1,721,048 research outputs found
Experimental study and evaluation of the performance of single phase flow meters in wet gas flows
No full textSimms, Nigel J. - Associate SupervisorWet gas, a mixture of gas and small liquid fractions, poses significant challenges
for accurate flow measurement, which is critical in the energy, chemical, and
power industries. While Coriolis meters are widely used, their application in wet
gas environments faces limitations, including significant over-reading (OR) and a
lack of optimal installation guidelines. These issues are believed to be part of a
fundamental question: how are the meter behaviours affected by multiphase flow
dynamics, such as flow patterns, flow conditions, and phase distributions? This
research evaluates the performance of three Coriolis meters in vertical and
horizontal 2” pipelines using air, water, and oil to simulate wet gas conditions.
Various sensor orientations (0°, 40°, 90°, and 180°) were tested in the horizontal
pipeline, with 40° and 90° proposed as novel configurations. The experiments
generated a new dataset, enabling detailed analysis of Coriolis behaviour under
wet gas conditions.
A novel wet gas model was developed based on internal Coriolis parameters,
demonstrating robustness and predictive accuracy. The 40° orientation was
identified as optimal for horizontal wet gas flow, minimising OR and improving
measurement precision. Further investigations revealed the significant influence
of flow patterns, with slug flow causing the greatest deviations. A novel correlation
was established between the damping factor, XLM , and total mass flow rate,
enabling the accurate prediction of gas and liquid flow rates. In high Froude
number and annular flow conditions, the model achieved Mean Absolute
Percentage Errors (MAPE) of 3.9% for gas flow rate and 4.3% for liquid flow rate,
with an uncertainty of 2.7%.
The study also innovatively employed the damping factor to estimate liquid
holdup, validated against conductance ring measurements. In vertical annular
flow, a robust correlation was established between the damping factor and liquid
holdup (!), achieving percentage errors below ±10% at higher gas flow rates.
This dual functionality—simultaneously measuring flow rates and void fraction
with a single-phase meter—represents a significant advancement for reducing
equipment needs and enhancing efficiency. For the first time, frequency data
were extracted to characterize the medium, introducing a "distance" parameter
from frequency waveform signals. Combined with damping factor data, this
enabled a medium detection index with classification accuracy exceeding 98%.PhD in Energy and Powe
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
Prediciton of the remaining service life of superheater and reheater tubes in coal-biomass fired power plants
Get PDFAs a result of concern about the effects of CO2 emssions on the global warming, there is increasing pressure to reduce such emissions from power generation systems. The use of biomass co-firing with coal in conventional pulverised fuel power plants has provided the most immediate route to introduce a class of fuel that is regarded as both sustainable and carbon neutral as it produces less net CO2 emissions. In the future it is anticipated that increased levels of biomass will be required to use in such systems to accomplish the desired CO2 emissions targets. The use of biomass, however, is believed to result in severe fireside corrosion of superheater and reheater tubing and cause unexpected early failures of tubes, which can lead to significant economic penalties. Moreover, future pulverised fuel power systems will need to use much higher steam temeptures and pressures to increase the boiler efficiency. Higher operating temperatures and pressures will also increase the risk of fireside corrosion damage to the boiler tubing and lead to shorter component life.
Predicting the remaining service life of superheater and reheater tubes in coal-biomass fired power plants is therefore an important aspect of managing such power plants. The path to this type of failure of heat exchangers involves five processes: combustion, deposition, fireside corrosion, steam-side oxidation, and creep. Various models or partial models each of these processes are available from existing research, but to fully understand the impact of new fuel mixtures (i.e. biomass and coal) and changing operating conditions on such failures, an integrated model of all of these processes is required.
This work has produced an integrated set of models and so predicted the remaining service life of superheater/reheater tubes based on the three frameworks which have been developed by analysing those models used in depicting the five processes: one was conceptual and the other two were based on mathematical model. In addition, the outputs of the integrated mathematical models were compared with the laboratory generated data from Cranfield University as well as historical data from Central Electricity Research Laboratories.
Furthermore, alternative models for each process were applied in the model and the results were compared with other models results as well as with the experimental data. Based on these comparisons and the availability of models constants the best models were chosen in the integrated model.
Finally, a sensitivity analysis was performed to assess the effect of different model input values on the residual life superheater and reheater tubing. Mid-wall metal temperature of tubes was found to be the most important factor affecting the remaining service life of boiler tubing. Tubing wall thickness and outer diameter were another critical input in the model. Significant differences were observed between the residual life of thin-walled and thick-walled tubes
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
Co-firing fossil fuels and biomass: combustion, deposition and modelling
Get PDFThe application of advanced technologies employing combustion/co-firing of coal and
biomass is seen as a promising approach to minimising the environmental impact and
reducing CO2 emissions of heat/power production. The existing uncertainties in the
combustion behaviour of such fuel mixes and the release of alkali metals with other
elements during the combustion (or co-firing) of many bio-fuels are some of the main
issues that are hindering its application. The potential presence of high levels of alkali
chlorides and low levels of sulfates in the deposits formed on heat exchanger can cause
enhanced corrosion and/or limit the heat transfer between the hot combustion gases and
the water/steam system within the process plant.
This work has investigated the detailed gas compositions and deposition characteristics
of the combusted gas streams produced from fossil and biomass fuels pure and/or blend
in a pilot-scale combustors (PF and FBC) at Cranfield University. Combustion gas
analysis were obtained on-line by a high resolution multi-component Fourier Transform
Infra-Red (FTIR) gas analyser and deposits samples were collected from the flue gas
using air-cooled probes with surface temperatures of about 500, 600, 700
o
C and
analysed using SEM-EDX and XRD techniques. Fuels included several biomass fuels
(cereal co-product (CCP) straw, miscanthus (pulverised), oil seed rape straw (against
stored pellets), miscanthus (pellets), willow, fast pyrolysis bio-oil) and two
commercially-used coals (El-cerrejon and Daw Mill). The results of the experimental
studies have been compared with thermodynamic equilibrium predictions.
High combustion efficiency was maintained throughout the range of fuel mixes. The
SO2 and HCl levels were low in pure biomass combustion and increased as the biomass
fraction of the fuel decreased when co-fired with these coals. However, the NOx output
remained stable except for Miscanthus:Daw Mill mixtures and OSR stored pellet
combustion. The deposition flux was highest on the coolest probes for each fuel. The
lowest deposition fluxes were found for the combustion of either fast pyrolysis bio-oil
or coppiced willow. There is evidence of significant differences deposition fluxes
between El-cerrejon coal and Daw Mill coal mixed with CCP and/or miscanthus. The
presence of chlorine was identified in deposits produced from combustion of pure
biomass or high biomass mixes. The lowest levels found here in fast pyrolysis bio-oil
combustion and only detected at higher shares (≥ 80 %) of biomass co-fired with Daw
Mill coal, whereas, mixed biomass with El-cerrejon coal produced Cl in deposits at a
low % biomass share.
The application of thermodynamic equilibrium modelling has been found to be useful
tool for providing a qualitative understanding of elements present and/or control by hot
gas in modern combustion processes
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