The major aim of this work is to develop a framework for the estimation of Evapotranspiration (ET) over the Indian landmass using remote sensing (RS) datasets in a repeated and consistent manner with improved spatial resolution. Different RS based ET models exist in the literature, out of which, the triangle, the S-SEBI and the Sim-ReSET models were compared for the estimation of daytime integrated latent heat flux (λEday). These three models were chosen as they can be driven only with RS based inputs without the need for any ground measurements. The results showed that the application of simpler contextual models may yield better results than physically based models when ground data is limited or not available. To improve the spatial resolution of one of the key surface variable, Land Surface Temperature (LST), the performance of five different vegetation indices Normalised Difference Vegetation Index (NDVI), Fraction Vegetation Cover (FVC), Normalised Difference Water Index (NDWI), Soil Adjusted Vegetation Index (SAVI) and Modified SAVI (MSAVI) were tested in the existing DisTrad disaggregation model. Results suggested that the most commonly used vegetation indices NDVI and FVC yielded better results only under wet conditions. Under drier surface conditions, using NDWI for disaggregation resulted in relatively higher accurate LST. A model for spatial disaggregation of Evaporative Fraction (EF) called DEFrac (Disaggregation of Evaporative Fraction) was developed based on the relationship between EF and NDVI to obtain finer spatial resolution EF from coarser resolution estimates. The experimental results suggested that the DEFrac model developed in this study, yielded more accurate disaggregated EF. The disaggregated EF was further used to get disaggregated λEday. Finally, The issue of lack of proper ET dataset over India was addressed by developing two data products one over entire India at 0.05° spatial resolution and the second product over the Kabini basin at 1 km spatial resolution. Both the products were developed with a temporal resolution of 8-day and for the period 2001–2014. The developed ET products were validated against ground observed data at seven sites across India and against ET simulated by a hydrological model over a forested watershed. Further the developed ET products were compared with some other global ET products such as MOD16, LandFlux Eval synthesis ET and GLEAM ET. Analyses revealed that only in regions where ET is predominantly driven by rainfall and where irrigation is not applied at very large scales, the global ET products tend to capture the ET patterns satisfactorily. On the other hand, the ET products developed in this work captured the spatial and temporal patterns of ET quite realistically all across India.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this study, simulated to net radiation and energy flux in a region with rotation of crops, for two distinct periods: Period 1 (01 / Feb / 2009 to 31 / Jan / 2010) and period 2 (14 / Dec / 2009 to 28 / Apr / 2010). In these simulations we used the NOAH LSM surface model. For the period 1 initially, without any calibration simulations were performed only with the input of the local weather conditions, an adjustment of an experiment controlfile file and spin up for the stabilization of the initial conditions. In these simulations, the results were very poor, indicating a need to test the sensitivity of the model especially because of the launch conditions of temperature and soil moisture. After these tests it was found that the initial predictions of impact can be considerable conditions for the two cases. It is noticed that the soil moisture changes generate greater impact in the model that temperature variations boot. As a result, proposed a calibration for the model. The calibration method was to make some simulations manually varying the parameters of soil and vegetation, or both, according to the deficiencies of the NOAH LSM. The tests were carried out until they could get a more optimized forecast for the period studied. The initial analysis of the local conditions of the experimental site was very important for calibration, as it allowed establishing previous parameters corresponding to values close to those parameters when calibrated. Simulation results after calibration applied satisfactorily exhibited liquid radiation and heat flows. So it can be said that the calibration is proposed representing characteristics of vegetation and soil correctly. Nevertheless, the corrections that the model still needs, especially in sensible and latent heat fluxes, may be associated with representation in heat distribution processes and water, or by the fact that the colder months had considerable regime rains. So when there is cloud cover, the model still has problems in representation. Results for long periods of data, as in this work, may lose some of representativeness due to the seasonality of the vegetation parameters, for which varied the parameters for periods culture and fallow. The most important contribution made in this work was a model fit for an agricultural ecosystem area and validate it for the future, it may be used as an initial boundary condition in numerical weather prediction models. The implementation variations in LAI and albedo parameter applied in the simulations of period 2 (soybean) improved the description of the heat flux and net radiation. / Neste estudo simulou-se a radiação líquida e os fluxos de energia para uma região com rotações de cultivos agrícolas, para dois períodos distintos: Período 1 (01/Fev/2009 até 31/Jan/2010) e período 2 (14/Dez/2009 até 28/Abr/2010). Nestas simulações utilizou-se o modelo de superfície NOAH LSM. Inicialmente, para o período 1, foram feitas simulações sem nenhuma calibração, apenas com a entrada das condições meteorológicas locais, um ajuste do arquivo controlfile e um experimento spin up para a estabilização das condições iniciais. Nestas simulações, os resultados foram muito insatisfatórios, indicando uma necessidade de testar a sensibilidade do modelo principalmente frente às condições de inicialização da temperatura e da umidade do solo. Após estes testes verificou-se que impactos das previsões às condições iniciais podem ser consideráveis para os dois casos. Percebe-se que as variações de umidade do solo geram maior impacto no modelo devido à temperatura do solo que é simulada. Na sequência, propôs-se uma calibração para o modelo. O método de calibração consistiu em fazer algumas simulações variando-se manualmente os parâmetros de solo e vegetação, ou ambos, de acordo com as deficiências do NOAH LSM. Assim, os testes foram realizados até que se conseguisse uma previsão mais otimizada para o período estudado. A análise inicial das condições locais do sítio experimental foi de suma importância para a calibração, pois ela possibilitou estabelecer parâmetros prévios que correspondem a valores próximos dos parâmetros quando calibrados. Os resultados das simulações, após a calibração aplicada, representaram satisfatoriamente a radiação líquida e os fluxos de calor. Portanto, pode-se dizer que a calibração proposta está representando as características de vegetação e de solo de forma correta. Apesar disso, as correções que o modelo ainda necessita, principalmente nos fluxos de calor sensível e latente, podem estar associadas a representação nos processos de distribuição do calor e da água, ou ainda pelo fato de que os meses mais frios tiveram um considerável regime de chuvas. Assim, quando há nebulosidade, o modelo ainda apresenta problemas na representação. Os resultados para períodos longos de dados, os quais foram considerados neste trabalho podem perder um pouco da representatividade em função da sazonalidade dos parâmetros de vegetação, motivo pelo qual variou-se os parâmetros para períodos com cultura e com pousios. A contribuição mais importante realizada neste trabalho foi um ajuste do modelo para uma região de ecossistema agrícola e a sua validação para que futuramente, possa ser utilizado como condição de contorno inicial em modelos de previsão numérica do Tempo. A implementação das variações diárias no parâmetro IAF e no albedo, aplicada nas simulações do período 2 na cultura de soja, melhorou a descrição dos fluxos de calor e da radiação líquida.

With the demand of computing power from electronic chips on a constant rise, innovative methods are needed for effective and efficient thermal management. Forced convection cooling through an array of micro pin-fins acts not only as a heat sink, but also allows for the electrical interconnection between stacked layers of integrated circuits. This work performs a multi-objective optimization of three shapes of pin-fins to maximize the efficiency of this cooling system. An inverse design approach that allows for the design of cooling configurations without prior knowledge of thermal mapping was proposed and validated. The optimization study showed that pin-fin configurations are capable of containing heat flux levels of next generation electronic chips. It was also shown that even under these high heat fluxes the structural integrity is not compromised. The inverse approach showed that configurations exist that are capable of cooling heat fluxes beyond those of next generation chips. Thin film heat spreaders made of diamond and graphene nano-platelets were also investigated and showed that further reduction in maximum temperature, increase in temperature uniformity and reduction in thermal stresses are possible.

Ce mémoire présente une étude sur le refroidissement passif de batteries lithium-ion. Il se compose de deux grandes parties. La première partie est une étude expérimentale et numérique du comportement thermique d’une batterie et la seconde partie est l’étude expérimentale d’un système passif pour le refroidissement de plusieurs batteries. Un banc d’essais expérimental a été conçu pour suivre l’évolution thermique des batteries soumises à différents courants de sollicitation. Les batteries prismatiques étudiées sont de type LFP et de capacité 60 Ah. Dans un premier temps, le comportement thermique d’une batterie soumise à des cycles de charge / décharge, est caractérisé expérimentalement. Nous montrons que la température n’est pas uniforme à la surface de la batterie et la zone la plus chaude est identifiée. Dans un second temps, un modèle numérique tridimensionnel a été développé pour prédire la température en tout point de la batterie. Ce modèle thermique permet de prédire notamment les températures à l’intérieur de la batterie, non mesurées expérimentalement et ceci, pour différents courants de sollicitation. Les données d’entrée du modèle sont issues des essais expérimentaux et de la littérature. Cette phase de caractérisation thermique de la batterie est essentielle pour la conception d’un système de refroidissement. Enfin, une étude expérimentale d’un système de refroidissement passif basé sur des caloducs et des plaques à ailettes est réalisée. Plusieurs configurations sont testées au fur et à mesure en apportant des améliorations aboutissant enfin à un système à dix caloducs munis de plaques à ailettes verticales au niveau du condenseur combinés à des plaques à ailettes placées sur les faces des batteries. / This thesis deals with the passive cooling of lithium-ion batteries. It consists of two large parts. The first part is an experimental and numerical study of the thermal behaviour of a battery and the second part is the experimental study of a passive system for the cooling of several batteries. An experimental test bench was designed to monitor the thermal evolution of batteries subjected to different currents. The prismatic batteries studied are made of lithium-iron-phosphate and have a capacity of 60 Ah. In a first step, the thermal behaviour of a battery subjected to charge / discharge cycles is experimentally characterized. We show that the temperature is not uniform at the surface of the battery and the hottest area is identified. In a second step, a three-dimensional numerical model was developed to predict the temperature at any point of the battery. This thermal model makes it possible to predict in particular the temperatures inside the battery, not measured experimentally and this, for different currents. The model input data are from experimental trials and literature. This phase of thermal characterization of the battery is essential for the design of a cooling system. Finally, an experimental study of a passive cooling system based on heat pipes and finned plates is carried out. Several configurations are tested progressively with improvements leading finally to a system with ten heat pipes with vertical finned plates at the condenser combined with finned plates placed on the faces of the batteries.

This thesis deals with the problem of critical heat flux (CHF) on technically smooth and treated surfaces at low pressures. The theoretical part presents the basic concepts of two-phase flow and an analysis of existing work on the influence of the surface on CHF. The main part of the work describes the built experimental apparatus for CHF research at low pressures of 100 -1500 kPa (1-15 bar) with a vertical internally heated annular test section. The internal annuli consists of an outer glass tube with an inner diameter of 14.8 mm and an inner tube made of Inconel ™ 625 / Optimized ZIRLO ™ with an outer diameter of 9.14 mm and a heated length of 380/365 mm. CHF experiments on technically smooth surface were performed at outlet pressures 120 kPa, 200 kPa and 300 kPa, at an inlet temperature of 64, 78 and 91 °C and at mass flux of 400, 500, 600 and 800 kg / m2s. The Inconel tubes were tested in two different surface modifications - abraded and bead blasted. Experiments were performed at mass flows of 400, 500 and 600 kg / m2s. The total number of 122 experimental runs were conducted and the results were compared with other literature experimental data. The maximum increase of CHF on abraded / bead blasted tube was 18.12% / 16.17%. The surface structure was analysed by laser microscopy. The wetting behaviour of the surface structures was measured by the sessile drop method. The elemental analysis of the surface was evaluated using the EDS method.

This thesis deals with the influence of the oxide layer on the spray cooling of steel surfaces. As part of the work steel samples with oxide layer are made and the thickness, porosity and surface roughness of this layer are characterized. The average thermal conductivity of porous oxide layer is determined for different regimes of oxidation. Further, the influence of the oxide layer on the heat transfer coefficient during the spray cooling is experimentally investigated on created samples and the basic numerical simulation of the cooling is done for selected experiment with oxide layer. The thesis also contains theoretical introduction to given issue.

Tato diplomová práce se zabývá předehřevem spalovacího vzduchu a jeho vlivem na parametry spalovacího procesu. V teoretické části je zpracován přehled nejčastějších znečišťujících látek z průmyslového spalování. Je popsána aktuálně platná relevantní legislativa v Evropské unii a jsou porovnány její implementace do národní legislativy v České republice a v Německu. Dále je provedena klasifikace hořáků z hlediska různých kritérií a rešerše předchozí práce v oblasti předehřevu spalovacího vzduchu. Na zkušebně hořáků byla provedena experimentální studie dvou různých hořáků na zemní plyn při konstantním tepelném příkonu 750 kW se spalovacím vzduchem předehřátým až na 250 °C. Výsledky odhalily pozitivní vliv předehřevu na účinnost spalování. Množství emisí NOx a CO naopak rostlo s teplotou spalovacího vzduchu.

The present thesis is focused on calculation prediction of characteristic parameters of combustion process in combustion chamber which is installed at burners testing laboratory. In the thesis basic theoretical knowledge needed for description of heat transfer in process combustion equipment are given. The Plug Flow Furnace Model is based on this knowledge. This model is used to evaluation of specific heat flux in tube furnaces. In the next step the Plug – Flow model is modified and adapted on the combustion chamber. Obtained results are compared with a measured data. By this comparison quality of this model is assessed.

The thesis is focused on the experimental investigation of the oxygen enhanced combustion technology (OEC), which uses the combustion air with higher concentration of oxygen, i.e. more than 21 %. The OEC technology is used in those industrial applications, which requires higher thermal efficiency, increased productivity, improved character of the flame, reduced equipment cost, lower volume of exhaust gases and improved product quality. Although this technology involves a number of advantages, it is appropriate to mention some of its disadvantages such as refractory damage, inconsistent heating, increased pollutant emission or flame disturbance and/or flashback. The combustion tests of OEC were carried out at the burners testing facility that enables to test many types of burners (gaseous, liquid, or combined). The two-staged low-NOx burner fired by natural gas was used during the tests. The observed parameters include the effect of oxygen concentration in the combustion air on the NOx emissions, heat flux into the wall of the combustion chamber, in-flame temperature distribution in the horizontal symmetry plane of the combustion chamber and also the shape and dimensions of the flame. The combustion tests of the air-enrichment, air-oxy/fuel and O 2 lancing OEC methods were carried out at the burner thermal input of 750 kW and air excess of 1,1 for two combustion regimes, namely one-staged and two-staged fuel supply.

This thesis deals with the evaluation of emissions of NOx and CO formed during the combustion process when the burner utilizing fuel staging and internal flue gas recirculation is used. In the theoretical part the NOx formation mechanisms and methods used to suppress their formation are described. This is followed with the currently valid legislation in the Czech Republic in terms of the emission limits for NOx and CO in stationary sources. In the work, combustion tests were performed at the burners testing facility at UPEI BUT. The tests revealed that the most important parameters, which influence the NOx formation, are fuel staging, increasing combustion air excess and the utilization of new equipment that induces the flue gas to be drawn back into the burner. The equipment is installed in the burner’s air channel. The dependence of flue gas temperature, heat flux to the combustion chamber’s section walls and in-flame temperatures distribution in the horizontal symmetry plane of the combustion chamber on various parameters were investigated. The parameters included the geometry of the equipment for flue gas recirculation, primary/secondary ratio, geometry of nozzles for secondary fuel supply, tangential orientation of these nozzles towards the burner axis, and the excess of combustion air.