Dissertations / Theses on the topic 'Cooling Systems'
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Syed, Athar. "Optimal solar cooling systems." Thesis, London South Bank University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434431.
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Cerrillo, Moreno Javier. "Laser cooling of quantum systems." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/12788.
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In this thesis novel methods for the laser cooling of quantum systems are presented. The use of quantum interference allows for the tailored cancelation of heating processes, so that an approximation to a cooling operator is possible that does not rely on the rotating wave approximation. This makes these schemes considerably faster and more efficient than existing ground state cooling methods, and allow for a significant relaxation of current experimental constraints. Several approaches are investigated in different systems. On the one hand, a special laser configuration, applicable to trapped ions, atoms or cantilevers, generates a double dark state that eliminates both the blue sideband and the carrier transition. As a consequence, vanishing phonon occupation up to first order in the perturbative expansion is achieved. Underlying this scheme is a combined action of two cooling schemes which makes the proposal very stable under parameter fluctuations. Its suitability as a cooling scheme for several ions in a trap or for a cloud of atoms in a dipole trap is shown. On the other hand, a pulsed cooling scheme for optomechanical systems is presented. It can be implemented for both strongly and weakly coupled optomechanical systems in both weakly and highly dissipative cavities. Its underlying mechanism is based on interferometric control of optomechanical interactions, and its efficiency is demonstrated with pulse sequences that are obtained by using methods from optimal control. Finally, it is shown how this pulsed method can be combined with continuous measurement to drive mechanical oscillators to highly squeezed steady states. Its mechanism relies on the modification of the dissipation and measurement terms, which drive the system towards a specific quadrature eigenstate. The scheme is robust to measurement inefficiencies and works also with highly dissipative cavities, which makes it accessible to implementation with state of the art technology.
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Tapanlis, Orpheas. "Turbine casing impingement cooling systems." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711623.
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Gilson, Gareth M. "Cooling of advanced aircraft actuation systems." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12568/.
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Electrical machines for aerospace applications often operate close to the allowable thermal limits due to high power density requirements. The power density of electrical machines is generally dependent on the machine and thermal management design. At flight level, a reduced pressure exists which in turn results in more challenging thermal management. Aerospace electric machine manufacturers are often limited with respect to the implemented cooling mechanisms. That is, natural convection systems are the norm, as fan cooled and fluid cooled machines may suffer from reliability issues. The original contribution of this work, is the design, testing, and implementation of an alternative forced cooling convective system (FCCS) based on piezoelectric fans. This thesis commences by an investigation of the capabilities of MotorCAD (a sophisticated analytical lumped thermal package) and how it can be utilised in a fully integrated way to optimise (for a maximum power density and an overall minimum motor mass) both the electromagnetic and thermal aspects of a typical traditional horizontally-mounted permanent magnet synchronous machine (PMSM) operating at flight level. The resultant analytical temperature values were then compared to actual experimental temperature data. Piezoelectric fans are then investigated as a potential, fault tolerant FCCS that may enhance the overall cooling of a motor. These fans could be implemented in the aerospace industry as they do not suffer from the same reliability issues as traditional FFCS’s. Detailed thermal results indicating the effective piezoelectric fan cooling range together with the overall cooling effectiveness over a traditional vertical straight-finned heat sink (unit – cell) , operating under different operating conditions are also presented. Furthermore, the fin/fan geometry that minimises the thermal resistance whilst minimising the overall cooling mass is presented. Particle Image Velocimetry (PIV) techniques were implemented to further understand the flow fields generated by an oscillating piezoelectric fan. Common parameters governing the fluid flow (vibration amplitude, separation distance, fin spacing and fan orientation) were investigated and the results are herewith presented. Designs of a supporting structure for the proposed FCCS implementation are drawn up and analysed through FEA. A prototype structure was built and its durability tested. Furthermore, the reliability (fault tolerance) of the suggested FCCS was evaluated. The feasibility of implementing this innovative cooling technique was further investigated by performing a study on the weight saving potential of the FCCS over traditional natural convective fins, and the FCCS geometry that minimises the thermal resistance whilst minimising the overall mass is selected. Furthermore, a prototype FCCS was built and tested.
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Ghaghazanian, Arash. "System Integration of PV/T Collectors in Solar Cooling Systems." Thesis, Högskolan Dalarna, Energiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:du-19554.
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The demand for cooling and air-conditioning of building is increasingly ever growing. This increase is mostly due to population and economic growth in developing countries, and also desire for a higher quality of thermal comfort. Increase in the use of conventional cooling systems results in larger carbon footprint and more greenhouse gases considering their higher electricity consumption, and it occasionally creates peaks in electricity demand from power supply grid. Solar energy as a renewable energy source is an alternative to drive the cooling machines since the cooling load is generally high when solar radiation is high. This thesis examines the performance of PV/T solar collector manufactured by Solarus company in a solar cooling system for an office building in Dubai, New Delhi, Los Angeles and Cape Town. The study is carried out by analyzing climate data and the requirements for thermal comfort in office buildings. Cooling systems strongly depend on weather conditions and local climate. Cooling load of buildings depend on many parameters such as ambient temperature, indoor comfort temperature, solar gain to the building and internal gains including; number of occupant and electrical devices. The simulations were carried out by selecting a suitable thermally driven chiller and modeling it with PV/T solar collector in Polysun software. Fractional primary energy saving and solar fraction were introduced as key figures of the project to evaluate the performance of cooling system. Several parametric studies and simulations were determined according to PV/T aperture area and hot water storage tank volume. The fractional primary energy saving analysis revealed that thermally driven chillers, particularly adsorption chillers are not suitable to be utilizing in small size of solar cooling systems in hot and tropic climates such as Dubai and New Delhi. Adsorption chillers require more thermal energy to meet the cooling load in hot and dry climates. The adsorption chillers operate in their full capacity and in higher coefficient of performance when they run in a moderate climate since they can properly reject the exhaust heat. The simulation results also indicated that PV/T solar collector have higher efficiency in warmer climates, however it requires a larger size of PV/T collectors to supply the thermally driven chillers for providing cooling in hot climates. Therefore using an electrical chiller as backup gives much better results in terms of primary energy savings, since PV/T electrical production also can be used for backup electrical chiller in a net metering mechanism.
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Woollen, Peter. "Gas in engine cooling systems : occurrence, effects and mitigation." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/11740.
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The presence of gas in engine liquid cooling systems can have severe consequences for engine efficiency and life. The presence of stagnant, trapped gases will result in cooling system hotspots, causing gallery wall degradation through thermal stresses, fatigue and eventual cracking. The presence of entrained, transient gases in the coolant flow will act to reduce its bulk thermal properties and the performance of the system s coolant pump; critically the liquid flow rate, which will severely affect heat transfer throughout the engine and its ancillaries. The hold-up of gas in the pump s impeller may cause the dynamic seal to run dry, without lubrication or cooling. This poses both an immediate failure threat should the seal overheat and rubber components melt and a long term failure threat from intermittent quench cooling, which causes deposit formation on sealing faces acting to abrade and reduce seal quality. Bubbles in the coolant flow will also act as nucleation sites for cavitation growth. This will reduce the Net Positive Suction Head available (NPSHA) in the coolant flow, exacerbating cavitation and its damaging effects in locations such as the cylinder cooling liners and the pump s impeller. This thesis has analysed the occurrence of trapped gas (air) during the coolant filling process, its behaviour and break-up at engine start, the two-phase character of the coolant flow these processes generate and the effects it has on coolant pump performance. Optical and parametric data has been acquired in each of these studies, providing an understanding of the physical processes occurring, key variables and a means of validating numerical (CFD) code of integral processes. From the fundamental understanding each study has provided design rules, guidelines and validated tools have been developed, helping cooling system designers minimise the occurrence of trapped air during coolant filling, promote its breakup at engine start and to minimise its negative effects in the centrifugal coolant pump. It was concluded that whilst ideally the prevention of cooling system gases should be achieved at source, they are often unavoidable. This is due to the cost implications of finding a cylinder head gasket capable of completely sealing in-cylinder combustion pressures, the regular use of nucleate boiling regimes for engine cooling and the need to design cooling channel geometries to cool engine components and not necessarily to avoid fill entrapped air. Using the provided rules and models, it may be ensured stagnant air is minimised at source and avoided whilst an engine is running. However, to abate the effects of entrained gases in the coolant pump through redesign is undesirable due to the negative effects such changes have on a pump s efficiency and cavitation characteristics. It was concluded that the best solution to entrained gases, unavoidable at source, is to remove them from the coolant flow entirely using phase separation device(s).
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Musa, Mu'azu. "Novel evaporative cooling systems for building applications." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10674/.
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The technology and applications of evaporative cooling to provide human comfort in buildings is not new and has been used in different places based on different methods and materials. Conventional air conditioning systems overshadowed the application of evaporative cooling for buildings despite their ozone layer depletion. Evaporative cooling using porous ceramic evaporators were experimentally investigated. Encouraging results in terms of temperature reduction and cooling effectiveness were reported. In this work also thermoelectric unit was integrated in to the evaporative cooling system containing porous ceramic evaporators. The warm inlet air cooled in the evaporative cooling chamber was passed over the hot-side fins of the thermoelectric cooling device to act as a better heat sink. Typical test results showed that the cold side temperature of thermoelectric unit was 5Deg.C lower and the hot side was 10Deg.Clower, respectively when operated on the wet and dry porous ceramics evaporative cooling chamber. Direct evaporative cooling is often associated with the rise in relative humidity which may result in uncomfortable feeling due to unwanted increase in moisture. Indirect evaporative cooling offers a solution but still requires improvements in the effectiveness. There is also need for using cheap and readily available materials for the construction, requiring simple fabrication technology without very complex engineering infrastructure. Most widely used common fibrous materials have very limited capillary effect. So a periodic water spray system with an automatic control is required for running the cooler which adds to the power consumption, rise in operation costs as well as construction and operational difficulties. As a compromise using horizontal arrangement was considered. Use of pump for supplying water required to moisten the evaporative cooling surface was eliminated. The system was constructed and tested under varying temperature, relative humidity and air flow rates. Results showed significant temperature reduction accompanied with acceptable increase in relative humidity. Temperature drop of 6-10Deg.C between the inlet and outlet temperatures of the product or supply air was recorded. Increase in relative humidity of the supply air was 6 - 10% less than the working air. Application of this novel system was demonstrated in the parasol self-cooling arrangement. The fibre tube vaporative cooler has the potential of cooling a building space to the acceptable comfort limits. The application of porous ceramics for building space cooling, integrating the system to be used as a heat sink and the use of horizontal fibre tubes for evaporative cooling are all novel ideas in this field of research. Other novel features also include the ability to minimise energy consumption by eliminating common methods of continuous water circulation.
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Chen, Xiangjie. "Investigations of heat powered ejector cooling systems." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/29721/.
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In this thesis, heat powered ejector cooling systems was investigated in two ways: to store the cold energy with energy storage system and to utilize low grade energy to provide both electricity and cooling effect. A basic ejector prototype was constructed and tested in the laboratory. Water was selected as the working fluid due to its suitable physical properties, environmental friendly and economically available features. The computer simulations based on a 1-0 ejector model was carried out to investigate the effects of various working conditions on the ejector performance. The coefficients of performance from experimental results were above 0.25 for generator temperature of lI5°C-130 °C, showing good agreements with theoretical analysis. Experimental investigations on the operating characteristics of PCM cold storage system integrated with ejector cooling system were conducted. The experimental results demonstrated that the PCM cold storage combined with ejector cooling system was practically applicable. The effectiveness-NTU method was applied for characterizing the tube-in-container PCM storage system. The correlation of effectiveness as the function of mass flow rate was derived from experimental data, and was used as a design parameter for the PCM cold storage system. In order to explore the possibility of providing cooling effect and electricity simultaneously, various configurations of combined power and ejector cooling system were studied experimentally and theoretically. The thermal performance of the combined system in the range of 0.15-0.25 and the turbine output between 1200W -1400W were obtained under various heat source temperatures, turbine expansion ratios and condenser temperatures. Such combined system was further simulated with solar energy as driving force under Shanghai climates, achieving a predicted maximum thermal efficiency of 0.2. By using the methods of Life Saving Analysis, the optimized solar collector area was 30m2 and 90m2 respectively for the system without and with power generation. The environmental impacts and the carbon reductions of these two systems were discussed.
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Twort, Charles Tyler. "An exergy analysis of mine cooling systems." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323333.
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Mohamed, Y. "Interactive analysis of power station cooling systems." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380600.
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Baudoin, Antoine. "Cooling Strategies for Wave Power Conversion Systems." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-306706.
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The Division for Electricity of Uppsala University is developing a wave power concept. The energy of the ocean waves is harvested with wave energy converters, consisting of one buoy and one linear generator. The units are connected in a submerged substation. The mechanical design is kept as simple as possible to ensure reliability. The submerged substation includes power electronics and different types of electrical power components. Due to the high cost of maintenance operations at sea, the reliability of electrical systems for offshore renewable energy is a major issue in the pursuit of making the electricity production economically viable. Therefore, proper thermal management is essential to avoid the components being damaged by excessive temperature increases. The chosen cooling strategy is fully passive, and includes no fans. It has been applied in the second substation prototype with curved heatsinks mounted on the inner wall of the pressurized vessel. This strategy has been evaluated with a thermal model for the completed substation. First of all, 3D-CFD models were implemented for selected components of the electrical conversion system. The results from these submodels were used to build a lumped parameter model at the system level. The comprehensive thermal study of the substation indicates that the rated power in the present configuration is around 170 kW. The critical components were identified. The transformers and the inverters are the limiting components for high DC-voltage and low DC-voltage respectively. The DC-voltage—an important parameter in the control strategy for the WEC—was shown to have the most significant effect on the temperature limitation. As power diodes are the first step of conversion, they are subject to large power fluctuations. Therefore, we studied thermal cycling for these components. The results indicated that the junction undergoes repeated temperature cycles, where the amplitude increased with the square root of the absorbed power. Finally, an array of generic heat sources was optimized. We designed an experimental setup to investigate conjugate natural convection on a vertical plate with flush-mounted heat sources. The influence of the heaters distribution was evaluated for different dissipated powers. Measurements were used for validation of a CFD model. We proposed optimal distributions for up to 36 heat sources. The cooling capacity was maximized while the used area was minimized.
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Abou-Khamis, Kamal A. "Analysis and Design of Desiccant Cooling Systems." Youngstown State University / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ysu999701887.
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Dipasquale, Chiara. "Expert Control Strategies for Solar Cooling systems." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1339.
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Between 1990 and 2009, household final energy consumption in EU-27 increased by 8%, caused by rising standards of living, an increase in comfort levels and broader ownership of domestic appliances. In 2009, the total electrical consumption due to residential sector amounted at 36%.
Space heating and cooling is the most significant component of household energy demand. The European Directive to promote renewable heating and cooling requires that 25% of EU heating and cooling to be supplied by renewables in 2020. In the building sector, a high energy saving potentials can be realized by energy efficient building design. The energy efficiency of buildings is significantly influenced by architectural design aspects, such as orientation, shape of the building structure, envelope.
Building design should look at the site where it is located in order to take into account the climatic conditions, too. Today, some modern architectures neglect these aspects and compensate inefficient building design with enormous effort concerning the energy supply for heating, cooling and lighting. A strong reduction of energy consumption may be achieved minimizing losses (i.e. appropriate insulation, reduction of thermal bridge, airtight façade components), minimizing solar gains in low latitudes or maximizing solar gains in high latitudes.
In addition to passive solutions, a reduction of energy consumption may be achieved with active parts of a building, as space heating and cooling and Domestic Hot Water (DHW) production. In this sense, solar thermal technologies offer a great potential for providing a carbon-free response to residential energy demand [2].
In accordance with these matters, the work here presented describes a SHC system installed in a low energy building located in the north Italy where cold winters and warm summers occur. The aim of the work is the reduction of energy consumption, with regard to the level of thermal comfort. The improvement of a system performances requires a reliable model and the individuation of relevant parameters to be optimized. The modelling of the whole system, the calibration of its parts (building model and supply energy plant), the individuation of the most relevant parameters on the energetic performances and quality level and the selection of best configurations have been here investigated.
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Kang, Di. "Potential advantages of applying a centralized chilled water system to high-density urban areas in China." Kansas State University, 2017. http://hdl.handle.net/2097/35490.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Fred L. Hasler
This paper discusses the advantages of applying a utility centralized chilled water system as the district cooling choice for facilities in the high-density urban areas of China and how it will influence China’s development in the next decades. Presently, the Chinese government is trying to contribute to the world’s energy-saving goals as well as determine its sustainable development framework. As air pollution has become one of the main problems in China, indoor air quality (IAQ) is likely to gain priority as a building design consideration in the future. Consistent with this fact, this paper proposes an optimum HVAC system for cooling purposes to the Chinese government. Compared to unitary HVAC systems, the centralized HVAC system has significant advantages in system efficiency, energy reduction and cost savings and can, therefore, be a better choice. Furthermore, the paper will focus on the centralized chilled water system and demonstrate why they better match the development model in China. The application of the system in high-density urban areas will also be discussed. Due to a lack of understanding that the energy consumption of unitary systems, the first comparison presented is between unitary HVAC systems and centralized HVAC systems in individual buildings. The comparison presented will focus on the energy-saving benefits of the centralized HVAC system in individual buildings and its contribution to sustainable development. Consequently, prescribing a centralized chilled water system as a utility district cooling system and applying a centralized chilled water system to each individual building in the highdensity urban areas will be compared. Cost savings, including initial cost and life cycle cost, are the metrics used in this comparison. Additionally, energy consumption and system reliability will be explored in determining which model will be more appropriate for China's development. The paper concludes that the centralized chilled water system should become the mainstream in the high-density urban area in China. Several recommendations are also made to the Chinese government on setting up utility centralized chilled water systems.
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SARASKETA, ZABALA ELIXABET. "Technological and economic evaluation of district cooling with absorption cooling systems in Gävle (Sweden)." Thesis, University of Gävle, Ämnesavdelningen för energi- och maskinteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-4762.
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Dello, Sbarba Hugo. "Heat Recovery Systems in Underground Mine Ventilation Systems and Novel Mine Cooling Systems." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/28862/28862.pdf.
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L’exploitation minière souterraine dans les régions froides du monde nécessite le chauffage de l’air frais de ventilation et des bâtiments de surface. L’air vicié est habituellement rejeté dans l'atmosphère à des températures beaucoup plus élevées que l'air ambiant. Un logiciel informatique a été développé afin d'évaluer la faisabilité de récupérer la chaleur de l'air vicié des mines. Le logiciel estime la quantité de chaleur d’air vicié récupérable dans une mine souterraine. Il déterminera ensuite les économies annuelles potentiels d'énergie et un coût capital du système pour obtenir le retour sur l’investissement initial. Le logiciel considère un circuit de glycol en boucle fermée avec des échangeurs de chaleur à tubes et ailettes situées à l'extrémité des installations de ventilations à la surface (à l’entrée et l’échappement d’air). Différents concepts des systèmes de récupération de chaleur sont énoncés. La plupart des sources de chaleurs habituelles trouvées sur un site minier sont répertoriés. Quelques concepts innovateurs qui exploitent le froid de l'hiver comme un atout pour refroidir l'air d'entrée sont exposés.
Mots clés : Sources de chaleurs, air vicié, récupération de chaleur, faisabilité, chauffage, refroidissementUnderground mining in cold regions of the world requires heating of surface buildings and intake fresh air. Exhaust return air is usually discharged to the atmosphere at much higher temperatures than the ambient air. A computer software application has been developed in order to evaluate the feasibility of recovering heat from return exhaust air. The software approximates the amount of heat that can be recovered on surface from the exhaust ventilation shaft of an underground mine. It will then determine the annual energy cost savings and a capital cost of the system. This software considers a closed-loop glycol circuit with tube and fins heat exchangers located at the extremity of the exhaust and intake shaft surface installations. Different concepts of the heat recovery system are as well described. Most common heat sources that can be found on mine sites are listed. Several innovative designs that exploit cold winter weather as an asset to cool mine intake air are explained. Key words: heat sources, return air, heat recovery, feasibility, heating, cooling
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Minko, A., and V. V. Shevchenko. "Turbogenerators of new generation with various cooling systems." Thesis, Національний університет біоресурсів і природокористування України, 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/38955.
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Vilarrubí, Montse. "Energy efficient active cooling in advanced microelectronic systems." Doctoral thesis, Universitat de Lleida, 2019. http://hdl.handle.net/10803/668020.
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Les solucions actuals de refrigeració en circuits integrats en 3D (3D-IC) no proporcionen sistemes capaços d'adaptar el seu comportament a condicions variables en el temps i l'espai, fet que comporta un sobre refredament quan la demanda de fred és baixa. Això implica caigudes de pressió addicionals al canal del fluid i per tant, potències de bombeig sobredimensionades per condicions variables. A més, en els treballs existents, la uniformitat de temperatura sobre la superfície del xip només està optimitzada per una distribució de càrrega de calor determinada i no pot adaptar-se a escenaris de càrregues de calor variables en el temps i l’espai.
Per abordar aquests problemes, aquesta tesi proposa un sistema basat en aletes auto-adaptatives que actuen com a actuadors tèrmics passius. El principi d’expansió tèrmica dels materials és el responsable del comportament intel·ligent d’aquestes aletes, que s’activaran, sense cap excitació externa, en funció de la seva pròpia temperatura. Les capacitats, ja demostrades, d’elements pertorbadors del flux dins de microcanals, s’utilitzen només quan la demanda de refrigeració és alta; en cas contrari, les aletes romanen en posició plana, reduint així la caiguda de pressió dins del dispositiu de refredament. Amb aquesta solució, el sistema és capaç d’adaptar la seva geometria interna a distribucions de flux de calor temporals i no uniformes, optimitzant la millora de la transferència de calor i la caiguda de pressió a les necessitats de refrigeració instantànies. Així, és redueix la potència de bombeig necessària, fent el sistema de refrigeració més eficient energèticament.
Dins d’aquest treball, s’ha avaluat el principi de treball, el disseny i la validació de les aletes auto-adaptatives per aconseguir el comportament desitjat d’adaptabilitat utilitzant la dilatació tèrmica dels materials. S'ha avaluat l’increment de la transferència de calor convectiva a causa de la presència d’aquest tipus d’elements pertorbadors del flux dins del canal fluid, definint un increment del 10% en comparació amb un canal buit. A més, s'ha observat un gradient tèrmic superficial més uniforme, experimentalment i numèricament, a causa de la presència d'aletes auto-adaptatives quan el dispositiu de refrigeració està sotmès a fluxos de calor no uniformes. Finalment, s’estima una reducció del 10% de la potència de bombeig degut al concepte d’auto-adaptació, comparat amb un sistema de refredament basat en elements pertorbadors del flux fixos.Las soluciones de refrigeración actuales en circuitos integrados 3D (3D-IC) no proporcionan sistemas capaces de adaptar su comportamiento a las cambiantes condiciones de calor en el tiempo y el espacio. Este hecho conduce a un enfriamiento excesivo cuando las demandas de refrigeración son bajas y, por lo tanto, se inducen caídas de presión adicionales en el canal de fluido y se obtienen potencias de bombeo sobredimensionadas para condiciones cambiantes. Además, en las obras existentes, la uniformidad de la temperatura de la superficie del chip solo se optimiza para una distribución de carga térmica dada y no se puede adaptar a los escenarios de carga térmica variable en el tiempo y el espacio. Para superar estos problemas, esta tesis propone un sistema basado en aletas auto-adaptativas que actúan como actuadores térmicos pasivos. El principio de expansión térmica de los materiales es el responsable del comportamiento inteligente de estas aletas, que se activarán, sin ninguna excitación externa, en función de su propia temperatura. Las capacidades demostradas de los elementos que perturban el flujo dentro de los microcanales se usan solo para altas demandas de enfriamiento; de lo contrario, las aletas permanecerán en posición plana, reduciendo la caída de presión dentro del dispositivo de enfriamiento. Con esta solución, el sistema podrá adaptar su geometría interna a distribuciones de flujo de calor dependientes y no uniformes de tiempo, optimizando la mejora de la transferencia de calor local y la caída de presión a la necesidad de enfriamiento instantáneo y, por lo tanto, reduciendo la potencia de bombeo necesaria para una Sistema de refrigeración más eficiente energéticamente. Dentro de este trabajo, se ha evaluado el principio de trabajo, diseño y validación de las aletas auto-adaptativas para alcanzar el comportamiento deseado de auto-adaptación mediante el uso de la expansión térmica de los materiales. Se ha evaluado el incremento de la transferencia de calor por convección debido a la presencia de este tipo de elementos perturbadores del flujo dentro del canal, que definen una mejora del 10% en comparación con un canal plano. Además, se ha observado un gradiente térmico superficial más uniforme, experimental y numéricamente, debido a la presencia de aletas auto-adaptativas cuando el dispositivo de enfriamiento se somete a flujos de calor no uniformes. Finalmente, se estima una reducción del 10% en la potencia de bombeo debido al concepto de auto-adaptación, en comparación con un sistema de enfriamiento de elementos perturbadores de flujo fijo.
Actual cooling solutions of 3D integrated circuits (3D-IC) do not provide systems able to adapt their behavior to changing boundary conditions in time and space, what leads to overcooling when refrigerating demands are low. That implies additional pressure drops in the fluid channel and so, oversized pumping powers for changing conditions. Also, in the existing works, the surface temperature uniformity of the chip is only optimized for a given heat load distribution and cannot be adapted to variable heat load scenarios in time and space. To overcome these problems, this thesis proposes a system based on self-adaptive fins acting as passive thermal actuators. The principle of thermal expansion of the materials is the responsible for the smart behavior of these fins, which will be activated, without any external excitation, in function of their own temperature. The demonstrated capabilities of flow disturbing elements inside microchannels are used only for high cooling demands; otherwise, the fins will remain in flat position, reducing the pressure drop inside the cooling device. With this solution, the system will be able to tailor its internal geometry to time dependent and non-uniform heat flux distributions, optimizing the local heat transfer enhancement and the pressure drop to the instantaneous cooling need and thus, reducing the needed pumping power for a more energy efficient cooling system. Within this work, the working principle, design and validation of the self-adaptive fins to reach the desired behavior of self-adaptation by using the thermal expansion of the materials have been evaluated. The increment of the convective heat transfer due to the presence of this type of flow disturbing elements inside the fluidic channel has been assessed, defining a 10 % enhancement compared with a plain channel. Also, a more uniform surface thermal gradient has been observed, experimentally and numerically, due to the presence of self-adaptive fins when the cooling device is submitted to non-uniform heat fluxes. Finally, a reduction of 10 % in pumping power is estimated due to the self-adaptation concept, compared with a cooling system of fixed flow disturbing elements.
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Björk, Erik. "Energy Efficiency Improvements in Household Refrigeration Cooling Systems." Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93061.
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This thesis is based on eight articles all related to the characteristics of the cooling system and plate evaporator of a household refrigerator. Through these articles, knowledge is provided that can be used to increase the operational efficiency in household refrigeration. Papers A, B and C focus on heat transfer and pressure drop in a commonly used free convection evaporator – the plate evaporator. Applicable correlations are suggested on how to estimate the air side heat transfer, the refrigerant side pressure drop and the refrigerant side heat transfer. Papers D, E and F hold a unique experimental study of the refrigerant charge distribution in the cooling system at transient and steady state conditions. From this cyclic losses are identified and estimated and ways to overcome them are suggested. In paper G the topic “charging and throttling” is investigated in an unparalleled experimental study based on more than 600 data points at different quantities of charge and expansions device capacities. It results in recommendations on how to optimize the capillary tube length and the quantity of refrigerant charge. Finally, Paper H holds a thermographic study of the overall cooling system operating at transient conditions. Overall, a potential to lower the energy use by as much as 25 % was identified in the refrigerator studied. About 10 % was found on the evaporator’s air side. 1-2 % was identified as losses related to the edge effect of the evaporator plate. About 8 % was estimated to be cyclic losses. About 5 % was found in cycle length optimization. It is believed that most of these findings are of general interest for the whole field of household refrigeration even though the results come from one type of refrigerator. Suggestions of simple means to reduce the losses without increasing the unit price are provided within the thesisQC 20120411
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Gillespie, David R. H. "Intricate internal cooling systems for gas turbine blading." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365831.
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Al-Ajmi, Rashed. "Evaluation of vortex cooling systems for turbine blades." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364475.
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Saulich, Sven. "Generic design and investigation of solar cooling systems." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13627.
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This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.
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Wetterdal, David. "Optimizing night cooling for two systems in Stockholm." Thesis, KTH, Uthålliga byggnadssystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277726.
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Buildings in the commercial sector in Sweden accounts for around 12 % of the final energy consumption of the whole country. Utilizing energy efficient methods for heating, cooling and ventilation without compromising the indoor environment is therefore important. The incentives for energy conserving techniques are not only related to cost but also to lower the environmental impact. The cooling demand is highest during summer and to meet the demand indirect or direct cooling methods could be utilized. Night cooling is an indirect method and operating a night cooling system could be an option to lower the cooling demand. Utilizing night cooling means that the building is ventilated with cold air during nighttime, when the outdoor air temperature is lower than the indoor air temperature. The thermal mass of the building and equipment is therefore cooled down and could then act as a heat sink during daytime. The night cooling system is controlled with several conditions that needs to be fulfilled to allow the system to activate. Several previous studies and experiments have concluded that utilizing night cooling results in energy and cost savings, but some studies have established the opposite. Discomfort in the indoor environment has also been reported when operating night cooling systems in colder climates. Since the prediction of the performance also depends on several parameters the decision to install a night cooling system is not obvious. This study investigates two existing buildings in Hammarby sjöstad, Stockholm with night cooling systems installed. The aim of the study is to establish if night cooling should be utilized in the two facilities and discus if the obtained results are relevant for night cooling systems in general. To determine the performance of the systems the energy demand, the energy cost, the indoor environment, and the environmental impact will be analyzed. The method in the study has been to create building models of the two buildings in a building simulation performance software called IDA ICE. The initial information of the two buildings had different levels of detail. Information about one of the buildings was well documented from previous projects, while the information about the other building was limited. The missing information was compensated with standardized values provided from research on existing buildings in Sweden. In IDA ICE the buildings’ information and details was then imported to create the building models. A parametric study was then performed to test the effect of the night cooling. The results from the parametric study concluded that operating night cooling during more hours resulted in an energy decrease compared to when no night cooling was utilized. Operating night cooling with this condition also resulted in increased fan energy of the air handling units. The total energy cost was mostly decreased when night cooling was utilized, but the environmental impact became higher. On the other hand, the indoor environment was improved with night cooling systems installed.Fastigheter inom den kommersiella sektorn, i Sverige, står för omkring 12 % av den slutgiltiga totala energianvändningen för hela landet. Användandet av energieffektiva metoder för kyla, uppvärmning och ventilation utan att kompromissa på inomhusklimatet är därför viktigt. Incitamenten för att använda energieffektivare metoder är inte bara relaterat till kostnaden utan också att sänka miljöpåverkan. Kylbehovet är som högst under sommaren, och indirekta eller direkta metoder för kylning kan användas för att möta behovet. Nattkyla är en indirekt metod och kan vara ett alternativ för att sänka den totala energianvändningen för en fastighet. Nattkyla är en energibesparingsmetod där en byggnad ventileras med kall luft under natten när utomhustemperaturen är lägre än inomhustemperaturen. Detta kyler ner byggnadens konstruktion som sedan kan sänka kylbehovet under dygnets varmare timmar. Nattkylningssystemen styrs mot flera olika villkor som skall vara uppfyllda innan systemen aktiveras. Ett antal tidigare studier och experiment har konstaterat att användandet av nattkyla har resulterat i energi - och kostnadsbesparingar, medan andra studier har påvisat motsatsen. Försämrat inomhusklimat har också rapporterats i fall där nattkyla används. Eftersom nattkylningssystemen beror av många olika parametrar för att prestera lönsamt är valet att använda sig av metod inte uppenbar. Detta projekt undersöker två existerande byggnader som ligger i Hammarby sjöstad i Stockholm där nattkyla är installerat. Syftet med projektet är att fastställa om de två fastigheterna ska använda sig av nattkyla och att diskutera om de slutsatserna gäller generellt. För att fastställa prestandan av nattkylningssystemen kommer systemens energibehov, energikostnad och miljöpåverkan att analyseras. Metoden i projektet har varit att skapa simuleringsmodeller av de två byggnaderna i ett simuleringsverktygsprogram som heter IDA ICE. Tidigare information om byggnaderna hade varierad detaljnivå. Den ena byggnaden hade mer detaljerad information från tidigare projekt, medan informationen om den andra byggnaden var begränsad. Avsaknad information blev ersatt med standardiserade värden som är framtagna ur studier på ett stort antal existerande byggnader i Sverige. I IDA ICE skapades sedan byggnadsmodellerna baserat på den tillgängliga informationen och de standardiserade värdena. En parameterstudie utfördes sedan för att testa effekten av nattkyla. Resultaten av parameterstudien påvisade att användandet av nattkyla under fler timmar resulterade i en energibesparing jämfört med om ingen nattkyla användes. Användandet av nattkyla under samma villkor resulterade i att energibehovet för ventilationsaggregatens fläktar ökade. Den totala energikostnaden var i stort sett reducerad under användandet av nattkyla, medan den totala miljöpåverkan ökade. Samtidigt blev inomhusklimatet förbättrat med nattkyla installerat.
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Hublitz, Astrid. "Efficient energy storage in liquid desiccant cooling systems." kostenfrei, 2008. http://mediatum2.ub.tum.de/node?id=637243.
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NURZIA, Giovanni. "Design and simulation of solar absorption cooling systems." Doctoral thesis, Università degli studi di Bergamo, 2008. http://hdl.handle.net/10446/51.
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The aim of this work is to improve the modeling of single stage absorption chillers and to asses a design procedure for solar cooling systems based on computer simulations. The absorption technology is reviewed in its fundamentals, with an effort on the phenomena that might be considered or not in a physical model. A basic version of the absorption chiller model, which assumes that the heat transfer characteristics of the standard components do not depend on working conditions, is applied to simulate generic commercial chillers. The procedure outlined requires the knowledge of the nominal working
condition of the chiller, a data which is usually available from manufacturers. The model applied to the simulation of a chiller produced by the Thermax company shows good agreement with the off design
curves declared by the manufacturer. The hypotheses of this basic model are then reviewed, in order to catch some important aspects in the simulation of the Yazaki WFC-10 chiller. It is the first attempt, and therefore susceptible of improvement, to model the entire Yazaki chiller taking into account the behaviour of its heat exchangers. A compromise between theoretical modeling and experimental correlations has been adopted, due to the complexity of the chiller and its barely accessible patented design. Some encouraging results have been obtained, but they point out that further research on the heat and
mass transfer phenomena in the Yazaki absorption chiller is needed.
The absorption chiller modeling is then exploited in a computer tool that gives valuable information on the planning of solar cooling systems. The design of these systems involves the choice of the main components, their sizing and an adequate control strategy of the whole. Several installations are present worldwide, but there is a lack of standard planning methodology. In the present thesis the focus is on the choice of the plant elements and their sizing. Energy savings and economic competitiveness are regarded as essential in guiding the design process. To find out an ideal sizing of the system the
optimization-simulation approach is introduced. Once a typical system layout is chosen the TRNSYS environment is employed to see how different sizes of the system components effect the overall energy performance. The main design variables considered are the orientation of the solar collector array, the collectors area, the nominal capacity of the absorption chiller, the nominal capacity of the back up compression chiller, the volume of the thermal storages. Several simulations are launched by an external optimization programme, that retrieves the value of an objective function and changes the variables consequently. The procedure has been applied to a real planning case, carried out in two different installation sites. The results show that the economic convenience of solar cooling systems is really not easy going in the present scenario. Primary energy savings and reduction of electrical peak loads during hot season.
Finally a section of the present work describes how the absorption cycle model can be exploited to design a novel chiller. The allocation of the heat transfer area among the standard components of a chiller is analysed to get the best compromise between cost and thermodynamic performance. The geometry of each exchanger is optimized looking for a trade off between primary cost of the tubes and running cost of the pump employed in the external circuits.
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Nordlander, Erik. "Modelling and Validation of a Truck Cooling System." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12220.
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In the future, new challenges will occur during the product development in the vehicular industry when emission legislations getting tighter. This will also affect the truck cooling system and therefore increase needs for analysing the system at different levels of the product development. Volvo 3P wishes for these reasons to examine the possibility to use AMESim as a future 1D analysis tool. This tool can be used as a complement to existing analysis methods at Volvo 3P. It should be possible to simulate pressure, flow and heat transfer both steady state and transient.
In this thesis work a cooling system of a FH31 MD13 520hp truck with an engine driven coolant pump is studied. Further a model of the cooling system is built in AMESim together with necessary auxiliary system such as oil circuits. The model is validated using experimental data that have been produced by Volvo 3P at the Gothenburg facility.
The results from validation and other simulations show that the model gives a good picture of the cooling system. It also gives information about pressure, flow and heat transfer in steady state conditions. Further a design modification is done, showing how a change affects the flow in the cooling system.
The conclusion is that a truck cooling system can be built and simulated in AMESim. Further, it shows that AMESim meets the requirements Volvo 3P in Gothenburg has set up for the future 1D analysis tool and thereby AMESim is a good complement to the already existing analysis method.
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Frick, Peyton M. "A hydraulic actuated thermal management system for large displacement engine cooling systems." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193080466/.
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Schurger, Uwe. "Investigation into solar powered adsorption cooling systems : adsorption technology and system analysis." Thesis, De Montfort University, 2007. http://hdl.handle.net/2086/4122.
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Due to the fact that the worldwide energy consumption caused by cooling devices in buildings has been increasing steadily and also the fact that the pressure has been rising to provide this cooling energy with environmentally friendly technology, solar powe.re~ DEC-systems (Desiccative and Evaporative Cooling) have begun capturing increasing interest over the past few years. , However, up to now little experience has been gained in the operation of these systems and thus currently little information is available about the performance, the efficiency, the control strategy and the best component choice. This lack of knowledge has resulted in a low rate of acceptance of, this technology so far. The studies presented in this thesis serve as a contribution to the advancement of DEC technology by providing fundamental knowledge about the operation and attainable performance of these systems. A comprehensive study of desiccant wheels was undertaken which provides detailed information about the operation and the achievable dehumidification performance of this component. A detailed simulation model for desiccant wheels was developed and verified with measured data from a desiccant wheel test plant. Additionally, two commercially used DEC-systems (one in a public library in Spain and the other in a plastics processing factory building in Germany) were monitored for the purposes of evaluating the performance of these systems and resolving existing problems in their operation and control strategies. In spite of the generally positive validation of the planned and expected cooling performances in both cases, the monitoring also showed that there are considerable possibilities· for improvement, especially with the regulation of the system.
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Chen, Jing Ping. "Thermo-mechanical behaviour of heavy-duty disc brake systems." Thesis, Cranfield University, 2001. http://dspace.lib.cranfield.ac.uk/handle/1826/10701.
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In heavy-duty disc brake systems, braking is a transient, non-linear and asymmetrical thermo-mechanical process. Surface cracking, rather than wear, is the major factor limiting the brake disc's life. The disc material (cast-iron), heat transfer boundary conditions and pad-disc frictional reactions are characteristically non-linear and asymmetrical during the friction process. Non-uniform deformation and surface cracks in brake discs result from the accumulation of excessive residual stress/strain. During braking processes, many factors affect the distributions of the residual stress and strain in discs, and hence the propagation of the surface cracks. The disc material, structure and boundary conditions are three of the crucial aspects. From the structure, a brake disc could be either solid or ventilated. In practice, solid structures always have higher anti-cracking performance than the same class of ventilated designs. However solid discs cost more material and have lower cooling efficiency. This thesis presents an improved finite element analysis for heavy-duty disc brakes and identifies design improvements. As the friction pads slide against the disc's surfaces continuously, the thermal and mechanical loads are functions of time and spatial coordinates. A 3-D asymmetrical finite element model was developed to achieve more accurate simulations of the thermo-mechanical behaviour of brake discs during braking processes. A non-linear inelastic material model for cast-iron was employed in the FE model. Permanent plastic stress and strain fields were predicted and analysed for multi-stop drag operations. The residual stress/strain fields in the discs are investigated to understand the differences between solid and ventilated discs in terms of the cracking resistance ability. Several engineering solutions are recommended for optimising the performance of the disc brake system. _ The thesis is organized in five chapters. Chapter One introduces the background concepts about the commercial disc brake system. In this part, the brake structure, material and previous researches are reviewed. The goals for this investigation are also summarised at the end of this chapter. Chapter Two introduces the general finite element modelling knowledge, procedures and the modelling boundary conditions and material models. Chapter Three presents an analysis of the disc brakes thermo-mechanical behaviour and the affecting factors. Chapter Four is focused on the residual stress field prediction and cracking behaviour analysis. The project conclusions and further research recommendations are presented in Chapter Five.
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Swedenborg, Samuel. "Modeling and Simulation of Cooling System for Fuel Cell Vehicle." Thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326070.
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This report is the result of a master’s thesis project which covers the cooling system in Volvo Cars’ fuel cell test vehicle. The purpose is to investigate if the existing cooling system in the fuel cell test vehicle works with the current fuel cell system of the vehicle, in terms of sufficient heat rejection and thus sustaining acceptable temperature levels for the fuel cell system. The project also aims to investigate if it is possible to implement a more powerful fuel cell system in the vehicle and keep the existing cooling system, with only a few necessary modifications. If improvements in the cooling system are needed, the goal is to suggest improvements on how a suitable cooling system can be accomplished. This was carried out by modeling the cooling system in the simulation software GT-Suite. Then both steady state and transient simulations were performed. It was found that the cooling system is capable of providing sufficient heat rejection for the current fuel cell system, even at demanding driving conditions up to ambient temperatures of at least 45°C. Further, for the more powerful fuel cell system the cooling system can only sustain sufficient heat rejection for less demanding driving conditions, hence it was concluded that improvements were needed. The following improvements are suggested: Increase air mass flow rate through the radiator, increase pump performance and remove the heat exchanger in the cooling system. If these improvements were combined it was found that the cooling system could sustain sufficient heat rejection, for the more powerful fuel cell system, up to the ambient temperature of 32°C.
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Adegoke, C. O. "Evaluation of a refrigerant/absorbent combination for vapour absorption refrigeration systems utilising solar heat." Thesis, King's College London (University of London), 1987. https://kclpure.kcl.ac.uk/portal/en/theses/evaluation-of-a-refrigerantabsorbent-combination-for-vapour-absorption-refrigeration-systems-utilising-solar-heat(5c32f1a2-b5f9-41ba-b671-0bbb4fbcf578).html.
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Hewitt, Neil James. "The development of an alternative refrigeration cycle." Thesis, University of Ulster, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258150.
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Gebreslassie, Berhane Hagos. "Optimization of environmentally friendly solar assisted absorption cooling systems." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/8499.
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La optimización de los sistemas de conversión de energía gana cada vez más importancia debido a su impacto ambiental y los limitados recursos de combustibles fósiles. Entre estos sistemas los de refrigeración tienen una contribución creciente en el consumo total de energía y en las emisiones de CO2. Los sistemas de absorción operados con energía solar son una de las alternativas más sostenibles frente a los sistemas de refrigeración convencionales. Por lo tanto, este trabajo se centra en su mejora siguiendo los métodos de optimización termo-económica y de programación matemática. El análisis exergético y la optimización termo-económica basada en el método estructural se han realizado para distintas configuraciones de ciclos de refrigeración por absorción con las mezclas de trabajo agua-LiBr y amoniaco-agua. En la sección de programación matemática se incluye la optimización multi-objetivo (frontera de Pareto), la optimización bajo incertidumbre de los precios de la energía, el uso de varios indicadores de impacto ambiental y el efecto del impuesto sobre las emisiones de CO2. Los resultados demuestran que se pueden obtener reducciones importantes del impacto ambiental frente a los sistemas convencionales. Los sistemas de refrigeración solar no sólo son atractivos para reducir el impacto ambiental, sino también pueden ser económicamente competitivos. Su implantación dependerá, en gran medida, del impuesto sobre las emisiones de CO2 y del coste de la energía.Optimizations of energy conversion systems become more important because of their environmental impact and the limitations of the fossil fuel resources. Among these systems cooling and refrigeration machines have an increasing share in the total energy consumption and contribution to CO2 emissions. Solar assisted absorption cooling systems are sustainable alternatives compared to the conventional cooling systems. Hence, this work is focused on improving the sustainability of cooling systems following the thermoeconomic optimization and mathematical programming approaches. In the first approach the energy, exergy and structural analysis are performed for different configurations of water/LiBr and ammonia/water absorption cooling cycles. In the second approach multi-objective optimization (Pareto frontier), optimization under uncertainty of energy prices, different environmental impact indicators, and the effect of CO2 emissions tax to reduce the global warming are discussed. The results of the multi-objective optimization show that a significant environmental impact reduction can be obtained. Results indicate that these systems are attractive not only to reduce the environmental impact but also in incurring the economic benefits. However, its practical impact largely depends on the CO2 emissions tax and the increase in the energy price.
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Fransen, Rémy. "LES based aerothermal modeling of turbine blade cooling systems." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/10012/1/fransen.pdf.
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This PhD dissertation, conducted as part of a CIFRE research project between TURBOMECA and CERFACS in partnership with the VKI, deals with improving performance of axial turbines from helicopter engines. One of the most critical design points of such engines is the control of the high pressure turbine blade lifetime which face the high temperatures from the combustor. Today, industrial numerical aerothermal predictions of the flows around the blade (in the vein and in its cooling system) are performed with the Reynolds Averaged Navier-Stokes (RANS). Thanks to the increasing computational power, Large Eddy Simulation (LES) becomes affordable to offer further flow predictions. Therefore, this thesis focuses on the capabilities of the LES to estimate the flow in turbine blade internal cooling channels. To simplify this analysis where several physical phenomenon are present, the problem is described in three parts with increasing complexity. The first part addresses simplified typical geometries of cooling channel (U-bend and ribbed channel) in a static configuration. Considering the flow regime, a wall-resolved approach using a hybrid unstructured mesh is proposed in view of the application on an industrial case. The second part extends the study of the ribbed channel in rotation using an inertial reference frame. LES provides mean and unsteady results in good agreement with the available experimental data and previous works, for the flow dynamic and the heat transfer. Finally, the third part presents the application of the method to an industrial case with conjugate heat transfer between a complex cooling channel and the blade. This last section is not present in the public manuscrit for confidential reasons. Results of the use of the wall-resolved approach in rotation in an inertial frame of reference are compared to RANS predictions and show the potential of the method with high local differences.
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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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Wong, Yiu-ming, and 黃耀明. "Biofouling treatment of seawater cooling systems in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B42574778.
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Best, Y. Brown Roberto. "An experimental study of heat driven absorption cooling systems." Thesis, University of Salford, 1990. http://usir.salford.ac.uk/14742/.
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The great need for cooling combined with Mexico's large availability of low enthalpy energy from non conventional energy resources such as geothermal energy, solar heat and waste heat from industrial processes, makes it very attractive to utilize these resources for cooling using heat driven absorption systems. The main purpose of the work described in this thesis is to obtain experimental and theoretical data on heat driven absorption cooling systems for the design of large scale systems. Thermodynamic design data have been theoretically derived for heat driven absorption heat pumps and heat transformers using the working pairs ammonia-water and ammonia-lithium nitrate for cooling, heating and simultaneous heating and cooling. The interaction between the operating parameters has been illustrated graphically. A computer model of the steady state thermodynamics of a heat driven ammonia-water system and an ammonia-lithium nitrate system has been developed. A comparison of both systems is made by assessing the effect of operating temperatures and heat exchanger effectiveness on the coefficient of performance for cooling and the heat transfer rates within the system. An experimental study on the performance of the absorber of an absorption cooling system operating on water-lithium bromide has been made. The experimental study of the adiabatic absorber was concerned with the determination of the effect of the evaporator heat load and the absorber reflux on the performance of the absorber. An experimental study of the operating characteristics of an experimental. absorption cooler using water-lithium bromide-lithium iodide and waterlithium bromide-zinc bromide as ternary systems has been made in order to achieve higher coefficients of performance and a lower risk of crystallization. Experimental studies with a small heat driven absorption cooling system operating on ammonia-water using a falling film generator were made. Low generator temperatures were achieved which will'enable the use of non focussing solar collectors as a heat source for the system. An ammonia-water absorption cooler operating on low enthalpy geothermal energy was installed and operated at two geothermal fields. The system was used to cool a small cold storage facility below freezing temperatures. The experimental and theoretical results on absorption cooling systems will provide a basis for the design of heat pump systems for industrial and commercial applications.
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Mott, Irene EsmeÌ Catherine. "Biofouling and corrosion studies using simulated cooling water systems." Thesis, University of Birmingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272612.
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Vetter, David B. (David Brian). "Design of multi-passage cooling systems for avionics applications." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/115475.
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Kendrick, Clint Edward. "Development of model for large-bore engine cooling systems." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/8721.
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Master of ScienceDepartment of Mechanical and Nuclear Engineering
Kirby S. Chapman
The purpose of this thesis is to present on the development and results of the cooling system logic tree and model developed as part of the Pipeline Research Council International, Inc (PRCI) funded project at the Kansas State National Gas Machinery Laboratory. PRCI noticed that many of the legacy engines utilized in the natural gas transmission industry were plagued by cooling system problems. As such, a need existed to better understand the heat transfer mechanisms from the combusting gases to the cooling water, and then from the cooling water to the environment. To meet this need, a logic tree was developed to provide guidance on how to balance and identify problems within the cooling system and schedule appropriate maintenance. Utilizing information taken from OEM operating guides, a cooling system model was developed to supplement the logic tree in providing further guidance and understanding of cooling system operation. The cooling system model calculates the heat loads experienced within the engine cooling system, the pressures within the system, and the temperatures exiting the cooling equipment. The cooling system engineering model was developed based upon the fluid dynamics, thermodynamics, and heat transfer experienced by the coolant within the system. The inputs of the model are familiar to the operating companies and include the characteristics of the engine and coolant piping system, coolant chemistry, and engine oil system characteristics. Included in the model are the various components that collectively comprise the engine cooling system, including the water cooling pump, aftercooler, surge tank, fin-fan units, and oil cooler. The results of the Excel-based model were then compared to available field data to determine the validity of the model. The cooling system model was then used to conduct a parametric investigation of various operating conditions including part vs. full load and engine speed, turbocharger performance, and changes in ambient conditions. The results of this parametric investigation are summarized as charts and tables that are presented as part of this thesis.
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Bornman, Waldo. "Energy optimization for mine cooling systems through flow control." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/62809.
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The mining sector in South Africa accounted for 14.3% of all electricity supplied by Eskom in 2016. Up to 25% of this energy was consumed by mine cooling systems, suggesting that more focus should be placed on the energy consumption of cooling systems. Notwithstanding previous significant reductions obtained through energy efficiency in mine cooling systems, it was found that the current initiatives were not necessarily optimised to achieve their full potential. Through a review, several variable-flow energy-saving strategies were identified in the literature with the objective of ultimate integrated optimisation. In this semi-empirical investigation, an integrated simulation model was developed to fully quantify the overall cooling system’s integrated energy consumption. This model was subsequently coupled to a commercial optimisation platform to arrive at a globally optimised system. The novelty of the current study lies in the development of a mathematically optimised mine cooling system which is not currently found in the literature. The optimisation-friendly simulation model was constructed and verified through suitable component models and a component-based calibration process as a case study. For these verifications, modelling accuracies with root mean square of relative error (RMSRE) values between 0.0114 and 0.0651 were obtained. The components were subsequently coupled to form the integrated cooling system simulation model that was validated through a baseline simulation conducted on various isolated weekly datasets to confirm its integrity for simulation during and outside of the system calibration period. For these validations, RMSRE values in the range of 0.0362 to 0.0704 were obtained with average absolute error values between 2.44% and 4.61%. The baseline simulation validation was concluded with an hourly annual simulation that obtained an RMSRE value of 0.860 with an average absolute error of 6.22%. During the case study, it was found that the use of an integrated optimised mine cooling system has the potential to reduce the total average annual energy consumption by roughly 18%. This translates to an annual energy saving of more than 7.1 GWh for the particular mine. Because the majority of underground mines in South Africa utilise similar cooling systems, the adoption of integrated mine cooling optimisation systems could result in significant reductions of energy consumption in this sector.Thesis (PhD)--University of Pretoria, 2017.
Mechanical and Aeronautical Engineering
PhD
Unrestricted
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Wong, Yiu-ming. "Biofouling treatment of seawater cooling systems in Hong Kong." Click to view the E-thesis via HKUTO, 1998. http://sunzi.lib.hku.hk/hkuto/record/B42574778.
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Afroz, Zakia. "Performance improvement of building heating, cooling and ventilation systems." Thesis, Afroz, Zakia (2019) Performance improvement of building heating, cooling and ventilation systems. PhD thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/54931/.
Full textAbstract:
Heating, Ventilation, and Air Conditioning (HVAC) systems are responsible for a substantial share of the energy consumed in commercial buildings. Energy used by HVAC systems has increased over the years due to its broader application in response to the growing demand for better thermal comfort within the built environment. While existing case studies demonstrate the energy saving potential of efficient HVAC operation, there is a lack of studies quantifying energy savings from optimal operation of HVAC systems when considering indoor environmental conditions. This research aims to improve the performance of HVAC systems by optimizing its energy consumption without compromising indoor environmental conditions.
The concept of maintaining indoor environmental conditions poses new challenges to the optimal operation of HVAC systems. While the primary objective of ensuring optimal operation is to minimize energy consumption, controlling the indoor environmental parameters, e.g., temperature, humidity, the level of carbon dioxide (CO2), and volatile organic compounds (VOCs) to remain within the acceptable range imposes excess energy use. These two conflicting objectives constitute a multi-variable constrained optimization problem that has been solved using a particle swarm algorithm (PSO).
A real-time predictive model has been developed for individual indoor environmental parameters and HVAC energy consumption using Nonlinear Autoregressive Exogenous (NARX) neural network (NN). During model development, efforts have been paid to optimize the performance of the model in terms of complexity, prediction results, and ease of application to a real system. The proposed predictive models are then optimized to provide an optimal control setting for HVAC systems taking into account seasonal variations. An extensive case study analysis has been performed in a real commercial building to demonstrate the effectiveness of developing predictive models and evaluating the relevance of integrating indoor air quality (IAQ) within the optimization problem.
Results show that it is possible to minimize 7.8% energy consumption from HVAC systems without compromising indoor environmental conditions. This study demonstrates that the proposed optimal control settings maintain the indoor environment within the acceptable limit of thermal comfort conditions (indoor air temperature between 19.60 to 28.20C and indoor air humidity between 30 to 65 %RH as per ASHRAE Standard 55-2017) and air quality (CO2 ≤ 800 ppm and VOC ≤ 1000ppm as per Australian Standard AS 1668.2 2016). The outcomes of this research will act as a guideline for energy management practices, not only for energy efficient building design and retrofitting but also for building energy performance analysis. This research provides insight into the aspects that affect the performance of predictive models for indoor temperature. The proposed feature selection approach establishes its efficacy to determine salient and independent input parameters without compromising prediction performance. The application of this approach will minimize the measurement and data storing cost of variables. Further, using fewer numbers of input parameters in the model will reduce the computational cost and time. Thus, the proposed model establishes its applicability in a real system for a more extended period of advanced prediction. In addition, the need to better account for building-occupant interactions as an important step to maintain a healthy indoor environment has been recognized through evaluating a real-life demand control (DCV) system. Lastly, the proposed optimization approach, where four defined environmental parameters are considered simultaneously presents a new outlook within the HVAC control system by eliminating the unseen interface between thermal comfort and IAQ.
Overall, this unexploited potential to simultaneously improve the performance of HVAC systems and indoor environmental conditions drives the discussion on reconsidering the set-point configuration standards of HVAC in commercial buildings, either as part of individual building retrofit planning or as part of building regulatory applications.
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Alessandrini, Stefano. "Experimental analysis and dynamic simulation of solar cooling systems." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11128.
Full textAbstract:
2013/2014Il continuo aumento della richiesta di energia elettrica e la conseguente crescita dei valori di anidride carbonica nell'atmosfera terrestre crea sempre più la necessità di attuare modifiche sostanziali non solo nei metodi di produzione dei settori energetico e industriale, ma anche nella vita di ogni abitante del pianeta. Questa tesi analizza la possibilità di utilizzare l'energia solare per la produzione di acqua fredda grazie alla contemporaneità tra la disponibilità di energia rinnovabile e la richiesta di raffrescamento durante il periodo estivo. Due diversi impianti sperimentali, dotati di collettori solari a tubi evacuati commerciali e chiller ad adsoprbimento di piccole dimensioni (20 kW), sono stati monitorati ed i primi risultati sperimentali sono presentati in questo studio. Per studiare soluzioni diverse e trovare un design ottimale, un modello di simulazione dinamica è stato creato e testato utilizzando il software commerciale TRNSYS 17.
XXVII Ciclo
1984
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Bornman, Waldo. "Improved mine cooling system performance through the control of auxiliary systems / W. Bornman." Thesis, North-West University, 2012. http://hdl.handle.net/10394/9105.
Full textAbstract:
Industrial and mining sectors are amongst the largest single energy consumers in South
Africa, making them a primary focus for implementing energy saving initiatives.
Refrigeration systems on mines are responsible for consuming up to25 % of the electrical
energy consumption on a typical South African deep level mine. Ample opportunities to
reduce the energy consumption of these systems exists, as many of the current systems rely
on old technology and function under partial or inadequate control management.
In compiling this thesis, various energy saving strategies on deep level mines were
investigated. In specific, the effects of controlling and improving the cooling auxiliaries.
Scenarios were investigated and simulated, where after an optimum solution was
implemented. Implementations, such as the ones covered in this dissertation, form part of the
IDM (Integrated Demand Management) energy efficiency incentive introduced by Eskom,
where funding is made available based on actual power saving; ensuring that the projects will
be financially viable to the clients.
Reduced electrical energy consumption realised from the abovementioned projects were
measured, captured and compared to the consumption before project implementation to
determine the achieved savings. Savings of up to 30 % of the plant installed capacity were
realised, providing average savings of up to 2.3 MW per day.Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013
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Nguyen, Thai. "Development of New Cooling Methods for Grinding." Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/1689.
Full textAbstract:
This research aimed to develop new cooling methods to replace, or at least minimise, the use of currently used grinding coolants which are known to be harmful to the environment. The methods used involved the application of a cold air and vegetable oil mist mixture (CAOM), and the use of liquid nitrogen as cooling media. Allied research focused on the development of a segmented grinding wheel equipped with a coolant chamber. The feasibility of a grinding system using CAOM was assessed on the surface grinding of plain carbon steel 1045. It was found that at low material removal rates, ground surfaces were obtained with a quality comparable to that from grinding with a conventional coolant in association with a reduction of grinding forces. There was no significant difference in the subsurface hardness of the components using CAOM, although the latter method showed a stronger dependence of surface residual stresses on the depth of cut due to the limit in cooling capacity of CAOM. The effects of using liquid nitrogen as a cooling medium on the microstructure of quenchable steel were explored. It was found that a martensite layer was induced on the ground surface. The microstructure featured a dispersion of very fine carbides within the martensite lattice, resulting in a remarkable increase in hardness and high compressive residual stresses within the layer. The topography of the ground surfaces indicated that the material was predominantly removed by brittle fracture. Furthermore surface oxidisation was suppressed. In the interest of coolant minimisation, a segmented wheel equipped with a pressurized coolant chamber was developed. A higher quality ground surface was obtained in conjunction with a coolant saving of up to 70%. In addition, the adhesion of ground chips on the wheel surface largely disappeared. Furthermore, surface tensile residual stresses caused by thermal deformation were minimised. The mechanism of coolant disintegration to form mists using this type of wheel system was studied. The Weber theory for Newtonian jet instability was applied to quantitatively determine the contribution of coolant flow rate to mist and ligament modes. A semi-analytical model was then developed to predict the mist flow rate by taking into account both grinding parameters and coolant properties. The model prediction was in agreement with experimental measurements. Based on the principles of fluid motion and the mechanisms of spin-off and splash, analytical models for both conventional and segmented wheels were established to provide a physical understanding of the mechanisms of coolant penetration into the grinding zone. Coolant minimisation was evident using the segmented wheel where the coolant pumping power into the grinding zone increased with wheel speed, but for the conventional wheel it decreased. A quantitative analysis was developed that accounted for the coolant properties and system design characteristics governing the penetration mechanism revealed by the theory established above. In conjunction with the mist formation analysis, the developed model offers a practical guideline for the optimal use of grinding coolants in achieving a balance between the demands of productivity and care for the environment.
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Nguyen, Thai. "Development of New Cooling Methods for Grinding." University of Sydney, 2005. http://hdl.handle.net/2123/1689.
Full textAbstract:
Doctor of PhilosophyThis research aimed to develop new cooling methods to replace, or at least minimise, the use of currently used grinding coolants which are known to be harmful to the environment. The methods used involved the application of a cold air and vegetable oil mist mixture (CAOM), and the use of liquid nitrogen as cooling media. Allied research focused on the development of a segmented grinding wheel equipped with a coolant chamber. The feasibility of a grinding system using CAOM was assessed on the surface grinding of plain carbon steel 1045. It was found that at low material removal rates, ground surfaces were obtained with a quality comparable to that from grinding with a conventional coolant in association with a reduction of grinding forces. There was no significant difference in the subsurface hardness of the components using CAOM, although the latter method showed a stronger dependence of surface residual stresses on the depth of cut due to the limit in cooling capacity of CAOM. The effects of using liquid nitrogen as a cooling medium on the microstructure of quenchable steel were explored. It was found that a martensite layer was induced on the ground surface. The microstructure featured a dispersion of very fine carbides within the martensite lattice, resulting in a remarkable increase in hardness and high compressive residual stresses within the layer. The topography of the ground surfaces indicated that the material was predominantly removed by brittle fracture. Furthermore surface oxidisation was suppressed. In the interest of coolant minimisation, a segmented wheel equipped with a pressurized coolant chamber was developed. A higher quality ground surface was obtained in conjunction with a coolant saving of up to 70%. In addition, the adhesion of ground chips on the wheel surface largely disappeared. Furthermore, surface tensile residual stresses caused by thermal deformation were minimised. The mechanism of coolant disintegration to form mists using this type of wheel system was studied. The Weber theory for Newtonian jet instability was applied to quantitatively determine the contribution of coolant flow rate to mist and ligament modes. A semi-analytical model was then developed to predict the mist flow rate by taking into account both grinding parameters and coolant properties. The model prediction was in agreement with experimental measurements. Based on the principles of fluid motion and the mechanisms of spin-off and splash, analytical models for both conventional and segmented wheels were established to provide a physical understanding of the mechanisms of coolant penetration into the grinding zone. Coolant minimisation was evident using the segmented wheel where the coolant pumping power into the grinding zone increased with wheel speed, but for the conventional wheel it decreased. A quantitative analysis was developed that accounted for the coolant properties and system design characteristics governing the penetration mechanism revealed by the theory established above. In conjunction with the mist formation analysis, the developed model offers a practical guideline for the optimal use of grinding coolants in achieving a balance between the demands of productivity and care for the environment.
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Le, Alex. "An economic comparison between two district cooling systems in Halmstad." Thesis, Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-25752.
Full textAbstract:
The supply of cooling has increased significantly in recent years, the trend shows that the increase will continue one reason is that the standard of living has increased, but EU has also set a requirement that energy consumption must be better at the same time. With “better” means more efficient and environmentally friendly. District cooling today uses either chillers or naturally available cold sources such as deep sea water, lake water or cold air. Cold air is, of course, only available when the seasons permit it and the cold air is not available when comfort cooling is needed for e.g. offices. The only alternative for areas that do not have a cold water source nearby is to use chillers. The most common chillers today are compressor chillers and absorption chillers. The most interesting chiller for the energy and environmental company HEM in Halmstad, is the absorption chiller which is driven by heat. HEM has, during the summer, surplus heat produced in Kristinehed plant which they want to use, they also have an increased inventory of waste during the summer which they get from the municipality of Halland. This heat is, of course, qualified to be used in the making of cold. Absorption chillers is today, however, not as common as compressor chillers which are capable of dealing with most cooling capacities, from small to large, and simultaneously works more or less flawlessly. Most of today’s absorption chillers are of a few hundred kW and upwards while there are no absorption chillers for the smaller effects, they are also very expensive and can have problems with crystallization of the absorbent if the operation is handled incorrectly. But it’s also expensive when it comes to piping of district cooling networks depending on where the pipes are desired, for example if it is the middle of town or over a grass field. A fictional project of the area Sannarp is used for a case study in this thesis where one investment alternative was to extend the existing district cooling pipes and another alternative was to invest in absorption chillers to meet the company's cooling demand. The results were obviously much affected by the area's layout and the distance to the first company starting from the existing pipe. The company's cooling demand also affected the results and the first alternatives investment cost could only be competitive with alternative 2 because the distance was just of the right length. If the distance to the company had been shorter, then the cooling demand for the same company has had to be less. The conclusion of the project was still in the end that and expansion of the current district cooling network to the company was the most feasible and economically advantageous.
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Klawunder, Shawn Eric. "Modeling and analysis of chilled water systems." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16383.
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Heyns, Johan Adam. "Performance characteristics of an air-cooled steam condenser incorporating a hybrid (dry/wet) dephlegmator." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/350.
Full textAbstract:
Thesis (MScEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008.This study evaluates the performance characteristics of a power plant incorporating a steam turbine and a direct air-cooled dry/wet condenser operating at different ambient temperatures. The proposed cooling system uses existing A-frame air-cooled condenser (ACC) technology and through the introduction of a hybrid (dry/wet) dephiegmator achieves measurable enhancement in cooling performance when temperatures are high. In order to determine the thermal-flow performance characteristics of the wet section of the dephlegmator, tests are conducted on an evaporative cooler. From the experimental results, correlations for the water film heat transfer coefficient, air-water mass transfer coefficient and the air-side pressure drop over a deluged tube bundle are developed. During periods of high ambient temperatures the hybrid (dry/wet) condenser operating in a wet mode can achieve the same increased turbine performance as an oversized air-cooled condenser or an air-cooled condenser rith adiabatic cooling (spray cooling) of the inlet air at a considerably lower cost. For the same turbine power output the water consumed by an air-cooled condenser incorporating a hybrid (dry/wet) dephlegmator is at least 20% less than an air- cooled condenser with adiabatic cooling of the inlet air.
Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University