1,721,055 research outputs found
Combined cycle power plants with post-combustion CO2 capture : Energy analysis at part load conditions for different HRSG configurations
No full textThe part-load behaviour of combined cycle power plants (CCPP) equipped with post-combustion CO2 capture is analyzed. Different CCPP configurations are compared, including single-, dual- or triple-pressure level steam generators. The gas turbine is a single shaft unit using the variable guide vanes and fuel flow to control the load. The 90% CO2 capture is achieved using monoethanolamine (MEA 30%wt) as absorbent. In all configurations, the reboiler duty to regenerate the absorbent is partly covered by the hot water of the economizer. This economizer-reboiler loop allows to increase the plant efficiency as the possibility to extract more energy from the economizer results in lowering the steam extraction from the turbine. The dual-pressure level CCPP with CO2 capture gives the best efficiency at the design operation. As the load is reduced, the efficiency of the single-pressure plant becomes comparable to the efficiency of the dual-pressure plant, due to the effective thermal integration between the heat recovery steam generator and the absorbent regeneration process. Hence, when CCPPs with CO2 capture operate at part-loads, a further benefit can be achieved with the single-pressure level plant, having it both design simplicity and low efficiency penalties for the CO2 capture
Dynamic modeling of a parabolic trough solar thermal power plant with thermal storage in Modelica
No full textConsulta en la Biblioteca ETSI Industriales (Riunet)[EN] The Master Thesis work focused on using the Dymola software with the physicalmodeling
language Modelica to develop thermo-hydraulic models of the turbine island,
steam generator, solar eld and thermal energy storage system of a 50 MW CSP plant.
Besides, the control loops were introduced and dynamic simulations of the plant and the
di erent subsystems were conducted. The models were successfully compared against
the reference plant key steady state performance data (Andasol-1, Spain), and time constants
were estimated due to the scarcity of published data regarding to the dynamics
of the plant. Furthermore, the plant was studied during a typical summer day including
e ects such as solar irradiation, charging and discharging the heat storage system, and
dumping heat in the solar eld. Nonetheless, start-up and shut-down were not modeled.
The results agreed with published behavior of the plant. All models can be used to
make steady state and dynamic simulations. Dymola with the Modelica language, has
shown to be a powerful tool to model thermo-hydraulic systems, due to its
exibility
and wide range of modeling options of the components included in the libraries provided
by Modelon.Mocholí Montañés, R. (2014). Dynamic modeling of a parabolic trough solar thermal power plant with thermal storage in Modelica. https://riunet.upv.es/handle/10251/43888.Archivo delegad
On Degradation and Monitoring Tools for Gas and Steam Turbines
No full textThe revenue from a power plant is strongly dependent on the life cycle cost. Today, when the market conditions for power-producing companies have shifted from a protected market to a deregulated market, the need for tools to monitor power plants has increased significantly. In this new competitive market, targeted revenues and operational economy drive the need for advanced monitoring tools. In this thesis, monitoring tools for both the gas turbine and the steam turbine are described. The thesis gives a thorough description of the state-of-the-art model-based gas turbine flow path analysis system. The underlying mechanisms for degradation are also described, together with some remedying actions. The main intention of the thesis is to provide guidance for the user of the plant on how a model-based system works. The information is presented in general terms, since it is impossible to cover all gas turbine based power plant configurations. The tools presented here have different levels of sophistication, from the most simple to state-of-the-art heat and mass balance programs. The level of sophistication that is achievable is dependent on the extent of knowledge about a specific engine type. The highest level of sophistication is reserved for systems delivered by the manufacturing companies (OEMs). This level of model-based monitoring system requires detailed propriety turbine data that are not available outside the OEM. A system delivered by an OEM is more costly in general, but the additional know-how is a very valuable commodity. When working with the operational aspects of a power plant, one needs to make quantitative estimations of the effects of deteriorated components. Usually, the software for more detailed analysis are not available to the users since they use in-house code developed by the manufacturers. Besides being proprietary, such code is normally neither user-friendly nor adapted for this type of analysis. However, there are commercially available software packages on the market, but these do not usually provide the required level of off-design prediction capability. Thus, it was decided to develop a flexible tool with open structure that would enable both general power plant simulation useful for the plant owners, and detailed component analysis that is of special interest for research purposes. This work resulted in three different tools, a gas turbine performance deck or off-design performance prediction tool, a steam cycle analysis tool, and a reduced-order through-flow program. The gas turbine performance deck is suitable for both gas turbine and complete combined cycle analysis. This tool has also been used to analyze the off-design behavior of advanced wet gas turbine based cycles. The steam cycle analysis tool was developed for general steam cycle studies, and is suitable for highly loaded turbine components such as control stages at partial load. This tool was calibrated against high-quality data measured from test code (DIN) performance tests, and the results are well within expectation. The steam cycle calculation tool has been used by the project partners as a tool for generating data for ANN training purposes and general power plant off-design performance studies. The first two calculation models presented are at the component level ? where the performance of a component is simulated ? rather than dealing with an individual stage in a compressor or a turbine. As a complement, the author developed a reduced-order through-flow program, where more detailed analysis at the stage level can be performed. This software can be used for an arbitrary number of cooled and choked turbine stages. The code was validated against data measured from a turbine test rig, and the results show that the accuracy is well within the figures expected. This program is available at the department's website as open source code in Matlab?. The theories behind these calculation programs are presented in this thesis in Chapters 5, 6 and 7. Knowing the underlying degradation mechanisms, and with the possibility of including these in a condition-monitoring system, the potential for improving the economics of operation is significant. The availability of a plant can be increased if early warnings can be obtained. Also, in the case of component breakdowns, the cost of secondary replacement parts can be avoided entirely
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
