In order to protect gas turbine blades from hot gases exiting the combustor, several intricate external and internal cooling concepts are employed. High pressure stage gas turbine blades feature serpentine passages where rib turbulators are installed to enhance heat transfer between the relatively colder air bled off from the compressor and the hot internal walls. Most of the prior studies have been restricted to Reynolds number of 90000 and several studies have been carried out to determine geometrically optimized parameters for achieving high levels of heat transfer in this range of Reynolds number. However, for land-based power generation gas turbines, the Reynolds numbers are significantly high and vary between 105 and 106. Present study is targeted towards these high Reynolds numbers where traditional rib turbulator shapes and prescribed optimum geometrical parameters have been investigated experimentally. A steady-state liquid crystal thermography technique is employed for measurement of detailed heat transfer coefficient. Five different rib configurations, viz., 45 deg., V-shaped, inverse V-shaped, W-shaped and M-shaped have been investigated for Reynolds numbers ranging from 150,000 to 400,000. The ribs were installed on two opposite walls of a straight duct with aspect ratio of unity. For very high Reynolds numbers, the heat transfer enhancement levels for different rib shapes varied between 1.3 and 1.7 and the thermal hydraulic performance was found to be less than unity. / Master of Science

Complex flow structures consisting of branching, multi-scale, hierarchically arranged flow paths can be a beneficial in certain applications by providing lower hydraulic and thermal resistances than conventional flow arrangements. In this study, an experimental approach was used to investigate the hydrodynamic and thermal effects of the complexity, or degree of branching, in microscale complex flow structures. The primary focus of this work was to develop new concepts to advance the current capabilities of complex flow structures through management of complexity. The effects of complexity were determined from experiments performed on a set of microfluidic test sections which were identical except for the complexity of the underlying microchannel configuration. Comparison of the relative hydrodynamic and thermal performance indicates that complexity has a strong effect on both the pressure drop and heat transfer. When the pumping power is taken into account, the results suggest that higher complexity arrangements improve the overall thermal-hydraulic performance. This conclusion was confirmed by the trends observed in the coefficient of performance, a measure of the device thermal efficiency. To address the limitations of conventional fixed-complexity designs, the concept of a variable-complexity flow structure is developed. With a variable-complexity design, the configuration of a branched flow structure can be dynamically controlled to improve performance as operational conditions vary. This concept was successfully demonstrated by developing and testing an active variable-complexity microfluidic device in which pneumatically controlled microvalves were used to create different flow channel configurations. The variable-complexity concept was further refined by developing a microfluidic device with a passive variable-complexity design in which the flow channel configuration changed autonomously based on local temperatures. By using microvalves containing a temperature sensitive polymer, the flow configuration of the device was made thermally adaptive. Experiments were performed to characterize the behavior of the polymer microvalves and the overall device performance. The results showed that the device was capable of tracking changes in external heat sources by adapting and reconfiguring its internal flow structure. The experiments also showed how this variable-complexity design can reduce the pumping power expenditure by automatically directing flow only to areas where it is required. / text

Made available in DSpace on 2014-06-11T19:23:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-24Bitstream added on 2014-06-13T19:29:20Z : No. of bitstreams: 1 martins_pes_me_jabo.pdf: 724580 bytes, checksum: 607174d21f5d018ec5e111b64424e116 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O trabalho teve como objetivo avaliar o perfil radial e a uniformidade de distribuição de água do aspersor fabricado pela empresa NaanDanJain, modelo 427 1/2”M e bocal de 2,8 mm de diâmetro interno, operando com pressões de 150, 200, 300 e 400 kPa em cinco posições do defletor de ajuste (0, 20, 50, 80 e 100%). Para a determinação dos parâmetros avaliados utilizou-se o método da malha, e com o auxílio do aplicativo computacional CATCH 3D calculou-se a sobreposição das lâminas de água com dez espaçamentos. Os resultados obtidos demonstram que o defletor de ajuste influencia o raio de molhamento, o perfil de distribuição e a uniformidade de aplicação de água e mostrou-se como um mecanismo importante, pois permite comportamento diferenciado para o aspersor, garantindo ampla faixa de utilização do equipamento / The study aimed to evaluate the radial profile and the uniformity of water distribution of sprinkler manufactured by the company NaanDanJain, model 427 1/2M and nozzle with 2.8 mm of internal diameter, operating at pressures of 150, 200, 300 and 400 kPa and five positions of the deflector (0, 20, 50, 80 and 100%). For the determination of the parameters rated, we used the method of the grid, and with the aid of computer application CATCH 3D, it was calculated overlapping layers of water with ten spacing. The results show that the deflector adjustment influences the radius of wetness, the distribution profile and the uniformity of water application and showed itself as an important mechanism, since it gave different behavior for the sprinkler, ensuring wide track usage of the equipment

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23172号 / 工博第4816号 / 新制||工||1753(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 准教授 竹門 康弘, 准教授 Sameh Kantoush / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Stormwater sewer infrastructure is at risk due to ageing, structural deterioration, population growth, and climate change. Since the consequences of the sewer system failure can adversely impact the community safety, environment and economy, a resilient infrastructure system is of essential importance. However, limited reinvestment budget and insufficient asset management practices impact the rehabilitation of urban sewerage systems. Therefore, an effective and efficient rehabilitation plan is needed to help proper investment decisions. An effective rehabilitation plan will maximize hydraulic performance while minimizing the overall failure risk within a limited budget. The current study aims to address this issue through designing a risk-informed methodology in three steps. First, the hydraulic risk index (obtained using the SWMM model) was combined with the ageing pipe index. The framework uses multi-objective optimization technique to generate solutions under specific sewerage conditions. We named this new framework as Hydraulics and Risk Combined Model (HRCM). Several scenarios including high hydraulic risk, high ageing risk, hydraulic risk and ageing risk (combined problems), and limited budget problems, are used to test the performance of the proposed methodology. The results show that the proposed model could provide a satisfactory solution. Then, in order to increase the calculation speed and improve the accuracy, sensitivity and cost-effectiveness analyses were also conducted for the proposed methodology with different algorithms. The results show that different algorithms offer various benefits. A new calculation method was offered by combining the advantages of the previous methods. Finally, a new optimization method named Phenotype Searching Method, which was enlightened by sexual selection processes, was offered. This method can enhance the selection processes to specific phenotypes (pipes) so that it can increase the convergence speed and increase the performance of the HRCM model.

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Au cours des dix dernières années, les gouvernements de l'Union Européenne ont été encouragés à collecter des données sur le volume et la qualité de tous les effluents d'eaux urbaines ayant un impact environnemental significatif sur les milieux aquatiques récepteurs. Les méthodes de surveillance de ces flux nécessitent des améliorations, en particulier pour les déversoirs d’orage, structures complexes responsables en grande partie de la dégradation de la qualité des milieux récepteurs. Le DSM-flux (Dispositif pour la surveillance et maîtrise des flux d'eaux et polluants des réseaux d'eaux pluviales et unitaires) est un nouveau dispositif préfabriqué et pré-étalonné qui garantit les conditions hydrauliques appropriées permettant de mesurer les débits et volumes déversés ainsi que les concentrations et masses de polluants qui y sont transportés. Dans cette thèse, une relation permettant de mesurer le débit au passage du DSM-flux a été construite grâce à une étude expérimentale sur modèle physique réduit, puis validée pour plusieurs configurations d'écoulement à l'amont du dispositif. Quelles que soient les conditions hydrauliques en amont, les incertitudes relatives sont inférieures à 15% et 2% pour les débits et les volumes étudiés, respectivement, ce qui reste équivalent, voire mieux, par rapport aux incertitudes des méthodes actuelles les plus fiables. La méthode de mesure a été validée in situ sur un dispositif à grande échelle construit sur le terrain et fonctionnant en conditions réelles, ce qui montre la robustesse de la méthode. De plus, grâce à sa conception originale, le DSM-flux favorise l'interception d'une fraction des polluants particulaires. L’hydrodynamique de ce dispositif de mesure a été analysée ainsi que les conditions qui engendrent la décantation des polluants particulaires. En fonction des conditions d'écoulement, ce dispositif peut retenir 50% de la masse totale des matières solides fines en suspension transitant par le dispositif, mais pour des écoulements à débits élevés, cette efficacité est significativement réduite. Sa capacité de rétention a été aussi observée sur le terrain et une méthodologie a été élaborée pour quantifier son efficacité de rétention lors d'études futures. Mise à part sa performance hydraulique, du point de vue opérationnel, le dispositif présente d’autres avantages par rapport à d’autres dispositifs existants : (i) il est pré-étalonné et peut être installé à l’aval de déversoirs d’orage déjà existants, (ii) il peut s’insérer directement au sein du canal de décharge (installation d’un regard de visite équipé d’un DSM), (iii) sa performance hydraulique est indépendante des conditions de l’écoulement à l’amont et (iv) il s’agit d’un dispositif intégré de mesure de débits et de leur qualité simultanément, en plus d’intercepter une partie de polluants particulaires. / Over the past decade, European Union governments have encouraged to collect data on the volume and quality of all urban water effluents with a significant environmental impact on receiving aquatic environments. Methods for monitoring these flows require improvements, particularly for combined sewer overflows, which are complex flows that contribute in significant proportion to the degradation of the quality of the receiving waters. The DSM-flux (Device for Stormwater and combined sewer flows Monitoring and the control of pollutant fluxes) is a new pre-calibrated and pre-designed device that guarantees the appropriate hydraulic conditions for measuring discharged flows and volumes as well as the concentrations and mass loads of pollutants carried in suspension by the flow. In this PhD work, a relationship allowing to measure the flow rates conveying through the DSM-flux was determined thanks to an experimental study on a small-scale physical model, and then validated for several flow configurations upstream of the device. Whatever the upstream hydraulic conditions are, the relative uncertainties are less than 15% and 2% for the flow rates and volumes studied, respectively, which is equivalent to the uncertainties of the most reliable current methods. The monitoring methodology was validated in situ in a large-scale device installed at the field and operating in real conditions, which shows the robustness of the method. Moreover, thanks to its original design, the DSM-flux allows the interception of a fraction of particulate pollutants. The hydrodynamics of this monitoring device were analysed as well as the conditions that cause the settling of particulate pollutants. Depending on the flow conditions, this device can retain 50% of the total mass of fine suspended solid matter transiting through the device, but for flows at high discharge rates, this efficiency is significantly reduced. Its retention capacity has also been observed in the field and a methodology has been developed to quantify its retention efficiency in future studies. Apart from its performance, from an operational point of view, the device has other advantages compared to other current devices: (i) it is pre-calibrated and can be installed downstream from existing combined sewer overflows, (ii) it can be directly installed through a manhole in the discharge channel, (iii) its hydraulic performance is independent from the flow conditions upstream, and (iv) it is an integrated monitoring device, measuring flow rates and their quality simultaneously, in addition to intercepting a part of the particulate pollutants.

This study focuses on the investigation of flow behavior at low Reynolds numbers by the experimental and numerical performance testing of micro-channel heat exchangers. An experimental study of the heat transfers and pressure drop of compact heat exchangers with louvered fins and flat tubes was conducted within a low air-side Reynolds number range of 20 < ReLp < 225. Using an existing low-speed wind tunnel, 26 sample heat exchangers of corrugated louver fin type, were tested. New correlations for Colburn j and Fanning friction f factor have been developed in terms of non-dimensional parameters. Within the investigated parameter ranges, it seems that both the j and f factors are better represented by two correlations in two flow regimes (one for ReLp = 20 – 80 and one for ReLp = 80 – 200) than a single regime correlation in the power-law format. The results support the conclusion that airflow and heat transfer at very low Reynolds numbers behaves differently from that at higher Reynolds numbers. The effect of the geometrical parameters on the heat exchanger performance was investigated. The numerical investigation was conducted for further understanding of the flow behavior at the range of experimentally tested Reynolds number. Ten different heat exchanger geometries with varied geometrical parameters obtained for the experimental studies were considered for the numerical investigation. The variations in the louver angle were the basis of the selection. The heat transfer and pressure drop performance was numerically investigated and the effect of the geometrical parameters was evaluated. Numerical results were compared against the experimental results. From the comparison, it is found that the current numerical viscous laminar models do not reflect experimentally observed transitional two regime flow behavior from fin directed to the louver directed at very low Reynolds number ranging from 20 to 200. The flow distribution through the fin and the louver region was quantified in terms of flow efficiency. The flow regime change was observed at very low Reynolds number similar to the experimental observations. However, the effect of two regime flow change does not reflect on the thermal hydraulic performance of numerical models. New correlations for the flow efficiency � have developed in terms of non-dimensional parameters.