Dissertations / Theses on the topic 'O expander'

Communication can be heard in many different ways and it is important for all businesses, especially in B2B. The construction and maintenance of a brand plays just like the communication a very important part. These parts also have a lot to common and affect each other in a large extent. One problem that may occur in many companies is the failure to grow and gain a larger share of the market even if they in various ways are trying. Expander is one of those companies and in this research report we studied communication and brand building, focusing on brand management, relationships and integrated marketing.  Here we drew the conclusion that all these areas are important for a company, especially in the Business-to-Business marketing in different ways. Many of the parts in these areas affects and is affected by each other and that is also why you need to understand and work with these parts. The research report was to be viewed as a baseline study in understanding the issues regarding the importance of communication for a company. It was not directly intended to give concrete answers or solutions to the problem.

Macro systems allow programmers abstractions over the syntax of a programming language. This gives the programmer some of the same power posessed by a programming language designer, namely, the ability to extend the programming language to meet the needs of the programmer. The value of such systems has been demonstrated by their continued adoption in more languages and platforms. However, several barriers to widespread adoption of macro systems still exist. The language Racket defines a small core of primitive language constructs, including a powerful macro system, upon which all other features are built. Because of this design, many features of other programming languages can be implemented through libraries, keeping the core language simple without sacrificing power or flexibility. However, slow macro expansion remains a lingering problem in the language's primary implementation, and in fact macro expansion currently dominates compile times for Racket modules and programs. Besides the typical problems associated with slow compile times, such as slower testing feedback, increased mental disruption during the programming process, and unscalable build times for large projects, slow macro expansion carries its own unique problems, such as poorer performance for IDEs and other software analysis tools. In order to improve macro expansion times for Racket, we implement an existing expansion algorithm for R5RS Scheme macros, which comprise a subset of Racket's macro system, and use that implementation to explore optimization opportunities. Our resulting expander appears to be the fastest implementation of a R5RS macro expander in a high-level language and performs several times faster than the existing C-based Racket implementation.

L’utilisation de l’algèbre pour résoudre des problèmes de graphes a conduit au développement de trois branches : théorie spectrale des graphes, géométrie et combinatoire des groupes et études des invariants de graphes. La notion de graphe d’expansions (invariant de graphes) est relativement récente, elle a été développée afin d’étudier la robustesse des réseaux de télécommunication. Il s’avère que la construction de familles infinies de graphes expanseurs est un problème difficile. Cette thèse traite principalement de la construction de nouvelles familles de tels graphes. Les graphes expanseurs possèdent des nombreuses applications en informatique, notamment dans la construction de certains algorithmes, en théorie de la complexité, sur les marches aléatoires (random walk), etc. En informatique théorique, ils sont utilisés pour construire des familles de codes correcteurs d’erreur. Comme nous l’avons déjà vu les familles d’expanseurs sont difficiles à construire. La plupart des constructions s'appuient sur des techniques algébriques complexes, principalement en utilisant des graphes de Cayley et des produit Zig-Zag. Dans cette thèse, nous présentons une nouvelle méthode de construction de familles infinies d’expanseurs en utilisant les G-graphes. Ceux-ci sont en quelque sorte une généralisation des graphes de Cayley. Plusieurs nouvelles familles infinies d’expanseurs sont construites, notamment la première famille d’expanseurs irréguliers
Applying algebraic and combinatorics techniques to solve graph problems leads to the birthof algebraic and combinatorial graph theory. This thesis deals mainly with a crossroads questbetween the two theories, that is, the problem of constructing infinite families of expandergraphs.From a combinatorial point of view, expander graphs are sparse graphs that have strongconnectivity properties. Expanders constructions have found extensive applications in bothpure and applied mathematics. Although expanders exist in great abundance, yet their explicitconstructions, which are very desirable for applications, are in general a hard task. Mostconstructions use deep algebraic and combinatorial approaches. Following the huge amountof research published in this direction, mainly through Cayley graphs and the Zig-Zagproduct, we choose to investigate this problem from a new perspective; namely by usingG-graphs theory and spectral hypergraph theory as well as some other techniques. G-graphsare like Cayley graphs defined from groups, but they correspond to an alternative construction.The reason that stands behind our choice is first a notable identifiable link between thesetwo classes of graphs that we prove. This relation is employed significantly to get many newresults. Another reason is the general form of G-graphs, that gives us the intuition that theymust have in many cases such as the relatively high connectivity property.The adopted methodology in this thesis leads to the identification of various approaches forconstructing an infinite family of expander graphs. The effectiveness of our techniques isillustrated by presenting new infinite expander families of Cayley and G-graphs on certaingroups. Also, since expanders stand in no single stem of graph theory, this brings us toinvestigate several closely related threads from a new angle. For instance, we obtain newresults concerning the computation of spectra of certain Cayley and G-graphs, and theconstruction of several new infinite classes of integral and Hamiltonian Cayley graphs

A single-stage pulse tube cryocooler was designed and fabricated to provide cooling at 50 K for a high temperature superconducting (HTS) magnet, with a nominal electrical input frequency of 50 Hz and a maximum mean helium working gas pressure of 2.5 MPa. Sage software was used for the thermodynamic design of the pulse tube, with an initially predicted 30 W of cooling power at 50 K, and an input indicated power of 1800 W. Sage was found to be a useful tool for the design, and although not perfect, some correlation was established. The fabricated pulse tube was closely coupled to a metallic diaphragm pressure wave generator (PWG) with a 60 ml swept volume. The pulse tube achieved a lowest no-load temperature of 55 K and provided 46 W of cooling power at 77 K with a p-V input power of 675 W, which corresponded to 19.5% of Carnot COP. Recommendations included achieving the specified displacement from the PWG under the higher gas pressures, design and development of a more practical co-axial pulse tube and a multi-stage configuration to achieve the power at lower temperatures required by HTS.

Title: Testing of mechanical expansion anchors and concrete screw anchors inhollow-core slabs For stabilization of prefabricated concrete elements during mounting obliquebraces are used. These oblique braces are occasionally attached into hollow-coreslabs. Abetong and Strängbetong are two companies using this method forstabilization and are in need of load values on what different fastenings canmanage attached into hollow-core slabs.Therefore this report is based on the testing of mechanical expansion anchors andconcrete screw anchors mounted in hollow-core slabs. The result of each fasteningis presented in tables with characteristic load values.After founding the concrete screw anchors most useful, an Excel-program wasdesigned where oblique loading can be presented.Keywords: Testing, mechanical expansion anchors, concrete screw anchors,hollow-core slabs, oblique loading, mechanical interlock, concrete fail, anchoragefail, concrete cone.

The growing global demand for energy and environmental implications have created a need to further develop the current energy generation technologies (solar, wind, geothermal, etc.). Recovering energy from low grade energy sources such as waste heat is one of the methods for improving the performance of thermodynamic cycles. The objective of this work was to achieve long-term steady state operation of a Free-Piston Linear Expander (FPLE) and to compare the FPLE with the currently existing expander types for use in low temperature energy recovery systems. A previously designed FPLE with a single piston, two chambers, and linear alternator was studied and several modifications were applied on the sealing and over expansion. An experimental test bench was developed to measure the inlet and outlet temperatures, inlet and outlet pressures, flow rate, and voltage output. A method of thermodynamic analysis was developed by using the first and second law of thermodynamics with air as the working fluid. The experimental tests were designed to evaluate the performance of the FPLE with varying parameters of inlet air pressure, inlet air temperature, and electrical resistance. The initial and steady-state operation of the FPLE were successfully achieved. An uncertainty analysis was conducted on the measured values to determine the accuracies of the calculated parameters. The trends of several output parameters such as frequency, average root mean square (RMS) voltage, volumetric efficiency, electrical-mechanical conversion efficiency, isentropic efficiency, irreversibility, actual expander work, and electrical power were presented. Results showed that the maximum expander frequency was found to be 44.01 Hz and the frequency tended to increase as the inlet air pressure increased. The FPLE achieved the maximum isentropic efficiency of 21.5%, and produced maximum actual expander work and electrical work of 75.13 W and 3.302 W, respectively.

Thesis (Ph. D.)--University of California, San Diego, 2010.
Title from first page of PDF file (viewed June 11, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

Expanders allow pressurized fluids to undergo a pressure decrease in a controlled environment via volumetric growth to extract fluid energy. There are many types of expanders, and the objective of this thesis is to model the efficiencies of the planetary rotor expander (PRE), a century-old design undeveloped due to insufficient manufacturing capabilities (until recently). Geometric relationships are derived and mathematical models are generated to determine the efficiency of the PRE as a function of design variables. Two industrially relevant case studies show that, to maximize isentropic efficiency, the planetary rotor expander (PRE) rotational frequency is maximized and rotor geometry optimized.

This research investigates the performance and impacts of integration of an internal expander within a typical heat pump system for the UK climate. In this novel system, the expansion process takes place within an expander rather than a traditional expansion valve, and it is expected that recovered work by the expander could provide a portion of the required power to drive the compressor. This project comprises a literature review, test rig design and fabrication, control system design instrument selection and calibration, data-logging system setup and installation, implementation of the BS standard for heat pumps performance testing, implementation of tests, and data collection according to relevant standards and data analysis. A test rig is developed and improved throughout this research. More than 20 sets of tests have been carried out between 2011 and 2014, and the most appropriate of them are presented and discussed. To determine the impact of expander integration, the rotary compressor-expander unit was tested with and without an expander, and the system COP, capacity, and isentropic efficiency are discussed. This thesis commences by introducing key drivers of this research, the energy crisis, global warming issues, and the contribution of the domestic sector to energy consumption in the UK. Then it continues by classifying heat pumps according to their energy sources. A detailed review and evaluation of major advanced heat pumps and refrigeration technologies then follows. Test rig design and development (according to the BS EN14511-2:2011) are discussed and outlined comprehensively. The test scenarios are presented, obtained data are discussed, test outcomes are evaluated, and the issues and their causes are addressed in detail. To address the issues and interpret the achieved results, theoretical analysis is carried out as well, then actual outcomes are compared with theoretical anticipated results and the differences are addressed. Results of compressor tests and system integration are presented separately and discussed comprehensively. The last chapter outlines conclusions and recommends further possible work on this research topic and offers practical suggestions to improve the performance of this developed system. However, this research reveals that such integration of an expander and compressor is not suitable in practice for typical UK winter conditions, though it may offer some benefits for extreme winter conditions where the ambient temperature drops to -10°C or below. In addition, it reveals that the designed compressor is not able to overcome a significant temperature increase (which is the case for medium-temperature heating applications and retrofit applications) due to internal refrigerant leakage.

Introduction: Impaction allografting has proved a successful means of restoring deficient bone stock during revision athroplasty of the hip.  Mechanical and clinical studies were performed to investigate the role of IG-Pore, a synthetic hydroxyapatite Graft expander, in impaction grafting. Methods: 32 synthetic femoral models underwent impaction grafting using allograft mixed with varying proportions of IG-Pore (0%, 50%, 70% and 90% IG-Pore).  The cyclical displacements induced by repetitive loading on an Instron were measured, and overall migration of the prosthesis was determined using radiostereometric analysis (RSA).  A randomised controlled clinical trial comparing impaction grafting using pure allograft and a 1:1 mixture of allograft and IG-Pore is also described.  Migration of the revised femoral and acetabular components was determined using RSA, and clinical outcomes were monitored.  A preliminary analysis of the first 14 patients in this study with follow-up of up to six months is presented. Results: The mechanical data indicate that IG-Pore confers a greater resistance to subsidence (p=0.034) and cyclical movement (p=0.005).  In particular, subsidence at the prosthesis-cement interface is lower than with pure allograft (p=0.019).  The clinical study shows similar patterns of migration, although it is too early for definite conclusions.  Movement of individual graft particles is greater with IG-Pore, however, and graft handling may be more difficult. Discussion: Synthetic hydroxyapatite graft expanders may indeed be beneficial in impaction grafting, and the clinical study which is described herein should, in due course, definitely characterise their role.

In dieser Arbeit sollte im Tierversuch die lokale Gewebeverträglichkeit der neuen, mit PVVV 80/20 beschichteten, hoch hydrophilen Expander (osmed GmbH, Ilmenau, Deutschland) getestet werden und allgemeine Indikationen für die Anwendung von Hydrogelexpandern erstellt werden. Material und Methoden: Für den Versuch standen 24 Kaninchen als Versuchstiere zur Verfügung, welche in vier Gruppen unterteilt wurden, wobei die Gruppe 1 als Kontrollgruppe (Expander mit Silikonhülle) diente. Die Gruppen 2 - 4 wurden mit den neu entwickelten Hydrogelexpandern („Cylinder M4 x 12“) beschickt. Die Implantation der Expander erfolgte bei allen Versuchstieren in die linke Kniefalte. Nach einem zeitlich vorbestimmten Explantationsplan (nach 10, 21 und 90 Tagen) wurden die Expander entnommen, gewogen und das, den Expander direkt umgebene Gewebe entnommen, histologisch aufbereitet und untersucht. Zusätzlich wurden Proben aus der rechten, nicht implantierten Kniefalte, als Referenzprobe entnommen. Desweiteren wurde die Anwendbarkeit von Hydrogelexpandern anhand von zwei Fallbeispielen vorgestellt und untersucht. Ergebnisse: Histologisch konnte bei beiden Expandertypen eine lokale Fremdkörperreaktion (Entzündungszellinfiltration, Granulationsgewebe), im Sinne einer Kapselbildung, nachgewiesen werden. Die Alterationen des direkt angrenzenden Gewebes der beschichteten Expander sind insgesamt nur geringgradig stärker ausgeprägt als in den Proben mit Verwendung des Implantats mit Silikonhülle. Somit ist die Gewebeverträglichkeit der neu entwickelten Expander mit den silikonumhüllten Expandern vergleichbar. Diese Arbeit konnten weiterhin zeigen, dass die „Cylinder M4 x 12“-Expander mit der PVVV 80/20-Beschichtung ein deutlich höheres Quellverhalten aufweisen als die herkömmlichen, mit Silikonhülle umgebenen, Expander. Die in den Fallbeispielen verwendeten Hydrogelexpander, zeigten in beiden Fällen das gewünschte kosmetische Endergebnis. Schlussfolgerung: Für beide Expandertypen lässt sich eine gute lokale Verträglichkeit ableiten. Damit bieten die getesteten Expander „Cylinder M4 x 12“ mit der PVVV 80/20-Beschichtung die Möglichkeit, die Silikonhülle in ausgewählten Indikationen zu ersetzen und neue Einsatzmöglichkeiten zu erschließen. Zudem bieten die beschichteten Expander den Vorteil, dass es durch ihre minimale Größe nur einer kleinen Inzision für die Implantation bedarf und sie damit besonders für den Einsatz in der minimal invasiven Chirurgie geeignet erscheinen. Einsatzmöglichkeiten der Hydrogelexpander in der Veterinärmedizin sind unter medizinischen und ästhetischen Gesichtspunkten zu betrachten. Im Vordergrund der medizinischen Indikationen stehen vor allem Wunden mit erheblichem Gewebeverlust (z. Bsp. nach Traumata, Verbrennungen u.a.), bei denen eine plastische Operation keine spannungsarme Adaptation der Wundränder gewährleisten kann. Auch die kosmetische Indikation gewinnt immer mehr an Bedeutung. Möglich ist der Einsatz des Expanders zum Beispiel als Hodenimplantat oder als Dauerimplantat nach Enukleatio bulbi und zur Narbenkorrektur. Ihr klinischer Einsatz bedarf jedoch weiterer experimenteller – vor allem – in-vivo-Untersuchungen, um ihre Einsatzmöglichkeiten beim Tier - und in Zukunft auch beim Menschen – zu evaluieren.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 81).
A single stage of a 3-stage Collins-type cryocooler designed to provide I W of cooling at 10 K was constructed and tested. A single stage of the cryocooler consists of a compressor, a counter-flow heat exchanger, and an expander to expand the working fluid. The work of the expanding cold gas is transmitted up a floating piston and is dissipated by gas flows in and out of a warm volume. Flow through the cold volume is controlled by smart electromagnetic valves. Models were developed to describe the thermodynamic processes that make up the expander cycle. In the first iteration, models were developed to determine the equilibrium states at various points in the cycle by assuming the thermodynamic processes that made up the expander cycle to be quasi-static. These models were used to determine appropriate values of parameters such as the cut-off volume, the recompression volume, and warm end reservoir pressures for expander operation. Experiments were done to determine the efficiency of the floating-piston expander. Tests were also done to determine the characteristics of the heat exchanger and compare them with the design characteristics. Finally, the stage was run as a refrigerator with zero heat-load. It was observed that the quasi-static models did not adequately describe the performance of the expander as most of the processes did not go to equilibrium.
(cont.) Therefore, these models were improved by incorporating the dynamics of the piston motion, the fluid flow through the warm and cold volumes, and the fluid flow through the high-pressure passages of the heat exchanger.
by Gunaranjan Chaudhry.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 96).
The multi-stage Collins-type cryocooler uses a floating piston design for the working fluid expansion in each stage. The piston floats between a cold volume, where the working fluid is expanded, and a warm volume. The piston's motion is controlled by opening and closing valves connecting several reservoirs at various pressures to the warm volume. Ideally, these pressures should be distributed between the high and low system pressure to gain good control of the piston motion. In past prototypes, helium flow through the piston-cylinder gap resulted in a loss of pressure in the reservoirs causing the piston to become immobile. A more complex control algorithm is required to maintain a net zero helium flow through this gap to allow for steady expander operation. A numerical quasi-steady thermodynamic model is developed for the piston cycle. The model determines the steady state pressure distribution of the reservoirs for an ideal expander with no helium flow through the piston-cylinder gap. This pressure distribution is dependent on the total mass of helium in pressure reservoirs as well as the points at which the warm helium intake as well as the cold helium exhaust end. The pressures in the pressure reservoirs show varying levels of dependence on the lengths of the intake and exhaust strokes. The model is extended to include helium flow through the gap and the inertia of the piston. The model is then used to determine how helium can be added to or removed from the reservoirs in the case that there is too much helium flow through the gap. These results are then integrated into a control algorithm that maintains zero net mass flow through the gap in each expander stage.
by Jake Hogan.
S.M.

Research to understand the mechanisms of wear within the main components of three different micro-CHP scroll expander systems was conducted. This was performed in order to identify the possible tribo-mechanical effects (abrasion, adhesion, cavitation, fatigue) which occur on the substrate of these components during the operation of the scroll which can seriously affect the lifecycle of the micro-CHP unit. Three-dimensional interferometer, surface scanning and scanning electron rnicroscopy (SEM) were used for surface analyses. The critical components for durability were identified on the tip seal and the steel plate of the scroll expander. Abrasive wear derived from a two-body contact on the interface of the tip seal and the steel plate. Three-body wear was found across the steel plate of the scroll. Finally, cavitation pits were revealed. Interestingly, cavitation was generated by the increment of pressure. It was found that sufficiently high pressure can liquefy instantaneously part of the refrigerant close to the bottom boundary, creating conditions for the generation of cavitation bubbles within the liquefied refrigerant. This finding resolves the puzzle of how the refrigerant which enters the scroll in gas phase produces cavitation. The wear mechanisms identified can significantly reduce the performance of the scroll. Specimens made from the steel plate (high carbon steel) and the tip seal (high performance reinforced fluoroelastomer) of the scroll expander were used for bench tests. The parts were used to perform sliding tribological tests using a special purpose-built modified micro-friction machine TE 57 in order to clearly identify the sliding wear and friction mechanisms. These tests were performed under a specific load and lubrication regime. The experimental conditions were adjusted to those of the industrial applications. Furthermore an experimental study using an ultrasonic transducer (submerged into the fluids) was utilised to produce cavitation bubbles. Using high-speed camera techniques the bubbles were observed within the working fluids. A thorough investigation of the dynamic behaviour of the bubbles and their cavitation mechanisms was conducted using the two scroll fluids (lubricant/refrigerant). The experimental results were effectively correlated with the computational ones. Additionally, the impact of the scroll fluid cavities across the surface of various commercial steel grades, including the actual steel plate of the scroll, was determined. Finally, their cavitation performance and durability, over a prolonged period of time was investigated.

Since the late 19th century, the average temperature on Earth has risen by approximately 1.1 °C because of the increased carbon dioxide (CO2) and other man-made emissions to the atmosphere. The transportation sector is responsible for approximately 33% of the global CO2 emissions and 14% of the overall greenhouse gas emissions. Therefore, increasingly stringent regulations in the European Union require CO2 emissions to be lower than 95 gCO₂/km by 2020. In this regard, improvements in internal combustion engines (ICEs)must be achieved in terms of fuel consumption and CO2 emissions. Given that only up to 35% of fuel energy is converted into mechanical power, the wasted energy can be reused through waste heat recovery (WHR) technologies. Consequently, organic Rankine cycle (ORC) has received significant attention as a WHR technology because of its ability to recover wasted heat in low- to medium-heat sources. The Expansion machine is the key component in ORC systems, and its performance has a direct and significant impact on overall cycle efficiency. However, the thermal efficiencies of ORC systems are typically low due to low working temperatures. Moreover, supersonic conditions at the high pressure ratios are usually encountered in the expander due to the thermal properties of the working fluids selected which are different to water. Therefore, this thesis aims to design an efficient radial-inflow turbine to avoid further efficiency reductions in the overall system. To fulfil this aim, a novel design and optimisation methodology was developed. A design of experiments technique was incorporated in the methodology toexplorethe effects of input parameters on turbine performance and overall size. Importantly, performance prediction modelling by means of 1D mean-line modelling was employed in the proposed methodology to examine the performance of ORC turbines at constant geometries. The proposed methodology was validated by three methods: computational fluid dynamics analysis, experimental work available in the literature, and experimental work in the current project. Owing to the lack of actual experimental works in ORC-ICE applications, a test rig was built around a heavy-duty diesel engine at Brunel University London and tested at partial load conditions due to the requirement for a realistic off-high representation of the performance of the system rather than its best (design) point, while taking into account the limitation of the engine dynamometer employed. Results of the design methodology developed for this projectpresented an efficient single-stage high-pressure ratio radial-inflow turbine with a total to static efficiency of 74.4% and an output power of 13.6 kW.Experimental results showed that the ORC system had a thermal efficiency of 4.3%, and the brake-specific fuel consumption of the engine was reduced by 3%. The novel meanlineoff designcode (MOC) was validated with the experimental works from three turbines. In comparison with the experimental results conducted at Brunel University London, the predicted and measured results were in good agreement with a maximum deviation of 2.8%.

The aim of this thesis is to create and describe the wireless system for lighting control. A part of the work is the creation of modules for switching lighting and the creation of their operating programs. The first chapter briefly describes the way how the lighting control works and contains general requirements for the intelligent home. Further, there is a description of IQRF system, which serves as a wireless platform for the system. Next part of the thesis describes individual modules in terms of hardware and software. One part of the work covers the description of the transmission protocol. The attachment includes a listing of all operating programs for this wireless control system.

Viele Anwendungen der Hochtemperatur-Supraleitung arbeiten vorteilhaft im Temperaturbereich zwischen 30 - 50 K. Für diesen Temperaturbereich existieren nur wenige geeignete Kältemaschinen mit kleiner Kälteleistung (1-2 W) u. gutem Wirkungsgrad. Neon ist aufgrund seiner Stoffeigenschaften ein hervorragendes Kältemittel für diesen Temperaturbereich, wie z.B. anhand einer realisierten Joule-Thomson (JT) Demonstrationsanlage deutlich wird. Als Ergebnis einer Prozessanalyse wird ein Kreislauf vorgestellt, der speziell den Eigenschaften von Neon angepasst ist. Durch die Überlagerung von Wärmeübertragung u. arbeitsleistender Expansion sowie der Einbeziehung einer JT-Stufe kann auch mit wenig effizienten Komponenten ein vergleichsweise hoher Gütegrad erreicht werden. Durch die Integration von Wärmeübertragerflächen in eine Kolbenexpansionsmaschine wird ein neues Konzept vorgeschlagen, um Kälte in einem großen Temperaturbereich in vielen Expansionsschritten zu erzeugen, ohne dafür viele Expander zu verwenden. Diese Einheit wird als Wärmeübertrager-Expander (WE) bezeichnet. Mit einem Arbeitsraum in konischer Grundform wird der Wärmeübergangskoeffizient günstig gestaltet u. die Wärmeübergangsfläche vergrößert. Mehrere Versuchsmaschinen wurden untersucht. Anhand der Versuche konnten die wesentlichen Verlustquellen u. Problembereiche identifiziert werden. Es wurde im Rahmen der Versuchsbedingungen nachgewiesen, dass für das vorgesehene Druckverhältnis eine nahe isotherme Expansion u. Kompression möglich ist. Es werden Möglichkeiten zur Verringerung der Längswärmeleitung vorgestellt. Zwei Simulationsprogramme wurden verwendet. Mit Hilfe des Wärmeübertrager-Programms wurden die Wärmeübertragungsvorgänge unter Berücksichtigung der Längswärmeleitung simuliert. Hierbei geht die Expansionsarbeit als stationäre Wärmesenke ein. Der im Ergebnis vorliegende stationäre Temperaturverlauf ist die Grundlage für die Berechnung der Expansionsarbeit unter Berücksichtigung der Realgaseigenschaften im Expander-Programm. Für die Neon-Tieftemperaturvariante wurde eine Grundvariante des WE definiert. Anhand dieser wurde mit Hilfe der Programme der Einfluss verschiedener Parameter auf Kälteleistung u. Gütegrad untersucht. Der WE wird als Teil des beschriebenen Prozesses mit einer JT-Stufe betrachtet. Die Kälteleistung weist sowohl in Abhängigkeit vom Massestrom als auch vom Hub ein Maximum auf. Der Shuttle-Verlust verschiebt durch Wärmetransport mittels des Kolbens die effektive Kälteleistung zu kleineren Hüben. Die durch die Güte (NTU) des JT-Wärmeübertragers bestimmte Eintrittstemperatur des Niederdruckstroms in den WE hat einen großen Einfluss auf die Kälteleistung. Mit steigender Eintrittstemperatur steigen der NTU-Wert für den Arbeitsraum u. somit auch die Kälteleistung. Das Maximum der Kälteleistung stimmt nicht mit dem Optimum für den Gütegrad überein. Der Gütegrad strebt mit sinkenden Masseströmen einem Optimum zu. Durch den zunehmenden Einfluss der Längswärmeleitung u. begrenzt durch die Minimalfüllung der Maschine aufgrund des Schadraumes ergibt sich ein Optimum. Der Einfluss des Massestroms ist entscheidend. Als untergeordnete Größen beeinflussen die Eintrittstemperatur des Niederdruckstroms u. der Hub den optimalen Gütegrad. Der Einfluss der Längswärmeleitung auf Kälteleistung u. Gütegrad wird exemplarisch anhand von vergleichenden Rechnungen gezeigt. Konkret kann für einen Eintrittsdruck von 200 bar, einen Austrittsdruck von 60 bar bei einer Eintrittstemperatur des Niederdruckstroms von 80 K für die Grundvariante eine maximale effektive Kälteleistung von 1,3 W mit einem Massestrom von 0,22 g/ s bei einem Hub von ca. 17 mm ausgewiesen werden. Der effektive Gütegrad für diese Bedingungen beträgt ca. 14%. Kommerzielle Split-Stirlingkühler erreichen bei 42 K einstufig Gütegrade von ca. 7%. Mit der vorgeschlagenen Konfiguration wird ein Konzept vorgestellt, das trotz technologisch offener Fragen das Gütegradniveau bekannter Kryokühler übertreffen kann
Many applications of high temperature superconductivity are working advantageously within a temperature range between 30 K and 50 K. But for this temperature range only few suitable cryocooler with small refrigerating capacity (1-2 W) and good efficiency exist.Due to its properties Neon is an excellent refrigerant for this temperature level as an example with realised Joule-Thomson plant shows. A process analysis results in the presented cycle which is especially adapted to the properties of Neon. By combination of heat exchange and work extracting expansion and integration of a Joule-Thomson stage a high efficiency could be reached in spite of less efficient components.By arranging heat exchanger surfaces into a piston expansion machine a new concept is suggested to produce refrigeration in a large temperature range with a lot of expansion steps with reduced number of expanders. This unit is referred hereinafter to as heat exchanger-expander.The conical shaped working space results in an increase of the heat transfer coefficient and the heat transfer area.Several test machines were investigated. By means of testing the main loss sources and critical zones could be identified. The test results prove the opportunity of a near isothermal expansion and compression for the specified pressure ratio.Options to reduce the axial heat conduction are presented.Two simulation programs were utilised. Using the heat exchanger program the heat transfer is simulated in consideration of the axial heat conduction. Thereby the expansion work is considered as a stationary heat sink. The resulting stationary temperature pattern is the base for the expansion work calculation using the real gas properties in the expander program. Referring to the defined basic neon low temperature application the influence of different parameters on refrigerating capacity and efficiency was researched with the programs. The heat exchanger-expander is part of the described process with a Joule-Thomson stage. The refrigerating capacity shows a maximum depending as well from the mass flow as from the stroke. In result of the shuttle loss smaller strokes lead to better capacity due to heat transport with the piston.The inlet temperature of the low pressure flow influenced by the quality (NTU) of the Joule-Thomson heat exchanger has a large influence on the refrigerating capacity. With increasing inlet temperature the number of transfer units (NTU) for the fluid in the working volume increases and so the refrigerating capacity, too. The location of refrigerating capacity maximum and efficiency optimum is different. While decreasing mass flow efficiency is increasing to an optimum caused by the increased influence of axial heat conduction but limited by the minimum charge of the machine due to the dead space. The influence of the mass flow is dominating. As lower range values the inlet temperature of the low pressure flow and the stroke are influencing the optimal efficiency. The influence of axial heat conduction on refrigerating capacity and efficiency is shown using comparing calculations.For an inlet pressure of 200 bar, an outlet pressure of 60 bar, an inlet temperature of the low pressure flow of 80 K, a mass flow of 0,22 g/ s and a stroke of about 17 mm for the basic version of heat exchanger-expander a maximal effective refrigerating capacity of 1,3 We could be shown. The effective efficiency therefore is 14 %. Current commercial split Stirling cryocooler reach with single stage operation efficiencies of about 7 % at 42 K. The suggested configuration represents a concept that could be able to master the efficiency level of known cryocooler

Viele Anwendungen der Hochtemperatur-Supraleitung arbeiten vorteilhaft im Temperaturbereich zwischen 30 - 50 K. Für diesen Temperaturbereich existieren nur wenige geeignete Kältemaschinen mit kleiner Kälteleistung (1-2 W) u. gutem Wirkungsgrad. Neon ist aufgrund seiner Stoffeigenschaften ein hervorragendes Kältemittel für diesen Temperaturbereich, wie z.B. anhand einer realisierten Joule-Thomson (JT) Demonstrationsanlage deutlich wird. Als Ergebnis einer Prozessanalyse wird ein Kreislauf vorgestellt, der speziell den Eigenschaften von Neon angepasst ist. Durch die Überlagerung von Wärmeübertragung u. arbeitsleistender Expansion sowie der Einbeziehung einer JT-Stufe kann auch mit wenig effizienten Komponenten ein vergleichsweise hoher Gütegrad erreicht werden. Durch die Integration von Wärmeübertragerflächen in eine Kolbenexpansionsmaschine wird ein neues Konzept vorgeschlagen, um Kälte in einem großen Temperaturbereich in vielen Expansionsschritten zu erzeugen, ohne dafür viele Expander zu verwenden. Diese Einheit wird als Wärmeübertrager-Expander (WE) bezeichnet. Mit einem Arbeitsraum in konischer Grundform wird der Wärmeübergangskoeffizient günstig gestaltet u. die Wärmeübergangsfläche vergrößert. Mehrere Versuchsmaschinen wurden untersucht. Anhand der Versuche konnten die wesentlichen Verlustquellen u. Problembereiche identifiziert werden. Es wurde im Rahmen der Versuchsbedingungen nachgewiesen, dass für das vorgesehene Druckverhältnis eine nahe isotherme Expansion u. Kompression möglich ist. Es werden Möglichkeiten zur Verringerung der Längswärmeleitung vorgestellt. Zwei Simulationsprogramme wurden verwendet. Mit Hilfe des Wärmeübertrager-Programms wurden die Wärmeübertragungsvorgänge unter Berücksichtigung der Längswärmeleitung simuliert. Hierbei geht die Expansionsarbeit als stationäre Wärmesenke ein. Der im Ergebnis vorliegende stationäre Temperaturverlauf ist die Grundlage für die Berechnung der Expansionsarbeit unter Berücksichtigung der Realgaseigenschaften im Expander-Programm. Für die Neon-Tieftemperaturvariante wurde eine Grundvariante des WE definiert. Anhand dieser wurde mit Hilfe der Programme der Einfluss verschiedener Parameter auf Kälteleistung u. Gütegrad untersucht. Der WE wird als Teil des beschriebenen Prozesses mit einer JT-Stufe betrachtet. Die Kälteleistung weist sowohl in Abhängigkeit vom Massestrom als auch vom Hub ein Maximum auf. Der Shuttle-Verlust verschiebt durch Wärmetransport mittels des Kolbens die effektive Kälteleistung zu kleineren Hüben. Die durch die Güte (NTU) des JT-Wärmeübertragers bestimmte Eintrittstemperatur des Niederdruckstroms in den WE hat einen großen Einfluss auf die Kälteleistung. Mit steigender Eintrittstemperatur steigen der NTU-Wert für den Arbeitsraum u. somit auch die Kälteleistung. Das Maximum der Kälteleistung stimmt nicht mit dem Optimum für den Gütegrad überein. Der Gütegrad strebt mit sinkenden Masseströmen einem Optimum zu. Durch den zunehmenden Einfluss der Längswärmeleitung u. begrenzt durch die Minimalfüllung der Maschine aufgrund des Schadraumes ergibt sich ein Optimum. Der Einfluss des Massestroms ist entscheidend. Als untergeordnete Größen beeinflussen die Eintrittstemperatur des Niederdruckstroms u. der Hub den optimalen Gütegrad. Der Einfluss der Längswärmeleitung auf Kälteleistung u. Gütegrad wird exemplarisch anhand von vergleichenden Rechnungen gezeigt. Konkret kann für einen Eintrittsdruck von 200 bar, einen Austrittsdruck von 60 bar bei einer Eintrittstemperatur des Niederdruckstroms von 80 K für die Grundvariante eine maximale effektive Kälteleistung von 1,3 W mit einem Massestrom von 0,22 g/ s bei einem Hub von ca. 17 mm ausgewiesen werden. Der effektive Gütegrad für diese Bedingungen beträgt ca. 14%. Kommerzielle Split-Stirlingkühler erreichen bei 42 K einstufig Gütegrade von ca. 7%. Mit der vorgeschlagenen Konfiguration wird ein Konzept vorgestellt, das trotz technologisch offener Fragen das Gütegradniveau bekannter Kryokühler übertreffen kann.
Many applications of high temperature superconductivity are working advantageously within a temperature range between 30 K and 50 K. But for this temperature range only few suitable cryocooler with small refrigerating capacity (1-2 W) and good efficiency exist.Due to its properties Neon is an excellent refrigerant for this temperature level as an example with realised Joule-Thomson plant shows. A process analysis results in the presented cycle which is especially adapted to the properties of Neon. By combination of heat exchange and work extracting expansion and integration of a Joule-Thomson stage a high efficiency could be reached in spite of less efficient components.By arranging heat exchanger surfaces into a piston expansion machine a new concept is suggested to produce refrigeration in a large temperature range with a lot of expansion steps with reduced number of expanders. This unit is referred hereinafter to as heat exchanger-expander.The conical shaped working space results in an increase of the heat transfer coefficient and the heat transfer area.Several test machines were investigated. By means of testing the main loss sources and critical zones could be identified. The test results prove the opportunity of a near isothermal expansion and compression for the specified pressure ratio.Options to reduce the axial heat conduction are presented.Two simulation programs were utilised. Using the heat exchanger program the heat transfer is simulated in consideration of the axial heat conduction. Thereby the expansion work is considered as a stationary heat sink. The resulting stationary temperature pattern is the base for the expansion work calculation using the real gas properties in the expander program. Referring to the defined basic neon low temperature application the influence of different parameters on refrigerating capacity and efficiency was researched with the programs. The heat exchanger-expander is part of the described process with a Joule-Thomson stage. The refrigerating capacity shows a maximum depending as well from the mass flow as from the stroke. In result of the shuttle loss smaller strokes lead to better capacity due to heat transport with the piston.The inlet temperature of the low pressure flow influenced by the quality (NTU) of the Joule-Thomson heat exchanger has a large influence on the refrigerating capacity. With increasing inlet temperature the number of transfer units (NTU) for the fluid in the working volume increases and so the refrigerating capacity, too. The location of refrigerating capacity maximum and efficiency optimum is different. While decreasing mass flow efficiency is increasing to an optimum caused by the increased influence of axial heat conduction but limited by the minimum charge of the machine due to the dead space. The influence of the mass flow is dominating. As lower range values the inlet temperature of the low pressure flow and the stroke are influencing the optimal efficiency. The influence of axial heat conduction on refrigerating capacity and efficiency is shown using comparing calculations.For an inlet pressure of 200 bar, an outlet pressure of 60 bar, an inlet temperature of the low pressure flow of 80 K, a mass flow of 0,22 g/ s and a stroke of about 17 mm for the basic version of heat exchanger-expander a maximal effective refrigerating capacity of 1,3 We could be shown. The effective efficiency therefore is 14 %. Current commercial split Stirling cryocooler reach with single stage operation efficiencies of about 7 % at 42 K. The suggested configuration represents a concept that could be able to master the efficiency level of known cryocooler.

Electricity generation is highly carbon intensive, associated with complex externalities. The preceding thirteen decades have witnessed improvements in efficiencies of rotary machines employed' for electricity generation through enhanced metallurgy, understanding of fluid mechanics and thermodynamics; consequently improving their conventional designs without much heed to environmental degradation, understanding of energy resources, and sustainability, until emergence and realisation of disastrous climate changes. This forced the environmentalists and scientists to explore new frontiers, and to harness renewable energies in any possible way. The situation required an innovative approach and unconventional design to satisfy the need of time. The aim of this research is to recommend a novel design for an expander-turbine that is suitable for generating electricity using compressed air as working fluid; investigating material suitability for cryogenic temperatures. The underlying endeavour is to promote reliable quality renewable energy generation that is sustainable, economical, and suggesting zero-carbon solution in commercial and domestic environment. The results of this venture are very promising and are expected to address UK's commitments to Kyoto protocol for reducing carbon footprint in energy generation. The methodology adopted was to investigate efficiency of individual mechanisms in relevant rotary machines that helped in identifying individual portfolio components that may improve efficacy of turbines if put together.

O presente trabalho aborda a análise da aplicação do expansor axial de estágio único e admissão parcial em ciclo Rankine orgânico para recuperação do calor rejeitado por um motor de combustão interna. O fluido adotado é o R245fa, cujos efeitos de gás real são relevantes nas condições estudadas, sendo representados pela equação Redlich-Kwong-Soave. Um modelo de perdas para o escoamento através das palhetas é proposto, tendo como base a teoria da camada limite, o conceito do fator de difusão, experimentos de grades em túnel de vento obtidos na literatura e as equações de conservação para escoamento compressível. O fator de difusão é o parâmetro responsável por quantificar o gradiente de pressão adverso na superfície do perfil das palhetas. A geometria e dimensões básicas para a máxima eficiência do expansor são determinadas para diversas condições subcríticas e supercríticas do ciclo a partir de um algoritmo de otimização com restrições. O valor ótimo da temperatura do evaporador em condições subcríticas é estabelecido de modo a obter a potência máxima do ciclo de recuperação, conforme as alternativas construtivas consideradas. O projeto do expansor de estágio único mostra ser grandemente influenciado pela compressibilidade do meio e a utilização de bocais com perfil convergente-divergente é promissora para alcançar o maior potencial de desempenho, principalmente nas condições de alta pressão do evaporador.
The present work deals with the analysis of the application of a single stage partial admission axial expander in organic Rankine cycle, in order to recover the heat rejected by an internal combustion engine. The selected fluid is R245fa, whose real gas behavior is relevant under the studied conditions, as modeled by the Redlich-Kwong-Soave equation of state. A loss model for the flow through the axial blades is proposed in this work, based on the boundary layer theory, the concept of diffusion factor, wind tunnel cascade tests available in literature and the conservation equations for compressible flow. The diffusion factor is the parameter responsible to quantify the adverse pressure gradient on the blade profile surfaces. The basic geometry and dimensions needed to achieve maximum expander efficiency are determined under several subcritical and supercritical cycle conditions by means of a restrained design optimization algorithm. The optimum value for the evaporator temperature under subcritical cycle is stablished so as to obtain the maximum power from the recovery cycle, according the constructive alternatives considered. The single stage expander design is shown to be greatly influenced by media compressibility and the use of convergent-divergent profiled nozzles is promising to achieve the highest performance potential, especially at high evaporator pressure conditions.

Une turbine diphasique est utilisée pour remplacer le détendeur classique des systèmes de réfrigération. Dans la turbine, une tuyère transforme l'enthalpie de l'écoulement en énergie cinétique. Remplacer la détente isenthalpique classique par une détente isentropique augmente le coefficient de performance d'un système de réfrigération d'une valeur qui peut aller jusqu'à 20 %, pour la même consommation électrique du compresseur. Pendant cette transformation, la pression statique de l'écoulement diminue et un changement de phase se produit au col de la tuyère. La détente d'un écoulement diphasique est étudiée analytiquement et simulée avec le logiciel de CFD Fluent 13. Un modèle d'évaporation adapté à la détente diphasique est ajouté à l'algorithme de dynamique de fluide dans Fluent 13, afin de créer et simuler le changement de phase à l'intérieur de la tuyère. Le modèle d'évaporation est basé sur la théorie de la nucléation et sur des résultats expérimentaux. Le modèle calcule le taux de nucléation hétérogène initiée par les cavités de la paroi intérieur de la tuyère, et le taux de nucléation hétérogène initiée par la présence de bulles de vapeur au cœur de l'écoulement. Outre les tuyères, la roue de la turbine est aussi conçue. La roue récupère l'énergie cinétique d'un écoulement diphasique et la transforme en un couple de moment. La géométrie des différents éléments de la roue est définie afin d'assurer l'intégrité mécanique et un bon rendement énergétique. La conception de la roue prend en considération le comportement de l'écoulement en contact avec les paliers de la roue, la perte de puissance due aux frottements aérauliques, ainsi que de nombreux autres facteurs. Fluent 13 est utilisé pour simuler l'écoulement diphasique à l'intérieur des augets de la roue, ainsi que pour calculer les pertes dues aux frottements aérauliques. Le rendement calculé de la turbine est vérifié avec des tests d'une turbine diphasique dans un groupe refroidisseur d'eau ayant une puissance de réfrigération de 700 kW
A two-phase turbine used to replace the usual expander in a refrigeration system needs a nozzle/expander to transform the flow enthalpy into kinetic energy. Replacing the isenthalpic expansion by the isentropic one, increases the coefficient of performance of refrigeration system up to 20% for the same compressor input power. During this transformation, the static pressure of the flow decreases and a phase change occurs at the nozzle throat. The expanding and flashing flow in the convergent and divergent parts of a nozzle is analytically studied and then simulated using the CFD software Fluent 13. A separate evaporation model is added to the fluid dynamics algorithms in Fluent 13 in order to create the phase change inside the nozzle. The evaporation model is based on the classical theory of nucleation and on experimental results: it calculates the heterogeneous nucleation initiated by the wall cavities and the heterogeneous nucleation initiated by the presence of vapor bubbles in the flow. The turbine is composed of the designed nozzles and a rotor that recovers the kinetic energy of the two-phase flow and transforms it into torque. The geometry of the rotor components is designed to provide mechanical integrity and high efficiency. The design takes into consideration the flow behavior inside the rotor, the power loss due to drag force, and many other factors. Fluent 13 is used to study the flow inside the rotor buckets and to estimate the power loss due to drag force. The turbine calculated efficiency is verified by testing a two-phase turbine in a water chiller having a refrigeration capacity of 700 kW

Regulations for ICE-based transportation in the EU seek carbon dioxide emissions lower than 95 g CO2/km by 2020. In order to fulfill these limits, improvements in vehicle fuel consumption have to be achieved. One of the main losses of ICEs happens in the exhaust line. Internal combustion engines transform chemical energy into mechanical energy through combustion; however, only about 15-32% of this energy is effectively used to produce work, while most of the fuel energy is wasted through exhaust gases and coolant. Therefore, these sources can be exploited to improve the overall efficiency of the engine. Between these sources, exhaust gases show the largest potential of Waste Heat Recovery (WHR) due to its high level of exergy. Regarding WHR technologies, Rankine cycles are considered as the most promising candidates for improving Internal Combustion Engines. However, the implementation of this technology in modern passenger cars requires additional features to achieve a compact integration and controllability in the engine. While industrial applications typically operates in steady state operating points, there is a huge challenge taking into account its impact in the engine during typical daily driving profiles. This thesis contributes to the knowledge and characterization of an Organic Rankine Cycle coupled with an Internal Combustion Engine using ethanol as working fluid and a swash-plate expander as expansion machine. The main objective of this research work is to obtain and quantify the potential of Organic Rankine Cycles for the use of residual energy in automotive engines. To do this, an experimental ORC test bench was designed and built at CMT (Polytechnic University of Valencia), which can be coupled to different types of automotive combustion engines. Using these results, an estimation of the main variables of the cycle was obtained both in stationary and transient operating points. A potential of increasing ICE mechanical efficiency up to 3.7% could be reached at points of high load installing an ORC in a conventional turbocharged gasoline engine. Regarding transient conditions, a slightly simple and robust control based on adaptive PIDs, allows the control of the ORC in realistic driving profiles. High loads and hot conditions should be the starting ideal conditions to test and validate the control of the ORC in order to achieve high exhaust temperatures that justify the feasibility of the system. In order to deepen in the viability and characteristics of this particular application, some theoretical studies were done. A 1D model was developed using LMS Imagine.Lab Amesim platform. A potential improvement of 2.5% in fuel conversion efficiency was obtained at the high operating points as a direct consequence of the 23.5 g/kWh reduction in bsfc. To conclude, a thermo-economic study was developed taking into account the main elements of the installation costs and a minimum Specific Investment Cost value of 2030 €/kW was obtained. Moreover, an exergetic study showed that a total amount of 3.75 kW, 36.5% of exergy destruction rate, could be lowered in the forthcoming years, taking account the maximum efficiencies considering technical restrictions of the cycle components.
Las normativas anticontaminantes para el transporte propulsado por motores de combustión interna alternativos en la Unión Europea muestran límites de emisión menores a 95 g CO2/km para el año 2020. Con el fin de cumplir estos límites, deberán ser realizadas mejoras en el consumo de combustible en los vehículos. Una de las principales pérdidas en los Motores de Combustión Interna Alternativos (MCIA) ocurre en la línea de escape. Los MCIA transforman la energía química en energía mecánica a través de la combustión; sin embargo, únicamente el 15-32% de esta energía es eficazmente usada para producir trabajo, mientras que la mayor parte es desperdiciada a través de los gases de escape y el agua de refrigeración del motor. Por ello, estas fuentes de energía pueden ser utilizadas para mejorar la eficiencia global del vehículo. De estas fuentes, los gases de escape muestran un potencial mayor de recuperación de energía residual debido a su mayor contenido exergético. De todos los tipos de Sistemas de Recuperación de Energía Residual, los Ciclos Rankine son considerados como los candidatos más prometedores para mejorar la eficiencia de los MCIA. Sin embargo, la implementación de esta tecnología en los vehículos de pasajeros modernos requiere nuevas características para conseguir una integración compacta y una buena controlabilidad del motor. Mientras que las aplicaciones industriales normalmente operan en puntos de operación estacionarios, en el caso de los vehículos con MCIA existen importantes retos teniendo en cuenta su impacto en el modo de conducción cotidianos. Esta Tesis contribuye al conocimiento y caracterización de un Ciclo Rankine Orgánico acoplado con un Motor de Combustión Interna Alternativo utilizando etanol como fluido de trabajo y un expansor tipo Swash-plate como máquina expansora. El principal objetivo de este trabajo de investigación es obtener y cuantificar el potencial de los Ciclos Rankine Orgánicos (ORC) para la recuperación de la energía residual en motores de automoción. Para ello, una instalación experimental con un Ciclo Rankine Orgánico fue diseñada y construida en el Instituto Universitario "CMT - Motores Térmicos" (Universidad Politécnica de Valencia), que puede ser acoplada a diferentes tipos de motores de combustión interna alternativos. Usando esta instalación, una estimación de las principales variables del ciclo fue obtenida tanto en puntos estacionarios como en transitorios. Un potencial de mejora en torno a un 3.7 % puede ser alcanzada en puntos de alta carga instalando un ORC en un motor gasolina turboalimentado. Respecto a las condiciones transitorias, un control sencillo y robusto basado en PIDs adaptativos permite el control del ORC en perfiles de conducción reales. Las condiciones ideales para testear y validar el control del ORC son alta carga en el motor comenzando con el motor en caliente para conseguir altas temperaturas en el escape que justifiquen la viabilidad de estos ciclos. Para tratar de profundizar en la viabilidad y características de esta aplicación particular, diversos estudios teóricos fueron realizados. Un modelo 1D fue desarrollado usando el software LMS Imagine.Lab Amesim. Un potencial de mejora en torno a un 2.5% en el rendimiento efectivo del motor fue obtenido en condiciones transitorias en los puntos de alta carga como una consecuencia directa de la reducción de 23.5 g/kWh del consumo específico. Para concluir, un estudio termo-económico fue desarrollado teniendo en cuenta los costes de los principales elementos de la instalación y un valor mínimo de 2030 €/kW fue obtenido en el parámetro de Coste Específico de inversión. Además, el estudio exergético muestra que un total de 3.75 kW, 36.5 % de la tasa de destrucción total de exergía, podría ser reducida en los años futuros, teniendo en cuenta las máximas eficiencias considerando restricciones técnicas en los componentes del ciclo.
Les normatives anticontaminants per al transport propulsat per motors de combustió interna alternatius a la Unió Europea mostren límits d'emissió menors a 95 g·CO2/km per a l'any 2020. Per tal d'acomplir aquests límits, s'hauran de realitzar millores al consum de combustible dels vehicles. Una de les principals pèrdues als Motors de combustió interna alternatius (MCIA) ocorre a la línia d'escapament. Els MCIA transformen l'energia química en energia mecànica a través de la combustió; però, únicament el 15-32% d'aquesta energia és usada per produir treball, mentre que la major part és desaprofitada a través dels gasos d'escapament i l'aigua de refrigeració del motor. Per això, aquestes fonts d'energia poden ser utilitzades per millorar l'eficiència global del vehicle. Considerant aquestes dues fonts d'energia, els gasos d'escapament mostren un potencial major de recuperació d'energia residual debut al seu major contingut exergètic. De tots els tipus de Sistemes de Recuperació d'Energia Residual, els Cicles Rankine són considerats com els candidats més prometedors per millorar l'eficiència dels MCIA. No obstant, la implementació d'aquesta tecnologia en els vehicles de passatgers moderns requereix un desenvolupament addicional per aconseguir una integració compacta i una bona controlabilitat del motor. Mentre que les aplicacions industrials normalment operen en punts d'operació estacionaris, en el cas dels vehicles amb MCIA hi han importants reptes a solucionar tenint en compte el funcionament en condicions variables del motor i el seu impacte en la manera de conducció quotidiana del usuari. Aquesta Tesi contribueix al coneixement i caracterització d'un Cicle Rankine Orgànic (ORC) acoblat amb un motor de combustió interna alternatiu (MCIA) utilitzant etanol com a fluid de treball i un expansor tipus Swash-plate com a màquina expansora. El principal objectiu d'aquest treball de recerca és obtenir i quantificar el potencial dels ORCs per a la recuperació de l'energia residual en motors d'automoció. Per aconseguir-ho, una instal·lació experimental amb un ORC va ser dissenyada i construïda a l'Institut "CMT- Motores Térmicos" (Universitat Politècnica de València). Esta installació pot ser acoblada a diferents tipus de MCIAs. Mitjançant assajos experimentals en aquesta installació, una estimació de les principals variables del cicle va ser obtinguda tant en punts estacionaris com en punts transitoris. Un potencial de millora al voltant d'un 3.7% pot ser aconseguida en punts d'alta càrrega instal·lant un ORC acoblat a un motor gasolina turboalimentat. Pel que fa a les condicions transitòries, un control senzill i robust basat en PIDs adaptatius permet el control del ORC en perfils de conducció reals. Les condicions ideals per a testejar i validar el control de l'ORC són alta càrrega al motor començant amb el motor en calent per aconseguir altes temperatures d'escapament que justifiquen la viabilitat d'aquests cicles. Per tractar d'aprofundir en la viabilitat i característiques d'aquesta aplicació particular, diversos estudis teòrics van ser realitzats. Un model 1D va ser desenvolupat usant el programari LMS Imagine.Lab Amesim. Un potencial de millora al voltant d'un 2.5% en el rendiment efectiu del motor va ser obtingut en condicions transitòries en els punts d'alta càrrega com una conseqüència directa de la reducció de 23.5 g/kWh al consum específic. Per concloure, un estudi termo-econòmic va ser desenvolupat tenint en compte els costos dels principals elements de la installació i un valor mínim de 2030 €/kW va ser obtingut en el paràmetre del Cost Específic d'Inversió. A més, l'estudi exergètic mostra que un total de 3.75 kW, 36.5% de la taxa de destrucció total d'exergia, podria ser recuperat en un pròxim, considerant restriccions tècniques en els components del cicle i tenint en compte les màximes eficiències que es poden aconseguir.
Royo Pascual, L. (2017). Study of Organic Rankine Cycles for Waste Heat Recovery in Transportation Vehicles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84013
TESIS

Les contraintes législatives, environnementales et économiques poussent les constructeurs automobiles à envisager toutes les solutions possibles pour optimiser au mieux la consommation de carburant des véhicules. La récupération d'énergie à l'échappement fait partie de ces solutions envisageable et le moteur à cycle de Rankine offre de nombreux avantages.Le choix de cette technologie de récupération d'énergie à l'échappement est justifié au moyen d'un état de l'art complet ainsi qu'au moyen d'une comparaison basée sur des simulations au moyen de modèles calibrés. Ces simulations ont permis également de donner un ordre de grandeurs des gains de consommation attendus sur différents cycles de conduite.L'expanseur du moteur à cycle de Rankine est un des éléments-clés du système. Aucun expanseur disponible sur le marché n'est adapté pour l'application véhicule. Dès lors, le dimensionnement d'un nouvel expanseur a été entrepris. Ce dimensionnement a nécessité le développement d'un modèle détaillé de l'expanseur scroll. Le moteur à cycle de Rankine fonctionne avec de l'eau et les expériences passées ont montré que la gestion d'un mélange eau-huile est particulièrement délicate. Le choix d'opérer sans lubrification a été réalisé et une attention particulière s'est portée sur la lubrification sèche des volutes de l'expanseur. Des essais expérimentaux ont permis de mettre en évidence les propriétés tribologiques de divers couples de matériaux. La définition des matériaux du joint radial et des volutes de l'expanseur a donc pu être réalisée.Finalement, cet expanseur a pu être testé sur un banc d'essais. Ce banc a également permis de tester plusieurs autres composants du moteur à cycle de Rankine. Les performances de ces composants ont pu être mesurées lors d'essais stabilisés et ils ont également permis de calibrer des modèles semi-empiriques. Ces modèles peuvent être utilisés dans l'évaluation des performances du système de récupération
Automotive manufacturers seek every possibility to reduce passenger car fuel consumption due to several constraints such as legislative, environmental or economical ones. Waste heat recovery is one of those possibilities and, among the waste heat recovery solutions, Rankine cycle heat engines provide numerous advantages.A complete state of the art and a comparison based on calibrated semi-empirical models justified the choice of a Rankine cycle heat engine as the waste heat recovery technology to be investigated in this thesis. The simulation of different technologies also provided some orders of magnitude of the achievable fuel consumption reduction.The expander of the Rankine cycle heat engine is one of the key element of the system. No commercially available expander is suitable for a waste heat recovery application on passenger cars. Therefore, a new expander has been sized and manufactured. A detailed model of the scroll expander has been built in order to size the expander.The working fluid of the Rankine cycle heat engine is water and previous experimental works have shown that a mix of steam and lubricating oil is not easy to manage. Dry lubrication has therefore been chosen and experimental test have been run to study tribological properties of different couples of materials. Those tests allowed to choose the material of the involute and the tip seal of the expander.Finally, the expander has been tested in a Rankine cycle heat engine. Other components of the Rankine cycle heat engine have also been tested. Performances of those components have then been measured in steady conditions. These measurements allowed the calibration of semi-empirical models that can therefore be used to evaluate the performance of the system

Introduction: Orthodontic and orthopedic expansion is necessary to create space to resolve crowding due to arch deficiency or tooth size discrepancy. The Invisalign First clear aligner appliance as a modality for early interceptive orthodontic treatment has become incorporated into orthodontic practices in very recent years. The present study aims to investigate the magnitude of expansion of the Invisalign First clear aligner appliance compared to a Schwartz removable expander in patients with mixed dentition. Additionally, the study aims to compare the efficacy and predictability of Invisalign First clear aligners in this population. Materials & Methods: In this retrospective study, a sample was collected from a single orthodontist practitioner. The sample consisted of 34 patients, 16 patients treated with Invisalign First clear aligners only (Group1) and 19 patients treated with a Schwartz removable appliance and Invisalign First clear aligners (Group 2). Intraoral scans of four timepoints, initial (T1), post-expansion for Group 2 only (T1Exp), first refinement (T2), and final (T3), and planned Clincheck goal (P) model from Clincheck software were imported to Align Technology’s digital measure program (Quantify©). Arch widths and molar inclinations were measured at each timepoint and the changes between timepoints were calculated. Predictability of arch expansion was calculated as T13 (change between initial and final) divided by the Planned dimension multiplied by one hundred. A two sample t-test was used to assess differences in the changes in arch widths and predictability of expansion between two groups. Results: There were statistically significant differences found in the magnitude of expansion and predictability of arch expansion between two groups. Group 2 showed a greater amount of expansion and predictability. Group 1 showed about 50-60% of the planned expansion at the end of treatment. In regards to magnitude of expansion when comparing the two groups, the efficacy predictability of transverse dimensional changes were significantly greater in the Group 2 compared to Group 1, 83% vs 56% (p = 0.001), respectively. The changes in inclination were similar in both groups, with no statistically significant differences.Conclusions: There is a significantly greater amount of expansion and greater predictability with the Schwartz removable appliance compared to the Invisalign First clear aligner appliance in the mixed dentition. The predictability of Invisalign First was 56% and indicates a significant overcorrection of arch expansion is required at the virtual treatment planning stage in Clincheck in order to obtain the arch expansion that was planned

This thesis deals with technologies for gas liquefaction and storage. The first section summarizes the development of liquefaction technology using expanders and throttling valves, followed by current technology. This is especially a rotary expanders. The storage technology is the above-ground storage of cryogenic tanks. The thesis includes proposals turbine wheels for liquefaction lines and included two proposals liquefaction cycles.

The master´s thesis is focused on design of ADSR filter and voltage controlled amplifier (VCA). Three additional circuits performing analog signal processing are added. Functionality of designed circuits is verified in simulation program. All designed circuits are practically realized. Thesis includes complete design of the mentioned circuits and all necessary informations for its practical realization. All designed circuits are measured and the results are presented.

The present master thesis deals with the technologies for gas liquefaction focused on helium. The first part of the thesis contains a description of the history of liquefaction, production and usage of liquid helium, as well as the principles of liquefaction and cooling cycles. In the following part of the thesis is a detailed model of the liquefaction cycle for which radial-axial turbine wheels were designed. The last part of the thesis contains financial analysis of the suitability of using the expander with eddy current brake and the expander with an electric generator.

Development of innovative thermodynamic cycles is important for the efficient utilization of low-temperature heat sources such as solar, geothermal, and waste heat sources. Binary mixtures exhibit variable boiling temperatures during the boiling process, which leads to a good thermal match between the heating fluid and working fluid for efficient heat source utilization. This study presents a theoretical and an experimental analysis of a combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as the working fluid and produces power and refrigeration, while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low to mid-temperature sources such as geothermal and solar energy. A thermodynamic analysis of power and cooling cogeneration was presented. The performance of the cycle for a range of boiler pressures, ammonia concentrations, and isentropic turbine efficiencies were studied to find out the sensitivities of net work, amount of cooling and effective efficiencies. The thermodynamic analysis covered a broad range of boiler temperatures, from 85 °C to 350 °C. The first law efficiencies of 25-31% are achievable with the boiler temperatures of 250-350 °C. The cycle can operate at an effective exergy efficiency of 60-68% with the boiler temperature range of 200-350 °C. An experimental study was conducted to verify the predicted trends and to test the performance of a scroll type expander. The experimental results of vapor production were verified by the expected trends to some degree, due to heat transfer losses in the separator vessel. The scroll expander isentropic efficiency was between 30-50%, the expander performed better when the vapor was superheated. The small scale of the experimental cycle affected the testing conditions and cycle outputs. This cycle can be designed and scaled from a kilowatt to megawatt systems. Utilization of low temperature sources and heat recovery is definitely an active step in improving the overall energy conversion efficiency and decreasing the capital cost of energy per unit.

The assignment, which has been carried out on behalf of Troax AB was to develop suggestions on one sided fasteners that will be used to attach the anti-collapse system for pallet racks. The problem, as it is today, is that the installers of the mesh panels for the anti-collapse system find it difficult to reach behind and inside the pallet racking beam when they screw together the screw and the nut to hold up the anti-collapse system. Therefore, there is a desire to use a fastener which does not have to handle screws or bolts on the back of the beam. One design requirements is that it should fit most hole patterns and hole sizes available for pallet racks today. It also has the requirement that it must hold for a pendulum test. The energy is then converted into a force for easier calculations. When a safety factor is applied the force that the system is subjected to is approximately 10KN. SolidWorks was used to model and structurally analyze the various design proposals. The best design proposal was put into a simulations study to be analyzed. Then the proposal was compared with the screw which is currently in use. The results of the structural analysis of the current screw show that it withstands the applied loads. The proposed suggestion lacks credibility due to the fact that the stresses shown in the simulations are too high. Based on the results from the structural analysis, it is concluded that further studies are needed and also that the other design suggestions should be examined further in case they could be improved to make them meet the requirements.
Detta arbete är utfört på uppdrag av Troax AB där uppgiften var att ta fram förslag på ensidesfästade fästelement som ska användas till att fästa rasskydd till pallstallage. Problemet som det är idag är att montörerna av rasskyddet anser att det är svårt att komma åt bakom och innanför balken då man ska skruva dit skruv och mutter för att hålla upp rasskyddet. Därför finns det en önskan att kunna använda ett fästelement där man inte behöver hantera skruvar eller muttrar på baksidan av balken. Kravet som sattes på fästelementet är att den ska passa till de flesta hålbilder och hålstorlekar som finns på stallagebalkar idag. Den ska även hålla för ett pendeltest då en pendel med vikten 160kg och rörelseenergin 2500J slås in i ett gallernät. Energin räknas sedan om till en kraft för enklare beräkning och för att kunna föra in kraften i datorsimuleringar. Kraften som systemet utsätts för blir enligt uträkning ca 7100N och med en säkerhetsfaktor blir den resulterande kraften 10000N. SolidWorks används för modellering samt för analys av designförslagen. Först sätts hela systemet med alla balkar, konsoler, paneler och skruvar upp i SolidWorks och Simulation för att se hur allt hänger ihop. Därefter förenklas uppsättningen och ger resultatet att skruven utsätts för dragkraft och skjuvkraft där hela kraften appliceras. Det designförslag som bäst uppfyllde kraven sattes in i Simulation för att studeras. Där undersöks och jämförs förslaget med dagens skruv där båda utsätts för både dragkraft och skjuvkraft. Dagens skruv visar resultatet att den håller för de uppsatta krafterna. Förslagets resultat vid drag är dock opålitliga då uppsättningen av denna inte är optimal. Utifrån resultatet dras slutsatsen att det krävs ytterligare studier på förslaget och att man även bör titta på de övriga förslagen som togs fram för att se om det finns eventuella förbättringar på dessa som gör att de uppfyller kraven.

This thesis presents a series of algorithmic innovations in Combinatorial Compressed Sensing and Persistent Homology. The unifying strategy across these contributions is in translating structural patterns in the underlying data into specific algorithmic designs in order to achieve: better guarantees in computational complexity, the ability to operate on more complex data, highly efficient parallelisations, or any combination of these.

Nahlížíme-li na profesi kameramana jakožto na určitou formu umění, pak toto umění dnes stojí na rozcestí. Kolem pojmu kameramanství je dnes určitá kontroverze, zejména v kontextu filmů, u kterých byla klasická kamera podřízena virtuálním technikám (např. Matrix, Life of Pi, Gravitace). Následující práce se zaobírá historickým vývojem kameramanských technik a jejím cílem je ověřit, zda je virtuální kinematografie krokem kupředu v evoluci práce kameramana. Ve snaze dobrat se co nejpravdivější odpovědi, rozhodl jsem se analyzovat práci kameramanů výše zmíněných celovečerních snímků ve smyslu spolupráce se supervizory vizuálních efektů a celým kreativním týmem. V této studii se snažím objasnit, jak tito kameramani použili nové techniky za účelem podpoření dramaturgie příběhu.

This project presents a model of expanded musical form. Arguing that music’s expanded field is a field of experiences, rather than of discrete things, it sets out an approach to composition that centres not on the creation of aesthetic works, but on supporting an aesthetic attitude. Integrating theory and practice, this research endeavours to give definition to an attitude that apprehends music as experience. Under this attitude, the perceiver assumes no distance from the perceived as she produces the content of her musical experience in and through her dynamic bodily interactivity. This project comprises a thesis and four ephemeral performance sound installations. The thesis sets out the terms of music’s expanded condition, drawing upon a range of disciplines – artistic, aesthetic, philosophical – to chart the pluralistic, indeterminate, open-ended structure of the expanded field. The performance sound installations explored the operations of expanded artistic practice, critiquing conceptual, ideological, and institutional terms of music and sound installation to foreground the productivity of the perceiver. In both theory and practice, this research contests the concept of “sound art” as a distinct category. It makes the case that expanded musical form is not a break with the musical past, but its background made focal. It proposes that the presence, physicality, and place in which expanded musical form consists are music’s always presupposed foundation.

Ce travail de recherche est motivé par les contraintes environnementales qui imposent une réduction des émissions de gaz à effet de serre. L'objectif de cette thèse est d'explorer les possibilités de réduction de consommation des moteurs à combustion interne en les munissant d'un dispositif de récupération de chaleur. Cette étude est focalisée sur la valorisation des rejets thermiques d'installations de faible puissance. Le cycle de Rankine est la technologie qui a été sélectionnée. Une installation d'essais a été construite. Un générateur de gaz chaud simule le moteur thermique ; une part de cette chaleur est collectée par le système de récupération de chaleur et partiellement convertie en énergie mécanique. L'échangeur de chaleur a été conçu et construit en interne ainsi que la machine de détente à piston. Un modèle numérique statique validé expérimentalement pour l'évaporateur a été développé. Celui-ci permet d'explorer les performances du cycle de Rankine sur un large champ de fonctionnement. Avec des hypothèses restrictives le modèle numérique fait apparaître qu'un gain de consommation de l'ordre de 3 % à 4 % sur un tracteur agricole serait possible. Un modèle dynamique de moteur à piston adapté aux cycles de Rankine de faibles puissances a été développé pour aider à son dimensionnement. Ce modèle a permis de mettre au point un concept de machine de détente à piston avec un mécanisme de distribution simplifié. Bien qu'offrant des performances en retrait sur les machines de détente à piston à distribution commandée ce concept est à approfondir pour les systèmes de faible puissance nécessitant une simplicité de construction et un faible coût
This research was motivated by environmental constraints which impose a reduction in greenhouse gas emissions. The aim of the thesis was to explore the possibility of reducing the consumption of an internal combustion engine using a bottom waste heat recovery system. The study focused on waste heat recovery for low power installations. The Rankine cycle technology was selected to exploit the heat source. An experimental test bench was designed and set up. A hot gas generator simulates an internal combustion engine. Part of the thermal power is absorbed by the evaporator and partially converted into mechanical power. The heat exchanger and piston expander were designed and built in-house. A numerical static model with experimental validation of the evaporator was developed. The model was used to explore the performances of the Rankine cycle over a large operating range. Under restrictive hypotheses, the numerical model showed that is possible to reduce the consumption of a tractor by about 3 to 4 %. A piston expander dynamic model was developed to assist in sizing the expander. The model was used to define a piston expander concept with a simple distribution mechanism. Although a classical distribution mechanism offers better performances, this concept is promising for systems that are simple, small-scale and low-cost

Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Charles A. Eckert; Committee Co-Chair: Charles L. Liotta; Committee Member: J. Carson Meredith; Committee Member: Rigoberto Hernandez; Committee Member: William J. Koros

In Uppsala CHP Plant, there are six pressure reducing valves to reduce the pressure from 15 to 3 bars, before six absorption heat pumps. During the process the energy is conserved but losses occur in form of exergy. The aim of this thesis is to reduce the losses of exergy. This can be done by letting turbines replace the pressure reducing valves. In this thesis an investigation has been done of the conditions today, the conditions after the change from pressure reducing valves to turbines and a comparison of three different types of turbine solutions. The three examined solutions are one turbine, several helical screw expanders and several small turbines in parallel with asynchronous generators. The six absorption heat pumps have been divided into two groups; one group of four and one group of two absorption heat pumps. An investigation of locations and space in nearby switchgears has been done for each group. Contacts with retailers of the examined turbine solutions have been taken to gather technical specifications. These technical specifications have been used to simulate the electricity production and the economical yield of each type of examined solution. The investigation shows that the best solution is the solution with several small turbines with asynchronous generators. It has lower investment cost (15 [MSEK]) and the best yield. The proposed solutions will have an installed capacity of 2.65 [MW] to a cost of 5 601 [SEK/kW]. The electric energy production will be 15.7 [GWh/year]. An investment is recommended to a future electric energy price around 400 [SEK/MWh]. Before an investment it is recommended to investigate how to optimize the regulation of the new system with absorptions heat pumps and turbines.

The aim of this project was to produce expanded graphite (EO) and modified EO-filled electrically conductive polymer composites and to investigate the effects of different additive modifications and preparation conditions on the microstructure and electrical properties of these composites. Modifications included the use of dry blending and ultrasound to reduce their size, use of various suspension media and surfactants to stabilize particle suspensions. To compare the effectiveness of different filler modification processes on electrical conductivity, unmodified and treated EO were incorporated into polypropylene (PP) by melt mixing and EO based dispersions were used to make polyvinyl alcohol (PV A) composites by solution casting. The PP composites were made using various processing methods and conditions at filler concentrations up to 12 wt%, while the polyvinyl alcohol samples contained graphite concentrations up to 8 wt%. To analyse the crystalline morphology of sample and the dispersion of the filler in the composites samples were analysed by light and electron microscopy, DSC and X-ray diffraction. TOA was also used to investigate the thermal stability of the composites. It was found that the presence of graphite, significantly changed the crystal morphology of PP. Solution mixed PVA samples showed improved dispersion and the particle size was effectively reduced.

Thesis (S.M.M.O.T.)--Massachusetts Institute of Technology, Sloan School of Management, Management of Technology Program, 2001.
Includes bibliographical references.
The awareness of disruptive technologies and their potential effects on established firms was recently brought to the forefront of business thinking by Clayton Christensen in his book "The Innovator's Dilemma: When New Technologies Cause Great Firms to Fail". While Christensen's work offers a fascinating view of technology change and the potentially lethal impact it may have on incumbent firms, his perspective on the contribution of technology change on product attributes and resultant firm disruption, appears, in my opinion, to be too limiting. The specific areas addressed by my thesis include: -- The expansion of Christensen's definition of disruptive technologies, -- An expanded understanding of the product attributes and subsequent competitive advantage that may result from the exploitation of an emerging technology, -- The role of market segmentation and technology interaction on the diffusion of an emerging technology and potential disruption of an incumbent technology, -- Inclusion of the potential for the down-market migration of products based on disruptive technologies in addition to the up-market scenario. The objective of my thesis is to broaden the spectrum of outcomes associated with technology change in order to help firms formulate a more comprehensive technology strategy. A framework for thought is provided regarding the potential outcomes of the exploitation of an emerging technology (possibly disruptive) in the context of product attributes and market influence in which the reader is encouraged to consider his or her own experiences.
by Hap Acee.
S.M.M.O.T.