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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Thermodynamic Modeling of HVAC Plant Cooling Equipment for Quantification of Energy Savings Through Continuous Commissioning Measures

Rivera, Steven 2011 December 1900 (has links)
The Continuous Commissioning (CC) process is applied to existing buildings in order to reduce energy consumption by optimizing HVAC system operation and improving occupant comfort. The CC process consists of implementing energy saving measures for the air-side and plant-side of HVAC systems. Current development of a computer program (WinAM) by the Energy Systems Laboratory allows the expected energy savings from applying air-side CC measures to a given building to be estimated. However, there is no means for quantifying the potential energy savings from applying plant-side CC measures. The quasi-steady-state method and a regression of EnergyPlus library data were used for chiller modeling and the Merkel method was used for cooling tower modeling. Implementation of the models developed provides a means for quantifying the energy savings associated with plant cooling equipment CC measures. Chiller models have been developed for the following, with capacity range, average error, and standard deviation in parenthesis: air-cooled scroll chillers (15-168 tons, 8.07%, 9.13%), air-cooled screw chillers (69-513 tons, 7.38%, 6.13%), water-cooled scroll chillers (20-200 tons, 8.16%, 9.72%), water-cooled reciprocating chillers (20-364 tons, 10.30%, 7.81%), water-cooled screw chillers (194-498 tons, 9.87%, 3.65%), and water-cooled centrifugal chillers with inlet guide vane capacity control (233-677 tons, 12.07%, 5.96%) and with VSD capacity control (210-677 tons, 12.18%, 4.61%). From the chiller models developed, energy consumed by the chiller can be calculated as building cooling loads and fluid operating temperatures vary. Cooling tower models have been developed to predict cooling tower energy consumption as building cooling loads, added load from chillers, fluid operating temperatures, and ambient air temperatures vary. The models developed provide for predicting energy consumption when fan operation is by single-speed, two-speed, variable-speed with modulating outlet dampers, or variable-speed with VFD control. Implementation of the chiller and cooling tower models developed will allow WinAM users the ability to quantify the potential energy savings associated with changing plant cooling equipment operation.
2

Métodos expeditos indirectos de análise de eficiência de equipamentos de produção de energia térmica, nomeadamente Chillers.

Lemos, Carlos Miguel Rodrigues de January 2011 (has links)
Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2011
3

Projeto e simulação de resfriadores de líquidos. / Chillers design and simulation.

Lopes, Marco Aurélio 20 March 2007 (has links)
Na última década, o mundo passou por uma transformação importante. O aumento do número de empresas e a globalização fizeram com que a concorrência obrigasse os diversos setores da indústria a aumentarem a produtividade e a qualidade para se manterem competitivos. Neste contexto, os sistemas de refrigeração proporcionam redução do tempo de ciclo em diversos processos de manufatura e, conseqüentemente, aumento de produtividade, maior confiabilidade, repetibilidade e qualidade do produto acabado. Diante desse cenário, fica evidente a importância de um estudo sobre refrigeração industrial. Neste trabalho é apresentado um estudo do projeto, dimensionamento e simulação de resfriadores de líquidos utilizados em refrigeração industrial. São analisados os principais aspectos relevantes ao projeto do sistema hidráulico e de refrigeração, além do dimensionamento dos principais componentes do equipamento. Após análise do projeto, são desenvolvidos modelos matemáticos para simulação do sistema de refrigeração em regime permanente. Os resultados de simulação são comparados com resultados obtidos em bancada experimental, verificando-se diferenças máximas de 3ºC na temperatura de evaporação, 2ºC na temperatura de condensação e 20% na capacidade efetiva de refrigeração. Adicionalmente, os resultados obtidos mostram que o equipamento não atinge a capacidade projetada e são propostas alterações no compressor e no condensador a ar. É sugerida a substituição do compressor, o aumento da área de troca do condensador e diminuição do número de aletas por polegadas para aumentar a vazão de ar. Por fim, o desenvolvimento do trabalho resulta em um programa de simulação de resfriadores de líquidos, que constitui importante ferramenta de análise e otimização. / In the last decade, the world passed trough an important transformation. The raise in the number of companies and globalization obligated the industry to increase production and quality to be competitive. This scene turns clear the importance of researches in the industrial refrigeration area. The cooling systems allow reduction in the manufacture time cycle, and consequently, rise in productivity, more reliability and quality of the final product. In this work, an analysis of the design, dimensioning and simulation of liquid chillers used for industrial refrigeration is presented. The main aspects of the hydraulic and refrigeration systems and the dimensioning of the components used in the equipment are analyzed. After the analysis of the project, a mathematical model of the system for simulation in equilibrium state is developed. The results of the simulations are compared with the data obtained during the tests and the maximum differences was 3ºC in the evaporating temperature, 2ºC in condensing temperature and 20% of cooling capacity. Additionally, the results show that the equipment hasn?t achieved the design capacity and changes were proposed in the compressor and air cooled condenser. The equipment has been tested and the data obtained has been compared with the simulation. It?s suggested to change the compressor for another model with higher capacity, to increase the heat exchange area and to reduce the number of fins in the air cooled condenser. Finally, the development of this work resulted in a simulation program of liquid coolers, very useful tool for analysis and optimization.
4

Projeto e simulação de resfriadores de líquidos. / Chillers design and simulation.

Marco Aurélio Lopes 20 March 2007 (has links)
Na última década, o mundo passou por uma transformação importante. O aumento do número de empresas e a globalização fizeram com que a concorrência obrigasse os diversos setores da indústria a aumentarem a produtividade e a qualidade para se manterem competitivos. Neste contexto, os sistemas de refrigeração proporcionam redução do tempo de ciclo em diversos processos de manufatura e, conseqüentemente, aumento de produtividade, maior confiabilidade, repetibilidade e qualidade do produto acabado. Diante desse cenário, fica evidente a importância de um estudo sobre refrigeração industrial. Neste trabalho é apresentado um estudo do projeto, dimensionamento e simulação de resfriadores de líquidos utilizados em refrigeração industrial. São analisados os principais aspectos relevantes ao projeto do sistema hidráulico e de refrigeração, além do dimensionamento dos principais componentes do equipamento. Após análise do projeto, são desenvolvidos modelos matemáticos para simulação do sistema de refrigeração em regime permanente. Os resultados de simulação são comparados com resultados obtidos em bancada experimental, verificando-se diferenças máximas de 3ºC na temperatura de evaporação, 2ºC na temperatura de condensação e 20% na capacidade efetiva de refrigeração. Adicionalmente, os resultados obtidos mostram que o equipamento não atinge a capacidade projetada e são propostas alterações no compressor e no condensador a ar. É sugerida a substituição do compressor, o aumento da área de troca do condensador e diminuição do número de aletas por polegadas para aumentar a vazão de ar. Por fim, o desenvolvimento do trabalho resulta em um programa de simulação de resfriadores de líquidos, que constitui importante ferramenta de análise e otimização. / In the last decade, the world passed trough an important transformation. The raise in the number of companies and globalization obligated the industry to increase production and quality to be competitive. This scene turns clear the importance of researches in the industrial refrigeration area. The cooling systems allow reduction in the manufacture time cycle, and consequently, rise in productivity, more reliability and quality of the final product. In this work, an analysis of the design, dimensioning and simulation of liquid chillers used for industrial refrigeration is presented. The main aspects of the hydraulic and refrigeration systems and the dimensioning of the components used in the equipment are analyzed. After the analysis of the project, a mathematical model of the system for simulation in equilibrium state is developed. The results of the simulations are compared with the data obtained during the tests and the maximum differences was 3ºC in the evaporating temperature, 2ºC in condensing temperature and 20% of cooling capacity. Additionally, the results show that the equipment hasn?t achieved the design capacity and changes were proposed in the compressor and air cooled condenser. The equipment has been tested and the data obtained has been compared with the simulation. It?s suggested to change the compressor for another model with higher capacity, to increase the heat exchange area and to reduce the number of fins in the air cooled condenser. Finally, the development of this work resulted in a simulation program of liquid coolers, very useful tool for analysis and optimization.
5

Model based control optimisation of renewable energy based HVAC Systems

Pietruschka, Dirk January 2010 (has links)
During the last 10 years solar cooling systems attracted more and more interest not only in the research area but also on a private and commercial level. Several demonstration plants have been installed in different European countries and first companies started to commercialise also small scale absorption cooling machines. However, not all of the installed systems operate efficiently and some are, from the primary energy point of view, even worse than conventional systems with a compression chiller. The main reason for this is a poor system design combined with suboptimal control. Often several non optimised components, each separately controlled, are put together to form a ‘cooling system’. To overcome these drawbacks several attempts are made within IEA task 38 (International Energy Agency Solar Heating and Cooling Programme) to improve the system design through optimised design guidelines which are supported by simulation based design tools. Furthermore, guidelines for an optimised control of different systems are developed. In parallel several companies like the SolarNext AG in Rimsting, Germany started the development of solar cooling kits with optimised components and optimised system controllers. To support this process the following contributions are made within the present work: - For the design and dimensioning of solar driven absorption cooling systems a detailed and structured simulation based analysis highlights the main influencing factors on the required solar system size to reach a defined solar fraction on the overall heating energy demand of the chiller. These results offer useful guidelines for an energy and cost efficient system design. - Detailed system simulations of an installed solar cooling system focus on the influence of the system configuration, control strategy and system component control on the overall primary energy efficiency. From the results found a detailed set of clear recommendations for highly energy efficient system configurations and control of solar driven absorption cooling systems is provided. - For optimised control of open desiccant evaporative cooling systems (DEC) an innovative model based system controller is developed and presented. This controller consists of an electricity optimised sequence controller which is assisted by a primary energy optimisation tool. The optimisation tool is based on simplified simulation models and is intended to be operated as an online tool which evaluates continuously the optimum operation mode of the DEC system to ensure high primary energy efficiency of the system. Tests of the controller in the simulation environment showed that compared to a system with energy optimised standard control the innovative model based system controller can further improve the primary energy efficiency by 19 %.
6

Beiträge zur optimalen Auslegung und Betriebsführung von Absorptions-Kältemaschinen im Systemverbund

Dittmann, Lutz 30 May 2009 (has links) (PDF)
Die Arbeit bietet einen praxisbezogenen Überblick über den rationellen Einsatz von thermischen Kälteanlagen. Dabei wird von der Stoffdatenanlayse, bei der eine unfassende Analyse und Kritik und eine Korrektur der Ansätze durchgeführt wird, der darauf aufbauenden rechentechnischen Simulation der wichtigsten Maschinen über eine Optimierung der Kaltwasserspeicherung durch einen neuartigen Speicherbehälter bis zur Darlegung einer effizienten Einbindung in eine Systemschaltung und der energetischen Bewertung die gesamte Bandbreite der thermisch betriebenen Kälteerzeugung abgedeckt. In diesem umfassenden Ansatz stellt die Arbeit ein Novum dar. Insbesondere im Bereich der Kaltwasserspeicherung wird eine konstruktiv neue Lösung vorgeschlagen, die einen wirtschaftlichen Einsatz der Anlagen gerade im innerstädtischen Bereich, der ein hohes Entwicklungspotenzial besitzt, verbessert oder überhaupt erst ermöglicht. In Verbindung mit den Erkenntnissen zur Anlagensimulation und Einsatzoptimierung trägt die Arbeit zu einem verstärkten Einsatz von thermischen Kälteanlagen und damit zur Erschließung energetischer Einsparpotenziale bei. Des Weiteren wurde die Effizienz zweier momentan nicht genutzter Technologien dargestellt und eine Umsetzung empfohlen. Die Ergebnisse lassen sich auf mehrere Arten kommerziell nutzen. Einerseits wird die Erstellung von effizienten Simulationstools für verschiedene thermisch betriebene Kälteanlagen und Wärmepumpen ermöglicht, andererseits die Umsetzung einer neuen effizienten Speicherlösung beschrieben und die Rahmenbedingungen des Einsatzes innovativer Technologien dargelegt (Resorptions- und Absorptionsanlage mit mechanischer Kompression) und eine sinnvolle Nutzung im energiepolitischen Rahmen der Bundesrepublik anhand von Bewertungsalgorithmen ermöglicht. Gerade im Hinblick auf den von der Bundesregierung angestrebten Ausbau der Fernwärmenutzung in Deutschland lassen sich durch die Nutzung von KWK-Wärme im Sommer neue wirtschaftliche Potenziale erschließen. Durch die kritische Analyse der thermodynamischen Grundlagen der Mischung der Stoffe Lithiumbromid und Wasser erstellt die Arbeit die Basis für eine wissenschaftlich korrekte Berechnung von Simulationswerkzeugen und konstruktive Umsetzungen von thermischen Kälteanlagen / Wärmepumpen und ermöglicht sowohl Planern und Wissenschaftlern als auch Studenten oder interessierten Laien einen umfassenden Blick auf die Technologien und ihre energiepolitisch sinnvollen Einsatzchancen. / The thesis contains a practical overview of the rational use of thermal chillers. Based on an extensive analysis of the data on chemical media, a computer simulation of the most important absorption chillers / heat pumps was realised. Furthermore an optimisation of the cold water storage by a novel storage tank construction and explanations of the efficient integration of absorption chillers into an integrated network are given. Especially the novel horizontal cold water storage advances the general conditions of the application of absorption chillers in municipal areas. Also the efficiencies of two currently neglected technologies are shown.
7

Développement d’une méthodologie de qualification de systèmes complexes par des essais de fiabilité / Development of a qualification methodology for complex systems by reliability tests

Delage, Sylvain 16 January 2018 (has links)
Le secteur du chauffage, de la ventilation et de la climatisation (Heating Ventilation and Air-Conditioning,HVAC) se doit, comme toute industrie d’envergure, de maîtriser la fiabilité de ses produits pour garantir un service optimal au client, réduire les délais de développement et maîtriser ses coûts. Pour ce faire, il est indispensable de connaitre et savoir appliquer les outils de fiabilité prévisionnelle, expérimentale et opérationnelle. Seule une méthodologie robuste permettant de définir une stratégie de qualification permet de garantir la tenue de l’objectif de fiabilité.La première partie de ce travail définit les problématiques ayant attrait à la fiabilité et fait l’inventaire des méthodes existantes dans des domaines connexes et surtout dans le domaine HVAC.Dans un second temps la méthodologie de qualification est proposée, avec un focus sur l’exploitation du retour d’expérience, la définition des objectifs de fiabilité et tous les plans d’essais possibles. Enfin, des exemples concrets mis en place chez CIAT (UTC) sont détaillées dans une dernière partie. / The heating, ventilation and air conditioning (HVAC) field, as any other large industry, must control the reliability of its products in order to guarantee an optimal service to customers, reduce development limits and master its costs. To achieve it, predicted, experimental and operational reliability tools should be known and well applied. Only a strong methodology leading to a qualification strategy can ensure the holding of the reliability target. The first part of this work defines reliability terms and inventories existing methods in related fields and specifically in HVAC. Following that, the qualification methodology is detailed, focusing on feedback, definition of reliability targets and possible test plans. Finally, specific examples implemented at CIAT (UTC) are detailed in final part.
8

Modelling the performance and dynamics of vapour compression refrigeration systems

Grace, Iain Nicholas January 2000 (has links)
The impact of refrigeration systems on the environment can be reduced by the use of alternative reffigerants which are less harmful to the atmosphere and the optimisation of systems and control strategies to deliver increased levels of energy efficiency. Mathematical modelling offers the opportunity to test the performance of systems under different operating conditions and with alternative refrigerants. Dynamic models allow comparison of both transient and steady-state behaviour and this is of particular importance for liquid chillers, since these systems can operate under transient conditions for long periods. This thesis details the development of a general dynamic model for the simulation of liquid chillers. Mathematical models of the reciprocating compressor, expansion valve, evaporator and condenser are presented. The models are integrated to form the overall system model by passing conditions from one component to another. A series of steady-state and transient experimental tests were carried out on a liquid chiller and the model was used to simulate these tests. Validation was carried out by comparison of these measured results to those predicted by the simulation for both the steady-state and transient tests. Once validated, the model was used to investigate the steady-state and dynamic performance of liquid chillers operating with various refrigerants. The effect of the mass of the system refrigerant charge was examined for a number of refrigerants. The steady-state performance for a range of evaporator and condenser coolant temperatures was also investigated. Finally, the effect of different system refrigerants on start-up transients was examined and the losses in cooling capacity due to cycling quantified. The effect of the expansion valve's initial superheat spring setting on the dynamic response and transient losses was also investigated.
9

Uso de redes neurais artificiais para a modelagem da temperatura e da retenção de água no processo de resfriamento de carcaças de frangos por imersão / Use of artificial neural networks for the modelling of the temperature and the water retention in the process of chilling of chicken carcasses by immersion

Klassen, Túlio 11 February 2008 (has links)
Made available in DSpace on 2017-07-10T18:08:07Z (GMT). No. of bitstreams: 1 Tulio Klassen.pdf: 1461464 bytes, checksum: 02d111496a486b94ea73232034f2aeb6 (MD5) Previous issue date: 2008-02-11 / The Artificial Neural Networks have been used with success for the description and modeling of processes in the most several areas of the knowledge, from economy, administration, artificial intelligence and even control of complex industrial processes. The process of chilling of chickens for immersion in cold water ("chillers") is complex and difficult to be modeled phenomenologicaly, because it involves transfer of heat, mass and transient regime, besides a great number of variables. In this work several architectures of artificial neural networks were used in the description and modeling of the process of chilling of the chickens, foreseeing the final temperature and the growth of weight of the carcasses. Also for comparison effect they were used an empiric model proposed by CARCIOFI & LAURINDO (2007) to describe the absorption of the water for the carcasses and the chilling model according to Newton's Law for the temperature of the carcasses. Different situations were tested changing the numbers of neurons of the entrance and hidden layers, and the number of layers. The data used were supplied by the SADIA - Toledo company for training and validation of the net. For the model twenty-five entrance variables were selected, as weight of the carcass, temperature before the chillers, temperature of the propilenoglicol shirt, flow of water in each module of the tanks, time of chilling and temperature of the renewal water, bubble intensity and amount of ice. The results obtained by the neural network and for Newton's Law they were not efficient to represent the final temperature of the carcass. The neural networks and the empiric model of CARCIOFI & LAURINDO (2007) went very efficient to esteem the amount of water absorbed for the carcasses. The obtained results showed that the net type with 4 x 12 x 4 neurons in the entrance layer, first and second hidden layers respectively was the best to represent the investigated system. / As Redes Neurais Artificiais têm sido empregadas com sucesso para a descrição e modelagem de processos nas mais diversas áreas do conhecimento, desde economia, administração, inteligência artificial e até controle de processos industriais complexos. O processo de resfriamento de frangos por imersão em água gelada ( chillers ) é complexo e difícil de ser modelado fenomenologicamente, pois envolve transferência de calor, massa e regime transiente, além de um grande número de variáveis. Neste trabalho foram empregadas diversas arquiteturas de redes neurais artificiais na descrição e modelagem do processo de resfriamento dos frangos, prevendo a temperatura final e o ganho de peso das carcaças. Também para efeito de comparação foram empregados um modelo empírico proposto por CARCIOFI & LAURINDO (2007) para descrever a absorção da água pelas carcaças e o modelo de resfriamento segundo a Lei de Newton para a temperatura das carcaças. Foram testadas diferentes situações alterando-se os números de neurônios das camadas de entrada e intermediária, e o número de camadas. Foram utilizados dados fornecidos pela empresa SADIA Toledo para treinamento e validação da rede. Para o modelo foram selecionadas vinte e cinco variáveis de entrada, como peso da carcaça, temperatura antes do resfriamento, temperatura da camisa de propilenoglicol, vazão de água em cada módulo dos tanques, tempo de resfriamento e temperatura da água de renovação, borbulhamento e quantidade de gelo. Os resultados obtidos pelas redes neurais e pela Lei de Newton não foram eficientes para representar a temperatura de saída da carcaça. As redes neurais e o modelo empírico de CARCIOFI & LAURINDO (2007) foram muito eficientes para estimar a quantidade de água absorvida pelas carcaças. Os resultados obtidos mostraram que a rede tipo 4 x 12 x 4 neurônios na camada de entrada, primeira intermediária e segunda intermediária respectivamente foi a que melhor representou o sistema investigado.
10

Beiträge zur optimalen Auslegung und Betriebsführung von Absorptions-Kältemaschinen im Systemverbund

Dittmann, Lutz 20 March 2009 (has links)
Die Arbeit bietet einen praxisbezogenen Überblick über den rationellen Einsatz von thermischen Kälteanlagen. Dabei wird von der Stoffdatenanlayse, bei der eine unfassende Analyse und Kritik und eine Korrektur der Ansätze durchgeführt wird, der darauf aufbauenden rechentechnischen Simulation der wichtigsten Maschinen über eine Optimierung der Kaltwasserspeicherung durch einen neuartigen Speicherbehälter bis zur Darlegung einer effizienten Einbindung in eine Systemschaltung und der energetischen Bewertung die gesamte Bandbreite der thermisch betriebenen Kälteerzeugung abgedeckt. In diesem umfassenden Ansatz stellt die Arbeit ein Novum dar. Insbesondere im Bereich der Kaltwasserspeicherung wird eine konstruktiv neue Lösung vorgeschlagen, die einen wirtschaftlichen Einsatz der Anlagen gerade im innerstädtischen Bereich, der ein hohes Entwicklungspotenzial besitzt, verbessert oder überhaupt erst ermöglicht. In Verbindung mit den Erkenntnissen zur Anlagensimulation und Einsatzoptimierung trägt die Arbeit zu einem verstärkten Einsatz von thermischen Kälteanlagen und damit zur Erschließung energetischer Einsparpotenziale bei. Des Weiteren wurde die Effizienz zweier momentan nicht genutzter Technologien dargestellt und eine Umsetzung empfohlen. Die Ergebnisse lassen sich auf mehrere Arten kommerziell nutzen. Einerseits wird die Erstellung von effizienten Simulationstools für verschiedene thermisch betriebene Kälteanlagen und Wärmepumpen ermöglicht, andererseits die Umsetzung einer neuen effizienten Speicherlösung beschrieben und die Rahmenbedingungen des Einsatzes innovativer Technologien dargelegt (Resorptions- und Absorptionsanlage mit mechanischer Kompression) und eine sinnvolle Nutzung im energiepolitischen Rahmen der Bundesrepublik anhand von Bewertungsalgorithmen ermöglicht. Gerade im Hinblick auf den von der Bundesregierung angestrebten Ausbau der Fernwärmenutzung in Deutschland lassen sich durch die Nutzung von KWK-Wärme im Sommer neue wirtschaftliche Potenziale erschließen. Durch die kritische Analyse der thermodynamischen Grundlagen der Mischung der Stoffe Lithiumbromid und Wasser erstellt die Arbeit die Basis für eine wissenschaftlich korrekte Berechnung von Simulationswerkzeugen und konstruktive Umsetzungen von thermischen Kälteanlagen / Wärmepumpen und ermöglicht sowohl Planern und Wissenschaftlern als auch Studenten oder interessierten Laien einen umfassenden Blick auf die Technologien und ihre energiepolitisch sinnvollen Einsatzchancen. / The thesis contains a practical overview of the rational use of thermal chillers. Based on an extensive analysis of the data on chemical media, a computer simulation of the most important absorption chillers / heat pumps was realised. Furthermore an optimisation of the cold water storage by a novel storage tank construction and explanations of the efficient integration of absorption chillers into an integrated network are given. Especially the novel horizontal cold water storage advances the general conditions of the application of absorption chillers in municipal areas. Also the efficiencies of two currently neglected technologies are shown.

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