1,720,979 research outputs found
Modeling the performance of MCFC for various fuel and oxidant compositions
No full text100 cm2 molten carbonate fuel cells (MCFC) was used for testing the fuel and oxidant composition influence on MCFC performance as a temperature function.
The fuel composition varies over the cell surface, and throughout the stack, because inlet fuel is rich in H2 (and CO2), while the exhaust stream is depleted. The cell performance is usually not uniform over the entire surface. It is thus necessary to examine the cell performance as a function of fuel utilization. In a laboratory-sized cell, this is usually difficult to do. An alternative approach is to investigate performance as a fuel composition function.
Based on the obtained experimental data for different compositions, the MCFC mathematical model was calibrated. The new approach for modeling the voltage was used. Electrochemical, thermal, electrical and flow parameters are collected in the 0-D mathematical model. A validation process for various experimental data was made and adequate results are shown
CHARACTERIZATION OF 100W SOFC STACK FED BY CARBON MONOXIDE RICH FUELS
No full textThe rapid growth in terms of efficiency and performance of the solid oxide fuel cell (SOFC) technology in recent years has led SOFC to be one of the possible solutions for the exploitation of different types of fuels obtained from fossil or renewable sources.
A lot of processes, such as waste incineration or anaerobic digestion, during operation produce exhaust gases that can be efficiently exploited in SOFC systems.
SOFCs, thanks to their operating condition, run with standard fuels such hydrogen and methane as well as fuel waste gas, like biogas or landfill gas, or gas plant, like pyrogas.
The aim of this work is to compare the performance of an 100W stack SOFC when it is fed by different fuel compositions
Sulphur compounds removal from natural gas using porous materials for high temprature fuel cell applications
No full textSulfur compounds present as odorants in natural gas like thiophenes,mercaptans,and sulifdes, cuase severe poisoning on high tempreature fuel cell catalysts evev at very low concentration, below 1 ppm.
Therefore a deep sulpfur removal from inlet gas mixture is strongly needed and it has to be coupled with an accurate determination of sulfur concentration in the gas stream. Among the different developed filtering solutions, adsorption using porous materials represents a very attractive option, mainly in view of systems simplicity and costs.
In this work, adsorptive removal of organic and inorganic sulfur compounds was carried out ina fixed bed floew reactor, using different types of porous materials, such as virgin and impgregnated activated carbons and zeolites.
The purpose was to evaluate sorbet capacity of singulkra adsorbents varying process paramaters such as space velocity. The sorbents display differences in adsorpitve capacity among the individual sulfur compounds in natural gas: a comparison among odorants and H2S adsorption is in particular shown. A composite sorbent was realized and tested in order to exploit the selectivity of singular adsorbent materials
EXPERIMENTAL ANALYSIS OF SOFC FUELLED BY AMMONIA
No full textAmmonia (NH3) has very interesting features as fuel for solid oxide fuel cell (SOFC). This study presents preliminary experimental results on a single cell SOFC fueled by ammonia. The study focuses on the cracking reaction that permits to transform ammonia into N2 and H2. This reaction offers to the fuel cell a perfect mix for the operation in safety and efficient conditions. The study compares several polarization curves realized with pure H2, a mix of H2/N2 and a mix of H2/NH3 and pure NH3 at high operation temperature (800°C). The results show how a complete reaction of NH3 can be predicted and an equivalent performance can be obtained substituting the H2/N2 mix with equivalent amount of ammonia
Theoretical study and performance evaluation of hydrogen production by 200 W solid oxide electrolyzer stack
No full textHigh temperature steam electrolyzers, taking advantage of high temperature heat, can produce more hydrogen by using less electrical energy than low temperature electrolyzers. This paper presents an experimental study on hydrogen production by using a 200 W solid oxide stack working in reverse mode. A thermodynamic study of the process was performed by measuring the heat and mass balance of stack at different operating conditions. Different definitions of efficiency were used to highlight the limit and potential of the process. The I–V curve, the flow rate measurements and the GC analysis on outlet flows were used to calculate the hydrogen and oxygen productions. In addition, the influence of steam dilution, water utilization and operating temperature on conversion efficiency and stack's thermal balance was evaluated. With this aim, the tests were performed at three operating temperature (700 °C, 750 °C and 800 °C) over a range of steam inlet concentration from 50% to 90% and water utilization up to 70%. The hydrogen and oxygen flows produced by electrolysis, at different loads, were directly measured after water condensation: net flows up to 2.4 ml/(min cm2) of hydrogen and 1.2 ml/(min cm2) of oxygen were measured and compared to the theoretical ones, showing a good agreement
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
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