Conversion of a scroll compressor to an expander for organic Rankine Cycle: modeling and analysis / UOIT

壓縮機是空調系統的心臟，也是空調系統中最重要及成本最高的元件。即使如此，最終使用者熟悉的仍是各空調OEM生產的成品及其品牌，幾乎沒有消費者會熟悉壓縮機的品牌或其功能。因此壓縮機一向的銷售方式，大多採取推（Push）的方式來銷售。 變頻式系統是過去幾年來被認為是能量控制或是一對多空調系統的最佳技術，這項技術主要是掌握在日本品牌空調公司手中，尤其Daikin為其中居領導地位。C公司推出了一項新的壓縮機技術稱之為數碼渦旋，功能也是可能量控制，預備在市場與變頻式系統競爭，提供給空調OEM作為另一項選擇。 中國大陸近幾年已成為亞洲空調市場成長最大的地區，中國的各地空調OEM除了滿足於內需市場，同時也大量的外銷，成為世界的工廠。因此C公司的數碼渦旋就鎖定中國大陸為主要推廣的市場。不過C公司的新產品技術並不為消費者或OEM熟悉，因此採用傳統推的方式來銷售也面臨許多困難。 本研究以4C的架構來分別分析數碼渦旋系統與變頻式系統在購買者與OEM的外顯與內隱成本，從而推擬數碼渦旋系統可行的市場行銷策略，來與已建立高知曉度及高度信任感的變頻式系統競爭。

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.

<div>Vapor compression cycles are the most common method used to provide cooling to environments. In the residential area, refrigerator/freezers as well as air conditioners/heat pumps almost exclusively use vapor compression cycles. The driving force behind a vapor compression cycle is the compressor, where a variety of compressor types are used in the same application. While reciprocating compressors are found in the majority of refrigerator/freezers, scroll compressors are predominantly used in residential air conditioners. Yet other compressors have emerged as replacements due to increased efficiency. A R134a oil-free prototype scroll compressor and a R134a reciprocating compressor are operated in a hot-gas bypass test stand under refrigerator/freezer conditions to compare performance. Additionally, a R407C scroll compressor and a R410A rotary compressor are operated in a compressor calorimeter under air conditioning/heat pump conditions to compare performance. Experimental results show that the reciprocating compressor far outperforms the prototype scroll compressor in the refrigerator/freezer application, while the performance between the scroll and rotary compressors are almost equal in the air conditioning application.</div><div>Pressure fluctuation at compressor discharge is also measured in the compressor calorimeter to determine feasibility of applying a novel muffling design to air conditioning compressors, although it was found that traditional muffling methods currently used are effective to a degree such that this new method is unwarranted. Data from the compressor calorimeter is also used to investigate the accuracy of the AHRI 540 10-Coefficient Correlation compressor map in predicting performance both inside and outside the tested operating conditions. The AHRI 10-Coefficient Correlation achieves high accuracy inside tested operating conditions but is inept in extrapolating performance, where other map correlations are more accurate.</div>

In this thesis, an experimental research is conducted on scroll-based Organic Rankine Cycle (ORC) focusing on the expansion process. An important feature of the ORC is the ability to utilize low or moderate temperature heat sources derived from renewable energy such as concentrated solar radiation, biomass/biofuels combustion streams, geothermal heat and waste heat recovery. The ORC is more appropriate than steam Rankine cycle to generate power from low capacity heat sources (5-500 kW thermal). For example, expansion of superheated steam from 280oC/1000 kPa to a pressure corresponding to 35oC saturation requires a volume ratio as high as 86, whereas for the same operating conditions toluene shows an expansion ratio of 6 which can be achieved in a single stage turbine or expander. The objective of this work is to experimentally study the performance of a selected refrigeration scroll compressor operating in reverse as expander in an ORC. To this purpose, three experimental systems are designed, built and used for conducting a comprehensive experimental programme aimed at determining the features of the expansion process. In preliminary tests the working fluid utilized is dry air while the main experiments are done with the organic fluid R134a. Experimental data of the scroll expander are collected under different operating conditions. Power generation in various conditions is analyzed in order to determine the optimum performance parameters for the scroll expander. In addition, thermodynamic analysis of the system is conducted through energy and exergy efficiencies to study the system performance. Based on the experimental measurements, the optimum parameters for an ORC cycle operating with the Bitzer-based expander-generator unit are determined. The cycle energy and exergy efficiencies are found 5% and 30% respectively from a heat source of 120oC. / UOIT

This study analyzes the performance of variable capacity heat pump scroll compressor which is equipped with vapour injection and permanent magnet motor. Refrigerant used in the system is R410A. The study is divided in two phases. In first phase, tests are carried out for heat pump without vapour injection. Heat pump’s performance including COPs, heating/cooling capacities, inverter losses, heat transfer behaviour in condenser/evaporator are analyzed. Inverter losses increase but the ratio of inverter losses to the total compressor power decreases with increase in compressor speed. Electromechanical losses of compressor are much higher than the inverter losses and so make most part of the total compressor losses (summation of inverter and electromechanical losses). In second phase benefits of vapour injection are analyzed. For vapour injection, heat pump’s performance is evaluated for two different refrigerant charges: 1.15kg and 1.28kg. It is noted that heat pump performs better for refrigerant charge 1.15kg even at lower compressor speeds as compared to refrigerant charge 1.28kg. For refrigerant charge 1.15kg, heat pump COP cool with vapour injection increases by an average of 10.66%, while COP heat increases by an average of 9.4%, at each compressor speed except for 30Hz, as compared to conventional heat pump cycle with no vapour injection. Similarly refrigerant temperature at outlet of compressor also reduces with vapour injection which leads to the better performance of heat pump.

Många unga vuxna använder sig av sociala medier innan de ska sova för natten. Majoriteten av dessa sociala medier använder funktionen ”infinite scroll”, ett oändligt flöde som är designat i syfte att förlänga användarens tid på plattformen. Samtidigt är det många unga vuxna som upplever att de inte får tillräckligt med sömn. Denna studie utgick från frågeställningen “hur sömnkvalitet hos studenter påverkas av att använda sociala medier med oändliga flöden innan läggdags”. Detta undersöktes med hjälp av tre olika metoder för att bedöma sömnkvalitet. Tidigare forskning på området har funnit samband mellan sömnstörningar och volymen sociala medier som konsumeras innan läggdags. I denna studie undersöktes om liknande samband kan finnas hos specifikt sociala medier med oändliga flöden. Undersökningen pågick under två veckor och var uppdelad i en normalvecka och en vecka där studiedeltagarna inte fick använda sociala medier med oändliga flöden innan läggdags. De tre olika metoderna för att bedöma sömnkvalitet innefattade att studiedeltagarna varje morgon bedömde sin sömn på en femgradig skala, loggade sin sömn med hjälp av sömnanalysapplikationen Sleep Cycle varje natt och besvarade en enkät baserad på Pittsburgh Sleep Quality Index (PSQI) i slutet av varje vecka. Resultatet visade att användningen av sociala medier med oändliga flöden generellt sett endast var en liten andel av studiedeltagarnas totala användningen, och att det istället var videoapplikationer som användes mest extensivt innan läggdags. De tre metoderna indikerade på olika resultat. PSQI visade på att sömnkvaliteten blev bättre när sociala medier med oändliga flöden uteslöts. De dagliga bedömningarna visade inte på några större skillnader i sömnkvalitet mellan veckorna. Sleep Cycle visade å andra sidan att de flesta studiedeltagare hade en sämre sömnkvalitet den andra veckan. Studien tyder på att det är flera faktorer som påverkar sömnen vilket gör den komplicerad att undersöka. Dessutom har de faktorer som påverkar sömnen olika inverkan på demetoder som bedömer sömnkvalitet. Majoriteten av tidigare forskning kretsar kring självbedömningar och uppskattningar, något som i denna undersökning försökte kompletteras med hjälp av mer okonventionella metoder. De motsägande resultaten kan bland annat förklaras av metodernas tillförlitlighet och studiedeltagarnas oväntade vanor kring deras mobilanvändning. Utifrån resultatet väcktes frågan om att det inte är vilken typ av sociala medier som används, utan snarare hur dem används, som påverkar sömnkvaliteten. / Many young adults use social media before bed. The majority of social media have adopted “infinite scroll”, endless feeds that are designed to prolong the user’s sessions on the platform. Simultaneously, many young adults experience insufficient sleep. This study examined “how sleep quality in students is affected by the use of social media with infinite scroll before bed”. This was examined using three different methods of assessing sleep quality. Previous research in this field found connections between sleep disturbances and the usage of social media before bed. Therefore, this study examined if similar connections exist in specifically social media with infinite scroll. The study was conducted over a two week period and was split into one regular week and one week where social media with infinite scroll was unallowed before bed. The three different methods for assessing sleep quality consisted of the study participants evaluating their sleep on a five-point scale every morning, logging their sleep using the sleep analysis application Sleep Cycle every night, and answering a questionnaire based on the Pittsburgh Sleep Quality Index (PSQI) at the end of each week. The results show that there generally was no extensive usage of social media with infinite scroll among the study participants. Instead, the majority of study participants used video applications more before bed. The three different methods indicated contrasting results. PSQI showed that the sleep quality improved when social media with infinite scroll were excluded before bed. The daily assessments did not show any major differences in sleep quality between the weeks. Sleep Cycle, on the other hand, showed that most study participants experienced worse sleep quality in the second week. The study found that there are several factors affecting sleep which makes it complicated to examine. Additionally, the factors that affect sleep could have differentimpact on themethods that assess sleep quality. The majority of previous research was conducted using self- assessments and estimations, something that this study tried to complement with the use of unconventional methodology. The conflicting results can partly be explained by the reliability of the methods and the study participants' unexpected smartphone habits. Following the results, the question was raised whether it is the type of social media, or rather how social media is used, that impacts the sleep quality.

This essay is a product of our examination work on candidate level in Interaction Design. The aim in this project was to design a digital wallet integrated into a cellular phone and make it as an electronic payment tool. In our project the goal has been to create a digital wallet not just for payment, but also develop it into a complete digital wallet, replacing visa, membership card, student cards, id card and receipt. Our ambition is to take care of current qualities of today's wallet and improve where it is possible so that can be replaceable with the digital wallet.

Syftet med uppsatsen är att undersöka två olika designmönster gällande för utveckling av webbsidor och att utreda vilket av de två olika designmönstren som användare föredrar att navigera på och varför, även att ta reda på om användare föredrar att navigera webbsidor med surfplatta eller med PC. De två designmönster vilka granskas är infinite scroll och multi-page.Uppsatsen är baserad på artiklar och teorier. / The purpose of this paper is to investigate the two different designs paradigms regarding web development and to investigate which one of these two technologies that is the most preferable to use and navigate from an user perspective and why this technology is the most preferable. The two design patterns that are being examined are, infinite scroll and multi-page development of websites.

This thesis is devoted to the study of the dynamics of spiral and scroll waves in a mathematical model for cardiac tissue. We study the effects of the presence of heterogeneities on electrical-wave dynamics. The heterogeneities in the medium occur because of the variation in the electrophysiological properties of the constituent myocytes in the tissue, or because of the presence of cells like fibroblasts and pathological myocytes that can trigger early afterdepolarizations (EADs). We study how these heterogeneities can lead to the formation of spiral and scroll waves and how they can affect the stability of the spiral and scroll waves in cardiac tissue. We also investigate the role of abnormal cells, which can trigger pathological excitations like EADs, on the formation of spiral and scroll waves, and how such cells can trigger premature electrical pulses like premature-ventricular-complexes (PVCs) in cardiac tissue. Earlier studies have examined the role of ionic heterogeneities on spiral-wave initiation and their effects on spiral-wave stability. However, none of these studies has calculated, in a controlled way, the effects of individual ion-channel conductances on spiral- and scroll-wave properties, such as the frequency of these waves, and the effects of the spatial gradients, in each ion-channel conductance, on their stability; we present these results in Chapter 2. Although many studies in the past have studied the effects of fibroblast coupling on wave-dynamics in cardiac tissue, a detailed study of spiral-wave dynamics in a medium with a well-defined, heterogeneous distribution of fibroblasts (e.g., with a gradient in the fibroblast density (GFD)) has not been performed; therefore, in Chapter 3 we present the effects of such GFD on spiral- and scroll-wave dynamics. Then, in Chapter 4, we present a systematic study of how a clump of fibroblasts can lead to spiral waves via high-frequency pacing. Some studies in the past have studied the role of early afterdepolarizations (EADs) in the formation of arrhythmias in cardiac tissue; we build on such studies and present a detailed study of the effects of EADs on the formation of spiral waves and their dynamics, in Chapter 5. Finally, in Chapter 6 we provide the results of our detailed investigation of the factors that assist the triggering of abnormal electrical pulses like premature ventricular complexes by a cluster of EAD-capable cells. A brief summary of the chapters is provided below: Chapter 2: In this chapter we investigate the effects of spatial gradients in the ion-channel conductances of various ionic currents on spiral-and scroll-wave dynamics. Ionic heterogeneities in cardiac tissue arise from spatial variations in the electrophysiological properties of cells in the tissue. Such variations, which are known to be arrhythmogenic, can be induced by diseases like ischemia. It is important, therefore, to understand the effects of such ionic heterogeneities on electrical-wave dynamics in cardiac tissue. To investigate such effects systematically, of changing the ion-channel properties by modifying the conductances of each ionic currents, on the action-potential duration (APD) of a myocyte cell. We then study how these changes in the APD affect the spiral-wave frequency ω in two-dimensional tissue. We also show that changing the ion-channel conductance not only changes ω but also the meandering pattern of the spiral wave. We then study how spatial gradients in the ion-channel conductances affect the spiral-wave stability. We find that the presence of this ionic gradient induces a spatial variation of the local ω, which leads to an anisotropic reduction of the spiral wavelength in the low-ω region and, thereby, leads to a breakup of the spiral wave. We find that the degree of the spiral-wave stability depends on the magnitude of the spatial variation in ω, induced by the gradient in the ion-channel conductances. We observe that ω varies most drastically with the ion-channel conductance of rapid delayed rectifier K+ current GKr, and, hence, a spiral wave is most unstable in the presence of a gradient in GKr (as compared to other ion-channel conductances). By contrast, we find that ω varies least prominently with the conductances of the transient outward K+ current Gto and the fast inward Na+ current (GNa); hence, gradients in these conduc-tances are least likely to lead to spiral-wave breaks. We also investigate scroll-wave instability in an anatomically-realistic human-ventricular heart model with an ionic gradient along the apico-basal direction. Finally, we show that gradients in the ion-channel densities can also lead to spontaneous initiation of spiral waves when we pace the medium at high frequency. Chapter 3: In this chapter we study the effects of gradients in the density of fibroblasts on wave-dynamics in cardiac tissue. The existence of fibroblast-myocyte coupling can modulate electrical-wave dynamics in cardiac tissue. In diseased hearts, the distribution of fibroblasts is heterogeneous, so there can be gradients in the fibroblast density (henceforth we call this GFD) especially from highly injured regions, like infarcted or ischemic zones, to less-wounded regions of the tissue. Fibrotic hearts are known to be prone to arrhythmias, so it is important to understand the effects of GFD in the formation and sustenance of arrhythmic re-entrant waves, like spiral or scroll waves. Therefore, we investigate the effects of GFD on the stability of spiral and scroll waves of electrical activation in a state-of-the-art mathematical model for cardiac tissue in which we also include fibroblasts. By introducing GFD in controlled ways, we show that spiral and scroll waves can be unstable in the presence of GFDs because of regions with varying spiral or scroll-wave frequency ω, induced by the GFD. We examine the effects of the resting membrane potential of the fibroblast and the number of fibroblasts attached to the myocytes on the stability of these waves. Finally, we show that the presence of GFDs can lead to the formation of spiral waves at high-frequency pacing. Chapter 4: In this chapter we study the arrhythmogenic effects of lo-calized fibrobblast clumps. Localized heterogeneities, caused by the regional proliferation of fibroblasts, occur in mammalian hearts because of diseases like myocardial infarction. Such fibroblast clumps can become sources of pathological reentrant activities, e.g., spiral or scroll waves of electrical activation in cardiac tissue. The occurrence of reentry in cardiac tissue with heterogeneities, such as fibroblast clumps, can depend on the frequency at which the medium is paced. Therefore, it is important to study the reentry-initiating potential of such fibroblast clumps at different frequencies of pacing. We investigate the arrhythmogenic effects of fibroblast clumps at high- and low-frequency pacing. We find that reentrant waves are induced in the medium more prominently at high-frequency pacing than with low-frequency pacing. We also study the other factors that affect the potential of fibroblast clumps to induce reentry in cardiac tissue. In particular, we show that the ability of a fibroblast clump to induce reentry depends on the size of the clump, the distribution and percentage of fibroblasts in the clump, and the excitability of the medium. We study the process of reentry in two-dimensional and a three-dimensional mathematical models for cardiac tissue. Chapter 5: In this chapter we investigate the role of early afterdepolarizations (EADs) on the formation of spiral and scroll waves. Early after depolarizations, which are abnormal oscillations of the membrane poten-tial at the plateau phase of an action potential, are implicated in the de-velopment of cardiac arrhythmias like Torsade de Pointes. We carry out extensive numerical simulations of the TP06 and ORd mathematical models for human ventricular cells with EADs. We investigate the different regimes in both these models, namely, the parameter regimes where they exhibit (1) a normal action potential (AP) with no EADs, (2) an AP with EADs, and (3) an AP with EADs that does not go back to the resting potential. We also study the dependence of EADs on the rate of at which we pace a cell, with the specific goal of elucidating EADs that are induced by slow or fast rate pacing. In our simulations in two- and three-dimensional domains, in the presence of EADs, we find the following wave types: (A) waves driven by the fast sodium current and the L-type calcium current (Na-Ca-mediated waves); (B) waves driven only by the L-type calcium current (Ca-mediated waves); (C) phase waves, which are pseudo-travelling waves. Furthermore, we compare the wave patterns of the various wave-types (Na-Ca-mediated, Ca-mediated, and phase waves) in both these models. We find that the two models produce qualitatively similar results in terms of exhibiting Na-Ca- mediated wave patterns that are more chaotic than those for the Ca-mediated and phase waves. However, there are quantitative differences in the wave patterns of each wave type. The Na-Ca-mediated waves in the ORd model show short-lived spirals but the TP06 model does not. The TP06 model supports more Ca-mediated spirals than those in the ORd model, and the TP06 model exhibits more phase-wave patterns than does the ORd model. Chapter 6: In this chapter we study the role of EAD-capable cells, and fibroblasts on the trigerring of abnormal electrical pulses called premature ventricular complexes (PVCs). Premature ventricular complexes, which are abnormal impulse propagations in cardiac tissue, can develop because of various reasons including early afterdepolarizations (EADs). We show how a cluster of EAD-generating cells (EAD clump) can lead to PVCs in a model of cardiac tissue, and also investigate the factors that assist such clumps in triggering PVCs. In particular, we study, through computer simulations, the effects of the following factors on the PVC-triggering ability of an EAD clump: (1) the repolarization reserve (RR) of the EAD cells; (2) the size of the EAD clump; (3) the coupling strength between the EAD cells in the clump; and (4) the presence of fibroblasts in the EAD clump. We find that, although a low value of RR is necessary to generate EADs and hence PVCs, a very low value of RR leads to low-amplitude EAD oscillations that decay with time and do not lead to PVCs. We demonstrate that a certain threshold size of the EAD clump, or a reduction in the coupling strength between the EAD cells, in the clump, is required to trigger PVCs. We illustrate how randomly distributed inexcitable obstacles, which we use to model collagen deposits, affect PVC-triggering by an EAD clump. We show that the gap-junctional coupling of fibroblasts with myocytes can either assist or impede the PVC-triggering ability of an EAD clump, depending on the resting membrane potential of the fibroblasts and the coupling strength between the myocyte and fibroblasts. We also find that the triggering of PVCs by an EAD clump depends sensitively on factors like the pacing cycle length and the distribution pattern of the fibroblasts.