Dissertations / Theses on the topic 'Superheat'

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, February 2011.
"September 2010." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 219-225).
The conceptual design of an annular-fueled superheat boiling water reactor (ASBWR) is outlined. The proposed design, ASBWR, combines the boiler and superheater regions into one fuel assembly. This ensures good neutron moderation throughout the reactor core. A single fuel design is used in the core. Each annular fuel element, or fuel tube, is cooled externally by boiling water and internally by steam. Fuel pellets are made of low enrichment U0 2, somewhat higher than the traditional BWR fuel enrichment. T91 and Inconel 718 are selected as candidates for the cladding material in view of their excellent physical properties and corrosion resistance. The fuel-cladding gap is filled with pressurized helium gas, like the existing lighter water reactor fuels. The ASBWR fuel assembly contains sixty annular fuel elements and one square water rod (occupying a space of four fuel elements) in an 8 by 8 square array. Annular separators and steam dryers are utilized and located above the core in the reactor vessel. Reactor internal pumps are used to adjust the core flow rate. Cruciform control rods are used to control the reactivity of the core, but more of them may be needed than a traditional BWR in view of the harder spectrum. The major design constraints have been identified and evaluated in this work. The ASBWR is found promising to achieve a power density of 50 kW/L and meet all the main safety requirements. This includes a limit on the minimum critical heat flux ratio, maximum fuel and cladding operating temperatures, and appropriate stability margin against density wave oscillations. At the expected superheated steam of 520 °C, the plant efficiency is above 40%, which is substantially greater than the efficiency of 33 to 35% that today's generation of LWRs can achieve. In addition to generating electricity, the ASBWR may also be useful for liquid fuel production or other applications that require high temperature superheated steam. The uncertainties about this design include the performance of cladding materials under irradiation, the attainment of desirable heat transfer ratio between the external and internal coolant channels throughout the fuel cycle, and the response to the traditional transients prescribed as design basis events.
by Yu-Chih Ko.
Ph.D.

The Project in Canada to Search for Supersymmetric Objects (PICASSO) searches for cold dark matter through the direct detection of Weakly Interacting Massive Particles (WIMPs) via spin-dependent and spin independent interactions with 19F nuclei. The detection principle is based on the superheated droplet technique; the detectors consist of a gel matrix with millions of liquid droplets of superheated fluorocarbon (C4F10) dispersed in it. In order to reduce the background, it is essential to distinguish the signature of different background particles interacting in the detector. A dedicated setup was developed in order to study the response of the C4F10 droplets in the presence of different backgrounds. The main objectives of this research are to identify the actual size (diameter) of the droplet increases due to phase transition and to check and establish the correlation between the droplet size and the maximum amplitude of the signal. In addition, the alpha-neutron discrimination was studied by observing each event’s image frames and the associated acoustic signal to get the amplitude distribution. The mean ratio of bubble size to droplet size was found to be 5.48, independent of temperature and type of interacting particle. Furthermore, no correlation was found between the droplet size and the maximum amplitude of the signal. As for the discrimination studies, the analysis of the signal events has confirmed that alphas generated outside the active liquid in the gel are much more difficult to discriminate from neutron than when alphas are generated inside the active liquid.

[ES] Un porcentaje significativo de la energía se destina a la producción de Agua Caliente Sanitaria (ACS) en el sector comercial y residencial. Además, la mayor parte de la energía que contiene el agua se desperdicia en el ambiente tras su uso. Las bombas de calor han sido identificadas por su capacidad de producir ACS con una alta eficiencia y son una gran alternativa hacia la descarbonización de las ciudades. Además, son capaces de utilizar como fuente de calor, el calor contenido en el agua que actualmente se desperdicia. Sin embargo, la aplicación del uso de bombas de calor para ACS recuperando el calor de las aguas residuales presenta unas características diferentes a las usuales en bombas de calor. Por tanto, es necesario un análisis del problema más profundo y se require mayor investigación al respecto con el fin de lograr un desarrollo eficiente de la misma: 1. Un diseño de bomba de calor capaz de operar con alta eficiencia ante los grandes saltos de temperatura que tienen lugar en esta aplicación (ACS). 2. Un diseño de bomba de calor capaz de operar con alta eficiencia ante saltos de temperatura del fluido secundario variables (recuperación de calor). 3. La integración de esta bomba de calor en un sistema de ACS completo (estrategias de recuperación de calor, componentes, tamaño y estrategia de control). Normalmente, los ciclos transcríticos han sido considerados como una de las mejores soluciones para la producción de ACS (donde se tienen grandes saltos de temperatura en el agua, 10-60°C). Sin embargo, este tipo de ciclo presenta dos desventajas principales, la necesidad de altas presiones en la instalación y la dependencia de la eficiencia con el salto de temperatura del agua en el condensador. Sin embargo, los ciclos subcríticos han demostrado un gran potencial para saltos de temperatura del agua variables si se aplica un control del subenfriamiento adecuado. El objetivo de esta tesis es investigar la bomba de calor agua-agua más eficiente trabajando con un ciclo de refrigerante subcrítico para la producción de ACS utilizando como fuente de calor el calor disponible en las aguas residuales (a baja-media temperatura) para determinar el sistema más eficiente para este tipo de aplicación. El trabajo se divide en dos partes diferenciadas: ¿ Diseño de la bomba de calor El desarrollo de la bomba de calor es una continuación del trabajo realizado en la tesis de M. Pitarch [1]. En dicha tesis, se investigó el papel del subenfriamiento en una bomba de calor subcrítica para la apliación de ACS. Se desarrolló un prototipo de bomba de calor con el diseño de dos configuraciones distintas en función del modo en el que se realizaba el subenfriamiento. Los resultados permitieron concluir que este tipo de bombas de calor (subcríticas) eran capaces de operar con eficiencias similares a las de las bombas de calor basadas en ciclos transcríticos si se opera con un grado de subenfriamiento óptimo. Sin embargo, en ambas configuraciones se requiere un componente más que en las bombas de calor convencionales. En esta tesis, se ha realizado un estudio y análisis teórico de la bomba de calor. Se ha desarrollado e implementado una estrategia de control para el subenfriamiento y se ha construído el prototipo de bomba de calor propuesto en [1]. De todo este trabajo se ha obtenido el diseño de bomba de calor basada en ciclos subcríticos más interesante para este tipo de aplicaciones. ¿ Diseño e integración de la Bomba de Calor y el sistema de ACS La integración del prototipo seleccionado en un sistema para la producción de ACS con recuperación del calor de las aguas residuales ha sido analizada.El sistema más simple y eficiente necesario para este tipo de aplicaciones (producción de ACS con recuperación de calor de las aguas grises) se compone de un intercambiador de calor (recuperador), una bomba de calor con subenfriamiento optimizado y dos depósitos de almacenamiento.
[CAT] Un percentatge significatiu de l'energia es destina a la producció d'Aigua Calenta Sanitària (ACS) en el sector comercial i residencial. A més, la major part de l'energia que conté l'aigua es malgasta en l'ambient després del seu ús. Les bombes de calor han sigut identificades per la seua capacitat de produir ACS amb una alta eficiència i són una gran alternativa cap a la descarbonització de les ciutats. A més, són capaços d'utilitzar com a font de calor, el calor contingut en l'aigua que actualment es desaprofita. Contribuint així, a aconseguir un sector energètic més respectuós amb el Medi Ambient. No obstant això, l'aplicació de l'ús de bombes de calor per a ACS recuperant el calor de les aigües residuals presenta unes característiques diferents de les usuals en bombes de calor. Per tant, és necessari una anàlisi del problema més profund i es requereix una major investigació al respecte amb la finalitat d'aconseguir una alta eficiència: 1.Un disseny de bomba de calor capaç d'operar amb alta eficiència davant dels grans salts de temperatura presents en aquesta aplicació (ACS). 2.Un disseny de bomba de calor capaç d'operar amb alta eficiència davant de salts de temperatura del fluid secundari variables (recuperació de calor). 3.La integració d'aquesta bomba de calor en un sistema d'ACS complet (estratègies de recuperació de calor, components, grandària i estratègia de control). Normalment, els cicles transcrítics han sigut considerats com una de les millors solucions per a la producció d'ACS (on es tenen grans salts de temperatura en l'aigua, 10-60°C). No obstant això, aquest tipus de cicle presenta dos desavantatges principals, la necessitat d'altes pressions en la instal·lació i la dependència de l'eficiència amb el salt de temperatura de l'aigua en el condensador i evaporador. L'objectiu d'aquesta tesi és investigar la bomba de calor aigua-aigua més eficient treballant amb un cicle de refrigerant subcrític per a la producció d'ACS utilitzant com a font de calor el calor disponible en les aigües residuals (a baixa-mitja temperatura) per a determinar el sistema més eficient en aquest tipus d'aplicació. El treball es dividix en: ¿ Disseny de la bomba de calor El desenvolupament de la bomba de calor és una continuació del treball realitzat en la tesi de M. Pitarch [1]. En aquella tesi, es va investigar el paper del subrefredament en una bomba de calor subcrítica per a l'apliació d'ACS. Es va desenvolupar un prototip de bomba de calor amb el disseny de dues configuracions distintes en funció de la manera en què es realitzava el subrefredament. Els resultats van permetre concloure que aquests tipus de bombes de calor (subcrítiques) eren capaços d'operar amb eficiències semblants a les de les bombes de calor basades en cicles transcrítics si s'opera amb un grau de subrefredament òptim. No obstant això, en ambdues configuracions es requereix un component més que en les bombes de calor convencionals. En la present tesi, es va realitzar un estudi i anàlisi teòric de la bomba de calor. Es va desenvolupar i implementar una estratègia de control per al subrefredament i es va construir el prototip de bomba de calor proposat en [1]. De tot aquest treball s'ha obtingut el disseny de bomba de calor basada en cicles subcrítics més interessant per aquest tipus d'aplicacions. ¿Disseny i integració de la Bomba de Calor i el sistema d'ACS La integració del prototip seleccionat en un sistema per a la producció d'ACS amb recuperació de el calor de el calor de les aigües residuals ha sigut analitzada.El sistema més simple i eficient necessari per a aquest tipus d'aplicacions (producció d'ACS amb recuperació de calor provinent d'aigües grisas) està compost per un bescanviador de calor (recuperador), una bomba subrefredada i dos depòsits d'emmagatzemament.
[EN] A significant percentage of energy is destined to produce Domestic Hot Water (DHW) within the building sector. Furthermore, most of that energy contained in the water is wasted to the ambient after its use. Heat pumps have been clearly identified as an efficient technology for DHW production, and as a main vector towards future de-carbonization of cities. In addition, they could use the heat from the wastewater as a heat source. Thus, contributing in two ways towards a more environmentally friendly energetic sector. However, the use of heat pumps for DHW recovering heat from wastewater faces several challenges that require further analysis and development: 1. A heat pump design capable to operate with high performance when variable secondary temperature lifts at the heat sink take place. 2. A heat pump design capable to operate with high performance when variable secondary temperature lifts at the heat source take place. 3. The integration of the heat pump within a system (heat recovery strategies, components, sizing, operation strategy). Usually, transcritical cycles have been considered the most suitable cycle for DHW production (high temperature lifts of the heat sink, 10-60°C). However, this cycle involves several drawbacks as for instance the requirement of high pressures in the installation or a significant reduction of the performance with the increase of water inlet temperature at the condenser. Instead, subcritical cycles have demonstrated great potential for DHW applications if a proper control of subcooling is performed. The objective of this thesis is to investigate the most efficient water-to-water heat pump working with a subcritical cycle for DHW production using as a heat source wasted heat at medium-low temperature and to determine the most efficient system based on heat pumps for this application. The work is divided in two differentiated parts: ¿ Heat pump concept This development is a continuation from the PhD work of M. Pitarch [1]. In that PhD work, the role of the subcooling in the performance of a subcritical heat pump for DHW applications was investigated. Two different configurations of a heat pump prototype were designed based on the way subcooling was made. The results showed that a subcooling optimized subcritical heat pump was able to provide comparable performance than present HPs employing transcritical cycles. However, both configurations require one more component than usual heat pumps. Thus, a new prototype based only on the typical components (compressor, condenser, expansion valve and evaporator) was proposed as future work. In this thesis, a theoretic analysis of the heat pump was done. A subcooling control methodology was developed and tested. The proposed prototype in [1] has been built and characterized. From all the results, the most convenient heat pump design was obtained. ¿ Integral Heat pump-DHW system The integration of the most convenient heat pump prototype within a system for the DHW production based on heat recovery from wastewater has been analyzed. The research has included the development of a model of the entire system in Trnsys and the optimization of the main components of the system: their sizing and their operation with the objective of reaching the maximum global efficiency of the complete system. Due to the complexity of the problem, the analysis was performed in three main steps: first, a study of the direct heat exchange,second, an study focusing on the condenser side, that is, the consideration of an infinite heat source (large availability of sewage water for instance) and third, the focus was done on the evaporator side. That is, the optimization of the complete system in which a finite heat source is considered (grey waters collected from the building for instance). The simplest and most efficient system required in DHW production and heat recuperation from wastewater has been determined.
Esta tesis se enmarca dentro del proyecto “APROVECHAMIENTO DEL CALOR RESIDUAL A BAJA TEMPERATURA MEDIANTE BOMBAS DE CALOR PARA LA PRODUCCION DE AGUA CALIENTE” a través de una beca FPI del Ministerio de Economía y Competitividad.
Hervás Blasco, E. (2020). Aprovechamiento del calor residual a baja temperatura mediante bombas de calor para la producción de agua caliente [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/137776
TESIS

Die Erfindung der Kältemaschine macht es möglich, dass heute zu beliebiger Zeit Kälte in benötigter Menge und gewünschter Temperatur erzeugt werden kann. Aber für die Kälteerzeugung braucht man Antriebsenergie. Das Ziel dieser Doktorarbeit besteht darin, mit einer intelligenten Kombination von thermostatischem Expansionsventil (TEV) und innerem Wärmeübertrager (IWÜ) den Energieverbrauch von Kälteanlagen deutlich zu verringern, ohne dass dies zu einer Verschlechterung der Zuverlässigkeit oder wesentlichen Mehrkosten führt. Bis heute gelten die beiden bekannten Komponenten TEV und IWÜ als inkompatibel miteinander, weil die einfache Aneinanderreihung zu einem instabilen Regelverhalten führt. Nach detaillierter Analyse der Ursachen dieser Instabilität wird die Hypothese aufgestellt, dass durch eine absichtliche „Verschlechterung“ des IWÜ ein stabiler Arbeitsbereich gefunden werden kann. Bei dieser „Verschlechterung“ kann es sich z. B. um den Bypass eines Teils des Hochdruckstromes oder um eine Gleichstromanordnung der Ströme im Wärmeübertrager handeln. Diese Hypothese wurde primär durch Experimente, aber zusätzlich auch durch Simulationsrechnungen bestätigt. Dafür wurde ein Versuchsstand aufgebaut, mit welchem verschiedene Konfigurationen und Regelstrategien getestet wurden. Es wurde eine deutliche Verringerung des Energieverbrauchs gegenüber herkömmlichen Anordnungen erreicht.

Die Erfindung der Kältemaschine macht es möglich, dass heute zu beliebiger Zeit Kälte in benötigter Menge und gewünschter Temperatur erzeugt werden kann. Aber für die Kälteerzeugung braucht man Antriebsenergie. Das Ziel dieser Doktorarbeit besteht darin, mit einer intelligenten Kombination von thermostatischem Expansionsventil (TEV) und innerem Wärmeübertrager (IWÜ) den Energieverbrauch von Kälteanlagen deutlich zu verringern, ohne dass dies zu einer Verschlechterung der Zuverlässigkeit oder wesentlichen Mehrkosten führt. Bis heute gelten die beiden bekannten Komponenten TEV und IWÜ als inkompatibel miteinander, weil die einfache Aneinanderreihung zu einem instabilen Regelverhalten führt. Nach detaillierter Analyse der Ursachen dieser Instabilität wird die Hypothese aufgestellt, dass durch eine absichtliche „Verschlechterung“ des IWÜ ein stabiler Arbeitsbereich gefunden werden kann. Bei dieser „Verschlechterung“ kann es sich z. B. um den Bypass eines Teils des Hochdruckstromes oder um eine Gleichstromanordnung der Ströme im Wärmeübertrager handeln. Diese Hypothese wurde primär durch Experimente, aber zusätzlich auch durch Simulationsrechnungen bestätigt. Dafür wurde ein Versuchsstand aufgebaut, mit welchem verschiedene Konfigurationen und Regelstrategien getestet wurden. Es wurde eine deutliche Verringerung des Energieverbrauchs gegenüber herkömmlichen Anordnungen erreicht.

Le BLEVE (Boiling Liquid Exploding Vapor Explosion) est l’un des accidents les plus craints dans l’industrie. Bien qu’il soit étudié depuis plus de soixante ans, certains dangers et situations restent mal anticipés, tels que : quelles seraient les conséquences de la surpression d’un BLEVE dans un milieu urbain confiné ? Qu’adviendrait-il si un camion de transport de GPL venait exploser sur un pont ? Ces questions nécessitent d’étudier la physique du BLEVE au plus proche du conteneur. Ce travail explore les phénomènes physiques générant la surpression aérienne en champ proche de l’explosion, en essayant de comprendre la contribution des phases du contenu (liquide et vapeur) dans les dangers en champ proche du BLEVE. Un prototype expérimental petite échelle a été conçu dans le but de reproduire les BLEVE de cuves cylindriques de manière réaliste. Vingt-quatre BLEVEs de propane ont été effectués. Un large spectre de données a été collecté lors de ces tests : surpression aérienne dans de multiples directions autour du conteneur, variations de pression dans le conteneur avant et après rupture, chargement au sol dû à l’explosion, visualisations en imagerie rapide selon un certain nombre d’angles. Les résultats montrent une dépendance forte entre les caractéristiques de la phase vapeur et la suppression maximale générée par l’explosion. La reconstruction chronologique du phénomène confirme ce résultat. Cependant, la phase liquide joue un rôle capital dans la génération du chargement au sol, qui est un danger considérable, mais peu considéré jusque-là
Boiling Liquid Exploding Vapor Explosion (BLEVE) is one of the most feared accident in the industry. Even though it has been studied for over 6 decades, many safety questions remain poorly answered: what happens if a BLEVE occurs in a congested urban or industrial area? What if a road tanker BLEVE happens on a bridge? These questions require to look closer to the vessel. This work focuses on understanding the physics involved in overpressure generation in the near field surrounding of the vessel, to understand the contribution of the fluid phases (liquid and vapor) in the near-field hazards of a BLEVE. For this purpose, a small scale experimental prototype was designed to reproduce realistic BLEVE failure. Twenty-four propane BLEVEs were performed. A wide range of data was recorded from these tests: blast overpressure all around the vessel, transient pressure inside the vessel, ground loading under the vessel, and high speed imaging through various angles. Results give more insight on the anisotropy of the pressure field around the cylindrical vessel. It also shows a strong dependency between vapor content and maximum overpressure from the lead shock. Moreover, the chronology of the phase change observed through transient pressure measurements show that the main contributor of the maximum overpressure is the vapor phase. The phase change is studied through pressure transient in the vessel and high speed imaging, giving a better understanding of the time scales involved with this phenomenon. Finally, ground loading measurements are analyzed to give insight on the order of magnitude involved in this hazard

A BLEVE is a physical explosion characterized by the sudden expansion of a liquefied gas under pressure and the vapor space above it. In this work, the analysis of a set of water BLEVE experiments was carried out both in terms of data processing and numerical modelling. The main purpose of the project was to investigate safety implications of a pipe rupture containing superheated water that may affect a steam generation system in a nuclear or chemical plant. The experimental campaign consisted in 27 explosive tests in which an instantaneous depressurization of the content was enabled by the use of a calibrated rupture disk. A flange calibrated for different dimensions of the releasing orifice was incorporated in the prototype to replicate a pipe failure for various nominal sizes. The analysis primarily focused on the pressure field distribution generated in the surroundings, in the form of multiple shock waves. First observations came directly from high-speed pressure data recorded, showing a high directionality of the blast, stronger in the vertical direction, and the independence of the lead shock on the initial liquid fill level. The intensity of the overpressure of the lead shock was found to be increasingly correlated with the opening size. Available theoretical methods were used to preliminarily estimate the first overpressure peak. Models based on real gas behaviour and adiabatic irreversible expansion gave the best approximation of the vertical overpressure, providing an energy conversion factor (energy contributing to the blast overpressure over the total expansion energy) comparable with values found in the literature. A few CFD simulations were then performed under a shock tube configuration to validate the widely accepted assumption that the lead pressure peak is exclusively depending on the expansion of the pressurized vapor space.

Superheated water has been used successfully as an eluent in liquid chromatography and has been coupled to various modes of detection, ultraviolet (UV), fluorescence, and nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). A number of compounds were examined on poly(styrene-divinylbenzene) (PS-OVB), polybutadiene (PBO), and octadecylsilyl bonded silica (OOS) column with isothermal and temperature programmes.

La vaporisation explosive, ou flashing, par dépressurisation rapide du C6F14 au travers d'une vanne à boisseau sphérique est analysée expérimentalement sur une grande plage de surchauffe. Les visualisations rapides montrent un jet s’ouvrant très largement en aval, preuve de l'existence d'un fort gradient de pression. Des mesures locales par sonde optique et par vélocimétrie phase Doppler ont permis de caractériser tailles, vitesses, concentration et flux numérique des gouttes en fonction de la surchauffe. La faible influence du degré de surchauffe sur la remontée en pression et sur les tailles et flux de gouttes suggère que le champ de pression s’adapte, et que par conséquent le liquide est soumis à une surchauffe locale bien plus faible que la surchauffe globale imposée. Différents scenarii sont discutés pour expliquer les observations, dont le fait que les tailles de gouttes sont peu sensibles à la surchauffe. Celui basé sur l’existence d’un front d’ébullition est le plus probable
Depressurization (flashing) experiments through a ball valve were conducted with C6F14 for a large range of superheat. High-speed imaging shows a rapid and wide expansion of the jet, which evidences strong pressure gradients. Local measurements with phase detection optical probes and phase Doppler velocimetry were used to characterize size, speed, concentration and volumetric flux of drops as a function of superheat. The level of superheat has little influence on the vaporized fraction and on drop size and flux: this suggests that due to strong pressure gradients the liquid sees a much weaker level of superheat than the global superheat imposed on the system. Different scenarii are discussed to explain observations, in particular the fact that drop size remains approximately constant independent of the superheat. A scenario based on the existence of a boiling front seems to be the most consistent

In an important initiative to reduce carbon dioxide emission from pulverized fuel boilers, coal is now co-fired with biomass. During the combustion process, however, chlorine and sulphur in chemical compounds associated with sodium and potassium are released in a form which can deposit onto and then corrode the steel heat exchanger tubes. The deposition and corrosion can have serious implications for the power generation industry because the corrosive damage on heat exchange tubes can shorten the operational life of the boilers and lead to significant economic penalties. The deposition and corrosion processes have been widely studied but eliminating the deposits and corrosive materials is still a challenging problem. Computational fluid dynamics (CFD) has been used to model the deposition processes and it mainly focuses on experimentally deriving constants in the models that capture some aspects of the problem such as the motion behaviour of aerosols. However, using CFD has a limitation that results in periodic instability when solving the models with numerical computation. Modelling deposition environments around superheater tubes is a complex problem as many aspects, such as particle motion, condensation of matter and continuous combustion of particles, should be considered.This thesis has: (1) developed a new mathematical approach that uses mesh-free methods to solve Hamilton’s equations with a consideration of the total energy of the system, where the Hamilton’s equation is scale independent; (2) developed a model that can simulate the mass accumulation process based on graph and combinatorics theory; (3) developed a model depicting the continuous combustion of particles in motion; (4) developed a model depicting the behaviour of changing matter states; (5) developed a model depicting the vapour phase deposition on particles; and (6) verified the developed models with case studies. This work shows the importance of homogenous and heterogeneous vapour depositions on binding particles onto superheater tubes.

This project focused on the comparison of conventional liquid chromatography and superheated water chromatography. It examined the differences in efficiency and retention of a range of different stationary phases. Alkyl aryl ketones and eight aromatic compounds were separated on PBD-zirconia, Xterra™ RP 18, Luna™ C18(2) and Oasis HLB™ columns using conventional LC and superheated water chromatography system. The retention indices were determined in the different eluents. On changing the organic component of the eluent from methanol to acetonitrile to superheated water considerable improvements were found in the peak shapes and column efficiencies on the PBD-zirconia and Oasis HLB™ columns.

The aim of this research project is to provide the academic and industrial community with a numerical tool that can be used for describing extreme flow cavitation scenarios and the atomisation process of these multiphase jets in a low-pressure environment. The research lies in the intersection of Numerical Analysis, Applied Physics and programming. From the physical point of view, the project has two different strands: The first is developing a methodology for channel flows due to a rapid pressure drop which is possible to result into various flow regimes inside the channel. The second step is to track the liquid fragmentation of the liquid jet downstream the channel exit and describing the atomisation process to liquid ligaments and blobs to droplets. Using a fully Eulerian approach, this research aims towards a holistic approach that addresses some of the major challenges that govern superheated jets atomisation. The finite volumes method in a compressible framework is used utilising various models for modelling the underpinning physics of flashing jets. Flashing occurs either if a liquid follows an isothermal depressurisation or isobaric heating. In both cases, the fluid fails to adjust to the local changes in pressure and temperature admitting a metastable state which makes the process more challenging to understand. The Homogeneous-Relaxation-Model (HRM) is used for modelling the heat transfer under sudden depressurisation conditions accounting for the non-equilibrium vapour generation. A new pressure equation is proposed which employs the continuity equation indirectly. The pressure responds to compressibility and density changes due to the rapid phase change and includes the surface tension contribution in the pressure-velocity coupling algorithm. The coupling of the continuity and momentum equation with the HRM and the interface tracking method is thoroughly described. The result of this coupling is a conserved numerical method that is capable of characterising the flow regimes and the impact of bubble nucleation on the mass flow rate. The present study presents a numerical approach for simulating the atomisation of flashing liquids accounting for the distinct stages, from primary atomisation to secondary break-up to small droplets Following the Eulerian-Lagrangian-Spray-Atomisation approach, the concept of the surface density Σ is introduced into the methodology for the spray dynamics. The proposed approach has the advantage of avoiding the unrealistic common assumption of pure liquid at the nozzle exit. It models the change in the regime inside the nozzle treating flashing in a unified approach simulating the metastable jet both inside and outside the nozzle. Important mechanisms such as thermal non-equilibrium, aerodynamic break-up, droplet collisions and evaporation are modelled in a novel atomisation model. The modified Σ- equation employed a new source term proposed for cryogenic jets. A wide range of numerical tests is presented for validation and obtaining insights for the underlying physics. Short and long nozzle geometries are tested for both low and high-pressure releases for flashing water, R134A, liquid nitrogen and LNG. Results for turbulent flows for both sub-cooled and superheated liquids are presented showing that the proposed approach can accurately simulate the primary atomisation.

This project has focused on the applicability of using superheated water as an alternative eluent for use in reversed phase high performance liquid chromatography (RP-HPLC). A system based on instrumentation from gas chromatography (GC), HPLC, and supercritical fluid chromatography (SFC) was utilised with some success. Of particular importance was the stability of the column stationary phases commonly employed in RP-HPLC. The most popular phases based on alkyl bonded silica proved unsuitable due to excessive dissolution of the base silica at high temperatures. Nevertheless, two other phases—one a poly(styrene-divinylbenzene) material and the other a porous graphitic carbon—proved stable to temperatures as high as 240°C. At such temperatures compound stability was good, except for a notable case with nitrobenzene. The mechanism of elution remained reversed phase mode throughout, with polar solutes being eluted before non-polar ones.

This project explores the question of originality and appropriation in the creative world by using mashup video as a medium. How can old repetitive stories be deconstructed and transformed into something new? I have created alphabetically ordered montages of shots/scenes containing words/letters from superhero films. By doing so, I do not provide a concrete answer to what is really original in today’s world, but rather encourage the audience to actively participate in the viewing experience of the carefully structured ontology and see the infinite possibility of the modern-day mashup culture.

In recent years, there has been increasing interest in the idea of using a superheated superconducting colloid (SSC) as a detector for neutrinos and dark matter candidates. The primary objective of this work has been to investigate the basic properties of an SSC, consisting of 7 μm radius tin grains imbedded in epoxy, using a pumped ⁴He cryostat with a low vibrational noise RF-SＱUID readout system. The superheating-supercooling hysteresis curves of the colloid have been measured in applied magnetic fields ranging from 3.1 x 10⁻⁴T to 1.4 x 10⁻²T. The superconducting to normal phase transition in individual grains inside the colloid has been observed and the measured signal size is in reasonable agreement with the calculated values. Finally, it was demonstrated that the colloid could withstand up to 20Mrad of [omitted]-radiation without incurring a significant change in its superconducting-normal phase transition. A new type of sample, consisting of a planar array of 1 μm thick metal squares deposited on a mylar substrate, was developed. Both indium and tin were used as a. fabrication material. The characteristics of such samples were investigated, again using the pumped ⁴He cryostat. The full Meissner effect was only observed for applied magnetic fields less than 5 x 10⁻⁵T. For higher applied fields, the samples behaved like type-[omitted] superconductors in the mixed state regime, exhibiting flux penetration and trapping.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

The dimensional stability of superheated steam dried paper made from groundwood, thermomechanical, chemithermomechanical and bleached kraft pulps were investigated in terms of hygroexpansivity, drying shrinkage and wet expansion. For all the pulps tested these characteristics of dimensional stability were found to be improved by high temperature superheated steam drying.
The hygroexpansion coefficient, the dimensional change relative to paper moisture content, was reduced about 15% by superheated steam drying at 320°C, compared to paper dried in low temperature air. Irreversible shrinkage was reduced by up to 30% for sheets dried in superheated steam. However, these effects on hygroexpansivity were caused mainly by the high drying temperature and the resulting high drying rate regardless of the drying fluid. Drying shrinkage and wet expansion as well were reduced by about 10% and 15% respectively for paper dried in superheated steam.
In superheated steam drying the elevated web temperature at the start of drying is believed to affect paper properties through thermal softening of the lignin and relaxation of drying and wet-pressing stresses. Increased fiber bonding with softened lignin accounts for both the increased elastic modulus and decreased light scattering coefficient observed. These were obtained only for sheets from mechanical pulps with initial moisture content of about 0.4 kg-water/kg-fiber or more, consistent with the mechanism of thermal softening of plasticized lignin. High sheet temperature in the falling rate period improves hygroscopicity of paper through reducing its equilibrium moisture content.
Superheated steam drying improves the dimensional stability of paper from such pulps, including less anisotropy, thereby enhancing paper quality.

Captain America and Iron Man are both iconic American heroes, representing different American values. Captain America was created during the Golden Age of comics and represents a longing for the past, while Iron Man was created at the height of the Cold War and looks forward to a new America. This paper will first establish the historical and cultural relationship between comic books and propaganda, beginning with the first appearance of Superman. It will pay special attention to the similarities and differences of Captain America and Iron Man, focusing on their representation of American values over time, and discuss how that aspect of the characters affects their ongoing titles today.

Diagnostic ultrasound is a safe, inexpensive and highly portable real-time imaging modality for viewing the human body. For over two decades, lipid-coated fluorocarbon microbubble contrast agents have been developed to help improve the diagnostic and therapeutic capabilities of ultrasound, but they have certain limitations. Recently, it was found that the microbubbles can be condensed into superheated liquid nanodrops capable of being vaporized by external optical or acoustic triggers. The compact form and vaporization effects of these phase-shift nanodrops may offer advantages over microbubbles for a number of current and future therapeutic and diagnostic applications. The goal of this dissertation work was to study the molecular thermodynamics and interfacial phenomena of these superheated phase-shift nanodrops.

In the first part of this work, a custom microscopy pressure chamber with control over temperature and pressure was used to observe microbubbles during condensation. Compression behaviors of fluorocarbon microbubbles constructed with lipid shells of varying acyl chain lengths were quantified over a broad temperature range. Microbubbles containing lipids of longer acyl chains were found to resist ideal compression and condensation. Dissolution was found to dominate as temperature approached the lipid main phase transition temperature, resulting in incomplete condensation. However, successful condensation of gas-filled microbubbles to liquid-filled nanodrops could be achieved at lower temperatures, and fluorescence microscopy showed that the lipid monolayer shell buckles and folds into surface-attached bilayer strands. The nanodrops were found to be remarkably stable when brought back to standard temperature and pressure. The temperature-pressure data were used to construct condensation phase diagrams to determine the thresholds for successful nanodrop formation.

In the second part of this study, the superheated nanodrops were vaporized back into microbubbles by changes in temperature and pressure. A custom optical chamber with control over temperature and pressure was used to track the kinetics of condensation, vaporization and dissolution of microbubble suspensions with varying fluorocarbon core and lipid shell compositions. A simple model was used to extract kinetic rates from the optical data, and Arrhenius plots were used to determine activation energies. The activation energy for thermal vaporization was found to vary with lipid acyl chain length, and a simple model of lipid intermolecular forces was used to explain this effect. Additionally, thermal vaporization was found to occur near 90% of the critical temperature of the fluorocarbon core, indicating that metastability of the superheated droplets was due to the low probability of homogenous nucleation rather than a Laplace overpressure. The superheated droplets could be reversibly vaporized and condensed to at least ten cycles, showing remarkable stability.

In the final part of this study, the tunability of vaporization was examined through the mixing of fluorocarbon gases in droplet core. A clinical ultrasound imaging system was used to track vaporization as a function of temperature and mechanical index. Discrepancies were found in the vaporization thresholds owing to mass transfer; the high solubility of the lower fluorocarbon caused it to rapidly deplete. However, a successful acoustic temperature probe was demonstrated. The experimental data from all three parts of this study were examined and explained by conventional molecular thermodynamics theory, providing new insights into the behavior and properties of these novel theranostic agents.

The ascent of ‘school-improvement’ discourses in recent educational development initiatives has often centred on the installations of senior teachers from other schools into those that are seen as ‘failing’. Specifically, the notion of ‘superhead’ has been introduced in recent years as a strategy for improving ‘failing’ schools, where such individuals are given a brief of ‘raising standards’. Education' texts have abundant literature on alternative conceptions of leadership and on the role of leadership in effecting change. Little exists, however, on the impact of external leaders or ‘superheads’ transforming schools in challenging circumstances. Less still has been written on how individuals assume such roles and how they understand the process of transformation. This study takes an insider-outsider perspective on the practical challenge entailed in transforming school performance. From working as a teacher and consultant in two of the three inner city case study schools in Northern England, I draw upon data generated by using a mixed methods approach across these schools, all emerging from challenging circumstances. I examine how leadership impacts upon middle leaders and pupils through the narratives of mainstream ideology. The voices of the adults and children in these data serve as a reminder of the human impact resulting from external and internal interventions in schools. Social theory is mobilised in support of this task by drawing upon the writings of Foucault to problematise taken-for-granted practices in education. Foucault’s tools provide a mechanism for inspecting the narrative, through which I align history, power and discipline to education. Thus, I argue that a ‘superhead’ being transported in to transform a school is too simplistic a notion and one that undermines the complexities visible within these data gathered in this study.

Liquid jet impingement is a technique ubiquitously used to rapidly remove large amounts of heat from a surface. Several different regions of heat transfer spanning from forced convection to nucleate, transition, and film boiling can occur very near to one other both temporally and spatially in quenching or high wall heat flux scenarios. Heat transfer involving jet impingement has previously shown dependency both on jet characteristics such as flow rate and temperature as well as surface material properties. Water droplets are known to bead up upon contact with superhydrophobic (SH) surfaces. This is due to reduced surface attraction caused by micro- or nanostructures that, combined with a natively hydrophobic surface chemistry, reduce liquid-solid contact area and attraction, promoting droplet mobility. This remarkable capability possessed by SH surfaces has been studied in depth due to its potential for self-cleaning and shear reduction, but previous research regarding heat transfer on such surfaces shows that it has varying effects on thermal transport. This thesis investigates the effect that quenching initially hot SH surfaces by water jet impingement has on heat transfer, particularly regarding phase change. Two comparative studies are presented. The first examines differences in transient heat transfer from hydrophilic, hydrophobic, and SH surfaces over a range of initial surface temperatures and with jets of varying Reynolds number (ReD), modified by adjusting flow rate. Comparisons of instantaneous local heat flux from the surfaces are made by performing an energy balance over differential control volumes across the surfaces. General trends show increased heat flux, jet spreading velocity and maximum jet spread radius when ReD is increased. An increase in inital surface temperature resulted in increased heat flux across all surfaces, but slowed jet spreading. The local heat flux, average heat rate, and total thermal energy transfer from the surface all confirmed that SH surfaces allow significantly less heat to transfer to the jet compared to hydrophilic surfaces, due to the enhanced Leidenfrost condition and reduced liquid-solid contact on SH surfaces which augments thermal resistance. The second study compares jet impingement heat transfer from SH surfaces of varying microstructures. Similar thermal effects due to modified jet ReD and initial surface temperature were observed. Modifying geometric pattern from microposts to microholes, altering cavity fraction, and changing feature pitch and width had little impact on heat transfer. However, reducing feature height on the post surfaces facilitated water penetration within the microstructure, slightly enhancing thermal transport.

Cette thèse a été réalisée en cotutelle entre l'Université Technique Nationale Ivan Pul'uj de Ternopil (TNTU, Ukraine) et l’Université Blaise Pascal (Clermont Ferrand, France). Les travaux ont été effectués au sein de l'Institut Pascal de l’Université Blaise Pascal - Clermont II, de l’IFMA et du CNRS, dans le thème scientifique Matériaux actifs et intelligents, modélisation multi-échelle de l'axe Mécanique, Matériaux et Structures, et au sein de l'Institut Français de Mécanique Avancée. Les travaux réalisés sont inscrits dans l'action transversale « Matériaux et Modélisations Multi-Echelles » de l'Institut Pascal et, en partie, dans l'action MAIM du Laboratoire d'Excellence Labex IMobS3. La thèse présentée appartient au domaine scientifique de la mécanique de la rupture et la science des matériaux.Le but de ce travail est l’étude de l'effet du temps de fonctionnement sur les dommages de la structure, les propriétés mécaniques et la ténacité d'acier de collecteur de surchauffe dans les centrales thermiques et de développer les méthodes qui sont basées sur l'évaluation de la résistance résiduelle du collecteur en tenant compte des dispersions des propriétés mécaniques, du chargement opérationnel et des défauts de taille. La thèse étudie l'influence de l'hydrogénation sur le comportement mécanique, la ténacité et les micro-mécanismes de rupture dans le matériau du collecteur de surchauffe à déformation lente
This thesis has been performed under the cotutelle agreement between Ternopil Ivan Pul’uj National Technical University (TNTU, Ukraine) and Blaise Pascal University (Clermont Ferrand, France). The thesis has been carried out within Pascal Institute of the Blaise Pascal University - Clermont II, the IFMA and the CNRS, in the Scientific Theme “Active and Smart Materials and Multiscale Modeling” of the Mechanics, Materials and Structures Department, and within the French Institute for Advanced Mechanics. The work is included in the Transversal Action "Materials and Multi-scale Modelling" of the Pascal Institute and in the Action MAIM of the Excellence Laboratory Labex IMobS3. The presented thesis belongs to the scientific field of fracture mechanics and material science. The aim of the thesis is to study the effect of operating time on damage of structure, mechanical properties and fracture toughness of superheater collector steel at thermal power plants (TPPs) and to develop the methods that are based on the assessment of the residual strength of collector taking into account the mechanical properties scatter, operational loading and defect sizes. The thesis studies the influence of hydrogenation on mechanical behavior, fracture toughness and fracture micromechanisms in the material of superheater collector at slow deformation

Heat exchangers and steam headers are at the heart of any boiler and are susceptible to a range of failures including tube leaks, ligament cracking, creep and fatigue. These common forms of header failure mechanisms can be exacerbated by local thermal stresses due to temperature and flow maldistribution at full and partial boiler load operations. The purpose of this project is to develop process models of the outlet stubbox header of a final superheater (FSH) heat exchanger in a 620MW coal-fired drum type boiler. The process models were used to assess the impact of steam flow and temperature distribution on the thermal stresses in the header material. The process models were developed using Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). Thermocouples were installed at key locations on the stubbox headers to monitor metal temperatures and the measured metal temperatures served as boundary values and for validation of the CFD results. The thermocouple data was analysed for three different steady state boiler loads, namely full load, 80% load and 60% load. It showed that the temperature distribution across these headers was not uniform, with a maximum temperature difference across the outlet stubbox of 40℃ at full load and 43℃ at partial loads. Other relevant power plant data, such as steam pressure, was provided from the power plant's Distributed Control System (DCS) and was used as boundary conditions for the CFD models. The exact mass flow distribution across the inlet stubs of the outlet stubbox header was unknown and was estimated using a CFD model of the inlet stubbox header and steam mass flow values from power plant's DCS system. A CFD model was created for each of the three boiler loads at steady state conditions. The CFD results provided the metal temperature profile, internal steam temperature distribution and pressure distribution across the header. The CFD solid temperatures were validated using the thermocouple readings and found to be in agreement. The CFD results were exported to the FEA models, where specific displacement constraints for thermal expansion were utilised. The FEA models were used to assess the extent of thermal stresses due to thermal expansion only, as well as stresses due to thermal expansion combined with internal pressure. High local stresses were found at the borehole crotch corners of the rear outlet branch and inlet stubs. However, these are below 0.2% proof strength at elevated temperatures. The high local stresses thus did not result in local plastic deformation but contribute to exacerbate steady state failure mechanisms such as creep.

The Planar Array of Superheated Spheres (PASS) has been put forward as a possible neutrino and dark matter detector. This work has concentrated on the characteristics of a 100x100 array of spheres, of indium or tin. The superheated-supercooled hysteresis curves, for magnetic fields ranging from the earth's to 16 mT, have been measured in a pumped ⁴He cryostat using an RF-SQUID readout system. Individual superconducting to normal grain flips were recorded with the indium sample due to exposure to 60 keV gammas. The effect of gravity on the shape and structure of the spheres was tested by remelting arrays in a microgravity environment. The hysteresis curves obtained for these arrays showed a decreased transition width, i.e. the temperature difference from where all the spheres are superconducting to where they are all normal.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

Source terms models for superheated releases of hazardous liquefied chemicals such as LPG have been developed, governing both upstream and downstream conditions. Water was utilised as the model fluid, not least for reasons of safety, but also for its ability to be stored at conditions that ensure it is superheated on release to atmosphere. Several studies have found that at low superheat jet break-up is analogous to mechanical break-up under sub-cooled conditions. Hence, a non-dimensionalised SMD correlation for sub-cooled liquid jets in the atomisation regime has been developed, based on data measured using a Phase Doppler Anemometry (PDA) system, for a broad range of initial conditions. Droplet SMD has been found to correlate with the nozzle aspect ratio and two non-dimensionalised groups i.e. the liquid Reynolds number and Weber number. An adaptation of the Rossm-Rammler distribution has been proposed for jets undergoing mechanical break-up. Through a high-speed photographic study (1000fps), three distinctive break-up regimes of superheated jets have been identified. Mechanical break-up has been confirmed to dominate jet disintegration at low superheat. Criteria for transition between regimes have been established based on the liquid Jakob number and Weber number. Using a PDA system, droplet SMD data has been produced for fully flashing jets at two sets of initial conditions and three axial downstream locations, with radial measurements performed at each position. Droplet SMD has been found to increase with nozzle diameter. An adaptation of the Rossm-Rammler distribution has been proposed for fully flashing jets. The proposed correlation for sub-cooled break-up, the PDA data for superheated releases and the established transition criteria have been compiled to produce a complete SMD model governing transition from mechanical break-up to full flashing. The model has been validated against three previous studies of flashing jets. An additional high speed photographic study (up to 50,000fps) of the upstream flow structure of superheated jets has been performed using Perspex nozzles. The downstream break-up regime has been found to depend on both the upstream bubble growth rate and concentration.

The academic study of comic books - especially superhero comic books - has predominantly focused on the analysis of these books as texts, as teaching and learning resources, or on children as comic book readers. Very little has been written about adult superhero comic fans and their responses to superhero comics. This thesis explores how adult comic book readers in New Zealand engage with superhero comics. Individual interviews and group conversations, both online and face-to-face, provide insights into their responses to the comics and the characters as well as the relationships among fans. Analysis of fans’ talk about superhero comics includes their reflections on how masculinities are represented in these comics and the complex ways in which they identify with superheroes, including their alter egos. The thesis examines how superhero comic book readers present themselves in their interactions with other readers. Comics ‘geekdom’, fans’ interactions with one another and their negotiation of gendered norms of masculinity are discussed. The contrast between the fan body and the superhero body is an important theme. Readers’ discursive constitution and management of superheroes’ bodies, and their engagement with representations of superheroes are related to analyses of multiplicity in individual identities and current theories of audience reception and identification.

Few superhero scholars, if any, are discussing physical age or definitions of maturity. It seems Hollywood and consumers are reluctant to associate "adult" content with anything other than pornography, immature language, and excessive violence—a reluctance that should be explored by scholars and critics alike. Most superhero characters only reflect the insecurities of audiences who are currently undergoing the transition between adolescence and young adulthood. There are very few older, middle-aged, or retired superheroes depicted juggling the demands of a family along with their daring rescues. It is possible that superhero films could continue to enjoy longer, lasting success if they include more than the previously targeted immature audience. Live-action superhero films can target all ages more efficiently by avoiding the static "mature" audience narratives and presenting relatable and realistic adulthood with novelistic maturity along with adolescence and childhood.

This thesis proposes a new analytical perspective to the interplay between the entertaining escapism afforded by spectacular action sequences and the expression of cultural themes in the 2000s-present contemporary superhero film cycle. In the introduction I give a review of the spectacle and narrative debate to explain how current studies on popular action film have tended to primarily focus on the way spectacular displays support narrative progression by driving forward the film plot’s narrative chain of cause-and-effect over time. However, the review then explains that whenever the cultural themes invested in these action film narratives are concerned, there is often an assumption that thematic values only surface intermittently as symbolic motifs at certain moments, and so do not really benefit from this kind of storytelling momentum to the same extent. The introduction then sets up my claim that spectacle not only aids the progression of plot by energising narrative causality and temporal progression, but spectacle also contributes other rhythmically kinetic arcs of narration able to developmentally evolve thematic tales of cultural conflict, which I term as narrativised spectacle. I explain my method as one combining a genre theory framework to uncover the cultural contradictions invested in action narratives alongside a neoformalist analysis of the rhythmic components of physical motion, editing, framing, composition and digital visual effects that express these thematic tensions. Examples are then given to show why contemporary superhero films depend on such kinetic kinds of spectacular rhythm, and provide a key case study to work with. Each chapter finds evidence for my claim by analysing how different kinds of kinetic arc are generated by the audio-visual rhythms of spectacle: able to introduce, challenge, destabilise, conflate, reinstate and eventually reconcile a series of conflicting cultural themes akin to an evolving tale. In the first chapter I explore the physical and spatial spectacle of action sequences. In the second chapter I look at the melodramatic theatrics of performance techniques. In the third chapter I critically interrogate the violent action of the superhero film alongside the themes of masculinity invoked therein. In the final chapter I deal with superheroines. Although these heroines employ these same thematic rhythms as male superheroes, the kinetic arcs are noticeably far more interrupted, due to being burdened with themes of androcentrism. The conclusion then summarises exactly what narrativised spectacle contributes to existing debates on spectacle and narrative, and why it is particularly useful for studying the contemporary superhero-action film.

Effects of superheated steam drying were determined for surface properties and pore structure of paper, properties which are important in the end use of paper. Two furnishes were investigated, thermomechanical pulp (TMP) and a TMP/kraft pulp blend. Drying of handsheets under matched conditions in air was used as the basis of comparison.
TMP paper dried in superheated steam has a slightly higher surface roughness, by about 0.5 $ mu$m at a roughness around 8 $ mu$m. This difference decreases with drying fluid temperature. It is also reduced by about half after a very light blade coating. Surface roughness of paper from 50/50 TMP/kraft blend is unaffected.
Superheated steam drying reduces substantially the linting propensity of TMP paper, by about 30%-60% depending on the criteria used. Improved lignin softening by higher web temperature from the beginning of drying in superheated steam drying is believed an important mechanism in improving bonding of surface fines and short fibre fragments.
The Z-direction bond strength of TMP paper after surface treatment with water is about 20% higher for sheets dried in steam. Time for water absorption is 100%-150% longer for superheated steam dried TMP paper and contact angle of water is also substantially increased.
Superheated steam drying substantially reduces the volume of micropores of diameter 0.2-0.6 $ mu$m while having no significant effect on larger pores. Thus superheated steam drying affects only the pore structure of the micronetwork. The decrease of micropore volume in superheated steam drying is associated with an increase of Z-direction bond strength and a decrease of light scattering coefficient.

Thesis (Ph.D.)--Indiana University, Dept. of Communication and Culture, 2007.
Source: Dissertation Abstracts International, Volume: 68-09, Section: A, page: 3642. Adviser: Barbara Klinger. Title from dissertation home page (viewed Apr. 30, 2008).

Conventional power plants are major emitters of CO2 gases, which are believed to be contributing to global warming. An efficient, co-firing biomass-coal power plant with oxy-firing combustion system (running at high steam temperature and pressure), can play a vital role in CO2 emission reduction. However, these techniques will further worsen the issue of fireside corrosion of heat exchangers. An increase in fireside corrosion rates can cause short component lives and unexpected failures if not dealt with appropriately. The aim of this PhD study was to use laboratory-based testing to assess the performance of alloy materials under superheater conditions in simulated co-fired (biomass and coal) air and oxy-fired combustion. In this PhD project five different alloys were used. Synthetic deposits were also prepared to simulate superheater deposit compositions. Tests were carried out at temperatures appropriate for metal temperatures in superheaters/reheaters of future power plants. The performance of samples was determined using: mass change data, advanced microscopy techniques, x-ray diffraction and dimensional metrology. Additional tests were carried out to investigate deposit stability and the effect of high concentrations of salts. The results achieved have confirmed the hypothesis that increased fireside corrosion rates are due to the combined effect of extreme environment: high temperatures, SO2 and HCl gases, aggressive deposits. Corrosion damage follows trends that resembles ‘bell-shaped’ curve in both air and oxy-fired conditions. Alloy corrosion damage in novel oxy-firing compared to air-firing conditions was significantly higher at 700C. The peak of the curve shifts from 650 to 700C in oxy-fired conditions. The alloys with higher chromium content clearly showed better corrosion resistance. The work on deposit chemistry and exposure to high salt concentrations has improved the understanding of corrosion reaction mechanisms. Corrosion damage data have been used to produce basic fireside corrosion mathematical model; which can be used as a stepping stone towards further development of fireside corrosion models.

This thesis analyses the representation of gender and its intersection with sexuality and race by examining twelve mainstream comic book superheroes in their socio-historical context, particularly those published by the ‘Big Two’ publishers in the industry: Marvel and DC. The superheroes are: Superman, Captain America, Iron Man, Supergirl, Wonder Woman, Wiccan, Hulkling, Batwoman, Black Panther, Falcon, Storm and Ms Marvel. Focusing on superheroes’ first appearance in World War II up to their current iterations, this thesis discusses how superheroes have changed and adapted to either match or challenge prevailing ideas about gender, including dominant views on masculinity and femininity in the US military, attitudes to American national identity and the Other, homonormativity and minority communities. Engaging with Butler’s theory of gender performance and Critical Race Theory, this thesis extends existing comic scholarship by moving beyond justification or condemnation of the genre. It contends that superheroes create gendered scripts that are increasingly pro-diversity, supporting gender, sexual and racial equality, and yet fail to construct anti-hegemonic narratives that challenge the status quo.

With iconic characters like Superman, Batman, Spider-Man, and Iron Man representing the wider culture’s understanding of comics, popular perceptions of the medium are that comics are a male-centric medium focused on male experience and readers. As the medium and the dominant superhero genre has gained attention, focus and research has been placed on the medium and how these narratives deal with representation. With the perception and stereotypes of comic readers and comic narratives as predominantly male, the question of female representation, especially within the dominant superhero genre, is a topic that has garnered attention. In my thesis, I look at the history, sources, and perpetuation of gendered performances within superhero comics. By looking at the field of comics, the perceived dominant reading position, and the constrained meaning of texts, I show that the act of creating, reading, and talking about comics are parts of a logonomic system. This system functions to deliver an expected and constrained representation and meaning about female characters and female experience. In superhero comics, female characters are constrained to performances of the monster or angel. Through the way their powers, costumes, and identities are narratively constructed, female characters are forced to be either submissive and objectified angels who conform to patriarchal power structures, or dangerous and monstrous women who need to be punished and normalized. Superhero comics work to interpolate the perceived dominant reading position, deliver pleasure, assuages fear, and transmits an expected meaning of male/female relationships and performances.