1,720,956 research outputs found
Combustion efficiency improvement in a rotary furnance using a post combustion chamber
No full textCombustion Efficiency Improvement in a Rotary Furnace using a Post Combustion
Chamber. Luwaya Edwin. Department of Mechanical Engineering, University of Zambia.Geometric parameters, of a rotary furnace, necessary for the improvement of combustion efficiency are analysed using Computational Fluid Dynamics (CFD). The simulation is based on a real Rotary Furnace at Kabwe Power and Metals Limited in Kabwe. A Post Combustor Chamber (PCC) was incorporated in the numerical model at the exit of the combustor and the results compared with the case where no post combustor was used. Performance optimisation of the furnace was done by varying the fuel-air ratio and the size of the PCC.
The flow characteristic results obtained, for the case of PCC and no PCC incorporated were contrasted. Flow characteristics were looked at in the wake of combustion,focusing on convection, temperature distribution, conduction, and radiative heat transfer.
The k-e model is used for turbulence flow prediction. Combustion of premixed fuel is
simulated by the Simple Chemical Reacting Scheme (SCRS). The eddy break-up (EBU)
model is used to determine the rate of the reaction. The six-flux model is used for the
radiative heat transfer without turbulence-radiation interaction i.e. only the products of combustion are participating in radiative heat transfer. The SIMPLEST algorithm is employed to solve the transport equations of momentum and other scalar variables. Radiation field is determined using a modification of the SIMPLEST scheme.
The computation has shown that improvement of the thermal performance of the Rotary
Furnace can be done using the post combustion chamber. The PCC improves the thermal performance of the furnace by increasing the intensity of recirculation and mixing of hot vitiated products with fresh charge in the primary combustion zone thus increasing residence time of combusting materials in the furnace space. This reduces the exhaust gas loss therefore increasing the useful heat value in the combustor. The heat flux to the sink is equally increased. The combustion efficiency improved by 0.53 percent. For the rotary furnace at Kabwe the PCC should be optimised as demonstrated in this stud
Improvement of conversion efficiency of Charcoal KILN using a numerical method( Higher yield of Charcoal and reduced environmental impacts)
No full textToday approximately one-and-half billion people around the world, especially in the developing world, use biomass based source of energy for cooking and heating. Conversion efficiency of the biomass in many cases is low resulting in unsustainable use of the biomass resource and negative environmental impacts. In the earth charcoal-making kiln widely used in the developing nations, the conversion efficiency is on average as low as 6 - 10 percent on dry basis. The low conversion efficiency is a source of greenhouse gases and causing deforestation around most African cities. However, the earth charcoal-making kiln has been reported to have potential for improvement of the kiln conversion efficiency.
This research work was about improving the conversion efficiency of the earth charcoal-making kiln by applying a scientific approach using a numerical method. To achieve this, a 3-Dimensional transient numerical model of the earth charcoal-making kiln was developed. The CFD software code of PHOENICS was used to mathematically model and simulate the major factors influencing carbonisation processes in the kiln for their effect on the kiln conversion efficiency.
The results showed that several factors have some influence on the carbonisation process and the kiln conversion efficiency. Low moisture content wood gave relative conversion efficiency of 57.7 percent and fresh wood had 27.2 percent on a dry basis. The smaller diameter logs gave 92.8 percent relative conversion efficiency and large diameter logs 60 percent. The wood weight distribution of smaller diameter logs (5.0 - 20.0 cm) gave a relative conversion efficiency of 92.8 percent while distribution of large diameter logs (35.0 - 50.0 cm) resulted in 16.2 percent relative conversion efficiency. The crosswise type of wood Arrangement gave a relative conversion efficiency of 49.1 percent as opposed to 41.2 percent for longitudinal loading. A kiln of width 1.5 m resulted in a relative conversion efficiency of 3.6 percent while kilns of width between 2.0-2.5 m had a relative conversion efficiency of up to 92.8 percent. The kilns of length 3.5 m had relative conversion efficiency of 85.2 percent. The thinner insulation thickness of 10.0 cm gave relative conversion efficiency of 48.2 percent. A thicker insulation layer of 40.0 cm had relative conversion efficiency of 28.4 percent. A crosswise loaded kiln carbonizing against the prevailing wind direction had a relative conversion efficiency of 64.2 as opposed to 36.9 percent for one carbonising along the prevailing wind direction. The relative conversion efficiency for the longitudinal loaded kiln carbonising along the prevailing wind direction was 63.2 percent and 52.0 percent for similar kiln carbonising agaist the wind direction.
From the numerical model results, the optimised overall conversion efficiency and charcoal yield for the crosswise loaded kiln were calculated to be 12.36 percent and 14.05 percent respectively, while for the longitudinally loaded kiln these figures were 18.50 percent and 21.02 percent respectively. In both cases, this is an improvement on the reported unimproved earth charcoal making kilns average conversion efficiencies of 6 – 10 percent. The figures also agree well with other researchers findings in the field on related works
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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