e em 2008, aumentou, devido às chuvas, para 272 W/m².

Made available in DSpace on 2014-06-11T19:33:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-10-24Bitstream added on 2014-06-13T20:05:37Z : No. of bitstreams: 1 oliveira_al_dr_jabo.pdf: 487509 bytes, checksum: 21986f8f6599c47af5da518d2f78570b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Foi estudada a eliminação de calor latente e estimado o fluxo térmico total ao sol e à sombra em cabras da raça Saanen mantidas em ambiente tropical, visando determinar importância da termólise evaporativa para esses animais e proporcionar subsídios para o estabelecimento de métodos de manejo em ambiente tropical. A evaporação total foi determinada por processo gravimétrico, usando-se um sistema de pesagem de precisão. A evaporação cutânea foi obtida por determinação direta através de uma cápsula ventilada; e a evaporação respiratória estimada a partir do fluxo térmico entre aparelho respiratório e o ambiente; determinaram-se ainda a estocagem térmica e as trocas convectivas e radiativas. Por ocasião de cada determinação, foram registradas a temperatura retal, a freqüência respiratória e a temperatura da superfície corporal, bem como variáveis ambientais: temperatura e umidade do ar, velocidade do vento e temperatura do globo negro. Foram avaliadas as características morfológicas do pelame (espessura da capa, comprimento médio, densidade numérica e ângulo dos pêlos) para cada animal. As análises estatísticas basearam-se no método dos quadrados mínimos para dados não-balanceados, tendo o modelo linear geral proposto incluído os efeitos: ambiente (fixo), animal (aleatório), interação animal x ambiente e regressão sobre a temperatura do ar, a umidade relativa, a temperatura radiante média, a temperatura da superfície corporal, a temperatura retal, a freqüência respiratória e a idade do animal, além das características morfológicas do pelame, no caso da evaporação cutânea. A termólise evaporativa compreendeu 61,5% da perda de calor para o ambiente, sendo a única via de perda térmica possível ao sol sob temperaturas radiante média acima de 35ºC... / The present work aimed at to study the elimination of latent heat and esteem the total thermal flow to the sun and the shade in Saanen goats in tropical environment, to determine importance of evaporative heat loss these animals and to provide subsidies for the establishment of methods of handling in tropical environment. The total evaporation was determined by means of gravimetrical process, for a weighing system of precision. The cutaneous evaporation was gotten by direct determination, by means of a ventilated capsule; the respiratory evaporation gotten by calculations of heat flow of respiratory device for environment. It was determined still the heat storage and the convective and radiative exchanges. For occasion of each determination, the rectal temperature, respiratory rate and surface temperature of the animal, as well as meteorological data: air temperature, relative humidity, wind speed and black globe temperature were register. The morphologic characteristics of the hair coat (coat thickness, hair length, numerical density and hair angle to skin) had been evaluated for each animal. The statistical analyses were carried through by the lest-squares method for not-balanced data. The considered model included the effect of environment and animal and the covariates: air temperature, relative humidity, mean radiating temperature, surface temperature, rectal temperature, respiratory rate and age of animal, beyond the morphologic characteristics of the hair coat for cutaneous evaporation. Heat loss evaporative understands 62.2% of the heat carried for environment exchange, being the way possible to the sun under radiant temperatures above of 35º...(Complete abstract, click electronic access below)

Orientador: Kamal Abdel Radi Ismail / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T03:46:08Z (GMT). No. of bitstreams: 1 Moraes_RaykleisonIgordosReis_M.pdf: 1558122 bytes, checksum: e287784c470caf116d151f9f9cc61f17 (MD5) Previous issue date: 2008 / Resumo: O presente trabalho procurou obter de uma forma detalhada o processo de formação de gelo no interior de cápsulas esféricas e geometrias alternativas recicláveis para o armazenamento de energia térmica, utilizando água e água-polietilenoglicol como PCM. Foi montada uma bancada de teste composta de um tanque de resfriamento e controlada com precisão de. As cápsulas utilizadas nos testes foram incrementadas com termopares tipo T, calibrados e localizados no centro da cápsula para investigar o efeito da solidificação do material. A faixa de variação de temperatura para os ensaios foram de - 25 à 5 ºC. Em seguida é apresentado um modelo matemático transiente em coordenadas esféricas e simulado usando a aproximação por diferenças finitas com o esquema da grade móvel. Os resultados experimentais são discutidos e as variáveis pesquisadas incluíram alguns parâmetros tais como: tempo de solidificação, temperatura do fluido de trabalho, concentração de polietilenoglicol, material da cápsula, velocidade, posição da frente de solidificação e o tamanho da cápsula no processo térmico de solidificação. O modelamento, junto com os resulta- dos experimentais forneceram parâmetros para construção de um armazenador modular para fins residenciais / Abstract: The present work looked for to get of a detailed form the similar process of icing in the interior of spherical capsules and geometrias for the storage of thermal energy being used water and water-polietilenoglicol as PCM. A composed group of benches of test of a controlled tank of cooling and with precision was mounted of ±1 ºC. Capsules used in the tests had been developed with thermocouples type T, calibrated and located in the center of the capsule to investigate the effect of the solidification of the material. The band of variation of temperature for the assays had been of 25 a 5 ºC. After that a transient in spherical coordinates is presented and simulated mathematic model using the approach for finite differences with the project of the movel scheme. The experimental results had been presented and argued some parameters such as: time for solidification, working fluid, concentration, capsule material , velocity and position of the solidification front and the size of the capsule in the thermal process of solidification. However, the together modeling with the experimental results had supplied parameters storing construction of a modular one for residential ends / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Orientadores: Luiz Fernando Milanez, Alcides Padilha / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T14:21:28Z (GMT). No. of bitstreams: 1 Oliveira_SantiagodelRio_D.pdf: 2035815 bytes, checksum: 7d72e5c223058fb0ce3675f4600214f5 (MD5) Previous issue date: 2008 / Resumo: O objetivo desse trabalho é fazer uma otimização exergética de um sistema térmico de energia solar. Esse sistema é composto por um coletor solar e por um tanque armazenador de água retangular que contém material de mudança de fase distribuído em um conjunto de barras. Esse estudo leva em consideração ambas transferências de calor por condução e convecção para a água no coletor solar, e também o processo de mudança de fase para o PCM no armazenador térmico. Assim, no coletor solar são determinadas a temperatura ótima de saída e vazão mássica ótima da água em função das condições de radiação solar. Além disso, para o tanque armazenador, são determinadas a temperatura ótima de fusão do PCM e o máximo trabalho que pode ser obtido levando em consideração o processo de mudança de fase. O processo de fusão do PCM é analisado por meio de uma solução analítica aproximada. Finalmente, foram feitas uma análise energética e exergética de cada componente do sistema bem como de todo o sistema e foram calculadas eficiências de primeira e segunda lei da termodinâmica. Resultados numéricos de um estudo de caso são apresentados e discutidos. / Abstract: This work deals with the exergetic optimization of a solar thermal energy system. This consists of a solar collector and a rectangular water storage tank that contains a phase change material distributed in an assembly of slabs. The study takes into account both conduction and convection heat transfer modes for water in the solar collector, and also the phase change process for the PCM in the storage tank. Thus, in the solar collector, optimal output temperature and optimal mass flow rate are determined as a function of solar radiation conditions. Moreover, for the storage tank, optimal melting temperature and the maximum power output taking into account the phase change process are determined. The melting process in a PCM is analyzed by means of an approximated analytical solution. Finally, energetic and exergetic analysis were done for each system component and for the overall system, and efficiencies of first and second law of thermodynamics were calculated. Results of a numerical case study are presented and discussed. / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

The Royal Botanic Gardens (RGB) is used as an umbrella name for the institution that runs Kew and Wakehurst Place gardens in Sussex The RBG has a large number of glasshouses at Kew and Wakehurst sites that consume lots of heating energy which is a major concern and the group is looking for an alternative heating system that will be more efficient and sustainable to save energy, cost and reduce CO2 emissions. Glasshouse due to greenhouse effect trap solar energy in the space with the slightest solar gains but the energy trapped in the space most often is vented through the roof wasted to keep the space temperature to the required level. An environmental measurement was carried out in twenty one zones of the glasshouse to establish the temperature and humidity profiles in the zones for at least three weeks. The investigation established that large amount of heat energy is vented to the atmosphere wasted and therefore need a heating system that could absorb and store the waste thermal energy. Phase change material (PCM) thermal energy storage technique was selected to be the best options compared to the others. It has been established that active and passive solar systems could provide enough thermal energy to meet the glasshouse heating requirements. PCM filled heating pipes will be installed to absorb the heat energy trapped in the glasshouse and use it when needed. The research analysis established that 204 MWh of the trapped energy wasted could be saved. The space temperature of the glasshouse could be maintained through melting and freezing of the PCM filled in the heating pipes. The site CHP waste heat could be useful. The research results have shown that nearly zero CO2 emission heating system could be achieved and the project is technically, economically and environmentally viable.

The thesis deals with the mathematical model for Stefan phase change problems. The model is then used in optimization procedures aimed at extremization of quantities describing the thermal behavior. The thesis also includes the derivation of the diferential heat equation, methods of energy accumulation and an introduction to phase change materials used for accumulation.

This thesis deals with simulation of cooling of rail during its passing through cooling device which has been designed by the heat transfer and fluid flow laboratory. Inputs of the computational model have been set up to get best possible correspondence between outputs of the computational model and results of experimental measurement. The solution with using of model of austenitic stainless steel is provided in first part of the thesis. The solution with considering model of carbon steel is performed in next part. Using of model of carbon steel allows including evolution of latent heat during phase changing. A fields of residual stress has been calculated for different cooling conditions in the last part of this thesis.