1,721,007 research outputs found
OPTIMIZING MESH CONFIGURATIONS IN SOLAR CHIMNEY SYSTEMS: A COMPUTATIONAL FLUID DYNAMICS (CFD) BASED APPROACH FOR ENHANCED ENERGY EFFICIENCY AND PERFORMANCE
Full text linkThe present study investigates the effect of mesh configurations on the performance of a solar chimney (tower) system using Computational Fluid Dynamics (CFD) simulations. This research focuses on optimizing mesh density to enhance the accuracy of temperature, velocity, and pressure predictions in the solar tower, which significantly impact energy efficiency. Unlike previous studies, which primarily focused on geometrical design and system layout, this article introduces a novel meshing strategy that balances computational efficiency and simulation accuracy. Four different mesh types were analyzed, with the finest meshes (M3and M4) showing the closest alignment to experimental data, achieving an error margin below 4%. The results revealed that finer meshes provided more accurate representations of temperature profiles, pressure gradients, and velocity distributions, particularly near the chimney’s axis, optimizing the overall system’s performance. The minimum total pressure values for meshes were 5.61Pa, 6.25 Pa, 6.61 Pa, and 6.86 Pa, respectively, indicating how mesh density influences internal pressure dynamics. This study highlights the importance of mesh selection in CFD simulations and recommends future designs to incorporate adaptive mesh refinement techniques for better simulation efficiency. The findings offer valuable insights into the design and optimization of solar tower systems, promoting enhanced power generation and efficiency, which are essential for scaling renewable energy projects. Future research could explore broader applications of this methodology to optimize other renewable energy systems.
Key words: Computational Fluid Dynamics, mesh effect, numerical analysis, solar energy, solar tower
Effect of reference state on the exergoeconomic evaluation of geothermal district heating systems
No full textWOS: 000325830900037The exergy cost structure of the geothermal district heating system (GDHS) is investigated by using an exergoeconomic method called as the modified productive structure analysis (MOPSA). A parametric study is also conducted to show how exergy cost flow rates change with the reference state (ambient temperature). As a comprehensive case study, the Afyon GDHS in Afyonkarahisar, Turkey is considered. The actual thermal data taken from the technical staffs as 2.3 degrees C for January (case 1) and 10.2 degrees C for February (case 2), 2010 in 100% load condition are collected for this study. Mechanical and thermal exergy flow rates, entropy production rates and exergy cost flow rates for each component in the Afyon GDHS are calculated using these two actual data sets. The results show that the exergy efficiencies of the overall system for these two cases are found to be 25.34% and 22.78%, respectively. And, the largest exergy cost loss occurs in the heat exchangers with 52.49% and 64.91% for cases 1 and 2, respectively. The unit exergy costs are found as C-P > C-T > C-S > C-Q. for the actual data sets in each case. In addition, ambient temperature has a big impact on the exergies and costs of GDHSs. (C) 2013 Elsevier Ltd. All rights reserved.Afyon Geothermal Inc.The author would like to thank for the support provided by the Afyon Geothermal Inc
Energetic, exergetic, economic and environmental evaluations of geothermal district heating systems: An application
Full text linkThis study deals with an energetic and exergetic analysis as well as economic and environmental evaluations of Afyon geothermal district heating system (AGDHS) in Afyon, Turkey. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, specific exergy index, exergetic improvement potential and exergy losses. And, for economic and environmental evaluations, actual data are obtained from the Technical Departments. The energy and exergy flow diagrams are clearly drawn to illustrate how much destructions/losses take place in addition to the inputs and outputs. For system performance analysis and improvement, both energy and exergy efficiencies of the overall AGDHS are determined to be 34.86% and 48.78%, respectively. The efficiency improvements in heat and power systems can help achieving energy security in an environmentally acceptable way by reducing the emissions that might otherwise occur. Present application has shown that in Turkey, geothermal energy is much cheaper than the other energy sources, like fossil fuels, and makes a significant contribution towards reducing the emissions of air pollution. (C) 2012 Elsevier Ltd. All rights reserved.Afyon Geothermal Inc.; City Health Administration; Environmental and Forestry authorities of Afyon, TurkeyThe author would like to thank for the supports provided by the Afyon Geothermal Inc., the City Health Administration and the Directorship of Environmental and Forestry authorities of Afyon, Turkey
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Performance and thermo-economic assessments of geothermal district heating system: A case study in Afyon, Turkey
Full text linkIn this study energy, exergy and exergoeconomic analysis of the Afyon geothermal district heating system (AGDHS) in Afyon, Turkey is performed through thermodynamic performances and thermoeconomic assessments. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, exergy losses and loss cost rates. Energy and exergy losses throughout the AGDHS are quantified and illustrated in the flow diagram. The energy and exergy efficiencies of the overall system are found to be 37.59% and 47.54%, respectively. The largest exergy loss occurs in the heat exchangers with 14.59% and then in the reinjection wells with 14.09%. Besides, thermo-economic evaluations of the AGDHS are given in table. Energy and exergy loss rates for the AGDHS are estimated to be 5.36 kW/, respectively. (c) 2010 Elsevier Ltd. All rights reserved.Afyon Geothermal Inc.The author would like to thank for the support provided by the Afyon Geothermal Inc. and the personal support of the managing director, Mr. Erhan Ozsakaci
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