A major addition to European research facilities is the Oxford University Engineering Laboratory (O.U.E.L.) blowdown tunnel which can provide full-scale Reynolds and Mach number simulations on large and small models of turbine stage components. The facility was designed to provide extended aerodynamic capabilities to complement the existing heat transfer research in the Isentropic Light Piston Tunnel (ILPT) at O.U.E.L. The blowdown tunnel will be used for fundamental investigations of the boundary layers and flow fields around turbine blades in a linear cascade. The study of these flow fields is necessary for the prediction of heat transfer rates and for the optimisation of materials and cooling schemes required to improve gas turbine efficiencies. As a commissioning exercise measurements were made on cascades of similar geometry to those which had been previously tested in the ILPT and in other European facilities in order to compare results and analyse differences which occur due to the influence of tunnel geometry. Measurements made on various rotor profiles identified regions on the suction surface where surface pressure data is sensitive to the various types of exit plenums and exit pressure gradients. A second phase of work included measurements and a theoretical study of the boundary layer on a large-chord turbine rotor profile. Measurements on the pressure surface of the blade suggested the presence of secondary longitudinal vortices which rapidly lose an identifiable structure towards the trailing edge. On the suction surface, boundary layer measurements were compared with theoretical models, and it was shown that current numerical models of compressible turbulent boundary layers approximately correspond with the data. An adjunct to the boundary layer work was research on the use of a hot-wire anemometer, intended for future boundary layer measurements, and for which calibration laws and temperature effects were studied.

This research studies the effects of a postulated Main Steam Line Break accident in a nuclear plant on the transient loading of steam generator tubes. The problem involves complex transient two-phase flow dynamics and fluid-structural loading processes. A better understanding of this phenomenon will permit the development of improved design tools to ensure steam generator safety. This Thesis presents the results of an experimental laboratory study of the transient loading of a sectional model of steam generator tubes during a simulated two-phase blowdown. The research was carried out in a purpose designed and built experimental facility. The thermodynamic phenomena were investigated through dynamic pressures and temperatures. The transient tube loads were directly measured using dynamic load cells. The working fluid was R-134a and the tube bundle was a normal triangular array with a pitch ratio of 1.36. Preliminary testing indicated parasitic loading on the instruments and remedial actions were taken to ensure measurement accuracy. The success of the instrumentation development methodologies was validated in a series of single- phase blowdowns. Two-phase blowdown experiments were then conducted with various levels of liquid and numbers of tube rows. The results provided hitherto unknown information relating the nature of the fluid-structure interaction and flow development during a two-phase transient blowdown across a tube bundle. The pressure drop across the tube bundle established the thermal hydraulic fluid behaviour in the pressure vessel and controlled the upstream fluid discharge from the system. The flow through the bundle was choked for the majority of the transient. The transient tube loading was explained in terms of the associated fluid mechanics and the maximum load was compared with existing models obtained under steady flow conditions. An empirical model was developed that enables the prediction of the maximum tube loads once the pressure drop is known. / Thesis / Doctor of Philosophy (PhD) / The design of nuclear plant systems requires that public safety be ensured for the worst-case imaginable accident scenarios. This means that radioactive materials produced by nuclear fission must be safely contained. If the main steam pipe from a nuclear steam generator were to break, the water in the steam generator would rapidly boil off in what is called a blowdown. Such an event could produce significant loading on the heat exchanger tubes. Should the tubes rupture, radioactive materials may breach reactor containment. Thus, knowing the tube loading during this hypothetical scenario is an important input for safe design. The goal of this research is to improve our understanding of the effects of this postulated accident on the transient loading of the tubes. A laboratory study was carried out to simulate the blowdown. The experimental results provided valuable insights and guidance for the development of improved design tools.

No description available.

The uprooting of trees due to high winds, or blowdown, is a common occurrence throughout the world. Rare, large scale blowdown events have the ability to drastically alter forest landscapes on a timescale of hours. Alone or when combined with other forest disturbances such as fires and insect outbreaks, blowdowns have the potential to modify existing watershed characteristics. Little information is known about how large-scale blowdowns affect the physical environment in general and watershed-wide sediment yield and deposition rates in particular. The few studies that have taken place have yielded inconclusive or somewhat contradictory results. Given the large scale of some events and the potential impact of such events it is important that the geomorphological effects of blowdowns be better understood, not only from a basic process but also from an applied perspective. Lakes receive and store a significant fraction of the disturbed sediment formerly found in the soil column and lake sediments have proven to be reliable and accurate records of sedimentation characteristics within their catchments. For the purpose of this study, it was hypothesized that areas subjected to blowdown will have increased erosion rates. It was also hypothesized, that lakes within blowdown areas will be subjected to accelerated sedimentation rates following events. In order to test these hypotheses and isolate the effects of a blowdown on sedimentation rate three small mountain lakes in the Mt. Zirkel Wilderness Area, Colorado were cored. The lakes selected consist of a control lake with no known recent history of blowdown in its watershed and two lakes that receive direct runoff from watersheds and slopes that were affected by a major blowdown event in 1997, the Routt-Divide Blowdown. One core was dated using the 210Pb method and multiple cores were analyzed for organic and inorganic matter concentrations to determine if changes in sedimentation rates and/or sediment compositions occurred following the event. In the case of the two lakes studied that had catchment slopes affected by blowdown, somewhat surprisingly, no significant change was observed with respect to sedimentation rates or sediment composition. In fact, sedimentation rates obtained from the dated core exhibited a decreasing trend that began decades prior to and continued through the blowdown event. This suggests that in the area affected by the Routt-Divide Blowdown it is likely that long-term changes in climate and the effect these changes have on the amount and type of vegetation present are the dominant influence on sedimentation rates, and that the Routt-Divide Blowdown of 1997 did not increase the rates. Based on further evaluation of the sites and the event it appears that slope characteristics and treefall orientation may be significant factors controlling the amount and type of disturbed sediment that moves downslope. In the case of future large-scale blowdowns, where their effect on water quality or sedimentation rates is in question, dominant treefall orientation with respect to slope should be an integral part of initial assessment, especially in remote area, and be considered when interpreting data from any similar study.

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

No description available.

[pt] O gas-lift na base do riser é um dos vários métodos que se provaram eficientes para aumento de produção. Em alguns casos, ele também pode ser utilizado para aumentar a viabilidade do blowdown para prevenção de hidratos. Além disto, o gas-lift pode ser utilizado como um método efetiv para suprimir o fenômeno de golfada severa, que ocorre geralmente em linhas descendentes. Este método tem, então, um grande potencial de viabilizar arquiteturas submarinas mais enxutas, como anel de coleta, aumentando a economicidade de projetos, sem reduzir funcionalidades. A necessidade da aplicação do gas-lift nem sempre é óbvia, pois sua efetividade depende da performance do reservatório, propriedades de fluido, relevo do solo marinho, arquitetura submarina, além de características da flowline e riser. Em muitos casos, o gas-lift para aumento de produção só traz ganhos no fim da vida produtiva, quando o watercut é mais alto. A aplicabilidade do gas-lift como método de elevação artificial e o local ideal de injeção do gás é uma análise direta e objetiva. Por outro lado, sua aplicabilidade no contexto de garantia de escoamento é mais subjetiva, tendo influência forte da filosofia operacional e tolerância ao risco. Baseado em uma envoltória típica do présal brasileiro, no que tange a características de reservatório, fluido e sistema de produção, foi realizado um conjunto de simulações para avaliação da aplicação do gas-lift na base do riser como uma solução multi propósito. Isto inclui quando o gas-lift é benéfico para aumento de produção e para garantia de escoamento, em especial as operações de remediação e prevenção de hidratos. Os resultados da aplicação do gas-lift na base do riser como método de auxílio ao blowdown são muito promissores. É possível realizar as operações de remediação com sucesso, mesmo para vazões baixas de injeção de gás. Nas operações de prevenção, foi possível observar redução da pressão residual em todas as combinações de características de fluido e geométricas, em especial para geometrias descendentes. Para poços de alta produtividade, o gas-lift na base do riser só apresenta desvantagens em relação ao gas-lift downhole, do ponto de vista de aumento de produção, quando o watercut é da ordem de 60 a 70 por cento. / [en] Riser base gas-lift is one of several methods that have been proven to work in subsea developments for production enhancement. In some cases, gas-lift can be used to increase feasibility of blowdown for hydrate prevention. In addition, gas-lift can be used as an effective method to supress severe slugging that usually occurs with downhill inclination. Hence, this method has great potential to enable more compact subsea architectures, such as production loops, enhancing project economics, without reducing functionalities. Meanwhile, the necessity of gas-lift application is not always obvious because its effectiveness depends on reservoir performance, fluid properties, seabed terrain, subsea architecture, and flowline and riser specifications. In many cases, gas-lift for production enhancement is only advantageous at late life production, when oil production rates are low and water rates might be high enough. Whether gas-lift is suitable as an artificial lift method and where the lift-gas should be injected is a direct and objective analysis. On the other hand, its application in a flow assurance context is more subjective, being strongly influenced by operational philosophy and risk tolerance. Based on a typical envoltory from Brazilian pre-salt, concerning reservoir characteristics, fluid and production system, a set of simulations has been performed to evaluate the application of riser base gas-lift as a multi purpose solution. These include when gas-lift is beneficial for production enhancement and for flow assurance. The results of the application of riser base gas-lift as a blowdown method are very promising. It is possible to complete remediation operations successfully, even for low gas injection rates. In prevention operations, it is possible to observe a reduction in residual pressure for all combinations of fluid and geometrical characteristics, specially in downward flow. For high productivity wells, riser base gas-lift is only disadvantageous in comparison with downhole gas-lift, from production enhancement point of view, when watercut is around 60 to 70 per cent.

Oregon State University has hosted an International Atomic Energy Agency (IAEA) International Collaborative Standard Problem (ICSP) through testing conducted on the Multi-Application Small Light Water (MASLWR) facility. The MASLWR facility features a full-time natural circulation loop in the primary vessel and a unique pressure suppression device for accident scenarios. Automatic depressurization system (ADS) lines connect the primary vessel to a high pressure containment (HPC) which dissipates steam heat through a heat transfer plate thermally connected to another vessel with a large cool water inventory. This feature drew the interest of the IAEA and an ICSP was developed where a loss of feedwater to the steam generators prompted a depressurization of the primary vessel via a blowdown through the ADS lines. The purpose of the ICSP is to evaluate the applicability of thermal-hydraulic computer codes to unique experiments usually outside of the validation matrix of the code itself. RELAP5-3D 2:4:2 was chosen to model the ICSP. RELAP5-3D is a best-estimate code designed to simulate transient fluid and thermal behavior in light water reactors. Modeling was conducted in RELAP5-3D to identify the strengths and weaknesses of the code in predicting the experimental trends of the IAEA ICSP. This extended to nodalization sensitivity studies, an investigation of built-in models and heat transfer boundary conditions. Besides a qualitative analysis, a quantitative analysis method was also performed. / Graduation date: 2013

A Osmose Inversa (OI) é amplamente utilizada nos processos de desmineralização, onde são utilizados módulos espirais que após 3 a 5 anos de uso são descartados devido à queda de seu desempenho. Estes módulos ainda podem ser reaproveitados em tratamentos que não exijam um efluente final com qualidade tão elevada, como por exemplo, em correntes de reuso. Um efluente com potencial para ser reutilizado é a purga, a qual é drenada da bacia da torre de resfriamento com a finalidade de reduzir a concentração de sais e outras impurezas da água de recirculação. Estes processos industriais utilizam grandes quantidades de água, sendo de grande importância estudos que visem o seu reaproveitamento. Uma alternativa seria o tratamento desta corrente utilizando as membranas de OI descartadas, porém um fator limitante é a qualidade do efluente que irá alimentar os módulos de OI descartados, devido à pequena espessura dos canais de alimentação. A proposta deste trabalho foi ajustar o pré-tratamento para um sistema de filtração com membranas de OI descartadas com o objetivo de tratar e reutilizar a corrente de purga de uma torre de resfriamento, como água de reposição. Foram avaliados como pré-tratamentos processos de coagulação/floculação, filtração com filtro de areia,sorção com carvão ativado comercial e combinações destes. A avaliação da eficiência dos tratamentos foi realizada através de análises de pH, condutividade elétrica, turbidez, dureza total, DQO, sílica e SDI. Após cada pré-tratamento, o efluente tratado foi alimentado no sistema de OI, avaliando-se o fluxo de permeado, permeabilidade hidráulica, retenção salina e a propensão ao fouling, para, então, determinar a eficiência do tratamento proposto. O permeado foi analisado e os parâmetros foram comparados com a água de reposição utilizada na torre de resfriamento. Verificou-se que o melhor tratamento obtido foi utilizando a coagulação/floculação seguida do filtro de areia, apresentando SDI5 5,5 e turbidez de 0,3 NTU; o processo de sorção com carvão ativado não demonstrou bons resultados para as condições testadas. Através das análises das membranas utilizadas para as medidas de SDI e dos valores dos contaminantes presentes após os pré-tratamentos, pôde-se perceber uma diminuição de incrustações referentes aos teores de sílica e dureza, principais causadores de fouling, indicando uma melhora na qualidade da corrente de purga pré-tratada, que apresentou características adequadas para alimentação do sistema de OI. Ainda, as membranas de OI apresentaram uma retenção salina em torno de 97% e as análises dos permeados obtidos indicaram valores de contaminantes inferiores aos da água de reposição da torre, demonstrando a possibilidade de reutilização. / Reverse Osmosis (RO) is widely used in demineralization processes, where spiral wound modules are used, which after 3-5 years are discarded to lose their performance. However, these modules can be reused for treatments that do not require final effluent with so high quality. The blowdown is drained from the basin of the cooling tower in order to reduce the concentration of salts and other impurities from recirculating water. These industrial processes use large quantities of water, so it’s important to study reuse possibilities. An alternative would be treating this stream using RO discarded membranes, but some limiting factors are the quality of the feed water and the thin feed channels. Thus, the aim of the study is to set a pretreatment to a RO system that uses discarded membranes from the demineralization process to treat the blowdown stream of a cooling tower, with will reuse as make-up water. Steps of coagulation and flocculation, sand filter filtration, sorption with activated carbon and combinations of these were proposed as pre-treatments. Analysis of pH, conductivity, turbidity, total hardness, COD, silica and SDI were used to evaluate the efficiency of the pretreatments. After each proposed pre-treatment, the treated effluent was tested in RO system and the permeate flow, salt retention and hydraulic permeability were evaluated to identify the presence of fouling and the membranes performance. Also the permeate analysis were compared with the makeup water used in the cooling tower. The sand filter as only step treatment is not effective for good treatment of the stream, obtaining the best result when coupled with coagulation/flocculation process. The GAC had not shown good results for the tested conditions. RO discarded membranes presented high salt retention, about 97% and analysis of the permeates indicate the reuse possibility. Through MEV and EDS analysis of SDI membranes, we could notice a decrease of scale related to silica and hardness, which are the main cause of fouling, indicating an improvement of the quality of the treated stream, which presents suitable characteristics for feed RO systems with discarded modules.