1,722,215 research outputs found
The influence of multiple tubes on the tube-to-bed heat transfer in a fluidised bed
Full text linkThere have been few studies modelling both flow and heat transfer in fluidised beds. The kinetic theory of granular flow (KTGF) has been used for flow prediction in the past without heat transfer modelling. In the present study, a two-fluid Eulerian-Eulerian formulation incorporating the KTGF was applied first to a tube-to-bed reactor with one immersed tube and compared with the results in the literature. The bed was then modified to introduce two and three heated tubes. The effects on the flow and temperature distribution, local heat transfer coefficients and averaged heat transfer coefficients over a 3.0s time period were carried out. Results showed that increasing the number of tubes promotes heat transfer from tubes to the particles and flow. The heat transfer coefficients extracted from the single-tube to three-tube cases were analyzed in detail, confirming the importance of linking flow/particle and heat transfer calculation
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
A study of liquid droplet disintegration for the development of nanostructured coatings
No full textThermal spray coatings produced from a liquid feedstock are receiving an increasing level of interest due to the advanced, nanostructured coatings which are obtainable by these processes. In this article, a high-velocity oxy-fuel (HVOF) thermal spray system is computationally investigated to make a scientific assessment of the liquid droplet behavior on injection. An existing liquid-fuelled HVOF thermal spray gun is simulated using the computational fluid dynamic approach. The steady-state gas-phase dynamics are initialized by the introduction of liquid kerosene and oxygen which react within the combustion chamber producing a realistic compressible, turbulent jet. Discrete-phase water droplets are injected at the powder injection port. On injection, the water droplets breakup and vaporize, while being entrained through the acceleration barrel of the HVOF system. The results obtained give an insight to the mechanism which control the water droplet sizes and disintegration process, and serve as a fundamental reference for future development of liquid feedstock devices
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
Computational validation of an isentropic plug nozzle design for gas atomisation
No full textDuring high pressure gas atomisation (HPGA), the molten metal stream is disintegrated to produce spherical powders when energy is transferred from the gas to the melt. Conventional annular-slit nozzle (ASN) in close-coupled atomisation generates an under-expanded gas jet with characteristic shock waves which consume a great deal of energy through expansion. An isentropic plug nozzle (IPN) is developed in this paper to reduce the shocks and maximize kinetic energy being transferred from the gas to instablize the melt stream. The performance of the IPN is examined using a numerical model which includes gas flow dynamics, droplet break-up mechanism and particle tracking. The numerical results demonstrate a good improvement of gas dynamics and powder yield from the IPN design in comparison with the ASN, in particular when hot gas is employed
Numerical modelling of in-flight particle dynamics of non-spherical powder
No full textHigh velocity oxygen fuel (HVOF) is an important thermal spraying technology in depositing high quality coatings. Its ability to produce high particle velocities and relatively low particle temperatures is its most salient feature. Several computational fluid dynamic (CFD) models have been developed to study the in-flight particle behavior during thermal spraying. These models are limited to spherical particles, which are only appropriate for modelling gas atomised powders. On the other hand, hardmetal powders such as WC-Co are created using high energy ball milling and are not normally spherical. To examine the effect of particle morphology on particle dynamics, mathematical models are developed in the present paper to predict the in-flight particle behavior in a liquid fuelled HVOF thermal spray gun. The particle transport equations are coupled with the three-dimensional, chemically reacting, turbulent gas flow, and solved in a Lagrangian manner. The melting and solidification within the particles as a result of heat exchange with the surrounding gas flow are solved numerically. The results demonstrate that non-spherical particles gain more momentum and less heat during the HVOF process than spherical particles. Non-spherical particles are also predicted to stay closer to the center of the gas jet than spherical particle
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