Aquesta recerca es centra en el desenvolupament de models en règim estacionari de màquines d’absorció de petita potència, els quals estan basats en dades altament fiables obtingudes en un banc d’assajos d’última tecnologia. Aquests models podran ser utilitzats en aplicacions de simulació, o bé per a desenvolupar estratègies de control de supervisió dels sistemes d’aire condicionat amb màquines d’absorció. Per tant, l’objectiu principal d’aquesta investigació és desenvolupar i descriure una metodologia comprensible i que englobi el procés sencer: tant els assajos, com la modelització, com també el desenvolupament d’una estratègia de control per a les màquines d’absorció de petita potència. Basant-se en la informació obtinguda de forma experimental en el banc d’assajos, s’han desenvolupat cinc models, cadascun amb una base teòrica diferent. Els resultats mostren que és possible obtenir models empírics summament precisos utilitzant únicament com a paràmetres d’entrada les variables dels circuits externs d’aigua. Aquest treball finalitza amb la proposta de dues estratègies òptimes de control i el seu ús per al control on-line de sistemes basats en refredadores tèrmiques d’absorció. / This research deals with the development of the simple, yet accurate steady-state models of small capacity absorption machines which are based on highly reliable data obtained in the state-of-the-art test bench. These models can further be used in simulation tools or to develop supervisory control strategies for air-conditioning systems with absorption machines. Therefore, the main aim of this research is to develop and to describe a comprehensive methodology which encloses entire process which consists of testing, modelling and control strategy development of small capacity absorption machines. Five different models are developed based on the experimental data obtained in the test bench. The results show that it is possible to develop highly accurate empirical models by using only the variables of external water circuits as input parameters. Finally, two optimal control strategies are developed to demonstrate how these models can be used for on-line control of absorption systems.

Made available in DSpace on 2014-06-12T17:34:40Z (GMT). No. of bitstreams: 2 arquivo1979_1.pdf: 4262749 bytes, checksum: 6592fa1ffeccb983a84926eb95aa4c5e (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Este trabalho tem como finalidade o estudo numérico do funcionamento de um chiller de absorção (LiBr-água) de simples efeito em regime permanente, com capacidade de 10TR, acionado por água quente e tendo como fonte de calor os gases de exaustão de uma micro-turbina a gás natural de 30kW de potência, localizado no laboratório Cogencasa da Universidade Federal de Pernambuco. Foi desenvolvida uma metodologia computacional na plataforma EES-32 (Engineering Equation Solver), para avaliar a influência dos principais parâmetros de operação do sistema sobre a capacidade de resfriamento e o COP. A modelagem termodinâmica baseia-se nos princípios de conservação de energia, massa e das espécies, além das correlações de transmissão de calor, sendo conformado por uma serie de funções para a determinação das propriedades termodinâmicas (entalpia e entropia da mistura H2O-BrLi) e coeficientes dos trocadores de calor. A análise exergoeconômica é baseada nos sistemas de unidades produtivas, para avaliar a viabilidade técnica do sistema de cogeração. Para a análise exergética foi calculada a Exergia total dos fluidos de trabalho levando em consideração as parcelas físicas e químicas. O sistema de cogeração foi integrado ao modelo computacional com o propósito de estudar os custos exergéticos e monetários do sistema, verificando o balanço monetário da geração de energia elétrica pela microturbina e a produção de água gelada, mediante a recuperação dos gases da combustão para o acionamento do chiller de absorção. Analisam-se as irreversibilidades para a identificação dos pontos críticos nos componentes do sistema de cogeração. Da análise exergoeconomica, foram analisados os custos mínimos de produção de energia elétrica para produzir lucros para o empreendimento, além da determinação dos custos gerais monetários da produção de água gelada, fria e quente do chiller. Finalmente foram determinados os valores da eficiência energética e exergética global do sistema de cogeração

Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2017-07-12T17:40:35Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese_Gutenberg da Silva Pereira_1.pdf: 6410667 bytes, checksum: ddf1e84a9a1b8bcce71836f13e8707fa (MD5) / Made available in DSpace on 2017-07-12T17:40:35Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese_Gutenberg da Silva Pereira_1.pdf: 6410667 bytes, checksum: ddf1e84a9a1b8bcce71836f13e8707fa (MD5) Previous issue date: 2016-02-22 / Com a atual escassez de energia, alta demanda e aumento do custo da energia elétrica, verifica-se que uma questão importante é a melhoria da eficiência dos sistemas de climatização dentro de um padrão de eficiência certificado possibilita-se, assim, para uma comparação real de qual é a melhor opção de layout e operação dos sistemas, já que os sistemas de climatização são responsáveis por uma alta parcela do consumo energético. O presente trabalho se propõe a comparar dois sistemas de refrigeração diferentes, usando chiller de compressão de vapor, para a climatização de ambientes. Foram propostas diferentes modalidades para a comparação em operações isoladas e ações combinadas. Essas operações são avaliadas nos conceitos de edifícios verdes. Foi desenvolvido um modelo matemático baseado nos princípios de conservação de massa e energia, complementado por várias funções, de modo a determinar as propriedades termofísicas e eficiências dos compressores. O modelo avalia a influência dos parâmetros operacionais principais do sistema de refrigeração a água gelada operando em três configurações diferentes. As equações do modelo foram resolvidas pelo programa EES (Engineering Equation Solver). Os resultados mostraram que o sistema com compressão diferenciada apresenta COP igual ao do sistema com chiller parafuso na faixa de 0 a 300 TRs, e um COP superior em média de 9% na faixa de 400 a 800 TRs. / With the current energy shortages, high demand and rising cost of electricity, it turns out that an important issue is the improvement of the air conditioning efficiency within a standard of efficiency certificate for a real comparison of what is the better layout option and operation of systems, as the HVAC systems account for a high share of energy consumption. This study aims to compare two different cooling systems using vapor compression chiller for air conditioning environments. They were different proposals modalities for comparison in isolated and combined action operations. These transactions are valued on the concepts of green buildings. A mathematical model was developed based on the principles of conservation of mass and energy, supplemented with various functions in order to determine the thermophysical properties and efficiencies of the compressors. The model evaluates the influence of the main operating parameters of the cold water cooling system operating in three different configurations. The model equations were solved by EES program (Engineering Equation Solver). The results showed that the system presents differentiated compression COP equal to the screw chiller systems in the range from 0 to 300 RTs and a higher COP (average of 9%) in the range of 400 to 800 TR.

This thesis presents a thermodynamic model for a screw chiller and cooling tower system for the purpose of developing an optimized control algorithm for the chiller plant. The thermodynamic chiller model is drawn from the thermodynamic models developed by Gordon and Ng (1996). However, the entropy production in the compressor is empirically related to the pressure difference measured across the compressor. The thermodynamic cooling tower model is the Baker & Shryock cooling tower model that is presented in ASHRAE Handbook - HVAC Systems and Equipment (1992). The models are coupled to form a chiller plant model which can be used to determine the optimal performance. Two correlations are then required to optimize the system: a wet-bulb/setpoint correlation and a fan speed/pump speed correlation. Using these correlations, a "quasi-optimal" operation can be achieved which will save 17% of the energy consumed by the chiller plant.

Abstract There is much rich solar energy in Taiwan situated at the subtropics;Therefore it¡¦s suitable for solar energy is utilized as the driving energy for absorption cooling system. Simultaneously the use of solar energyreduces our dependence on fossil fuel ,and reaches the goal of energy conservation and reduction of carbon footprint deeply.After establishing absorption cooling system in TRNSYS.16 platform, climate data TMY2 form for several cities of Taiwan are input to the simulation program. As a result of Taiwan climate variation, summer is getting more and more longer ; winter is getting shorter gradually .Hence we simulated program from March to October .Then system operating the parameters of solar collector area and the volume of the storage tank are varied to research those effects on the system performance. The research focuses on the simulation data for monthly solar fraction(f),seasonal solar fraction(F) as well as how much solar energy saved could transform carbon dioxide content for single effect and double effect absorption cooling system operated under the climate of the major cities in Taiwan .Those data could provide the design needs.

It takes 3~5 years to finish a power plaint project including location, reliability, environment evaluating, investigation, etc. In addition, it is difficulty to get a right place and hinder by the environment protection. So, it is an important class on boosting the existing power generation capacity. It was used to enhance power generation capacity by increasing the combustion chamber temperature in traditional way. However, it not only increases the exhaust temperature of gas turbine, but also increase the compressor ration. However, it is more difficulty on the design of gas turbine. And then we consider the other way in this thesis by reducing inlet air temperature of compressor to increase the density and flow of air and the power generation capacity. The result is magic that the power generation capacity enhance 10% ~20%. The analysis of Combustion Turbine Inlet Air Cooling System by Absorption refrigerant system(CTIAC-ABS) describe in chapter 2 including fundamental of a gas turbine, the absorption refrigerant chiller, the inlet cooling coil and cogeneration system. It lets us know how to select the style of cogeneration and specification of an absorption refrigerant chiller. It is important to consider the mass condensate water in the air side of inlet cooling coil. The author suggest to use the analysis method of wet-coil developed by Threlkeld(1970). The CTIAC system could be used to the Gas Turbine System, Gas Turbine with HRSG System and Combined System. Because of there is not high pressure steam, we can use the fired-gas absorption refrigerant system as the source of chiller on the CTIAC-ABS system. There is the high pressure steam of Gas Turbine with HRSG System and Combined System. So we can divided the high pressure steam into two part, one to process and the other could be used as the heat source of absorption refrigerant chiller There are two advantages of using CTIAC-ABS on cogeneration power plaint. 1.The new purpose of mass high pressure steam could be used in cogeneration power plaint in Taiwan. 2.Reduction operational cost of CTIAC-ABS The author finished the sensibility of power generation capacity with the analysis of practical operative data, classification of gas turbine and the power plaint Simulation program (GateCycle). When the compressor inlet temperature decrease from 30OC to 10OC, the results are : air flow rate increase 6.3%, fuel flow rate increase 5.95%, exhaust air temperature decrease 1.7% and exhaust air flow rate increase 6.3%, net power output increase 12.2%, heat rat decrease 3.7% and thermal efficiency upward 1.32%.Then, the author got a simulative equation of power capacity. The typical gas turbines operate at full-load condition, 52.25% of annual hours, in 1998 in Taiwan. Gas turbines were almost full load on daytime and half-load or closed at night. If we apply the CTIAC-ABS system on TPC's combined power plant, it can operate at 8:00~18:00 on daytime and shutdown at night. If there is high pressure steam in the cogeneration with HRSG, the CTIAC-ABS system can operate at the time that the cogeneration power plant is operative. How to decide the capacity of absorption refrigerant chiller? The author decided the maximum capacity of absorption refrigerant chiller operating at 31OC , 80%RH of weather condition that limit by 2.5% ***. The author forecasts the lowest compressor inlet air temperature will be 10OC. The steam double-effect CTIAC-ABS system could make the compressor inlet air temperature decrease from 30OC to 10 OC and enhances the heat rate 3.8%, the thermal efficiency 1.2%. The fired-direct CTIAC-ABS system also enhances the heat rate 5% and the thermal efficiency 1.5%. The results are close to the simulation of GateCycle program. So, the author compared the result of simulation with real data that the optimumal operative point of the CTIAC-ABS system is 10OC.

This thesis presents a thermodynamic model for a screw chiller and cooling tower system for the purpose of developing an optimized control algorithm for the chiller plant. The thermodynamic chiller model is drawn from the thermodynamic models developed by Gordon and Ng (1996). However, the entropy production in the compressor is empirically related to the pressure difference measured across the compressor. The thermodynamic cooling tower model is the Baker & Shryock cooling tower model that is presented in ASHRAE Handbook - HVAC Systems and Equipment (1992). The models are coupled to form a chiller plant model which can be used to determine the optimal performance. Two correlations are then required to optimize the system: a wet-bulb/setpoint correlation and a fan speed/pump speed correlation. Using these correlations, a "quasi-optimal" operation can be achieved which will save 17% of the energy consumed by the chiller plant.

The design of a chilled water plant involves selecting the size and type of chillers to be employed and determining the operating strategy. The types may include both gas engine and electric motor driven chillers. The issues that have to be considered in the selection problem are to incorporate external and internal factors into the decision making. External factors may include the utility rate schedules, the cooling load profile, and the outdoor temperature profile. Internal factors may include the chiller performance characteristics, initial and maintenance costs, and the chiller(s) operating strategy. A mathematical model representing the chilled water plant design problem is developed. The problem is approached as a mixed integer linear programming problem where non-linear chiller performance curves are transformed into linear constraints through the use of integer variables. The optimization task is to select the best cooling plant configuration and operating strategy to minimize life cycle cost. A solution procedure is developed which decomposes the optimization problem to reduce extensive computation time. Two case studies are provided to investigate the implementation of the mathematical model. / Master of Science

Made available in DSpace on 2015-05-08T14:59:46Z (GMT). No. of bitstreams: 1 ArquivoTotal.pdf: 9428315 bytes, checksum: 48c140981cf20867371ca9c0ebfcfec7 (MD5) Previous issue date: 2013-03-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The respective thesis aims to develop a cooling system that uses an adsorptive chiller for cooling water and subsequent use of this cold water for air conditioning environment, theoretically and experimentally verifying the performance of adsorption refrigeration system, these devices have several advantages, among them, the use of clean energy such as solar. Brazil is a country with high rates of stroke, with an average capacity 16-20 MJ / year / h, so it becomes quite conducive to harnessing this energy, and to be contributing to the reduction of fossil fuel consumption and reduction of harmful gases to the environment. The proposed system consists of flat solar collectors, which are used to convert solar energy into thermal, being last transferred to a heat transfer fluid that circulates through the collector which is then stored in a boiler, or a thermal fluid, to be used whenever required for heating the bed adsorptive a chiller, which is composed of bed adsorptive the finned annular ducts involved with the adsorbent (silica gel). Many studies have been developed with the aim of increasing the performance of these systems, these studies have focused primarily on increasing the mass transfer and heat of adsorption beds and using systems which run continuously through the use of two adsorption beds which work in different phases. Experimental studies in porous beds featuring different configurations were performed, observing thus which present higher rates adsorbent, and subsequently applied this setting in the construction of the porous bed adsorptive chiller. A computational model was developed theoretically allowing you to check your system's performance. / O respectivo trabalho de tese visa desenvolver um sistema de refrigeração que utiliza um chiller adsortivo para resfriamento de água e posterior uso desta água fria para climatização de ambiente, verificando teoricamente e experimentalmente o desempenho do sistema de refrigeração por adsorção, estes dispositivos apresentam várias vantagens, entre elas, o uso de energia limpa, como a solar. O Brasil é um país que apresenta grande índice de insolação, com uma capacidade média de 16 a 20 MJ/ano/h, desta forma torna-se bastante propício o aproveitamento desta energia, além de estar contribuindo para a redução do consumo de combustíveis fósseis e redução de gases nocivos ao meio-ambiente. O sistema proposto é composto por coletores solares planos, que são usados para converter a energia solar em térmica, sendo está última transferida para um fluido térmico que circula pelo coletor que posteriormente é armazenado em um boiler, podendo este fluido térmico, ser usado sempre que necessário para o aquecimento do leito adsortivo de um chiller, sendo este leito adsortivo composto por dutos aletados na forma anular envolvidos com o adsorvente (sílica gel). Muitos trabalhos vem sendo desenvolvidos com o intuito de aumentar o desempenho destes sistemas, estes estudos estão concentrados basicamente no aumento da transferência de massa e calor dos leitos adsortivos e utilização de sistemas que funcione continuamente através do uso de dois leitos adsortivos que trabalham em fases diferentes. Ensaios experimentais com leitos porosos apresentando configurações diferentes foram realizados, observando deste modo, qual apresentaria maiores taxas adsortivas, sendo posteriormente aplicada esta configuração na construção do leito poroso do chiller adsortivo. Um modelo computacional foi desenvolvido permitindo verificar teoricamente o desempenho do sistema.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-28T15:11:55Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese - Kamylla Alexandre - Engenharia Química.pdf: 4003208 bytes, checksum: 7181a381a784e64a2607a30d6852175a (MD5) / Made available in DSpace on 2016-07-28T15:11:55Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese - Kamylla Alexandre - Engenharia Química.pdf: 4003208 bytes, checksum: 7181a381a784e64a2607a30d6852175a (MD5) Previous issue date: 2016-02-24 / A redução da disponibilidade de combustíveis e o aumento das restrições ambientais à emissão de poluentes, inerente à geração de energia, têm justificado o investimento em projetos industriais que minimizem seu consumo energético. A Petrobras é um dos maiores consumidores de energia do país e, dados os custos decorrentes das tarifas de energia, a geração própria sempre foi uma preocupação da Companhia. Nesse contexto os fluidos refrigerantes secundários, que possuem propriedades de transmitir calor a longas distâncias, são de especial interesse para unidades nessa área de desenvolvimento tecnológico. Os sistemas de refrigeração são empregados em diversos setores industriais, como nas petroquímicas, e em termelétricas utilizadas como unidades de cogeração em refinarias. Esses sistemas são constituídos, comumente, por compressores, trocadores de calor, torres de resfriamento, tubulações, bombas, ventiladores e instrumentação para controle. Uma “Unidade de Refrigeração” utiliza refrigerantes primários para armazenamento e transporte de calor ou frio a curtas distâncias em sistemas à compressão de vapor ou por absorção. Para o transporte de energia calorífica a longas distâncias são geralmente utilizados os refrigerantes secundários compostos de água e glicóis (anti-congelantes) ou salmouras e aditivos. Contudo, essas substâncias anticongelantes reduzem a capacidade calorífica e a condutividade térmica da água. Por outro lado, nanopartículas metálicas têm a propriedade de aumentar a condutividade térmica do meio onde são adicionadas. O presente trabalho investigou, através de experimentos em um arranjo experimental de bancada de testes de um grupo gerador diesel, a influência da adição de nanopartículas em uma solução de etilenoglicol utilizada como refrigerante secundário. Para isso utilizou-se injeções de água gelada, produzida por um chiller de compressão de vapor (R22), na linha de alta temperatura (HT) do motor do grupo gerador. Para armazenamento e registros dos dados foi utilizado um equipamento do tipo datalogger. Foram testadas diferentes set-points de temperatura de entrada da água da linha de HT no motor (64oC, 67 oC, 70 oC, 73 oC e 76 oC). Essas temperaturas foram testadas com água pura e com solução aquosa de etilenoglicol a 30%, sem e com a adição de nanopartículas (2%, 4% e 6%). Em todas as condições foram realizadas medidas do consumo específico de combustível e avaliadas as velocidades de resposta no sistema. Um percentual de 2,0% de nanopartículas, em volume, apresentou-se como ideal para o desempenho do nanofluido. Em função da ausência, no mercado brasileiro, de unidades de refrigeração por absorção com potência menor que 64 TR, foi elaborado um modelo dinâmico e simulado um chiller de absorção (H2O-LiBr), visando uma construção futura e utilização desse tipo de equipamento em escala piloto. / The reduced availability of fuel and increasing environmental restrictions on emissions, inherent in the power generation, have justified the investment in industrial projects that minimize their energy consumption. Petrobras is one of the country's largest energy consumers and, given the costs of the tariffs, the very generation has always been a concern of the Company. In this context the secondary refrigerants, which have properties of transmitting the heat over long distances, are of particular interest for technological development units in this area. Cooling systems are employed in various industrial sectors such as the petrochemical, and power plants used as cogeneration units in refineries. These systems are made, usually for compressors, heat exchangers, cooling towers, pipes, pumps, fans and instrumentation control. A "cooling unit" uses primary refrigerant for storage and transport of heat or cold at close range systems in the vapor compression or absorption. For the heat energy transport over long distances are usually used secondary refrigerants composed of water and alcohols (anti-freeze) or pickles and additives. However, such antifreeze substances reduce the heat capacity and thermal conductivity of water. Moreover, metal nanoparticles have the property of increasing the thermal conductivity of the medium in which they are added. This study investigated through experiments in an experimental test bench arrangement of a diesel generator set, the influence of the addition of nanoparticles in a solution of ethylene glycol used as secondary coolant. For this used ice water injections, produced by a vapor compression chiller (R22), in the high temperature line (HT) of the engine generator set. For storage and records of the data was used an equipment type datalogger. They tested different set-points for the HT line of the engine inlet water temperature (64 °C, 67 °C, 70 °C, 73 °C and 76 °C). These temperatures were tested with pure water and ethylene glycol 30% aqueous solution, with and without the addition of nanoparticles (2%, 4% and 6%). In all conditions were performed measurements of specific fuel consumption and evaluated the response speeds in the system. A percentage of 2.0% nanoparticles by volume was presented as ideal for the performance of nanofluid. Due to the absence, in the Brazilian market of refrigeration units by absorbing less power than 64 TR, it designed a dynamic model and a simulated absorption chiller (H2O-LiBr), aimed at future construction and use of such equipment in pilot scale.