Investigation into methods for the calculation and measurement of pulverised coal boiler flue gas furnace exit temperature

The boiler flue gas furnace exit temperature (FET) is a key operating parameter of coal fired steam boilers. From the design perspective, the FET is vital for materials selection and sizing of heat transfer surfaces. From an operating perspective, it is a major indicator of the rate of combustion and heat transfer that is occurring within the furnace. Downstream of the furnace, the FET has a significant impact on both the performance and reliability of the boiler heat exchangers, which ultimately impacts on both boiler efficiency and availability. Monitoring of the FET can advise operating and engineering corrective actions which will ultimately result in better efficiency, reliability and availability together with the associated economic benefits. Therefore, methods of determining FET are investigated. Two methods are focused on for this study, one indirect and one direct. The indirect method studied is a mass and energy balance method which begins with a global boiler mass and energy balance to calculate the major boiler flow rates of coal, air and flue gas which are difficult to measure online. These parameters are then used as inputs into a furnace or backpass mass and energy balance to calculate the furnace exit temperature. The method is applied to a case study, and is evaluated in terms of the measurement uncertainties which are propagated on the intermediate parameters calculated, as well as on the final calculated FET. The main conclusions are that this indirect method contains various uncertainties, due to parameters which have to be assumed such as (i) the distribution of ingress air (also called tramp air) in the different sections of the boiler and (ii) the estimation of the share of water evaporation heat transfer occurring in the water walls of the furnace part of the boiler. The method is however still useful and can be easily applied to any boiler layout and can be used as a reference tool to verify other measurements. The direct method studied is acoustic pyrometry. The work specifically focuses on the sources of error in determining the temperature from the measurement of the time of flight of sound, the impact of particle concentration on the speed of sound through a gas-particle mixture, and the temperature profile reconstruction from acoustic time of flight measurements. A limited set of physical testing was also carried out using one acoustic generator and receiver to take measurements on a real coal power plant. As part of this physical testing, the detection of time of flight from acoustic signals was explored. Already installed radiation pyrometers were also used as a reference for interpreting the acoustic measurements. The indications are that the acoustic pyrometer provides a more representative temperature measurement than the radiation pyrometers. The uncertainty of the acoustic measurement for the same case study as the indirect method was determined and compared with the calculated result. While many aspects still need to be researched further, this initial study and experimental testing produced very promising results for future application of acoustic pyrometry for better monitoring of the coal combustion processes in power plant boilers

Theoretical and computational modelling of compressible and nonisothermal viscoelastic fluids

This thesis is an investigation into the modelling of compressible viscoelastic fluids. It can be divided into two parts: (i) the development of continuum models for compressible and nonisothermal viscoelastic fluids using the generalised bracket method and (ii) the numerical modelling of compressible viscoelastic flows using a stabilised finite element method. We introduce the generalised bracket method, a mathematical framework for deriving systems of transport equations for viscoelastic fluids based on an energy/entropy formulation. We then derive nonisothermal and compressible generalisations of the Oldroyd-B, Giesekus and FENE-P constitutive equations. The Mackay-Phillips (MP) class of dissipative models for Boger fluids is developed within the bracket framework, complimenting the class of phenomenological models that already exist in the literature. Advantages of the MP models are their generality and consistency with the laws of thermodynamics. A Taylor-Galerkin finite element scheme is used as a basis for numerical simulations of compressible and nonisothermal viscoelastic flow. Numerical predictions for four 2D benchmark problems: lid-driven cavity flow, natural convection, eccentric Taylor-Couette flow and axisymmetric flow past a sphere are presented. In each case numerical comparisons with both empirical and numerical data from the literature are presented and discussed. Numerical drag predictions for the FENE-P-MP model are presented, displaying good agreement with both numerical and experimental data for the drag behaviour of Boger fluids

Assessing and responding to audit risk : international auditing standards

https://egrove.olemiss.edu/aicpa_guides/2669/thumbnail.jp

The ideological uses of the past

The thesis is divided into four parts. Each part deals with one aspect of ideological thought.The first part attempts to define the area for study by indicating how the terms ideology and ideological will be understood, and some reasons for dissatisfaction with previous attempts to define the term. It then considers the objection that any attempt to examine the concept of ideology must itself be a rival ideological version of events. This objection is examined by contrasting philosophy as an activity with ideology and offering reasons for holding that they are a) different activities b) philosophy does not underpin a particular ideological model. Thus, it is possible to offer a disinterested study of our subject.The second part examines the relationship between history and ideology. It attempts to show that history is an autonomous enterprise and that it offers a special and particular understanding of the past. In contrast, it is suggested that there are other ways of understanding the past (of which ideology may be one) but that we can distinguish between them and the historical understanding of the past by looking at the appropriate context.The third part looks at three particular ideologies - Marxism, Liberalism, and Conservatism. It attempts to illustrate the part played by the past in these ideologies and to thus make concrete the argument of part II that ideologiets are interested in the past, but not in history. The argument looks at the relationship between the past and the other aspects of each ideology, for example, the view of human nature, of political activity and of social change. It is suggested that the important feature of the past for ideologists is the practical information it can provide, rather than the knowledge it can generate at a theoretical level. The vision of the past which Marxists, Liberals and Conservatives have is determined by these other elements, such that even if we wanted to, examining the Marxists view of the past, as history, would be to distort it.Having contrasted ideological understanding of the past with an 'academic' understanding in the shape of history, part four looks at the relation¬ ship between ideology and religion. The purpose here is to see whether understandings of the past which are not academic (they are termed 'practical' here) are of the same type. The conclusion is that there are as many differences between two 'practical' entities such as ideology and religion, as there are between ideology and 'academic' disciplines. Thus the 'shape' of ideology is thrown into relief from two sides, that of 'academic disciplines' and that of 'practical activity'. The fourth part continues by raising the question of disagreements between ideologists and poses some questions about their capacity for resolution. It is argued that disputes between ideologists are not like disputes or arguments between scientists of philosophers, because they lack appropriate criteria. A more illuminating parallel, it is claimed, is with moral disagreements, where fundamental values rather than 'facts' are at stake.The thesis seeks, by looking at how ideologists understand the past, and by relating that understanding to the other aspects of ideological thought to try and make clear the status of ideologies in relation to other areas of thought. It concludes that though ideologies do not offer us an objective or theoretically illuminating understanding of events, they should not be dismissed as a mere parasite on political activity. They are closer to religion and to morality than to science, philosophy or history, without being identical to them. Thus, to dismiss them as if they were the poor relations of academic enquiry may be to misunderstand them

LIPIcs, Volume 244, ESA 2022, Complete Volume

LIPIcs, Volume 244, ESA 2022, Complete Volum

Energy Efficiency: A Guide to Current and Emerging Technologies. Volume 1: Buildings and Transportation

Energy Efficiency: A Guide to Current and Emerging Technologies is the fourth and final major CAE project, carried out between 1993 and 1996. It was published in 1996 in two volumes – Volume 1, Buildings and Transportation, dealing with domestic, commercial and industrial buildings and transport, and Volume 2, Primary Production and Industry, dealing with primary production, food processing, forestry processing and manufacturing and minerals. Volume 2 also includes a section on general energy efficiency technologies. The focus of the two volumes is on energy efficiency technologies currently available and applied overseas, but not widely used in New Zealand, and on emerging technologies that are likely to prove practical for New Zealand within the next decade. While the emphasis is on New Zealand experience, the technologies discussed have application worldwide. Barriers that might restrict the use of individual technologies are also discussed

Arc routing problems with drones

La tecnología emergente de vehículos aéreos no tripulados, comúnmente conocidos como drones, ha brindado nuevas oportunidades para los profesionales de la logística urbana en la última década. El transporte ha jugado siempre un papel crucial en la sociedad y en la economía, y un motor fundamental del desarrollo económico en los últimos tiempos ha sido la inversión en sistemas de transporte cada vez más eficientes. Los drones presentan ventajas atractivas en comparación con los vehículos terrestres estándar, como evitar la congestión en las redes viales, eliminar el riesgo del personal en operaciones de difícil acceso u obtener una mayor precisión de medición en la inspección de infraestructuras. Muchas empresas comerciales han mostrado recientemente interés en utilizar drones para realizar entregas de última milla más rentables y rápidas. Amazon anunció a finales de 2013 que entregaría paquetes directamente en cada puerta a través de Prime Air usando pequeños drones 30 minutos después de que los clientes presionaran el botón “comprar”. Unos años más tarde, lanzaría una versión de su dron de entrega Prime Air que era una aeronave híbrida robusta capaz de despegar y aterrizar verticalmente que podía volar hasta 15 millas y entregar paquetes de menos de cinco libras a los clientes en menos de 30 minutos. Junto con Amazon, otros servicios de entrega como UPS o Google han estado probando el uso potencial de drones para la entrega de paquetes. Dado que los drones aéreos no están restringidos por la infraestructura local, también se pueden utilizar de manera rentable en la distribución rural, la vigilancia y la intralogística, así como en el mapeo geológico y ambiental en 3D para la recopilación de datos. El uso de drones dentro de todos estos escenarios enfrenta múltiples problemas (y desafíos) que pueden ser abordados mediante problemas de rutas, cuyos modelos de solución apuntan a encontrar la ruta (o rutas) más eficiente relacionada con un recurso explícito como la distancia, el tiempo o la energía.The emerging technology of drones has provided new opportunities for practitioners in urban logistics in the last decade. Drones present attractive advantages compared with standard ground vehicles in transportation, such as avoiding the congestion on road networks, eliminating the risk of personnel in difficult access operations or getting higher measurement accuracy in infrastructure inspection. The use of drones within distribution, surveillance or intralogistics scenarios faces multiple issues (and challenges) that can be addressed by routing problems, whose solution models aim to find the most efficient route (or routes) related to an explicit resource such as distance, time or energy.This thesis focuses on the study of some extensions of arc routing problems in which drones are used to optimize a certain service. Given a graph representing a network, arc routing problems (ARPs) consist of finding a tour, or a set of tours, with total minimum cost traversing (servicing) a set of links (arc or edges) of the graph, called required links, and satisfying certain conditions. The use of drones to perform the service in ARPs involves significant changes in the traditional way of modeling and solving these problems. Since aerial drones have the capability to travel directly between any two points of the network, not necessarily between vertices of the graph, arc routing problems with drones are continuous optimization problems with an infinite and uncountable number of feasible solutions. One mathematical approach for their solution consists on approximating each curved line in the plane of a drone ARP instance by a polygonal chain with a finite number of segments, and solving the problem as a discrete optimization problem, where vehicles are allowed to enter and leave each curved line only at the points of the polygonal chain. Once discretized, the set of non-required edges of the instance forms a complete graph, and the deadheading cost between any pair of points is given by the Euclidean distance. In this context, we address three variants of arc routing problems with drones, which are modeled as combinatorial optimization problems and addressed with heuristic and exact mathematical approaches: the length constrained K-drones rural postman problem, where a fleet of K drones with limited autonomy has to jointly traverse a set of lines on the plane, the multi-purpose K-drones general routing problem, where a fleet of K multi-purpose drones (aerial vehicles that can both make deliveries and conduct sensing activities) has to jointly visit a set of nodes to make deliveries and also map one or more continuous areas, and the load-dependent drone general routing problem, an extension of the classical general routing problem in which the traversal time of each edge of the graph depends on the cargo carried by the drone