1,745 research outputs found

    Maximizing specific work output extracted from engine exhaust with novel inverted Brayton cycles over a large range of operating conditions

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    The heat contained in internal combustion engine exhaust gases can be converted into mechanical energy by using an Inverted Brayton Cycle (IBC). In this paper, five different IBC versions are numerically modeled and optimized to maximize their specific work output: (i) basic IBC, (ii) IBC with liquid water drainage (IBC/D), (iii) IBC with liquid water drainage and a steam turbine (IBC/D/S), (iv) IBC with liquid water drainage and a refrigeration cycle (IBC/D/R), and (v) IBC with liquid water drainage, a steam turbine and a refrigeration cycle (IBC/D/S/R). The three latter cycles are presented for the first time in literature. The optimization is performed for a wide range of inlet gases temperatures (600–1200 K) and heat sink temperatures (280–340 K). Among the five IBCs, the IBC/D/S/R has the highest specific work output for the whole range of operating temperatures. A comparison with the subcritical Rankine cycle and Organic Rankine Cycles using isobutane and benzene shows that an IBC system might be a better choice for specific operating temperatures. Liquid water addition in the IBC/D/S/R leads to optimized designs using only the steam turbine at high inlet gas temperatures, indicating that a Rankine cycle is better suited for these conditions

    Process optimization and revamping of combined-cycle heat and power plants integrated with thermal desalination processes

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    Optimal revamping, sizing, and operation of an existing gas-turbine combined-cycle dual-purpose power/desalination plant – simultaneous electricity and freshwater generation – which operates with a heat recovery steam generation with one-pressure level (1P-HRSG) and a multi-stage flash desalination process, is addressed. The sizes and configurations of the gas turbine and desalination unit are kept the same as in the existing plant through the study. However, the 1P-HRSG is conveniently extended to two- or three-pressure levels with different exchanger arrangements, including steam reheating. To this end, a superstructure-based representation of the HRSG simultaneously embedding several candidate structures was proposed and a mixed-integer nonlinear programming model was derived from it. One revamping case consisted in maximizing the ratio between the freshwater production rate and the heat transfer area of HRSG, keeping unchanged the electricity generation rate (around 73 MW). It was found that the inclusion of a 3P-HRSG resulted in an increase of 13.782 kg⋅s−1 in the freshwater production, requiring 22753 m2 of heat transfer area less in the HRSG. Another revamping case consisted in maximizing the profit, contemplating the possibility to sell extra amounts of electricity and freshwater. Sale prices, for which producing extra electricity and freshwater is beneficial, were determined.Fil: Manassaldi, Juan Ignacio. Universidad Tecnológica Nacional. Regional Rosario. Centro de Aplicaciones Informáticas y Modelado en Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Mussati, Miguel Ceferino. Universidad Tecnológica Nacional. Regional Rosario. Centro de Aplicaciones Informáticas y Modelado en Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo y Diseño. Universidad Tecnológica Nacional. Facultad Regional Santa Fe. Instituto de Desarrollo y Diseño; ArgentinaFil: Scenna, Nicolas Jose. Universidad Tecnológica Nacional. Regional Rosario. Centro de Aplicaciones Informáticas y Modelado en Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Morosuk, Tatiana. Technishe Universitat Berlin; AlemaniaFil: Mussati, Sergio Fabian. Universidad Tecnológica Nacional. Regional Rosario. Centro de Aplicaciones Informáticas y Modelado en Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo y Diseño. Universidad Tecnológica Nacional. Facultad Regional Santa Fe. Instituto de Desarrollo y Diseño; Argentin

    Spreadsheet of Dunlop Commission Testimonies and Reports

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    A complete listing of all documents related to the Commission on the Future of Worker-Management Relations (or Dunlop Commission) housed on Digital Commons. The spreadsheet is sortable by title, author, document type, and date. Links to each document are provided

    Maximizing power output of heat engines through design optimization : Geothermal power plants and novel exhaust heat recovery systems

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    Le design de machines thermiques menant à une puissance maximale dépend souvent des températures de la source chaude et de la source froide. C’est pourquoi dégager des lignes directrices à partir des designs optimaux de ces machines selon diverses températures d’opération peut faciliter leur conception. Une telle étude est proposée par cette thèse pour deux types de systèmes thermiques. En premier lieu, le cycle de Rankine organique (ORC) est un cycle thermodynamique de puissance utilisé entre autres dans les centrales géothermiques exploitant des réservoirs à basse température. Depuis quelques années, ce type de centrales suscite un vif intérêt à travers le monde, étant un des modes de production de puissance parmi les plus respectueux de l’environnement. Il s’agit de pomper un géofluide du sol pour transférer sa chaleur à un fluide de travail qui opère en cycle fermé, et de le réinjecter ensuite dans le bassin géologique. Les chercheurs tentent actuellement de mieux caractériser le potentiel géothermique de divers environnements géologiques. Le sous-sol du Québec est relativement froid, alors des études essaient de déterminer s’il serait possible d’y exploiter de manière rentable des centrales géothermiques. Une autre question de recherche importante est de savoir, pour un contexte donné, quel est le design optimal d’une centrale géothermique et quelle est la puissance que l’on peut espérer produire. Pour répondre à cette question, les cycles de Rankine organiques de base (de type souscritique ou transcritique) sont dans un premier temps simulés et optimisés pour des températures du géofluide de 80 à 180°C et pour des températures de condensation du fluide de travail de 0.1 à 50°C. Trente-six (36) fluides pures sont investigués pour toutes les combinaisons de températures. Par la suite, des cycles de Rankine organiques plus avancés sont aussi investigués (ajout d’une tour de refroidissement, d’un système de récupération, et d’une contrainte sur la température de réinjection du géofluide). Les ORCs avec deux pressions de chauffage souscritique et transcritique sont aussi simulés et optimisés. Les optimisations sont faites pour 20 fluides de travail selon la même plage de température du géofluide et selon des températures du thermomètre mouillé de l’air ambient de 10 à 32°C. En second lieu, le cycle de Brayton inversé (IBC) est un cycle thermodynamique qui pourrait être utilisé comme système de récupération de la chaleur perdue dans les gaz d’échappement de moteurs. Il s’agit d’un cycle ouvert comprenant dans sa configuration de base une turbine à gaz, un échangeur de chaleur et un compresseur. Il existe une configuration où l’eau qui se condense lors du refroidissement des gaz est évacuée avant le compresseur pour réduire le débit massique et améliorer le rendement global du système. Le Powertrain and Vehicle Research Centre (PVRC) de l’University of Bath s’est intéressé à savoir si certaines variantes de l’IBC découlant de cette configuration seraient des options viables. Ces variantes ont mené à la création de trois nouveaux cycles thermodynamiques couplant l’IBC avec (i) une turbine à vapeur, (ii) un cycle de réfrigération, et (iii) ces deux ajouts. En comptant les deux cycles déjà existants décrits au paragraphe précédent, cinq configurations de l’IBC sont simulées et optimisées pour des températures de gaz d’échappement de 600 à 1200 K et températures de la source froide de 280 à 340 K. La finalité de cette thèse est d’offrir un outil aidant les ingénieurs à concevoir les systèmes introduits précédemment (ORC et IBC) de sorte qu’ils aient un travail spécifique net maximisé. Sous forme d’un ensemble de diagrammes, cet outil peut ainsi être utilisé pour une large plage de température de la source chaude (géofluide ou gaz d’échappement) et de température de la source froide.Heat engines design leading to maximum power output often depends on the hot source temperature and the cold source temperature. This is why drawing guidelines from optimal designs of these machines according to diverse operating temperatures may facilitate their conception. Such a study is proposed by this thesis for two types of heat engines. In the first instance, the Organic Rankine Cycle (ORC) is a power thermodynamic cycle used among others in geothermal power plants exploiting low-temperature reservoirs. This type of power plants raises keen interest around the world for being one the most environmentally friendly power production modes. In these power plants, a geofluid is pumped from the ground to transfer its heat to a working fluid operating in a closed cycle. The geofluid is then reinjected in the geological basin. Researchers are currently attempting to characterize in a better way the geothermal potential of diverse geological environments. Considering the province of Québec’s relatively cold underground, studies try to determinate whether it is possible to profitably operate geothermal power plants. Another important research question is to determine, for a given context, the optimal geothermal power plant design, and the amount of power that could be generated. To answer this question, Organic Rankine Cycles (subcritical and transcritical) are first simulated and optimized for geofluid temperatures from 80 to 180°C and for condensing temperatures of the working fluid from 0.1 to 50°C. Thirty-six (36) pure fluids are investigated for each temperature combination. Next, cycles models are improved by adding a cooling tower, a recuperative system and a constraint on the minimum reinjection temperature. ORCs with dual-pressure heater are simulated and optimized as well. Optimization runs are performed considering 20 working fluids for the same range of geofluid temperature and for ambient air wet bulb temperature from 10 to 32°C. In the second instance, the Inverted Brayton Cycle (IBC) is a thermodynamic cycle that could be used as a waste heat recovery system for engines exhaust gases. This is an open cycle which includes a gas turbine, a heat exchanger and a compressor as a basic layout. There is a configuration where the water condensed during the cooling of the gases is evacuated upstream of the compressor in order to reduce the mass flow rate and improve the system global efficiency. The Powertrain and Vehicle Research Centre (PVRC) of the University of Bath is interested in finding out whether particular IBC variants arising from this configuration could be viable options. These variants led to the creation of three novel thermodynamic cycles that couple the IBC with (i) a steam turbine, (ii) a refrigeration cycle, and (iii) both additions. Including both already existing cycles described in the preceding paragraph, five IBC layouts are simulated and optimized for exhaust gases temperatures from 600 to 1200 K and for heat sink temperatures from 280 to 340 K. The purpose of this thesis is to offer a tool that help engineers designing the systems previously introduced (ORC and IBC), so that they produced a maximized specific work output. As a set of charts, this tool can be used for a large range of hot source temperature (geofluid or exhaust gases) and of heat sink temperature

    Coupled Chemical Pre-Oxidation and Aerobic Bioremediation of Buried MC252 Oil Across a Headlands Beach Profile

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    The release of MC252 crude oil following the Deepwater Horizon event has emphasized the need to investigate factors controlling the extent of contamination degradation in coastal environments. Dam structures created on Fourchon Beach, LA established conditions for PAH and n-alkane accumulation and burial along a vertical profile that persists today due to the anaerobic, often anoxic, and hypersaline conditions of the groundwater. The ability to remove the oxygen limitation present on in situ aerobic biodegradation of buried petroleum-based hydrocarbons in this environment was investigated through the coupled process of chemical oxidation and enhanced bioremediation using a proprietary formulation of activated persulfate and oxygen-release compound. To better understand the interactions of the chemical oxidant with the subsurface and to determine its compatibility with further bioremediation, bench and field-scale treatments were conducted in order to evaluate the efficacy the coupled process. Degradation of PAH and n-alkanes during field treatment were monitored in beach sediment and quantified through GC-MS. Results indicated that chemical oxidation with persulfate directly oxidized a differential portion of PAH and n-alkanes through a variety of non-specific reactions while satisfying a portion of the oxygen demand, indicated by sustained concentrations of dissolved oxygen following addition of oxygen-release compound. In spite of perturbations to groundwater, resilience of the microbial population was observed after the first phase of chemical oxidation, with a final increase in diversity as determined by next generation DNA sequencing. Laboratory studies were conducted to determine the oxygen demand exerted by buried crude oil and reduced chemical species before and after treatment and to further assess the extent of direct degradation from chemical oxidation. Results from this research can lead to an improved understanding of the limitations associated with applying aerobic bioremediation strategies for oil degradation in oxygen-limited environments

    Multi-objective optimization of organic Rankine cycle power plants using pure and mixed working fluids

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    For zeotropic mixtures, the temperature varies during phase change, which is opposed to the isothermal phase change of pure fluids. The use of such mixtures as working fluids in organic Rankine cycle power plants enables a minimization of the mean temperature difference of the heat exchangers, which is beneficial for cycle performance. On the other hand, larger heat transfer surface areas are typically required for evaporation and condensation when zeotropic mixtures are used as working fluids. In order to assess the feasibility of using zeotropic mixtures, it is, therefore, important to consider the additional costs of the heat exchangers. In this study, we aim at evaluating the economic feasibility of zeotropic mixtures compared to pure fluids. We carry out a multi-objective optimization of the net power output and the component costs for organic Rankine cycle power plants using low-temperature heat at 90 ◦C to produce electrical power at around 500 kW. The primary outcomes of the study are Pareto fronts, illustrating the power/cost relations for R32, R134a and R32/R134a (0.65/0.35mole). The results indicate that R32/R134a is the best of these fluids, with 3.4 % higher net power than R32 at the same total cost of 1200 k$

    Heat engines for waste heat utilization

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    Tato práce se zabývá tepelnými oběhy pro využití odpadního tepla a jejich srovnáním. V první části jsou popisovány jednotlivé tepelné oběhy, jejich základní modifikace a princip činnosti, jejich výhody a nevýhody a typické aplikace. Druhá část je věnována technickým parametrům, vytvoření idealizovaných modelů těchto oběhů na základě získaných dat. Je zde také provedeno jejich srovnání.This thesis deals with heat cycles for waste heat utilization and their comparison. The first part describes particular heat cycles, their basic modifications and working principle, their advantages and disadvantages and typical applications. The second part is dedicated to technical parameters and creating of idealized models of those cycles on the basis of gained data. The comparison of the cycles is also done.

    Mathematical Modelling of DNA Replication Reveals a Trade-off between Coherence of Origin Activation and Robustness against Rereplication

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    Eukaryotic genomes are duplicated from multiple replication origins exactly once per cell cycle. In Saccharomyces cerevisiae, a complex molecular network has been identified that governs the assembly of the replication machinery. Here we develop a mathematical model that links the dynamics of this network to its performance in terms of rate and coherence of origin activation events, number of activated origins, the resulting distribution of replicon sizes and robustness against DNA rereplication. To parameterize the model, we use measured protein expression data and systematically generate kinetic parameter sets by optimizing the coherence of origin firing. While randomly parameterized networks yield unrealistically slow kinetics of replication initiation, networks with optimized parameters account for the experimentally observed distribution of origin firing times. Efficient inhibition of DNA rereplication emerges as a constraint that limits the rate at which replication can be initiated. In addition to the separation between origin licensing and firing, a time delay between the activation of S phase cyclin-dependent kinase (S-Cdk) and the initiation of DNA replication is required for preventing rereplication. Our analysis suggests that distributive multisite phosphorylation of the S-Cdk targets Sld2 and Sld3 can generate both a robust time delay and contribute to switch-like, coherent activation of replication origins. The proposed catalytic function of the complex formed by Dpb11, Sld3 and Sld2 strongly enhances coherence and robustness of origin firing. The model rationalizes how experimentally observed inefficient replication from fewer origins is caused by premature activation of S-Cdk, while premature activity of the S-Cdk targets Sld2 and Sld3 results in DNA rereplication. Thus the model demonstrates how kinetic deregulation of the molecular network governing DNA replication may result in genomic instability

    Енергоінформаційна модель ORC

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    Рассмотрена энергоинформационная модель ORC, позволяющая определять статический и динамический КПД. Модель позволяет оптимизировать параметры ORC для достижения максимального значения КПД.Розглянуто енергоінформаційну модель ORC, що визначає статичний і динамічний ККД. Модель дозволяє оптимізувати параметри ORC для досягнення максимального значення ККД.We consider the model of energy – ORC, which allows to determine the static and dynamic efficiency. Model ORC optimizes settings to achieve maximum efficiency
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