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Gupta, Vishal. "Experimental investigations into rotary ultrasonic drilling of bones - an in vitro study." Thesis, IIT Delhi, 2017. http://localhost:8080/iit/handle/2074/7249.
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Bouzoukas, Asterios. "New approaches for cooling photovoltaic/thermal (PV/T) systems." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/11148/.
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Today the majority of UK's energy needs are met by fossil fuels. An energy sector that uses 30% of this energy and generates 28% of the total emissions is domestic sector. To reduce the emissions generated by fossil fuels UK government decided to increase the energy coming from renewable sources by 2020. A renewable energy that can contribute is solar energy. Solar thermal collectors and photovoltaics are two means of transforming solar energy to thermal and electrical energy. The limited space in the roofs and the cost of the technologies will prevent families to use both systems together in their roof A hybrid energy system combine the use of two or more alternative power sources will help to increase the system's total efficiency. The photovoltaic/thermal (PV/T) system is a hybrid structure that converts part of the sun's radiation to electricity and part to thermal energy. This research work focuses on the production of new approaches on hybrid PV/T systems. PV/T systems using water and air have been introduced and a literature review conducted in order to identify positives and negatives of these systems. Experiments also conducted by using water and air as heat transfer medium, and the results helped to work as a benchmark performance to the new approaches. These technologies were heat pipes, phase change materials and micro encapsulated phase change materials. The technologies exist for years but their use in the specific application is new. A literature review was undertaken to provide an understanding of these technologies and identified findings that have contributed to the design of the systems. Experimental work was carried out incorporating these technologies in the rear of a PV and the results indicated comparable performance with PV/T-water and PV/Tair. Five performance indicators were employed to help with the comparison of the systems. These were electrical and thermal efficiency, the total energy efficiency, the primary energy saving efficiency and the exergy efficiency. From these five indicators the primary energy saving efficiency that shows how much fossil fuel is saved and the exergy efficiency that could give the optimum working conditions of each system was the most valuable ratings. For the PV/PCM model a new simulation program was developed to help validate the experimental work. Also an environmental and economic study was undertaken to compare if the new systems could help reduce the C02 emissions and if they were feasible to become commercial products. Finally the conclusions gained have been presented and recommendations fo r future work have been made.
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McBee, Brian K. "Computational Approaches to Improving Room Heating and Cooling for Energy Efficiency in Buildings." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28911.
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With a nation-wide aim toward reducing operational energy costs in buildings, it is important to understand the dynamics of controlled heating, cooling, and air circulation of an individual room, the "One-Room Model Problem." By understanding how one most efficiently regulates a room's climate, one can use this knowledge to help develop overall best-practice power reduction strategies. A key toward effectively analyzing the "One-Room Model Problem" is to understand the capabilities and limitations of existing commercial tools designed for similar problems. In this thesis we develop methodology to link commercial Computational Fluid Dynamics (CFD) software COMSOL with standard computational mathematics software MATLAB, and design controllers that apply inlet airflow and heating or cooling to a room and investigate their effects. First, an appropriate continuum model, the Boussinesq System, is described within the framework of this problem. Next, abstract and weak formulations of the problem are described and tied to a Finite Element Method (FEM) approximation as implemented in the interface between COMSOL and MATLAB. A methodology is developed to design Linear Quadratic Regulator (LQR) controllers and associated functional gains in MATLAB which can be implemented in COMSOL. These "closed-loop" methods are then tested numerically in COMSOL and compared against "open-loop" and average state closed-loop controllers.Ph. D.
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Tauch, Jonas [Verfasser], and Matthias [Akademischer Betreuer] Weidemüller. "New approaches for cooling molecular anions to the Kelvin range / Jonas Tauch ; Betreuer: Matthias Weidemüller." Heidelberg : Universitätsbibliothek Heidelberg, 2021. http://d-nb.info/1236345460/34.
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Herrera, Santisbon Eunice. "Production-consumption system coordination by hybrid predictive approaches : application to a solar cooling system for buildings." Thesis, CentraleSupélec, 2015. http://www.theses.fr/2015SUPL0006/document.
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Garantir le confort thermique des bâtiments est directement lié à la consommation d'énergie. Dans les zones tropicales, les systèmes de refroidissement représentent l'un des postes les plus gourmands en énergie. Afin de réduire la consommation d'énergie mondiale, il est primordial d'améliorer l'efficacité de ces systèmes ou bien de développer de nouvelles méthodes de production de froid. Une installation de refroidissement solaire basé sur le cycle à absorption est une alternative pour réduire les émissions de gaz à effet de serre et la consommation d'électricité. Contrairement aux systèmes classiques de refroidissement à compression mécanique, la production de froid par absorption est un système complexe composé de plusieurs composants comme des panneaux solaires, un ballon de stockage, une tour de refroidissement et une machine à absorption. Outre le dimensionnement des composants, ce système complexe nécessite des actions de contrôle pour être efficace parce que la coordination entre le stockage d'eau chaude, la production et la consommation du froid est nécessaire. Le but de cette thèse est de proposer une structure producteur-consommateur d'énergie basée sur la commande prédictive (MPC). Le système de refroidissement par absorption solaire est considéré comme faisant partie de ce système de production-consommation d'énergie, le système de stockage d'eau chaude est le producteur et la machine à absorption qui distribue de l'eau froide au bâtiment est l'un des consommateurs. Pour que la structure de commande soit modulaire, la coordination entre les sous-systèmes est réalisée en utilisant une approche de partitionnement où des contrôleurs prédictifs locaux sont conçus pour chacun des sous-systèmes. Les contrôleurs des consommateurs calculent un ensemble de profils de demande d'énergie. Ces profils sont ensuite envoyés au contrôleur du producteur qui sélectionne le profil qui minimise le coût global. Dans une première partie, l'approche proposée est testée sur un modèle linéaire simplifié composé d'un producteur et plusieurs consommateurs. Dans une deuxième partie, un cas plus complexe est étudié. Un modèle simplifié d'un système de refroidissement à absorption est évaluée en utilisant l'outil de simulation TRNSYS. Le modèle de production n'est plus linéaire, il est décrit par un modèle non linéaire hybride qui augmente la complexité du problème d'optimisation. Les résultats des simulations montrent que la sous-optimalité induite par la méthode est faible. De plus, la performance de l'approche atteint les objectifs de commande tout en respectant les contraintesTo guarantee thermal comfort in buildings is directly related to energy consumption. In tropical climates, cooling systems for buildings represent one of the largest energy consumers. Therefore, as energy consumption is a major concern around the world, it is important to improve the systems efficiency or seeking new methods of cooling production. A solar cooling installation based on the absorption cycle is an alternative to mitigate greenhouse gas emissions and electricity consumption. In contrast to conventional vapor-compression based cooling systems, the absorption cooling production involves a complex system composed of several components as collector panel, storage tank, cooling tower and absorption chiller. Besides the sizing of the components, this complex system requires control actions to be efficient as a coordination between hot water storage, cooling water production and consumption is necessary. The aim of this research is to propose a management approach for a production-consumption energy system based on Model Predictive Control (MPC). The solar absorption cooling system is seen as part of this production-consumption energy system where the hot water storage system is the producer and the chiller-building system is one of the consumers. In order to provide modularity to the control structure, the coordination between the subsystems is achieved by using a partitioning approach where local predictive controllers are developed for each of the subsystems. The consumer controllers compute a set of energy demand profiles sent to the producer controller which selects the profile that better minimize the global optimization cost. In a first part, the proposed approach is tested on a simplified linear model composed of one producer and several consumers. In a second part, a more complex case is studied. A simplified model of an absorption cooling system is evaluated using the simulation tool TRNSYS. The producer model is no longer linear, instead it is described by a nonlinear hybrid model which increases the complexity of the optimization problem. The simulations results show that the suboptimality induced by the method is low and the control strategy fulfills the objectives and constraints while giving good performances
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Landi, Daniele. "Knowledge-based approaches to support the design and development of the electrochemical storage systems." Doctoral thesis, Università Politecnica delle Marche, 2014. http://hdl.handle.net/11566/242838.
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L’esigenza di abbreviare il cosiddetto “time-to-market” è prerogativa di tutte le imprese che operano nei vari settori industriali, al fine di ritagliarsi una vantaggiosa posizione nel mercato, nei confronti dei concorrenti.
Il processo di progettazione si è concentrato principalmente sulla riduzione dei costi, diminuendo i tempi di produzione, senza diminuire la qualità del prodotto. Al giorno d'oggi anche gli aspetti ambientali ricoprono un ruolo fondamentale e rappresentano un fattore importante per il successo sul mercato dei prodotti, infatti, tra i consumatori si sta sviluppando una sensibilità ambientale sempre crescente. Da queste considerazioni viene alla luce l’esigenza di studiare e sviluppare un approccio basato sulla conoscenza in grado di assistere i progettisti durante tutta la vita del prodotto, analizzando gli aspetti legati alle prestazioni, ai costi ed agli aspetti ambientali.
Di conseguenza una delle problematiche più importanti è quella di riuscire a diminuire i costi e i tempi di passaggio tra idea e lancio sul mercato; avere perciò a disposizione delle tecnologie, in grado di prevedere i comportamenti reali dei vari sistemi, determina un notevole vantaggio in termini economici ed organizzativi.
Le aziende di successo sono quelle in grado di migliorare le risorse umane e che hanno creato condizioni particolari in grado di far evolvere e sviluppare le conoscenze e know-how. Queste considerazioni sono sempre più necessarie quando si considera l'evoluzione dell'economia occidentale, in cui, ci troviamo di fronte a dover produrre prodotti personalizzati di elevata quantità.
La sfida per le imprese di ingegneria italiana è quello di vendere prodotti di qualità continuando a sviluppare soluzioni innovative in modo rapido, e mantenendo bassi i costi. Per poter rispondere a questa sfida le aziende devono investire sempre di più nel processo di progettazione al fine di garantire il futuro della stessa società con strategie dedicate per l'innovazione e la tecnologia.Gli obiettivi di questo lavoro possono essere sintetizzati come la definizione di un nuovo approccio di progettazione, basato sulla conoscenza in grado di fornire nuovi strumenti per l’analisi e le valutazioni delle prestazioni dei prodotti in differenti scenari applicativi.
Il lavoro svolto si sofferma sull’analisi dei sistemi di accumulo di ultima generazione costituiti da batterie agli ioni litio utilizzate sia nell’ambito dell’autotrazione che in applicazioni stazionarie. È comunque possibile applicare la metodologia di lavoro descritta anche ad altri casi applicativi. Per quanto riguarda la progettazione di pacchi batteria, il lavoro svolto rappresenta un primo passo per la definizione e progettazione dei sistemi di accumulo agli ioni di litio. In particolare, all’interno di questa tesi di ricerca è stato analizzato lo stato dell’arte dei principali sistemi di accumulo, soffermando l’attenzione sulla tecnologia al litio e dei loro principali problemi di utilizzo. Una profonda analisi è stata effettuata per la determinazione del calore generato dalle singole batterie al litio durante il loro funzionamento. I risultati della ricerca sono stati applicati a piccole produzioni personalizzate, sia di veicoli elettrici, sia di sistemi di accumulo per abitazioni.The need to shorten the "time-to-market" is the prerogative of all companies that operate in different industry sectors, in order to carve out a profitable position in the market against competitors. The design process has focused primarily on reducing costs, reducing production times, without decreasing the quality of the product. Nowadays also the environmental aspects play a key role and is an important factor for the success of the products on the market , in fact, a growing environmental awareness is developing among consumers . From these considerations it comes to light the need to study and develop a knowledge-based approach able to assist designers during the lifetime of the product , analyzing the aspects related to performance, cost and environmental aspects. Therefore one of the most important problems is to be able to decrease the cost and time of passage between idea and market launch; therefore have available technologies, able to predict the actual behavior of the various systems, determines a considerable advantage in terms of economic and organizational links. Successful companies are those that can improve human resources and having created special conditions able to evolve and develop the knowledge and know-how. These considerations are becoming more necessary when we consider the evolution of the western economy, in which we find ourselves faced with having to produce high quantities of customized products. The challenge for Italian engineering companies is to sell quality products while continuing to develop innovative solutions quickly, and keeping costs low . To meet this challenge, companies need to invest more and more in the design process to ensure the future of the company with dedicated strategies for innovation and technology. The objectives of this work can be summarized as the definition of a new design approach , based on knowledge which can provide new tools for the analysis and assessment of the performance of products in different application scenarios. The work focuses on the analysis of next generation storage systems consisting of lithium-ion batteries used both in automotive and stationary applications . You can still apply the methodology described also working with other application cases . With regard tothe design of battery packs , the work represents a first step in the definition and design of the lithium-ion storage systems battery . In particular , within this thesis the state of the main storage systems has been analyzed , our attention is on lithium-ion technology and their main usage problems . A deep analysis was performed for the determination of the heat generated by the individual lithium batteries during their operation . The research results have been applied to small-scale production customization, both of electric vehicles, and energy storage systems for homes.
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Sosa, Pieroni Jhosmar L. "Estimation of water footprints and review of water-saving/recovery approaches in coal-fired power plants' cooling systems." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367938141.
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Hasan, M. Mahmudul. "Investigation of energy efficient approaches for the energy performance improvement of commercial buildings." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/61050/1/M._Hasan_Thesis.pdf.
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Energy efficiency of buildings is attracting significant attention from the research community as the world is moving towards sustainable buildings design. Energy efficient approaches are measures or ways to improve the energy performance and energy efficiency of buildings. This study surveyed various energy-efficient approaches for commercial building and identifies Envelope Thermal Transfer Value (ETTV) and Green applications (Living wall, Green facade and Green roof) as most important and effective methods. An in-depth investigation was carried out on these energy-efficient approaches. It has been found that no ETTV model has been developed for sub-tropical climate of Australia. Moreover, existing ETTV equations developed for other countries do not take roof heat gain into consideration. Furthermore, the relationship of ETTV and different Green applications have not been investigated extensively in any literature, and the energy performance of commercial buildings in the presence of Living wall, Green facade and Green roof has not been investigated in the sub-tropical climate of Australia. The study has been conducted in two phases. First, the study develops the new formulation, coefficient and bench mark value of ETTV in the presence of external shading devices. In the new formulation, roof heat gain has been included in the integrated heat gain model made of ETTV. In the 2nd stage, the study presents the relationship of thermal and energy performance of (a) Living wall and ETTV (b) Green facade and ETTV (c) Combination of Living wall, Green facade and ETTV (d) Combination of Living wall, Green Roof and ETTV in new formulations. Finally, the study demonstrates the amount of energy that can be saved annually from different combinations of Green applications, i.e., Living wall, Green facade; combination of Living wall and Green facade; combination of Living wall and Green roof. The estimations are supported by experimental values obtained from extensive experiments of Living walls and Green roofs.
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Blake, Tony. "A quantum approach to cavity mediated laser cooling." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/2167/.
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Cavity-mediated cooling has the potential to become one of the most efficient techniques to cool molecular species down to very low temperatures. This thesis studies the use of rate equations to analyse the cooling process in such systems. In particular the master equation is used to find rate equations that can determine the rate of change of phonons in the system. The general idea behind cavity cooling is the continuous conversion of phonons into cavity photons. While there is no spontaneous emission and decay rate associated with the concept of phonons, photons are created after a change in the phonon number has occurred and can then leak out through the cavity mirrors easily. Hence the conversion of phonons into photons can result in the constant removal of phonon energy from the system. In this thesis we compare cavity mediated cooling with single particle laser cooling. It is shown that cavity cooling is essentially the same as ordinary laser cooling. This is done by calculating the stationary state phonon number mss and the cooling rate y as a function of the system parameters. For example, when the trap phonon frequency υ is either much larger or much smaller than the cavity decay rate k , the minimum stationary state phonon number scales as k²/16v² (strong confinement regime) and as k/4 (weak confinement regime), respectively. Replacing k with Ѓ yields the steady states associated with ordinary laser cooling.
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McGinley, Susan. "Cooling Cows: A Metabolic Approach to Managing Heat Stress." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2007. http://hdl.handle.net/10150/622131.
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Luque, Martínez Salvador G. "A fully-integrated approach to gas turbine cooling system research." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558543.
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A novel experimental facility for the testing of modern high pressure nozzle guide vanes, the Annular Sector Heat Transfer Facility, is described in this thesis. Non- dimensionally similar conditions to a thermal paint test are reproduced, in a warm flow field, by the use of actual engine hardware, contoured sidewalls, and an innova- tive system of deswirl vanes in a five-passage annular sector cascade. External Mach and Reynolds numbers, inlet turbulence intensity, and coolant-to-mainstream pres- sure ratio are all matched to engine conditions. The test vanes are heavily cooled both internally (by convection and impingement) and externally (by film cooling). Detailed aerodynamic measurements are discussed, which demonstrate that a peri- odic, transonic, and highly engine-realistic flow is established in the cascade. High resolution full coverage maps of overall cooling effectiveness are presented, acquired on the vane surfaces at steady state conditions by wide-band liquid crys- tals and infrared thermography. Experimental measurements are then scaled to en- gine conditions by a new theoretical procedure, argued from first principles, which extends the principle of superposition to fully-cooled compressible flows. A newly- defined recovery temperature is proposed, which accounts for the redistribution of heat between the internal and external vane flows in a fully-integrated manner. This technique makes the results analogous to those of a thermal paint test, but allows for fundamental research and early and inexpensive cooling system validation. Overall cooling effectiveness measurements are complemented by those of the re- quired cooling flow capacity to achieve them, conducted in a second test rig commis- sioned during this research: the Flow Testing Facility. To conclude, the approach developed is applied to the global thermal assessment of the dendritic geometry, an innovative turbine cooling system. Experimental results show promising benefits over the baseline vane, especially in regions of low coolant-to-mainstream pressure margin.
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Maletzke, Fabian. "Investigation Of The Influence Of Geometrical Parameters On Heat Transfer In Matrix Cooling : A Computational Fluid Dynamics Approach." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-177185.
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Modern gas turbine blades and vanes are operated at temperatures above their material’s melting point. Active external and internal cooling are therefore necessary to reach acceptable lifetimes. One possible internal cooling method is called matrix cooling, where a matrix of intersecting cooling air channels is integrated into a blade or vane. To further increase the efficiency of gas turbines, the amount of cooling air must be reduced. Therefore it is necessary that heat transfer inside a cooling matrix is well understood. In the first part of the thesis, a methodology for estimating heat transfer in the flow of matrix cooling channels was established using Computational Fluid Dynamics. Two four-equation RANS turbulence models based on the k-ε turbulence model showed a good correlation with experimental results, while the k-ω SST model underpredicted the heat transfer significantly. For all turbulence models, the heat transfer showed high sensitivity towards changes in the numerical setup. For the k-ω SST turbulence model, the mesh requirements were deemed too computationally expensive and it was excluded from further investigations. As the second part of the thesis, a parameter study was conducted investigating the influence of several geometric parameters on the heat transfer in a cooling matrix. The matrix was simplified as a channel flow interacting with multiple crossing flows. The highest enhancement in heat transfer was seen with changes in taper ratio, aspect ratio and matrix angle. Compared to smooth pipe flow, an increase in heat transfer of up to 60% was observed. Rounded edges of the cooling channels showed a significant influence on the heat transfer as well. In contrast, no influence of the wall thickness on the heat transfer was observed. While no direct validation is possible, the base case and the parameter sweeps show a good correlation with similar cases found in the literature.
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Leung, Ming. "A novel approach to determine building occupancy for cooling energy consumption prediction." Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/17403/.
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Building cooling load prediction is one of the key elements in the energy conservation achievements. Most of the mathematical models using in the industry nowadays include forward and inverse modeling approaches. However, these models consume much computer resources and require a longer computational time. Multi-layer perceptron (MLP) model of artificial neural network (ANN) is adopted in this thesis. The model is widely used in engineering approaches that render good performance in adaptability, nonlinearity and mapping. It also has good ability in predicting the cooling energy consumption of buildings. It is reported that the occupants’ activities inside the buildings can have significant impact on the accuracy of the model. The existing input parameters used for the ANN models could not represent the complexity of the activities inside the buildings well. Most of the traditional ANN models adopted fixed profile or historic load data to represent building occupancy in simulating building cooling energy consumption. However, building occupancy is never still. The dynamic changes occurred in the occupancy of the buildings therefore make the forecasting of building cooling load difficult and less accurate. This thesis aims at (i) introducing a novel model to represent occupants’ presence and activities; and (ii) investigating the effect of using the novel model on improving the predictive accuracy of building cooling energy consumption. The simulation results demonstrate that building occupancy data play a significant role in building cooling energy consumption prediction and the use of the novel approach significantly improves the predictive accuracy of building cooling energy consumption model.
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Jack, William Josiah. "A Six Sigma Approach to Implementing Conformal Cooling on Existing Processes in Injection Molding." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2214.
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Injection molding is one of the most common methods of mass production. After injecting molten plastic into a mold, the heat must leave the plastic material, enter the mold steel, enter the coolant, and exit the mold. This heat flow is critical to producing high quality parts rapidly. As plastic cools, the plastic shrinks. Uneven cooling causes uneven shrinkage which can cause the part to warp from the resulting internal stresses or create sink marks on the part. Thus the effect of uneven cooling is lower part quality, both in appearance and in dimension. Standard or conventional cooling channels are straight-drilled holes arranged such that they intersect and connect to form a loop for coolant, typically water, to flow through. This allows the mold to act as a heat exchanger, transferring heat to the coolant and carrying heated coolant away from the mold. While standard cooling channels have been used widely in the injection molding industry for their manufacturability and proven results, other methods have been developed for creating molds with cooling channels of any desired path or shape. These channels, called conformal due to how they conform to the shape of the part, provide uniform cooling, eliminate or reduce the quality issues of warpage and shrinkage, and provide faster, more economical cycle times. Conformal cooling is cannot be produced only by subtractive manufacturing methods that remove material from raw stock but rather through additive or hybrid manufacturing techniques that add material in layers of powder, sections, or sheets. Bonded sheet layer mold inserts can be made of any size and are currently the only feasible way of making large, conformally-cooled molds. Presented is a Six Sigma approach for implementing conformal cooling in existing molds to achieve the benefits of higher part quality and fast cycle times. Feasibility considerations include existing mold features such as slides and ejectors, choice of channel diameter, and the cooling channel path. Cost justification considerations include assessing part quality cost impact through calculation of the costs of poor quality and assessing machine capacity as relates to cycle time. With the approach presented, an injection molding company should be able to assess feasibility and cost effectiveness of implementing conformal cooling on its molds.
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Chinraj, Venkatesh Kumar. "Sustainability evaluation of seasonal snow storage for building cooling systems : a life cycle approach." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55194.
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In Canada, the residential building sector consumes 17% of the total energy and contributes 15% of the total GHG emissions. Predominantly, the energy demand for cooling in the residential sector is increasing due to large occupancy floor area and high usage of air-conditioning. Minimizing energy use and GHG emissions is one of the highest priority goals set for national energy management strategies in developed countries including Canada. In this research, a sustainability assessment framework is developed to evaluate the techno-economic and environmental performance of different building cooling systems, namely conventional snow storage system, watertight snow storage system, high-density snow storage system, and the conventional chiller cooling system. The framework is implemented in a low-rise residential building in Kelowna (BC, Canada) to appraise its practicality. The Life cycle assessment (LCA) approach is used to assess the environmental impacts of different building cooling systems. LCA results revealed that the systems have varying energy requirements and associated environmental impacts during the different life cycle phases (extraction and construction, utilization, and end of life). The annual cooling energy demands for different cooling systems are also estimated. The LCA is carried out using SimaPro 8.1 software and the TRACI 2.1 method. Multi-criteria decision analysis is employed using the ‘Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE-II)’ to evaluate the sustainability of different cooling systems over their life cycle. The results showed that the snow storage systems tend to reduce the greenhouse gas emissions and associated environmental impacts more than the conventional cooling system. A probabilistic feasibility evaluation tool is developed to evaluate the techno-economic performance of different cooling systems. The incremental economic performance of alternatives is estimated in terms of the total cooling cost per kWh at the facility. Monte-Carlo simulation was performed to consider the uncertainty factors involved in the techno-economic parameters of cooling systems. Results of this analysis verified that the snow storage systems are more energy efficient and low-cost options for building cooling systems. The developed frameworks will support decision-makers in evaluating the sustainability of building cooling systems. Moreover, socio-economic benefits, i.e. improving affordability, equity, and enhancing energy sustainability, could be achieved.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Kamali, Aslan. "Developing a Decision Making Approach for District Cooling Systems Design using Multi-objective Optimization." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-208228.
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Energy consumption rates have been dramatically increasing on a global scale within the last few decades. A significant role in this increase is subjected by the recent high temperature levels especially at summer time which caused a rapid increase in the air conditioning demands. Such phenomena can be clearly observed in developing countries, especially those in hot climate regions, where people depend mainly on conventional air conditioning systems. These systems often show poor performance and thus negatively impact the environment which in turn contributes to global warming phenomena. In recent years, the demand for urban or district cooling technologies and networks has been increasing significantly as an alternative to conventional systems due to their higher efficiency and improved ecological impact. However, to obtain an efficient design for district cooling systems is a complex task that requires considering a wide range of cooling technologies, various network layout configuration possibilities, and several energy resources to be integrated. Thus, critical decisions have to be made regarding a variety of opportunities, options and technologies. The main objective of this thesis is to develop a tool to obtain preliminary design configurations and operation patterns for district cooling energy systems by performing roughly detailed optimizations and further, to introduce a decision-making approach to help decision makers in evaluating the economic aspects and environmental performance of urban cooling systems at an early design stage. Different aspects of the subject have been investigated in the literature by several researchers. A brief survey of the state of the art was carried out and revealed that mathematical programming models were the most common and successful technique for configuring and designing cooling systems for urban areas. As an outcome of the survey, multi objective optimization models were decided to be utilized to support the decision-making process. Hence, a multi objective optimization model has been developed to address the complicated issue of decision-making when designing a cooling system for an urban area or district. The model aims to optimize several elements of a cooling system such as: cooling network, cooling technologies, capacity and location of system equipment. In addition, various energy resources have been taken into consideration as well as different solar technologies such as: trough solar concentrators, vacuum solar collectors and PV panels. The model was developed based on the mixed integer linear programming method (MILP) and implemented using GAMS language. Two case studies were investigated using the developed model. The first case study consists of seven buildings representing a residential district while the second case study was a university campus district dominated by non-residential buildings. The study was carried out for several groups of scenarios investigating certain design parameters and operation conditions such as: Available area, production plant location, cold storage location constraints, piping prices, investment cost, constant and variable electricity tariffs, solar energy integration policy, waste heat availability, load shifting strategies, and the effect of outdoor temperature in hot regions on the district cooling system performance. The investigation consisted of three stages, with total annual cost and CO2 emissions being the first and second single objective optimization stages. The third stage was a multi objective optimization combining the earlier two single objectives. Later on, non-dominated solutions, i.e. Pareto solutions, were generated by obtaining several multi objective optimization scenarios based on the decision-makers’ preferences. Eventually, a decision-making approach was developed to help decision-makers in selecting a specific solution that best fits the designers’ or decision makers’ desires, based on the difference between the Utopia and Nadir values, i.e. total annual cost and CO2 emissions obtained at the single optimization stagesDie Energieverbrauchsraten haben in den letzten Jahrzehnten auf globaler Ebene dramatisch zugenommen. Diese Erhöhung ist zu einem großen Teil in den jüngst hohen Temperaturniveaus, vor allem in der Sommerzeit, begründet, die einen starken Anstieg der Nachfrage nach Klimaanlagen verursachen. Solche Ereignisse sind deutlich in Entwicklungsländern zu beobachten, vor allem in heißen Klimaregionen, wo Menschen vor allem konventionelle Klimaanlagensysteme benutzen. Diese Systeme verfügen meist über eine ineffiziente Leistungsfähigkeit und wirken sich somit negativ auf die Umwelt aus, was wiederum zur globalen Erwärmung beiträgt. In den letzten Jahren ist die Nachfrage nach Stadt- oder Fernkältetechnologien und -Netzwerken als Alternative zu konventionellen Systemen aufgrund ihrer höheren Effizienz und besseren ökologischen Verträglichkeit satrk gestiegen. Ein effizientes Design für Fernkühlsysteme zu erhalten, ist allerdings eine komplexe Aufgabe, die die Integration einer breite Palette von Kühltechnologien, verschiedener Konfigurationsmöglichkeiten von Netzwerk-Layouts und unterschiedlicher Energiequellen erfordert. Hierfür ist das Treffen kritischer Entscheidungen hinsichtlich einer Vielzahl von Möglichkeiten, Optionen und Technologien unabdingbar. Das Hauptziel dieser Arbeit ist es, ein Werkzeug zu entwickeln, das vorläufige Design-Konfigurationen und Betriebsmuster für Fernkälteenergiesysteme liefert, indem aureichend detaillierte Optimierungen durchgeführt werden. Zudem soll auch ein Ansatz zur Entscheidungsfindung vorgestellt werden, der Entscheidungsträger in einem frühen Planungsstadium bei der Bewertung städtischer Kühlungssysteme hinsichtlich der wirtschaftlichen Aspekte und Umweltleistung unterstützen soll. Unterschiedliche Aspekte dieser Problemstellung wurden in der Literatur von verschiedenen Forschern untersucht. Eine kurze Analyse des derzeitigen Stands der Technik ergab, dass mathematische Programmiermodelle die am weitesten verbreitete und erfolgreichste Methode für die Konfiguration und Gestaltung von Kühlsystemen für städtische Gebiete sind. Ein weiteres Ergebnis der Analyse war die Festlegung von Mehrzieloptimierungs-Modelles für die Unterstützung des Entscheidungsprozesses. Darauf basierend wurde im Rahmen der vorliegenden Arbeit ein Mehrzieloptimierungs-Modell für die Lösung des komplexen Entscheidungsfindungsprozesses bei der Gestaltung eines Kühlsystems für ein Stadtgebiet oder einen Bezirk entwickelt. Das Modell zielt darauf ab, mehrere Elemente des Kühlsystems zu optimieren, wie beispielsweise Kühlnetzwerke, Kühltechnologien sowie Kapazität und Lage der Systemtechnik. Zusätzlich werden verschiedene Energiequellen, auch solare wie Solarkonzentratoren, Vakuum-Solarkollektoren und PV-Module, berücksichtigt. Das Modell wurde auf Basis der gemischt-ganzzahlig linearen Optimierung (MILP) entwickelt und in GAMS Sprache implementiert. Zwei Fallstudien wurden mit dem entwickelten Modell untersucht. Die erste Fallstudie besteht aus sieben Gebäuden, die ein Wohnviertel darstellen, während die zweite Fallstudie einen Universitätscampus dominiert von Nichtwohngebäuden repräsentiert. Die Untersuchung wurde für mehrere Gruppen von Szenarien durchgeführt, wobei bestimmte Designparameter und Betriebsbedingungen überprüft werden, wie zum Beispiel die zur Verfügung stehende Fläche, Lage der Kühlanlage, örtliche Restriktionen der Kältespeicherung, Rohrpreise, Investitionskosten, konstante und variable Stromtarife, Strategie zur Einbindung der Solarenergie, Verfügbarkeit von Abwärme, Strategien der Lastenverschiebung, und die Wirkung der Außentemperatur in heißen Regionen auf die Leistung des Kühlsystems. Die Untersuchung bestand aus drei Stufen, wobei die jährlichen Gesamtkosten und die CO2-Emissionen die erste und zweite Einzelzieloptimierungsstufe darstellen. Die dritte Stufe war ein Pareto-Optimierung, die die beiden ersten Ziele kombiniert. Im Anschluss wurden nicht-dominante Lösungen, also Pareto-Lösungen, erzeugt, indem mehrere Pareto-Optimierungs-Szenarien basierend auf den Präferenzen der Entscheidungsträger abgebildet wurden. Schließlich wurde ein Ansatz zur Entscheidungsfindung entwickelt, um Entscheidungsträger bei der Auswahl einer bestimmten Lösung zu unterstützen, die am besten den Präferenzen des Planers oder des Entscheidungsträgers enstpricht, basierend auf der Differenz der Utopia und Nadir Werte, d.h. der jährlichen Gesamtkosten und CO2-Emissionen, die Ergebnis der einzelnen Optimierungsstufen sind
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Wilde, Daniel G. "Validation of a CFD Approach for Gas Turbine Internal Cooling Passage Heat Transfer Prediction." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1384.
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This report describes the development and application of a validated Computational Fluid Dynamics (CFD) modelling approach for internal cooling passages in rotating turbomachinery. A CFD Modelling approach and accompanying assumptions are tuned and validated against academically available experimental results for various serpentine passages. Criteria of the CFD modelling approach selected for investigation into advanced internal cooling flows include accuracy, robustness, industry familiarity, and computational cost.
Experimental data from NASA HOST (HOt Section Technology), Texas A&M, and University of Manchester tests are compared to RANS CFD results generated using Fluent v14.5 in order to benchmark a CFD modelling approach.
Capability of various turbulence models in the representation of cooling physics is evaluated against experimental data. Model sensitivity to boundary conditions and mesh density is also evaluated.
The development of a validated computational model of internal turbine cooling channels with bounded error allows for the identification of particular shortcomings of heat transfer correlations and provides a baseline for future CFD based exploration of internal turbine cooling concepts.
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Moodley, Anand. "Development of a unified mass and heat integration framework for sustainable design an automated approach /." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-04222008-094925/.
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Lind, Malin, and Karl Johan Josefsson. "A CFD Method for Simulation of Gas-Liquid Flow in Cooling Systems : An Eulerian-Eulerian Approach." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129372.
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When designing modern engines it is important to construct a cooling system that cools the engine structure efficiently. Within the cooling system there is always a certain amount of air which can accumulate and form air pockets in critical areas, such as the water jacket, which can lead to wall degradation. A Computational Fluid Dynamics (CFD) method in STAR-CCM+ from CD-adapco, was derived at Volvo Cars in order to study the accumulation of air bubbles in the water jacket. The method was derived by investigating and evaluating already existing methods. The method initially considered as the best suited was the Eulerian-Eulerian approach. The method was validated against three simpler geometries where experimental data was available. The Eulerian-Eulerian approach treats both phases, liquid and gas, as continuous phases. The idea with the method is to solve the Navier-Stokes equation, the continuity equation and the energy equation for both phases using the Eulerian approach, therefore called Eulerian-Eulerian. The interaction between the two phases was important to model properly which was done by including several interaction models within STAR-CCM+. By tuning different coefficients, which were investigated by a thorough parameter study, the method resembled the experimental data in a satisfying way. The best suited mesh for these simpler geometries was a directed mesh. However, the mesh in the water jacket was automatically generated by STAR-CCM+ and the simpler cases were therefore validated with an automated mesh as well. To capture the experimental data the convection scheme for volume fraction had to be of second order when simulating with automated mesh. This resulted in convergence issues when implementing the method on the water jacket. Instead first order convection scheme, which did not present as satisfying results as second order, had to be implemented. Simulations of the water jacket were performed with two different velocities, that were 10 m/s and 19 m/s, and different flow split ratios for the three outlets. Air with volume fraction 0.1 was injected at the inlet during the first 0.5 s followed by 0.5-1.1 s of further simulation without injecting air. Increased velocity resulted in increased flow through of gas, whereas no big difference could be seen between the different outlet flow split ratios. At two different zones lower pressure was found which resulted in gas holdup. To be able to validate the results from the water jacket, experiments would be necessary to perform in order to provide experimental data for comparison. Velocity profiles from the derived two-phase method resemble the velocity profiles from the one-phase simulation from Volvo, which indicated that the two-phase method did not affect the solution in a remarkable way. Granted that the zones of lower pressure and gas holdup normally coincides, the pressure field from the one-phase simulation could be directly studied, which would lower the computational costs significantly.
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Tan, Zhi Bin. "Post-Welding Cooling Rate in TCW Joints: An Experimental and Numerical Approach to Understand its Effects." Thesis, The University of Sydney, 2019. https://hdl.handle.net/2123/21889.
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Thermoset Composite Welding (TCW) is a patented technology developed by CRC-ACS that can be used to build structural aircraft assemblies, potentially with a significant cost savings compared to the conventional methods. In TCW, a thermoset prepreg layup is surfaced with an integrated layer of thermoplastic before being welded together to form a welded assembly. As PVDF is a semi-crystalline polymer, its mechanical performance can be affected by post-welding cooling rate. This investigation focused on TCW joints treated with different cooling rates while FEA was used to complement the experimental section by providing strength predictions. Single lap joint was chosen as the main specimen type for its simplicity in manufacturing. Joints with different laminate configurations were tested in a variety of temperatures to study the effect of temperature on joint strength. Across all lay-ups and temperatures, a clear trend emerges where specimens with slower rate produced joints with higher strength. Investigation using DSC and SEM revealed that while percentage of crystallinity between slow and fast cooling rate are relatively similar, the observed spherulite size between two cooling rates are quite different. This indicates that slower cooling rate allows the crystallites to form slowly and grow to a larger size, which strengthen the PVDF material. In a novel approach to study TCW joints from the fracture perspective, a moment loading methodology was adopted and implemented with a custom designed rig to load the DCB specimen using pure equal moment on both sides to simulate a Mode I fracture. The measured G_IC value portrayed a similar picture with the strength-based test where slowly cooled specimen exhibits higher fracture toughness. It is worth noting that the rig design allows specimens to be tested in a mixed-mode configuration, which can be expanded in future work.
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Remella, Siva Rama Karthik. "Steady State Mathematical Modeling of Non-Conventional Loop Heat Pipes: A Parametric and a Design Approach." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353154991.
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Webbeer-Youngman, Ronald Clifford William. "An integrated approach towards the optimization of ventilation, air cooling and pumping requirements for hot mines / R.C.W. Webber-Youngman." Thesis, North-West University, 2005. http://hdl.handle.net/10394/467.
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This thesis contends that optimization of energy resources through active control and
predictive simulation modelling is possible, and that such monitoring l e d to large savings
in the electricity costs of hot mines (where refrigeration has to be employed). In addition,
active monitoring and control can positively affect the establishment of a safe, healthy and
productive working environment.
In the entire optimization process certain guidelines were set to ensure that the requirements
of the Mine Health and Safety Act were met. Varying the quantity of air supplied
underground by means of Variable Speed Drives (VSD's) is one of the crucial factors in the
interactive approach towards the optimization of ventilation, as is refrigeration and the
pumping requirements associated with refrigeration. This research highlights the interaction
between the amount of air supplied and the effect it has on refrigeration requirements
underground. This thesis also considers the effect that this would have on contaminant
control.
Various tools are available for ventilation and cooling design for mining. These tools are
based on the assumption of steady state conditions and do not take into account
instantaneous changes in conditions day to day or hour to hour (such as for temperature and
contaminants). They also do not take into account the optimization of energy resources
related to the creation of the acceptable underground conditions. With these tools worst case
and best-case scenarios are identified and strategic decisions are made accordingly.
Currently, the amount of the fresh air, the velocity of the air, and its general temperature in
the mine are only changed when one production phase changes into another (or when
unacceptable conditions occur as a result of poor design or neglect). This means that during
a specific production phase (which can last for several months), there can be an oversupply,
or undersupply, of energy resources, which will obviously affect the concentration levels of
the various contaminants (through under or oversupply of air).
Studies done at the Target Mine in the Free State, South Africa, investigated the possibility of
optimizing air cooling, air supply, and water pumping. A unique simulation programme was
designed for the mine - initially to monitor how the mine normally utilized energy resources
in air-supply cooling and water pumping. Once this had been done, an 'optimization
schedule' for energy use on the mine was established using predictive simulation. A
potential saving in energy costs of approximately R2.6 million per annum was identified
This study en& with recommendations for the implementation of simulation programmes, as
well as with suggestions for future work.Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2005.
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Tan, Meng Hor Freddie. "Theoretical and experimental investigations of porous cooling and adaptive thermal comfort approach for tropical and hot-and-humid climates." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326652.
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Pesic, Nikola. "Geo-climatic potential for advanced natural ventilation comfort cooling approach in mid-rise office buildings in the north-western Mediterranean." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670793.
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The objective of this investigation is to evaluate the geo-climatic potential for comfort cooling energy savings in mid-rise office buildings applying advanced natural ventilation (ANV) approach based on the stack-effect. The region of interest is the Mediterranean coastline of Catalonia with selected reference geographical locations—the cities of Barcelona, Terrassa and Tarragona. In the first part of this research is evaluated the climatic potential for natural ventilation (CPNV) for each location, as a theoretical level of availability of natural ventilation (NV) based on the model of adaptive thermal comfort. For a comparison of geo-climatic potentials in a wider regional context, additional reference locations are chosen along the Northern Mediterranean: Valencia, Marseille, Rome, Koper, Split, Athens and Nicosia. Generated results confirm that NV is feasible mainly from April to October while in July and August is considerably limited due to unfavourable climate conditions. The second part of the work examines cooling energy savings of the hypothetical mid-rise office-type building model “A”. Applied building performance simulations (BPS) demonstrates achieved total yearly cooling energy savings in the region of Catalonia between 22% and 51%. The same model positioned along the Northern Mediterranean displays cutting in yearly cooling energy loads in a wider range—from 6% to 51%.The following section evaluates levels of climate change vulnerability applying climate scenarios for the selected time-slices—the years 2050 and 2080. It is indicated that the potential of ANV will be reduced close to zero in July and August in 2080. However, the introduction of selected assisted cooling techniques demonstrates that this impact can be absorbed approximately back to the previously evaluated scale in the horizon of 2050. In the last part of the investigation, the new defined building model “B” displays an improvement of comfort cooling energy efficiency: selected NV techniques are merged in order to take advantage of lower nocturnal outdoor temperatures by passive means, whose potential is reflected on the decrease of active day-time cooling loads. For this purpose, the positioned model in Barcelona achieves the yearly reduction of cooling energy loads by 65% in present-time weather conditions. At the conclusion, under projected climate configurations for 2050 and 2080, in Barcelona Terrassa and Tarragona, the series of BPS displays a higher level of climate resilience and the overall reduction of cooling energy loads within 53% and 59%.
The key-contribution and the novelty of this research is in the performed series of experimental BPS of the building model “A” where are detected ANV system’s weaknesses as a result of estimated unfavourable climate effects. Relative to observed limited cooling performances, ANV is shifted from an autonomous comfort cooling concept to being a part of a complex ventilative system with specific day- and night-time cycles. Such a new established design approach based on dynamic heat storage is associated with an introduction of lower nocturnal and early morning outdoor air temperatures, as being less affected with future regional climate change. An achieved advantageous momentum in energy performances is categorized through strengths and opportunities. Thereby, the building model “B”, the outcome of this investigation, represents the climate responsive building form with an integrated climate sensitive comfort cooling system, which delivers a higher level of energy efficiency—seen as an acquired factor of resilience towards estimated climate change threats. Such a conceptualised hypothetical building prototype may prove to be a beneficial contributor in the current process of rapid deployment of renewable energy sources in the regional building sector, observed as well from the perspective of the ongoing European Union’s energy transition.El objetivo de esta investigación es evaluar el potencial geo-climático para el ahorro de energía de enfriamiento de confort en los edificios de oficinas de mediana altura aplicando el concepto de ventilación natural avanzada (ANV). El enfoque es en la costa Mediterránea de Cataluña y las ubicaciones geográficas seleccionadas: Barcelona, Terrassa y Tarragona. La primera parte de investigación evalúa el potencial climático de ventilación natural (CPNV), un nivel teórico de disponibilidad de ventilación natural (NV) aplicando el modelo de confort térmico adaptativo. Para una comparación de los potenciales geo-climáticos en un contexto regional más amplio, están elegidas las ubicaciones a lo largo del Mediterráneo Norte: Valencia, Marsella, Roma, Koper, Split, Atenas y Nicosia. Los resultados confirman que NV es factible principalmente desde abril hasta octubre, mientras que en julio y agosto es considerablemente limitada. La segunda parte del trabajo examina los ahorros de energía de enfriamiento de un hipotético modelo “A” del edificio de oficinas de media altura. Las simulaciones de rendimiento de edificios (BPS) en la región de Cataluña demuestran una reducción anual de cargas de enfriamiento entre 22% y 51%. El mismo modelo posicionado a lo largo del Mediterráneo Norte muestra la reducción de las cargas anuales en un rango más amplio, entre 6% y 51%. La siguiente sección evalúa los niveles de vulnerabilidad al cambio climático aplicando escenarios climáticos para los años 2050 y 2080. Se indica que el potencial de ANV se reducirá cerca de cero en julio y agosto de 2080. Sin embargo, la introducción de unas técnicas de enfriamiento asistidas demuestra que ese impacto puede ser absorbido aproximadamente a la escala previamente evaluada en el horizonte de 2050. La última parte de investigación exhibe que el modelo “B” tiene un mejor nivel de la eficiencia energética del enfriamiento de confort: se fusionan técnicas de NV seleccionadas para aprovechar las temperaturas exteriores nocturnas más bajas por medios pasivos, cuyo potencial se refleja sobre la disminución de las cargas de enfriamiento activo diurno. Para este propósito, el modelo posicionado en Barcelona consigue la reducción anual de las cargas de enfriamiento en un 65% en las condiciones meteorológicas actuales. En conclusión, bajo las configuraciones climáticas proyectadas para 2050 y 2080, en Barcelona, Terrassa y Tarragona, la serie de BPS muestra un mayor nivel de resiliencia climática con la reducción de las cargas de enfriamiento entre 53% y 59%. El aporte clave de la investigación se encuentra en BPS experimentales del modelo “A” donde se detectan las debilidades del sistema ANV como consecuencia del cambio climático estimado. En relación con los rendimientos de enfriamiento limitados, ANV se cambia de un concepto autónomo a ser parte de un sistema de ventilación más complejo con los ciclos específicos diurnos y nocturnos. Este nuevo enfoque de diseño establecido basado en el almacenamiento dinámico de calor se asocia con una introducción del aire exterior con temperaturas más bajas durante la noche y las primeras horas de la mañana, como menos afectado por el futuro cambio climático regional. Un impulso ventajoso logrado en el desempeño energético se categoriza a través de las fortalezas y oportunidades. Por lo tanto, el modelo "B" representa la forma del edificio receptivo al clima con un sistema de enfriamiento de confort integrado sensible, lo que ofrece un mayor nivel de eficiencia energética, visto también como un factor adquirido de resiliencia frente a las amenazas estimadas del cambio climático. Tal prototipo de edificio hipotético puede resultar como un contribuyente beneficioso en el proceso actual de despliegue rápido de fuentes de energía renovables en el sector de la construcción regional, observado también desde la perspectiva de la transición energética en curso de la Unión Europea
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Kamali, Aslan [Verfasser], Clemens [Akademischer Betreuer] Felsmann, and Nazar [Gutachter] Antwan. "Developing a Decision Making Approach for District Cooling Systems Design using Multi-objective Optimization / Aslan Kamali ; Gutachter: Nazar Antwan ; Betreuer: Clemens Felsmann." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://d-nb.info/1114067911/34.
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Lahti, Erik Anders. "An Experimental Approach to Assessing Material Corrosion Rates in a Reactor Containment Sump Following a Loss of Coolant Accident." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373990419.
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Wang, Shan. "Further study of the “GreenRoom” concept – an approach to sustainable datacenter cooling solution : Identification of improvement possibilities using Life Cycle Assessment (LCA) and discussion about the effect of the choice of Life Cycle Impact Assessment (LCIA) methods on the results." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116474.
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The growing industry of Information and Communication Technology requires higher computing capacity of data centers/technical sites. The air conditioning in data centers is the key to assure a sustainable computing environment. However, the traditional cooling systems cost are responsible for large environmental footprints especially on energy consumption and greenhouse gas emissions. As a result, a green innovation of data center cooling solutions is taking place. The telecommunication company Teliasonera is developing a high density data center cooling system - the “Green Room” and has been studying the environmental performance of this system using a Life Cycle approach. As an extension of the previous study, more aspects of the project i.e. the location, life span, alternative cooling solutions, energy recovery possibilities and uncertainty analysis is explored by using Life Cycle Assessment (LCA) methodology. The comparison of the locations of the Green Room indicates that the local temperature and electricity production sources are essential factors for the environmental performance of the Green Room. The analysis of the Green Room’s life span reveals that the utilization phase may not always cause the most significant impact during the whole life cycle of the Green Room. If the life span changes, the manufacture phase may predominate the life cycle of the Green Room. The comparative result of alternative cooling technologies addresses that utilizing “natural coolant” (e.g. geo cooling) is a key for sustainable cooling innovation as it would significantly reduce the environmental footprint of the cooling system. Besides, heating a single building (partly) by the waste heat generated from the Green Room could save 30% of cumulative energy input and could reduce more than half of the total environmental impact. Additionally, results uncertainties caused by the choice of different LCIA methods are discussed in the end of the study.The Teliasonera Green Room Concept for high and mid density of ICT equipment
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Bailey, John Denver. "AN APPROACH TO THE MEASUREMENT OF SEXUAL BEHAVIOR IN THE BULL (BOS TAURUS) USING VARIABLE FEMALE STIMULUS CONDITIONS." Lexington, Ky. : [University of Kentucky Libraries], 2003. http://lib.uky.edu/ETD/ukyansc2003d00105/JDBDiss.pdf.
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Thesis--University of Kentucky (Ph. D.), 2003.Title from document title page. Document formatted into pages; contains ix, 194 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 180-191).
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Zeaiter, Amal. "Thermal Modeling and Cooling of Electric Motors : Application to the Propulsion of Hybrid Aircraft Thermal Sensitivity Analysis of a High Power Density Electric Motor for Aeronautical Application Numerical Approach to Determining Windings’ Thermal Conductivity Electro-thermal Models and Design Approach for High Specific Power Electric Motor for Hybrid Aircraft Determination of electric motor losses and critical temperatures through an inverse approach." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0015.
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Le travail présenté dans ce mémoire concerne la modélisation thermique de moteurs électriques de forte densité de puissance. Le but est de trouver les techniques de refroidissement efficaces et adaptées aux moteurs conçus pour application à la propulsion de l’avion hybride du futur. Deux cibles de densité de puissance, 5 kW/kg pour le court terme (année 2025) et 10 kW/kg pour le long terme (année 2035), sont abordées avec leurs propres exigences. Les moteurs électriques étudiés sont de type synchrone à aimants permanents montés en surface du rotor. Ce type de moteur est caractérisé par un rendement élevé et contraint par les températures maximales admissibles relativement faibles de son bobinage et de ses aimants. Une fois atteintes, ces valeurs de température entraînent le dysfonctionnement du moteur ou la limitation de sa durée de vie. En outre, avec un design fermé imposé et des densités élevées de flux de chaleur dissipées dans la machine, une optimisation du refroidissement est incontournable.Pour se familiariser avec le problème, un état de l’art détaillé sur le refroidissement des machines électriques est réalisé. En conséquence, les différentes techniques utilisées et les avancements technologiques récents sont analysés vis-à-vis de notre cas d’application. Ensuite, afin de prédire le comportement thermique du moteur et d’assurer le suivi des températures critiques (surtout au bobinage et aux aimants), un modèle nodal transitoire est mis en place et résolu sous Matlab. Ce dernier est construit en considérant l’intégralité du système moteur avec son circuit de refroidissement. Les conditions externes liées à l’environnement sont prises en compte, en particulier la variation de la température d’air extérieur en fonction de l’altitude et le profil de mission de vol de l’avion. En effet, les pertes dans le moteur, qui constituent les sources de chaleur, varient en fonction de la puissance pendant le vol. Afin d’identifier précisément les paramètres intrinsèques du modèle, une étude par éléments finis a été menée et des corrélations permettant l’estimation de la conductivité thermique du bobinage en sont déduites par interpolation polynomiale. Plusieurs études ont ensuite été menées concernant l’influence des propriétés thermophysiques, de la température extérieure, de la nature du liquide de refroidissement, de son débit ainsi que la surface extérieure de l’échangeur sur les réponses en température du modèle. Plusieurs designs du moteur sont étudiés grâce à ce modèle afin de proposer des solutions de refroidissement adaptées. Pour chacune des cibles, une configuration optimale du moteur avec son système de refroidissement a été adoptée.Par ailleurs, les pertes électromagnétiques et mécaniques étant difficiles à estimer dans ces machines, un chapitre est consacré à leur identification par résolution d’un problème inverse. La technique est séquentielle et utilise la spécification de fonction de Beck comme méthode de régularisation. Trois cas, de complexité croissante, sont étudiés et montrent la fiabilité de la méthode qui permet également d’estimer les températures inaccessibles dans le moteur. C’est finalement ce modèle nodal à faible nombre de degré de liberté qui nous permet d’assurer, en temps réel, le suivi des points chaudsThe concern of this thesis is the thermal modeling of high-specific power electric motors. The aim is to allow finding the efficient and adequate cooling solutions of the motors designed for hybrid aircraft propulsion application. Two specific power values, 5 kW/kg for the short-term (year 2025) and 10 kW/kg for the long-term (year 2035), are targeted, each with specific requirements. The investigated type of electric motors is the synchronous machine with surface-mounted permanent magnets. This motor type is constrained by relatively low values of maximum allowed temperatures in windings and magnets. Once reached, these temperature values lead to a failure in motor operation or at least to shortening its lifetime. Moreover, with a closed motor design and high heat fluxes generated, the optimization of the cooling is essential.To become acquainted with the issue, a detailed state of the art on electric machine cooling is elaborated. Then, the commonly used techniques and the recent technological advancements are analyzed with respect to our case study. Afterward, in order to predict motor thermal behavior and ensure the monitoring of critical temperatures (windings and magnets), a nodal transient model is implemented and solved on Matlab software. This latter is built for the whole system of the motor and cooling circuit. Specific conditions of the flight are taken into account, particularly the outside air temperature variation in terms of altitude and the flight mission profile. Actually, the motor losses, generating the heat in the machine, vary depending on the motor power during the mission. For the identification of crucial parameters, a Finite-Element study was conducted and corresponding correlations were elaborated to estimate the windings thermal conductivity through polynomial interpolation.Several studies were carried out involving the influence of the thermo-physical properties, the outside temperature, the coolant nature, its flow rate as well as the exchanger surface, on the temperature response of the model. This model has allowed studying several motor designs and proposing adequate cooling solutions. For each target, a final optimal configuration of the motor with its cooling system was adopted.Besides, since the electromagnetic and mechanical losses are hardly estimated in this machine type, a chapter was dedicated to identifying them through an inverse approach. A sequential technique, that uses Beck’s function specification for regularization, was developed. Three cases of unknown losses, with increasing complexity, were studied, proving the method's reliability. Finally, using the same developed low-order model, the real-time procedure also allows monitoring low-accessibility motor temperatures (specifically hot spots)
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McGilligan, Charles. "Securing a pathway which leads to an 80% reduction in greenhouse gas emissions : effects of climate change on levels of space heating and space cooling, and analysis of the energy saving potential of the adaptive approach to thermal comfort in the built environment." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577755.
Full textAbstract:
Climate change brings with it a set of challenges if our buildings are to remain thermally comfortable whilst energy consumption is kept to a minimum and greenhouse gas emissions are reduced. As a means of addressing these issues, three models have been constructed using future climate data as forecast by the UK Climate Projections (UKCP09), and they have been used to inform the Department of Energy and Climate Change (DECC) 2050 Calculator. Observing there to be a correlation between regionalised National Grid non-daily metered gas demand and daily air temperature, the first model uses these data and UKCP09 data to estimate future energy savings deriving from a reduced requirement for space heating across the built environment. Using UKCP09 data, the second model estimates the increase in the uptake of residential air-conditioning if the UK were to follow the same experience as Canada, regression data showing a correlation between penetration levels of air-conditioning in the residential sector and air temperature in North America. Resultant levels of space cooling energy consumption are calculated using two different bottom-up approaches, the first of which uses the dwelling as the base unit, and the second of which uses the air-conditioner. Deriving from conventional degree-day theory and substantiated through a series of building simulations, the third model uses a novel metric, the Adaptive Comfort Degree-Day, to estimate the energy savings potential of employing adaptive comfort standards for future climates using UKCP09 data. Finally, it is found that pathways prescribed as achieving an 80% reduction in emissions levels by 2050 remain successful when the DECC 2050 Calculator is updated with correctly-weighted air temperatures. However, the demand for space heating is under-estimated by up to 99 TWh when the Calculator is amended so as to take account of data from the preceding space heating model.
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Wang, I.-Ting, and 王苡婷. "Approaches on the Construction and Performance of Radiant Cooling System." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/47280579247355784047.
Full textAbstract:
碩士國立臺灣科技大學
建築系
97
Taiwan, which is in a hot and humid climate zone, has been impacted by global warming. The average temperature slightly increases year over year, and the summer season is getting longer and longer. The interior room must be removed both sensible heat and latent heat by the mechanical control or other active control. The main task how to keep a healthy environment, a comfortable indoor environment, and maintain energy efficiency is an important approach in this study. This study is to build a new radiant cooling system with an all-air system in a testing chamber of the following dimensions, of 10m(L)×7.6m(W)×3.85m(H). This article is also meant to introduce and test the functional performance of each device (equipment) with the radiant cooling system. The radiant cooling system is divided into four parts: the chilling system, the air system, the power system, and the monitoring system. Now to describe the component equipment and functions of each system; for the test part of the system, record the indoor climate of the test chamber, temperature of chiller, temperature of radiant cooling ceiling, and inlet temperature of the air system. All measurement data were recorded and monitored by a remote computer. In addition, tests of the radiant cooling system were compared against an all-air system. There are some results which are abstracted below this paragraph: Indoor temperature was effected by the supply of air temperature, the inlet water temperature of radiant cooling ceiling, the opening percentage of the outdoor air damper, heater on/off, the opening percentage of the control valve, occupied / unoccupied. Indoor humidity was effected by supply air temperature, the opening percentage of the outdoor air damper, heater on/off, the opening percentage of the control valve, occupied / unoccupied. The inlet or outlet water temperature of chiller was effected by the opening percentage of the outdoor air damper and the opening percentage of the control valve occupied / unoccupied. The inlet or outlet water temperature of radiant cooling ceiling was effected by outlet water temperature of chiller, the opening percentage of the control valve and occupied / unoccupied. The dew point was effected by supply air temperature, the opening percentage of the outdoor air damper, heater on/off, the opening percentage of the control valve and occupied / unoccupied. By using different air-conditioning systems, the radiant cooling ceiling system kept indoor temperature balance which last at least for 30 minutes, whereas an all-air system just needed 20 minutes. The radiant cooling ceiling system has high performance of dehumidified but all-air system could dehumidify in a short time. For energy efficiency, the radiant cooling ceiling system was more efficient than all-air system by a rate of 3.27.
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Chen, Chia-jui, and 陳家瑞. "Approaches on the Construction and Performance of Cooling System Integrated with Ground Source Heat Pump." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04895638196613373999.
Full textAbstract:
碩士國立臺灣科技大學
建築系
101
Taipei City is located in the subtropical monsoon climate zone. The average summer temperature increases annually and the duration of summer lengthens because of humid air throughout the year, the greenhouse effect, and the urban heat island phenomena. Consequently, the energy required for air-conditioning continues to rise. In addition to optimizing the performance of air-conditioners and reducing power consumption, alternative energy should be searched or integrated with enthusiasm. In recent years, most attention is devoted to the utilization of shallow ground sources, which are one of the energy-saving techniques based on thermal environment control. As the conditions of earth energy and environments continue to deteriorate, ground source heat pump air-conditioning systems demonstrate high efficiency, zero pollution, and great research potential. This study investigated the construction of the ground source cooling air-conditioning experiment facility. In addition, the performance of the ground source heat pump air-conditioning equipment was preliminarily verified. The results of system construction and underground environment monitoring can serve as future reference for system type setup and thermal exchanger installation. The experiment results of the ground source heat pump provide information regarding system energy consumption and underground dissipation efficiency, which can be used to identify the application potential in regions of similar geological properties. The most drastic changes of underground temperatures were measured five meters below the earth surface, with an average change of 8℃. The average temperature change measured at six to ten meters underground was approximately 1.5℃. The temperature measured 11 meters underground was almost constant. The average temperature was slightly lower than 24℃, with a variation less than 0.2℃. In addition, the performance experiment of the ground source heat pump controlled the expected indoor temperature to change the thermal load of the air-conditioner. When the indoor equilibrium temperature was 30℃, the input of thermal load increased the underground temperature by 1.3℃. The increased temperature was fully dissipated after 20 hours, restoring to the initial underground temperature. Under these experiment conditions, the startup/shutdown ratio was 4:20 (4-hr startup:20-hr shutdown), which fulfilled the expectation that the system could be utilized on a daily basis.
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"Improving Urban Cooling in the Semi-arid Phoenix Metropolis: Land System Science, Landscape Ecology and Urban Climatology Approaches." Doctoral diss., 2018. http://hdl.handle.net/2286/R.I.50440.
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abstract: The global increase in urbanization has raised questions about urban sustainability to which multiple research communities have entered. Those communities addressing interest in the urban heat island (UHI) effect and extreme temperatures include land system science, urban/landscape ecology, and urban climatology. General investigations of UHI have focused primarily on land surface and canopy layer air temperatures. The surface temperature is of prime importance to UHI studies because of its central rule in the surface energy balance, direct effects on air temperature, and outdoor thermal comfort. Focusing on the diurnal surface temperature variations in Phoenix, Arizona, especially on the cool (green space) island effect and the surface heat island effect, the dissertation develops three research papers that improve the integration among the abovementioned sub-fields. Specifically, these papers involve: (1) the quantification and modeling of the diurnal cooling benefits of green space; (2) the optimization of green space locations to reduce the surface heat island effect in daytime and nighttime; and, (3) an evaluation of the effects of vertical urban forms on land surface temperature using Google Street View. These works demonstrate that the pattern of new green spaces in central Phoenix could be optimized such that 96% of the maximum daytime and nighttime cooling benefits would be achieved, and that Google Street View data offers an alternative to other data, providing the vertical dimensions of land-cover for addressing surface temperature impacts, increasing the model accuracy over the use of horizontal land-cover data alone. Taken together, the dissertation points the way towards the integration of research directions to better understand the consequences of detailed land conditions on temperatures in urban areas, providing insights for urban designs to alleviate these extremes.Dissertation/Thesis
Doctoral Dissertation Geography 2018
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Lo, Tzu-Yi, and 羅子益. "Effect of Coolant Passage Configuration on the Film Cooling Performance of Aero-Optic Infra-Real Window with CFD Approach." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/55205518479555994614.
Full textAbstract:
碩士國防大學理工學院
機械工程碩士班
97
The aim of this thesis is to investigate the thermal protection performance of cooled slot flow over an IR optical window equipped in the head of a hypersonic flight missile with CFD method. The seeker in the IR window is used to track the target then to guide the missile to the modified trajectory in high flight speed. As the anti-missile vehicle flight in the high attitude atmosphere layer, most of the kinetic energy will be transformed into the thermal energy over the surfaces of missile body due to the thin shock layer characteristics. Therefore, the flow field nearby the IR window is influenced by the interaction of shock wave and developing boundary layer flow. The variations in density, pressure and species concentration result in high temperature gradient over the IR window. Not only the structure strength of IR window but also the aero-optic performance in such a severe environment must be considered in the design stage. To reduce the heat load on the IR window, the external film cooling method from a slot with various mass flow rates is used in present work. The numerical code is validated with similar cases in literatures before conducting runs. Three different types of cooled flow passage configuration were tested when the flight Mach number is 6. Results indicate that the optimum configuration is the forward inclined angle of 225 degree cavity model over tested ranges of mass flow rate of coolant. Comparison of .area-averaged film cooling performance among tested cases shows that the mass flow rate of 0.125 kg/s is suitable for cooling down the surface temperature of IR window below 500K. There is a minor influence of attack angle on the film cooling performance of slot flow over present IR window.
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(11191899), Jie Ma. "A SEQUENTIAL APPROACH FOR ACHIEVING SEPARATE SENSIBLE AND LATENT COOLING." Thesis, 2021.
Find full textAbstract:
Current air conditioning systems generally operate with a relatively fixed moisture removal capacity, and indoor humidity conditions are usually not actively controlled in most buildings. If we focus only on sensible heat removal, an air conditioning system could operate with a fairly high evaporating temperature, and consequently a high coefficient of performance (COP). However, to provide an acceptable level of dehumidification, air conditioners typically operate with a much lower evaporating temperature (and lower COP) to ensure that the air is cooled below its dew point to achieve dehumidification. The latent (moisture related) loads in a space typically only represent around 20-30% of the total load in many environments; however, the air conditioning system operates 100% of the time at a low COP to address this small fraction of the load. To address issues associated with inadequate dehumidification and high energy consumption of conventional air conditioning systems, the use of a separate sensible and latent cooling (SSLC) system can dramatically increase system COP and provide active humidity control. Most current SSLC approaches that are reported in the literature require the installation of multiple components or systems in addition to a conventional air conditioner to separately address the sensible and latent loads. This approach increases the overall system installation and maintenance costs and complicates the controller design.
A sequential SSLC system is proposed and described in this work takes full advantage of readily available variable speed technology and utilizes independent speed control of both the compressor and evaporator fan, so that a single direct expansion (DX) air-conditioning (A/C) system can be operated in such a way to separately address the sensible and latent loads in a highly efficient manner. In this work, a numerical model of DX A/C system is developed and validated through experiential testing to predict the performance under varied equipment speeds and then used to investigate the energy saving potential with the implementation of the proposed sequential SSLC system. To realize the sequential SSLC system approach, various corresponding control strategies are proposed and explained in this work that minimizes energy consumption while provides active control over both space temperature and relative humidity. At the end of this document, the benefits of applying the SSLC system in a prototype residential building under different typical climate characteristics are demonstrated.
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Franco, André Filipe Romão. "Numerical Modeling of Cooling Water Droplets using a Two-Way Coupling Approach." Master's thesis, 2019. http://hdl.handle.net/10400.6/8567.
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The present dissertation focuses on the study of the process of cooling and freezing of free falling water droplets. The freezing phenomenon is of extreme relevance in aviation since the impact of drops on lifting surfaces of an aircraft and consequent accretion can lead to the occurrence of incidents and accidents.
In order to prevent the formation and accretion of ice, there are several systems to combat this hazard. Critical areas of an aircraft are usually protected by these de-icing systems. However, although these methods can evaporate drops of water or melt the accreted ice, there is still the possibility of downstream ice formation due to new freezing of the ice-water mixture in unprotected areas.
Thus, there is a need to study and adapt the existing physical and mathematical models for a better approximation to real-life situations, in order to contribute to a better understanding of this phenomenon and consequently lead to a reduction in the number of incidents and accidents, safety conditions.
The objective of this work is to perform a numerical study with the purpose of studying the cooling of free falling water droplets for different diameters and humidity ratios. Ranz-Marshall relations are used, with and without a correction factor, in addition to the Abramzon and Sirignano approach to take into account the effects of convection. A Two-Way Coupling approach is used being the predictions compared with experimental data and numerical predictions in a One-Way Coupling approach.A presente dissertação centra-se no estudo do processo de arrefecimento e congelamento de gotas de água em queda livre. O fenómeno de congelamento é de extrema relevância na área de Engenharia Aeronáutica, uma vez que devido ao impacto de gotas nas superfícies sustentadoras de uma aeronave e consequente acumulação de gelo poderão ocorrer incidentes e acidentes com as aeronaves. Como forma de impedir a formação e acumulação de gelo, existem diversos sistemas para combater este perigo. As áreas críticas de uma aeronave estão normalmente protegidas por sistemas anti gelo. No entanto, embora estes métodos consigam evaporar gotas de água ou derreter o gelo acumulado, existe ainda a possibilidade de formação de gelo a jusante devido a um novo congelamento da mistura gelo-água em áreas desprotegidas. Desta forma, surge uma necessidade de estudar e adaptar os modelos físicos e matemáticos existentes para uma melhor aproximação a situações reais, por forma a contribuir para uma melhor compreensão deste fenómeno e consequentemente levar a uma redução do número de incidentes e acidentes, melhorando as condições de segurança. O objetivo deste trabalho passa pela realização de um estudo numérico com o intuito de estudar o arrefecimento de gotas de água em queda livre para diferentes diâmetros e razões de humidade do ar. As correlações de Ranz-Marshall são utilizadas, com e sem a adição de um fator de correção, para além da abordagem de Abramzon e Sirignano, como forma de considerar os efeitos de convecção. O modelo utilizado é de Two-Way Coupling e as previsões são comparadas com dados experimentais e previsões numéricas cuja abordagem foi One-Way Coupling.
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Chen, Hsiang-Lun, and 陳相輪. "A simulation-optimization approach of free cooling for data centers in worldwide zones." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/b45sdf.
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博士國立臺北科技大學
機電科技研究所
101
Based on the climate classification of ASHRAE 90.1 and the required operating environment conditions for data centers suggested by the ASHRAE Technical Committee TC 9.9, we used a dynamic building energy simulation program (Energy Plus) to examine the energy efficiency of the air-side differential enthalpy control free cooling technology and water-side free cooling technology used in data centers in 17 climate zones. The results showed that the optimum air-side free cooling efficiency was achieved in data centers located in mixed-humid, warm-marine, and mixed-marine climate zones. Because significant humidification is required to adjust outdoor air in climate zones with a lower dew point temperature, such as very-cold, subarctic, cool-dry, and cold-dry climate zones, the power consumed is even higher. The energy saving in climate zones with a lower dew point temperature will be negative to positive when control outdoor air introduced with outside air dew point. The energy saving of HVAC in most climate zones is between 30% and 40 %( or above) when adopt the heat recovery chiller system to be heating source of the humidification system and none-control outdoor air introduced with outside air dew point. The optimum setting water temperature to start the water-side free cooling system is between 17℃ and 19℃ (according to climate zone) under the operating conditions of the air-conditioning system studied in this paper and does not cause humidification problems in condition zone. The results of this study indicate that the energy saving adopt air-side differential enthalpy control free cooling technology is higher than adopt water-side free cooling technology in climate zone 1B to 5A, 5C and 6A. However, it is suitable to use the water-side free cooling technology in climate zone 5B, 6B to 8. The energy saving will achieve the optimal in all climate zones when adopt air-side differential enthalpy control free cooling technology with heat recovery chiller system.
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Wu, Sung-Lin, and 吳松霖. "An Approach for Energy Efficiency Enhancement on The Cooling System of A Rack-Mounted Server." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/fmhn95.
Full textAbstract:
碩士大同大學
通訊工程研究所
102
As people gradually increased dependence on networks, servers and computer room have more demand. Reducing the power consumption of IT equipment is an important goal of each data center. Therefore, this paper proposes a better method to enhance the rack server by redesigned fan system which include the relationship of the CPU usage and current, the relationship of the CPU usage and server temperature, and fan speed impact on the temperature. Use measuring instruments to read the server temperatures of certain areas inside the server. After collecting temperatures as parameters, I coordinate the new deduced method of fan control on this paper to identify and keep similar temperature as original, also can reduce the power consumption to make the cooling system energy efficiency better. Besides, experiments found that the original fan control system will increase the fan speed during higher loading. But increase the fan speed can’t reduce the CPU temperature and the server temperature efficiently. Resulting the lower efficiency of power consumption when fan system is in higher loading. So this experiment improving energy efficiency by changing the fan speed to cooling the heat source. Experimental results confirmed that this method can reduce 17.35% of power consumption of the fan system while maintaining a similar average temperature.
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MAZZEI, LORENZO. "A 3D coupled approach for the thermal design of aero-engine combustor liners." Doctoral thesis, 2015. http://hdl.handle.net/2158/993808.
Full textAbstract:
The recent limitations imposed by ICAO-CAEP towards a drastic reduction of NOx emissions is driving the development of modern aeroengines towards the implementation of lean burn concept. The increased amount of air dedicated to the combustion process (up to 70%) involves several technological issues, including a signicant reduction of coolant available for the thermal management of combustor liners. This, from a design perspective, involves the continuous research for effective cooling schemes, such as effusion cooling, and the necessity of more accurate methodologies for the estimation of metal temperature, so as to properly assess the expected duration of hot gas path components.
The flame stabilization through swirler characterized by large effective area leads to extended recirculating zones, which interact considerably with the liner cooling system. As highlighted in the first part of this dissertation, the impact on the near-wall flow field makes any consideration based on a correlative approach untrustworthy, demanding for more reliable evaluations through CFD analysis. Unfortunately, the application of effusion cooling entails a huge computational effort due to the high number of film cooling holes involved, therefore many approaches have been proposed in literature with the aim of modelling the coolant injection through mass sources.
This work presents SAFE (Source based effusion model), a methodology for the CFD simulation of the entire combustor, which is based on the local coolant injection through point sources and a calculation of mass flow rate according to local flow conditions. A further step in reduction in the computational effort is represented by a different methodology, called Therm3D, which involves the simulation of the flame tube, whereas the solution of the remaining part of the combustor is fulfilled through the modelling of an equivalent flow network, which provides for the estimation of flow split and cold side heat loads.
Ultimately, this work introduces innovative approaches for the CFD investigation of effusion cooled combustor, with a special focus on the metal temperature prediction. A model for the film cooling injection is proposed to overcome the issues related to the necessity of meshing the perforation, nevertheless several improvable aspects have been highlighted, pointing the way for further enhancements.
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Radchenko, M., E. Trushliakov, A. Radchenko, S. Kantor, V. Tkachenko, М. Радченко, Є. Трушляков, А. Радченко, С. Кантор, and В. Ткаченко. "Approach to enhance the energetic efficiency of air conditioning systems by cooling load distribution in ambient air procession." Thesis, 2020. http://eir.nuos.edu.ua/xmlui/handle/123456789/4346.
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Approach to enhance the energetic efficiency of air conditioning systems by cooling load distribution in ambient air procession = Підхід до підвищення енергетичної ефективності систем кондиціювання повітря шляхом розподілу холодопродуктивності при обробці зовнішнього повітря / M. Radchenko, E. Trushliakov, A. Radchenko, S. Kantor, V. Tkachenko // Матеріали XI міжнар. наук.-техн. конф. "Інновації в суднобудуванні та океанотехніці". В 2 т. – Миколаїв : НУК, 2020. – Т. 1. – С. 490–500.У загальному випадку весь діапазон холодопродуктивності будь-якої системи кондиціювання повітря включає нестабільний діапазон і порівняно стабільну частину холодопродуктивності для подальшого охолодження повітря. Таким чином, стабільний діапазон холодопродуктивності може бути забезпечений роботою звичайного компресора, в той час як режим із значними коливаннями холодопродуктивності вимагає її модуляції. Пропонований підхід може бути використаний для проектування систем зі змінним потоком хладагента (VRF), забезпечених системою обробки зовнішнього повітря (OAP).
Abstract. In general case, an overall cooling load band of any air conditioning system comprises the unstable cooling load range and a comparatively stable cooling load part for further air cooling. Thus, the stable cooling load range can be covered by operation of conventional compressor, meantime mode with considerable cooling load fluctuation needs load modulation. A proposed method can be adopted for designing Variable Refrigerant Flow (VRF) systems provided with Outdoor Air Processing (OAP) system.
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Bertini, Davide. "High-fidelity prediction of metal temperature in gas turbine combustors using a loosely coupled multiphysics approach." Doctoral thesis, 2019. http://hdl.handle.net/2158/1155985.
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Aeroengine industry is being largely affected by the mid- and long-term targets of civil aviation, that is searching for increasingly efficient low-emission engines and new opportunities as in the segment of small aircraft. The dynamically evolving market requires prompt solutions for the combustor that cannot be easily provided by experiments because of technical issues and expensive campaigns. On the other hand, the progressive developments in the field of massively parallel computing is making Computational Fluid Dynamics the most effective tool for a deep insight of combustion chambers. Indeed, high-fidelity investigations on this component is a multiphysics problem requiring to model the interactions between turbulence, combustion, radiation and heat transfer. Thermal design is a key task in the development loop of novel combustors, being stressed by lower coolant availability and higher power density. For this purpose, CFD-based models are required to properly account for the 3-D heat load distribution. Nevertheless, the limits of standard RANS approaches in accurately modelling highly-turbulent reacting flow is well-known and nowadays scale-resolving methods, as Large-Eddy Simulation (LES), Detached Eddy Simulation (DES) and Scale Adaptive Simulation (SAS), are the most promising ones; the latter, in particular, is emerged as a valid trade-off for industrial applications.
In the present work a multiphysics tool, called U-THERM3D, is proposed as potential approach for the prediction of metal temperature in the context of scale-resolving simulations. The tool is validated on predictable solutions and applied to two burners, the DLR model aero-engine combustor and the LEMCOTEC combustor. The former is a laboratory sooting flame simulated using LES and the focus is on the tool capabilities in modelling the involved interacting phenomena. The latter is an effusion cooled lean-burn aeroengine combustor investigated from different perspectives using SAS to predict exit profile temperature, emissions and metal temperature.
To the author's knowledge no works can be found in literature on multiphysics simulations of lean burn combustors relying on Scale Adaptive Simulation. For this reason the present work aims to be a reference for high-fidelity final design as well as a starting point for future activities.
The results in both the burners are compared against steady THERM3D simulations and experiments emphasizing the detrimental effects of the swirling flow on the wall temperature, that acts increasing the heat transfer coefficient and reducing the film cooling coverage.
The improved prediction of metal temperature obtained by U-THERM3D shows the potential of this tool as a framework for the high-fidelity design of gas turbine combustors. Obviously, the accuracy of the coupled simulation can benefit from the improvement in the different involved models and further research efforts should be focused on this task.
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"Cooling Strategy for Effective Automotive Power Trains: 3D Thermal Modeling and Multi-Faceted Approach for Integrating Thermoelectric Modules into Proton Exchange Membrane Fuel Cell Stack." Master's thesis, 2014. http://hdl.handle.net/2286/R.I.26885.
Full textAbstract:
abstract: Current hybrid vehicle and/or Fuel Cell Vehicle (FCV) use both FC and an electric system. The sequence of the electric power train with the FC system is intended to achieve both better fuel economies than the conventional vehicles and higher performance. Current hybrids use regenerative braking technology, which converts the vehicles kinetic energy into electric energy instead of wasting it. A hybrid vehicle is much more fuel efficient than conventional Internal Combustion (IC) engine and has less environmental impact The new hybrid vehicle technology with it's advanced with configurations (i.e. Mechanical intricacy, advanced driving modes etc) inflict an intrusion with the existing Thermal Management System (TMS) of the conventional vehicles. This leaves for the opportunity for now thermal management issues which needed to be addressed. Till date, there has not been complete literature on thermal management issued of FC vehicles. The primary focus of this dissertation is on providing better cooling strategy for the advanced power trains. One of the cooling strategies discussed here is the thermo-electric modules.
The 3D Thermal modeling of the FC stack utilizes a Finite Differencing heat approach method augmented with empirical boundary conditions is employed to develop 3D thermal model for the integration of thermoelectric modules with Proton Exchange Membrane fuel cell stack. Hardware-in-Loop was designed under pre-defined drive cycle to obtain fuel cell performance parameters along with anode and cathode gas flow-rates and surface temperatures. The FC model, combined experimental and finite differencing nodal net work simulation modeling approach which implemented heat generation across the stack to depict the chemical composition process. The structural and temporal temperature contours obtained from this model are in compliance with the actual recordings obtained from the infrared detector and thermocouples. The Thermography detectors were set-up through dual band thermography to neutralize the emissivity and to give several dynamic ranges to achieve accurate temperature measurements. The thermocouples network was installed to provide a reference signal.
The model is harmonized with thermo-electric modules with a modeling strategy, which enables optimize better temporal profile across the stack. This study presents the improvement of a 3D thermal model for proton exchange membrane fuel cell stack along with the interfaced thermo-electric module. The model provided a virtual environment using a model-based design approach to assist the design engineers to manipulate the design correction earlier in the process and eliminate the need for costly and time consuming prototypes.Dissertation/Thesis
Masters Thesis Technology 2014
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RINALDI, Alessandro. "Building Energy Management Systems (BEMS) optimization, by modeling occupants' behavior towards an agent-based approach." Doctoral thesis, 2017. http://hdl.handle.net/11589/100386.
Full textAbstract:
In the last decades, in response to the high impact of buildings on global energy consumption and on the greenhouse gases emission, recent international directives have introduced the standard of "Nearly Zero Energy Building (NZEB)" to be realized from 2021.
Despite the increasing attention to the development of strategies and innovative technology solutions for the energy efficiency of building components and HVAC systems, the human dimension, especially regarding the operating modes of the building-HVAC system by occupants, is often neglected. In most cases, this causes a significant discrepancy between the designed and the real total energy use in build-ings. Indeed, monitoring studies for identical dwellings having the same type of installations have shown great variation in energy use.
Occupants constitute one of the major source of microclimate alteration in built environment, both as "passive agents" (for sensible and latent energy emissions, and emissions of pollutants), both as "active agents" as result of interaction with the buildings in order to achieve the desired comfort level (by acting on thermostats, by changing the state of opening or closing of windows and /or shading, by activating artificial lighting, etc.)
Above all in the buildings characterized by higher levels of the insulation and air tightness, the occupants behavior may have a great influence on the energy con-sumptions and on indoor environment conditions. If the occupants have the possibility to manipulate the set-points temperature, the ventilation rates etc., the performance of the building will be affected by the behavior of the occupants. As consequence, even the most efficient building, may give rise to waste in case of incorrect use by occupants.
Nowadays the understanding of occupant behavior results inappropriate, overly simplified, leading to inaccurate expectations of building energy performance. A common approach to model occupant behavior consists of assumptions based on scientists’ thoughts or literature reviews. Typically human actions (operation of lights, blinds, and windows) are modeled based on predefined fixed schedules or predefined rules. In contrast to the deterministic methods, stochastic and above all agent-based models (ABM) are the most powerful and suitable methods for modeling a system as complex as the human behavior.
Especially in residential buildings, where the interaction of the occupants on the building-HVAC system is significant and hence the occupant behaviors may affect highly on building performance, the integration of Building Energy Management Sys-tems (BEMS) may provide significant energy savings, going not only to remedy an incorrect or inadequate management by occupants, but also optimizing the activation timing and management methods.
Strictly connected with the “resilience” concept, the object of this research is to design “adaptive” Building Energy Management Systems (BEMS), able to maintain energy performance at the desired level despite the diverse operating conditions by occupants, by optimizing building components.
In detail, several control logics for BEMS are analyzed in the residential buildings, by optimizing the thermal and visual comfort and by modeling the occupant behav-iors by means of an agent based oriented approach. In this thesis the optimization goals are based on the adaptive thermal comfort according to EN 15251.
The thesis is structured in five chapters.
In the introduction chapter (chapter 1) the main factors influencing the building performance towards the design of the NZEB are presented.
Then, literature review regarding different studies that have analyzed the impact of occupant behaviors and the interaction with building-HVAC system (chapter 2) are reported.
The results of a questionnaire survey conducted on occupant behaviors in residential buildings are described in the chapter 3. Large differences in the behavior patterns of occupants are found between dwellings. Indeed, for the oldest buildings, where the thermal discomfort conditions are the highest, the occupants usually turn on active system, by causing more energy waste. Furthermore, it is resulted that while in winter occupants act less on the building components to improve their thermal comfort conditions, (indeed the main actions are wearing heavy clothes and turning on heating system), in summer season the occupants mostly interact with the building components, by changing the window and shading status or by adjusting set-point thermostat.
Because the actions on window and blind status are impactful on building perfor-mance, with the aim of reduce the thermal discomfort conditions and hence the vari-ability tied to the occupant behaviors, control logics of natural ventilation and of the solar shading system for passive cooling are designed. Indeed by reducing the ther-mal discomfort conditions, also the actions and the interactions of occupant with building components may be less.
In detail, in an Italian dwelling with technological/typological features of sixties buildings, several studies are conducted with the aim to design BEMS for passive cooling that minimize the thermal discomfort situations, by means of Particle Swarm Optimization (PSO) method. The results of these studies are reported in the chapter 4.
In the second part of the work, in order to have BEMS adaptable to the actions and preferences of occupants, a further study is conducted (Chapter 5), where occupant behaviors are simulated in more detail, by means of an agent-based approach. In detail, actions like opening/closing windows and shielding and cooling system activation are implemented in the energy software simulation (TRNSYS), using algorithms deduced by field investigations in real buildings.
The same control logics of the BEMS (reported in the Chapter 4) are then revalued in this different occupant behavior modeling and the comparison between the models where the occupant behavior is assumed in deterministic way and then though a probabilistic and agent-based approach, allowed to assess the impact of human behavior and the designed BEMS on building performance.
This work highlighted how the BEMS may ensure high levels of comfort and energy efficiency, through the dynamic control of some components based on external and internal environmental parameters and on the occupancy conditions.
The implementation of different occupant behaviors into energy simulation soft-ware, simulated by means of an ABM method and the coupling of optimization goal for BEMS represent an innovative contribution of the work. A co-simulation architec-ture is created between TRNSYS (for building-HVAC model), TRNFLOW (for building air flow network), MATLAB (for PSO optimization) and DAYSIM (for visive analysis).
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Del, Fabbro Giada Alessia. "A review of South African perspectives on serial murder." Diss., 2006. http://hdl.handle.net/2263/29232.
Full textAbstract:
Pistorius (1996) was the first individual to introduce research on serial murder in the South African context with her psychodynamic approach to the phenomenon. Since then, others have followed, namely Labuschagne (1998, 2001) with his search for interactional and communication connections; Du Plessis (1998) from a grounded theory approach; and Hodgskiss (2001) with his assessment of South African offender characteristics and behaviours. Four more studies have been conducted, namely Hook’s post-structural deconstruction of narratives of a person who committed serial murder (2003); De Wet’s psychosocial perspective (2005); Barkhuizen’s intrapsychic object relations approach (2006); and Del Fabbro’s exploration of the phenomenon from a family systems paradigm (2006). To date, no attempt has been made to review these research endeavors. In this article, these studies are reviewed and their strengths and weaknesses with regard to theory, methodology and research findings debated. The author concludes with several recommendations for future research on the phenomenon of serial murder: greater communication between various disciplines (e.g. psychology, criminology, law) investigating serial murder; expansion of Hodgskiss’ research (2001) on offence characteristics for profiling purposes; and the relationship between psychopathology and serial murder.Dissertation (MA (Clinical Psychology))--University of Pretoria, 2007.
Psychology
MA
unrestricted