Dissertations / Theses: 'Refrigeration compressor'

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Liang, Kun. "A novel linear electromagnetic-drive oil-free refrigeration compressor." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:a6b61f49-895d-4587-baa7-91d5d1feff14.

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There is a need to improve the capabilities of cooling technology to dissipate increasingly high heat fluxes (approaching 200 W/cm²) from electronic components in order to maintain acceptable operating temperatures. The linear compressor with clearance seal and flexure spring which has been used for many years for space application, is an attractive proposition for vapour compression refrigeration (VCR) systems in electronics cooling applications because it offers several advantages over traditional compressor technology. This thesis introduces a novel design of oil-free linear compressor and investigates the performance of the linear compressor system and the key issues with respect to the operations of the compressor. A comprehensive system analysis has been carried out for the linear compressor regarding the moving magnet motor characteristics, spring stiffness, damping, imbalance of current in coils, DC offset and leakage across the clearance seal. To measure the performance of the linear compressor, an experimental apparatus and a data acquistion system have been built. A harmonic fitting approach has been proposed to reconstruct current, voltage and displacement signals using fast Fourier transform (FFT) and minimisation algorithms. The piston dynamics have been modelled to infer pressure-volume (P-V) diagrams. Preliminary measurements of the linear compressor at resonance using nitrogen show that an adiabatic efficiency of 42% - 60% and a motor efficiency of 71% - 89% are maintained over a wide range of operating parameters, indicating that systems using this type of compressor could have good part load efficiency. At the design point (a pressure ratio of 3.0 and a stroke of 13 mm), pressure drop loss is responsible for 27% of the total losses and the most significant loss is the copper loss (34%). A commercial crank-drive compressor with comparable properties has also been evaluated for comparison, showing that the prototype linear motor has a much higher efficiency than the rotary induction motor, particularly at low electrical power inputs while the volumetric efficiencies in the crank-drive compressor are about 20% higher. The linear compressor in a refrigeration system using R134a has been measured for different strokes under each pressure ratio with a fixed condenser outlet temperature of 50°C and evaporator temperature ranging from 6°C to 27°C. A model of the resonant frequency using discharge and suction pressures and the stroke has been validated. A coefficient of performance (COP) of 3.2 has been achieved at a cooling capacity of 384 W and an evaporator temperature of 20°C. This is assumed to be a typical CPU cooling condition. A Proportional-Integral-Derivative (PID)/Pulse-Width-Modulation (PWM) control system using a solenoid operated valve has been developed for DC offset and clearance control. Operation of the linear compressor with a fixed clearance of 0.8 mm using nitrogen has been carried out in comparison with the fixed zero DC offset operation. When operated with a fixed clearance, the volumetric efficiency increases with a decreasing stroke but the fixed clearance operation requires a higher power input. This provides evidence that the piston control in a refrigeration system with capacity control should be for a zero DC offset.

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Chan, Kuan Yoong. "Investigation and performance optimisation of multi compressor refrigeration system." Thesis, Brunel University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247504.

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Rankle, Hugo Elias Camargo. "Acoustic prediction and noise control of a refrigeration compressor." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-09052009-040840/.

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4

Cain, Jason James. "Collision Analysis of the Reversible Crankshaft Mechanism in a Convertible Refrigeration Compressor." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33479.

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The purpose of this study is to analyze the behavior of a reversible two-cylinder refrigerant compressor manufactured by Bristol Compressor Incorporated. This compressor contains a specialized linkage that causes the compressor to transition from a two-cylinder compressor to a single-cylinder compressor when the direction of rotation of the crankshaft is reversed. The linkage accomplishes this by reducing the throw of one cylinder to zero. Of interest are the conditions to which this linkage is subjected when the direction of rotation is again reversed, causing the compressor to return to its two-cylinder functioning. When this reversal takes place, a collision occurs within the linkage. These repeated collisions are thought to be the cause of fatigue failure of the linkage in many of these compressors. To verify that this collision is the problem, an understanding of the stress state during the collision is needed. This thesis begins the work necessary to determine the dynamic stress state present within the system. A FORTRAN program was developed that modeled the kinematic behavior of the system under operating conditions. The program predicts the accelerations, velocities, positions, and internal forces present within the system during startup conditions. Also, a method has been developed to model rotary sliding contact between two cylindrical surfaces. This method is developed and investigated in hopes that it will facilitate the modeling of the behavior of the compressor linkage in a dynamic finite element analysis.
Master of Science

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Kelly, Allan D. "Dynamic finite element modeling and analysis of a hermetic reciprocating compressor." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-01242009-063231/.

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6

Ramani, Anand. "Finite element modeling of a refrigeration compressor for noise prediction applications." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-08182009-040538/.

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7

Boyle, R. J. "Valve design optimisation for a 3-cylinder semi-hermetic reciprocating refrigeration compressor." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381314.

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8

Craun, Matthew Ashby. "Identification of sound transmission paths within a hermetic reciprocating refrigeration compressor via multiple-input/single-output modeling." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09192009-040610/.

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Nóbrega, Claudia Rosa do Espírito Santo 1985. "Análise da eficiência energética de um sistema de refrigeração utilizando compressor de velocidade variável." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265752.

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Orientador: Luiz Felipe Mendes de Moura
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: O presente trabalho refere-se a uma investigação experimental do comportamento de um sistema de refrigeração utilizando um compressor de rotação variável. Diante da necessidade do uso racional de energia elétrica, estudos entorno da eficiência energética são desenvolvidos como alternativas de redução do desperdiço em equipamentos, como desenvolvimento de dispositivos que necessite de menos consumo de energia sem comprometimento de sua eficiência, e possibilitando a acessibilidade destas alternativas para comunidade em geral. O uso do compressor de rotação variável tem sido estudado como alternativa de redução no consumo de energia por ser responsável por 80% do consumo total de energia consumida pelo sistema de refrigeração, que está cada vez mais presente nas indústrias e residências. Foi implementada uma bancada de teste composta por um subsistema de refrigeração por compressão a vapor e um subsistema secundário de resfriamento. Este estudo visa investigar experimentalmente a potência consumida, potência de compressão, coeficiente de performance (COP) e eficiência do sistema de refrigeração variando-se a carga térmica solicitada utilizando um compressor de rotação variável e o compressor em rotação fixa máxima fornecida pelo fabricante. Os resultados encontrados experimentalmente com a utilização do compressor em rotação variável apresentaram valores satisfatórios para os parâmetros avaliados e um melhor desempenho do sistema se comparado aos valores obtidos com o compressor em rotação fixa variando-se a carga térmica solicitada
Abstract: The present work relates to an experimental investigation of the behavior of a refrigeration system using a variable speed compressor. Faced with the need for rational use of energy, environment studies of energy efficiency are developed as wasting reduction alternatives in equipment such as developing devices that need less power consumption without compromising its efficiency and allowing the accessibility of these alternatives community. The use of variable speed compressor has been studied as alternative reduction in energy consumption to be responsible for 80 % of total energy consumption consumed by the cooling system, which is increasingly present in industry and households. A test bench comprising a subsystem vapor compression refrigeration and secondary cooling subsystem has been implemented. This study aims to experimentally investigate the consumed power, compression power, coefficient of performance (COP) and the refrigeration system efficiency by varying the thermal load applied using a variable speed compressor and the compressor at maximum fixed speed provided by the manufacturer. The results experimentally using the variable speed compressor showed satisfactory values for the parameters evaluated and improved system performance compared to the values obtained with fixed speed compressor in varying the required heat load
Mestrado
Termica e Fluidos
Mestra em Engenharia Mecânica

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Thompson, Swen. "Analysis of the Dynamic Interferences Between the Stator and Rotor of a Refrigeration Compressor Motor." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/30364.

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This thesis involves the development and study of a finite element model of a hermetic, single-vane compressor and a single-phase alternating current induction motor assembled in a common housing. The manufacturer of this unit is experiencing a high scrap rate due to interference during operation between the stator and rotor of the motor. The rotor shaft of the motor is non-typical because of its cantilever design. The finite element model was first subjected to eigenvalue analysis. This revealed that the interference producing displacements were not the result of torque application to the rotor at a frequency close to an eigenvalue of the mechanical system. After a review of the literature and discussions with Electrical Engineering Department faculty possessing extensive motor experience, it was surmised that the physical phenomenon causing the rotor displacement was unbalanced magnetic pull. This phenomenon occurs in the air gap of rotating electric machines due to eccentricity in the air gap. The model was then subjected to simultaneous harmonic force inputs with magnitudes of unity on the rotor and stator surfaces to simulate the presence of unbalanced magnetic pull. It was found that the rotor shaft acts as a cantilever beam while the stator and housing are essentially rigid. The displacements due to these forces were examined and then scaled to develop the motor parameters necessary to produce the radial forces required for stator/rotor interference. Several recommendations were then made regarding possible solutions to the interference problem.
Master of Science

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Qureshi, Tauqir Qadir. "Investigation of the performance of alternative compressor technologies in variable speed refrigeration systems for air conditioning applications." Thesis, Brunel University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385281.

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12

Abou, Rached Ghady. "Experimental and numerical study of a cooled compression by oil injection in a screw compressor." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM057.

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L’objectif de cette thèse est de concevoir un système d’injection d’huile pour réussir la compression refroidie pour les compresseurs à vis utilisant le R134a, un réfrigérant à basse pression. Les atomiseurs bi fluides ont été identifiés pour générer des gouttelettes d’huile assez fine et adaptées du régime de pression du R134a. Une étude expérimentale est conduite pour caractériser cette famille d’injecteurs en termes de taille de particules et débits massiques. Des corrélations sont proposées pour déterminer ces deux entités en fonction des pressions aux terminaux de l’injecteur. Un système d’injection complet est conçu et construit pour un refroidisseur d’eau commercial utilisant le R134a comme réfrigérant, où les conditions d’injection ont été variées systématiquement. Un modèle 1D est aussi développé qui considère l'ensemble du compresseur. Il est divisé en 3 parties : Zones de pré-compression, compression et post compression. Les paramètres du modèle ont été identifiés à partir des données expérimentales. Une étude paramétrique a déterminé un point de fonctionnement optimal, avec les meilleurs résultats et conditions opératoires. Le résultat de cette thèse est une conception innovante avec une haute performance énergétique et un coût modéré d’un système de compression refroidie dédié aux compresseurs à vis. L’étude expérimentale a validé une augmentation du COP de 3% et une réduction maximale de la température de refoulement de 7°C. Le modèle prédit jusqu’à 20% d’amélioration du COP si certaines conditions sont remplies
This thesis’ objective is designing a dedicated oil injection system in order to achieve a cooled compression solution for compressors using R-134a, a relatively low pressure refrigerant. Bi fluid atomizers are identified as a technology capable of generating fine droplets of oil suitable with the pressure regime of R-134a. An experimental study was carried out to characterize this family of injectors in terms of particle sizes and mass flow rates. Correlations were suggested in order to determine these magnitudes as a function of pressure conditions at the outlet of the injector. A complete injection system is then designed and built for a commercial R134a screw compressor water chiller, where the injection conditions were varied systematically. A 1D model was also developed taking into consideration the whole compressor. It is divided into three main parts: Pre compression, compression and post compression zones. The model parameters were fitted using the experimental results. A parametric study was conducted to determine an optimal functioning point with best results and best operating conditions. The main result of this thesis is an innovative design with high energy performance and moderate cost of a compression cooling system dedicated for a screw compressor. The experimental study validated an increase of COP of 3% and a maximal temperature discharge reduction of 7°C. The model predicts up to 20% of COP improvement if certain operating conditions are met

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Silva, Gerson Barbosa da. "Análise exergo-econômica da microgeração com o uso de motores de combustão interna a biodiesel no acionamento do compressor do sistema por compressão de vapor." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/8990.

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This wort, its preset the theoretical and experimental study of a vapor compression system (SRCV), with cooling capacity of 26kW (7.5TR) developed at the Recogás at the Federal University of Paraíba. At first is analyzed the efficiency of the refrigeration system for vapor compression, where the circulation of refrigerant fluid is done by a hermetic compressor one piston that is driven by an electric motor, the second time, is analyzed circulation of refrigerant fluid system which is generated by a compressor opened, which is also triggered by the internal combustion engine. The two refrigeration systems working with fixed rotation compressor. Thermodynamic analyzes are performed and termoeconômicas of a plant expansion project a result of the CHP energy. Aimed to this research was to evaluate the performance of the system, working at different times with mineral diesel and biodiesel blends this with the proportions equivalent to B5 (95% mineral diesel and 5% biodiesel) B20 (80% mineral diesel and 20 % biodiesel), B40 (60% mineral diesel and 40% biodiesel), B60 (40% mineral diesel and 60% biodiesel) and) and B80 (20% mineral diesel and 80% biodiesel). Making use of computer platform fo Labview temperatures and pressures in real times and routines of computing platform Engineering Equation Solver - EES and Excel, to generate simulations of the refrigeration cycle, which has been validated with the experimental data.
Neste trabalho, apresenta-se o estudo teórico e experimental de um sistema de refrigeração por compressão de vapor (SRCV), com capacidade de refrigeração de 26kW (7.5TR) e que é desenvolvido na Recogás na Universidade Federal da Paraíba. No primeiro momento, é analisada a eficiência do sistema de refrigeração por compressão de vapor, no qual a circulação do fluido refrigerante é feita por um compressor hermético a pistão que é acionado por um motor elétrico; no segundo momento, é analisada a eficiência do sistema de refrigeração que usa um compressor aberto, acionado pelo motor de combustão interna para compressão de vapor. Estes dois sistemas de refrigeração trabalham com rotação do compressor fixa. São realizadas análises termodinâmicas e termoeconômicas de uma planta resultante do projeto de expansão do sistema de cogeração de energia. Objetivou-se com este trabalho avaliar o desempenho do sistema, funcionando em momentos distintos com diesel mineral e misturas deste com biodiesel nas proporções equivalentes a B5 (95% de diesel mineral e 5% de biodiesel) B20 (80% de diesel mineral e 20% de biodiesel), B40 (60% de diesel mineral e 40% de biodiesel), B60 (40% de diesel mineral e 60% de biodiesel) e) e B80 (20% de diesel mineral e 80% de biodiesel). Fazendo uso da plataforma computacional Labview para obter as temperaturas e pressões em tempos reais e de rotinas da plataforma computacional Engineering Equation Solver - EES e o Excel, para gerar simulações do ciclo de refrigeração, as quais foram validadas com os dados experimentais.

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Cavalheiro, Júnior Milton César [UNESP]. "Controle de válvulas de sucção de compressores de refrigeração usando limitador de abertura." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151661.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
A maioria dos sistemas de refrigeração por compressão de vapor utiliza compressores alternativos, considerados mecanismos importantes na era moderna. O ciclo de operação de um compressor alternativo é descrito por uma série de fenômenos complexos ocorrendo em um curto período de tempo. Dentre os fatores considerados importantes para e ciência termodinâmica dos compressores, destacam-se as válvulas que controlam os processos de sucção e de descarga, que são responsáveis por grandes perdas termodinâmicas no ciclo. Parte das perdas ocorre no sistema de válvulas, particularmente na válvula de sucção, onde as instabilidades do seu movimento reduzem a e ciência do processo de sucção. Como uma forma de reduzir os problemas gerados pelas instabilidades no funcionamento da válvula de sucção, propomos a utilização de um esbarro para limitar a abertura máxima da válvula, reduzindo sua instabilidade e aumentando a e ciência do compressor. Mostramos experimentalmente que existe uma posição de equilíbrio que mantém a válvula aberta sem instabilidades e que esta posição varia, aproximadamente, linearmente com o número de Reynolds.
Most of the vapor refrigeration systems use reciprocating compressors, which are considered important mechanisms in the modern era. The cycle of operation of a reciprocating compressor is described by a series of complex phenomena ocurring in a short period of time. Among the factors considered important for the thermodynamic efficiency of compressors are the valves that control the suction and discharge processes, which are responsible for large cycle thermodynamic losses. Part of that losses occurs in the valves system, particularly in the suction valve, where the movement instabilities reduce the efficiency of the suction process. In order to reduce the instabilities of the suction valve, we propose the use of a stop to limit the maximum aperture of the valve, reducing its instabilities and increasing the compressor efficiency. We show experimentally that does exist an static equilibrium position in which the valve remains opened without oscillation and that position varies almost linearly through the Reynolds number.

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Cavalheiro, Júnior Milton Cesar. "Controle de válvulas de sucção de compressores de refrigeração usando limitador de abertura /." Ilha Solteira, 2017. http://hdl.handle.net/11449/151661.

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Orientador: José Luiz Gasche
Resumo: A maioria dos sistemas de refrigeração por compressão de vapor utiliza compressores alternativos, considerados mecanismos importantes na era moderna. O ciclo de operação de um compressor alternativo é descrito por uma série de fenômenos complexos ocorrendo em um curto período de tempo. Dentre os fatores considerados importantes para e ciência termodinâmica dos compressores, destacam-se as válvulas que controlam os processos de sucção e de descarga, que são responsáveis por grandes perdas termodinâmicas no ciclo. Parte das perdas ocorre no sistema de válvulas, particularmente na válvula de sucção, onde as instabilidades do seu movimento reduzem a e ciência do processo de sucção. Como uma forma de reduzir os problemas gerados pelas instabilidades no funcionamento da válvula de sucção, propomos a utilização de um esbarro para limitar a abertura máxima da válvula, reduzindo sua instabilidade e aumentando a e ciência do compressor. Mostramos experimentalmente que existe uma posição de equilíbrio que mantém a válvula aberta sem instabilidades e que esta posição varia, aproximadamente, linearmente com o número de Reynolds.
Mestre

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Tipton, Russell C. "Simulation of a storage freezer operating with a binary nonazeotropic refrigerant blend part I. equation of state cycle selection compressor model and air-cooled condenser model." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182524272.

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Abrego, André Luís Severino. "Avaliação da metodologia numérica de solução do problema de interação fluido-estrutura em um modelo de válvula do tipo palheta." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153550.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
A maioria dos sistemas de refrigeração por compressão de vapor de uso doméstico utilizam compressores alternativos com válvulas automáticas do tipo palheta para controlar os processos de sucção e descarga do fluido refrigerante. O ciclo de operação dessas válvulas é descrito por uma série de fenômenos complexos que ocorrem em um curto período de tempo. Grande parte das perdas responsáveis pela redução da eficiência do compressor é devido aos fenômenos físicos que ocorrem nessas válvulas, predominantemente devido a interação fluido-estrutura. Assim, o estudo dessa dinâmica é essencial quando o objetivo é aumentar a eficiência do compressor. Estudar o problema usando técnicas da Mecânica dos Fluidos Computacional permite encontrar solução de forma relativamente rápida. Porém, desenvolver uma metodologia confiável exige o estudo detalhado de vários aspectos que podem influenciar os resultados e, principalmente, exige a validação experimental. Neste trabalho, propomos avaliar alguns desses aspectos para verificar suas influências na validação da metodologia por meio de dados experimentais. Para isso, uma modelo de válvula tipo palheta em escala ampliada, muito usado como válvula de sucção, é testado experimentalmente e os resultados são usados para validar a metodologia numérica aplicada. A solução numérica do problema é realizada usando o código Ansys® CFX para a solução do escoamento do fluido e o código Ansys® Mechanical para a solução do problema estrutural da válvula. A solução do problema de interação fluido-estrutura é obtida usando uma metodologia particionada, na qual a discretização e a solução do problema nos domínios do sólido e do fluido são realizadas separadamente. Dados do deslocamento instantâneo da válvula são usados para estudar a influência de vários parâmetros adotados na solução numérica do problema. Os resultados mostram que o fator normal de rigidez, a força de pré-carga, a força de gravidade e a condição de contorno usada na solução do problema da estrutura, influenciam na solução do problema.
Most domestic vapor compressor refrigeration systems use reciprocating compressors with automatic reed type valves to control the suction and discharge processes of the refrigerant fluid. The operating cycle of these valves is described by a series of complex phenomena that occur in a short period of time. Most of the losses responsible for reducing the efficiency of the compressor are due to physical phenomena occurring in these valves, mainly due to the fluid-structure interaction. To study this problem is essential to improve the efficiency of the compressor. Performing this study by using Computational Fluid Dynamic methodologies allows relative fast solution of the problem. However, developing a reliable methodology requires detail study of several aspects that can influence the results and, mainly, requires the experimental validation. In this work, we propose to evaluate some of these aspects to verify their influence in the validation process of the numerical methodology through experimental data. Here, we experimentally test a large scale model of a reed type valve usually used as suction valve and the results are used to validate the numerical methodology. The numerical solution is obtained by using the Ansys® CFX code to solve the fluid flow and the Ansys® Mechanical code to solve the structural problem of the valve. In this methodology, we solve the fluid-structure interaction by using a segregated method in which the discretization and the solution of the problem in the solid and fluid domains are performed separately. Data for the instantaneous displacement of the valve are used to analyze the influence of several parameters applied to solve the problem. The results show that the stiffness normal factor, the preload force, the gravity force, and the boundary condition used to solve the structure of the valve, influence the numerical solution of the problem.
CNPq: 131150/2015-4.

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Moimás, Gabriel Biancolin. "Análise experimental da dinâmica de válvulas tipo palheta usadas em compressores de refrigeração." Ilha Solteira, 2018. http://hdl.handle.net/11449/154271.

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Orientador: José Luiz Gasche
Resumo: Compressores herméticos alternativos são amplamente utilizados em sistemas de refrigeração por compressão de vapor de pequeno e médio porte. O sistema de válvulas automáticas utilizadas para controlar os processos de sucção e descarga é um componente importante deste tipo de compressor. O estudo experimental ou analítico/numérico destes processos é bastante complexo devido, principalmente, à interação fluido-estrutura entre as válvulas e o escoamento de fluido refrigerante. Uma revisão de literatura mostra que este tema ainda merece muita atenção dos pesquisadores, em particular daqueles que necessitam de dados experimentais acurados para validação de metodologias numéricas. Este é o contexto deste trabalho, cujo objetivo é descrever a dinâmica do movimento de um modelo de válvula usada neste tipo de compressor. Sensores óticos foram utilizados para medir o deslocamento instantâneo de modelos de válvulas fabricadas em aço mola SAE 1070 com 0,4 e 0,5 mm de espessura. Os testes foram realizados para escoamentos com números de Reynolds variando de 1.500 a 19.000. A descrição da dinâmica da válvula foi apresentada pela sua amplitude, frequência, pressão máxima à montante do escoamento da válvula e pelo coeficiente de restituição no impacto entre a válvula e o assento. De uma maneira geral, identificamos que a dinâmica da válvula depende significativamente de sua rigidez, do valor de força de pré-carga que está sujeita e do número de Reynolds do escoamento que incide sobre sua sup... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Hermetic reciprocating compressors are widely used in small and medium size vapor compression refrigeration systems. An important component of this type of compressor is the automatic valve system used for controlling the suction and discharge processes. The experimental or analytical/numerical study of this system is complex due to the fluid-structure interaction between the valves and the refrigerant flow. A literature review suggests that this theme still deserves attention from the researchers, in particular for those who need accurate experimental data to validate numerical methodologies. We aim to describe the dynamics of a suction valve model used in this type of compressor. Optical sensors were used to measure the instantaneous displacement of a spring-steel SAE 1070 valve model with 0.4 and 0.5 mm thickness. The tests were performed for Reynolds number of the flow ranging from 1,500 to 19,000. We present the dynamic behavior of the valve by its amplitude, frequency, maximum upstream pressure of the valve, and coefficient of restitution of the impact between valve and seat. Generally, we identify that the valve dynamics depends significantly on its stiffness, precharging force and Reynolds numbers of the flow. The impact between valve and seat also significantly change the dynamics of the movement.
Mestre

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Yildiz, Seyfettin. "Design And Simulation Of A Vapor Compression Refrigeration Cycle For A Micro Refrigerator." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612133/index.pdf.

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Cooling of electronic equipments has become an important issue as the advances in technology enabled the fabrication of very small devices. The main challenge in cooling is the space limitation. The use of miniature refrigerators seems to be a solution alternative for the cooling problem. The objective of this study is to design and simulate a vapor compression refrigeration cycle for a micro-scale refrigerator. A MATLAB code is developed for the simulations. The four components of the refrigerator, namely, the condenser, evaporator, compressor and the capillary tube are designed separately. The cycle is successfully completed nearly at the same point where it begins. The cold space temperature, ambient air temperature, condensation and evaporation temperatures, and the evaporator heat load are the predetermined parameters. A fan is used to cool the condenser, and the compressor is selected as isentropic. R-134A is selected as the refrigerant and a simple interpolation code is developed to obtain the thermophysical properties of R-134A. The original design is carried out with an isentropic compressor. For the purpose of comparison, a cycle with a polytropic compressor is also considered. Similarly, two alternative designs for the evaporator are developed and simulated. A second law analysis is performed at the end of the study.

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Kharazi, Amir Ahmadzadeh. "Study of a novel R718 turbocompression cycle." Diss., Connect to online resource - MSU authorized users, 2006.

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Thesis (Ph. D.)--Michigan State University. Dept. of Mechanical Engineering, 2006.
Title from PDF t.p. (viewed on June 19, 2009) Includes bibliographic references (p. 84-89). Also issued in print.

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Bassetto, Izeds Felipe Facchini. "Estudo de confiabilidade de compressores alternativos semi-herméticos de sistemas de refrigeração." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3150/tde-03082007-113232/.

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Sistemas de refrigeração são sistemas reparáveis. Isto significa que os componentes destes sistemas podem sofrer manutenção várias vezes durante a vida útil do sistema como um todo. Em sistemas de refrigeração o mais conhecido é o que opera com ciclo por compressão de vapor. Neste ciclo, o compressor é o equipamento mais complexo e de maior custo. Dessa forma, deve-se tomar especial cuidado, pois além de problemas como desgaste e falta de lubrificantes, ele está sujeito a sofrer danos decorrentes do funcionamento incorreto ou falho de todos os outros componentes. Dentro dos compressores existentes, o compressor alternativo pode ser comercialmente considerado o cavalo de batalha da refrigeração industrial, dominando a faixa de capacidades inferiores a 300 kW (85 TRs). O compressor alternativo também pode ser utilizado, com vantagens, quando o controle de capacidade se faz necessário, através do procedimento de desativação dos cilindros. Este compressor possui a possibilidade de manutenção no campo de, praticamente, qualquer item construtivo. O termo confiabilidade vem do inglês \"reliability\" que é a probabilidade de um item poder desempenhar sua função requerida, por um intervalo de tempo estabelecido, sob condições definidas de uso. Testes de confiabilidade possibilitam, através de estimativa, com base em estudos de confiabilidade, caracterizar os comportamentos de confiabilidade, da probabilidade de falha e da taxa de falha em relação ao tempo de um componente ou sistema. Uma das ferramentas para permitir avaliar ações que aumentem a confiabilidade é a Análise de Modos e Efeitos de Falha ou FMEA (\"Failure Mode and Effect Analysis\"). Basicamente, esta ferramenta parte da definição das funções dos sistemas e subsistemas analisados, verificando em seguida as falhas que afetam cada função e todos os modos de falha que levam a cada falha. Para cada modo de falha, analisam-se os efeitos e define-se a necessidade de ações para reduzir a possibilidade de ocorrência deste evento, eliminá-lo ou, simplesmente controlar os efeitos indesejáveis. O objetivo deste trabalho é o estudo das principais falhas, modos de falha de compressores semi-herméticos alternativos de sistemas de refrigeração, suas ocorrências e o comportamento destes equipamentos no seu período de garantia, sob a ótica da confiabilidade.
Refrigeration systems are reparable systems. This means that one can perform maintenance actions on them several times during the system life cycle. The most common refrigeration system is the vapor compression cycle. In this cycle, the compressor is the most complex and expensive component. So, the user should take special care because , beside problems like wear and lubricant lack, the compressor can also suffer damages caused by the incorrect work or fault from the others system components. Among the compressor types, the reciprocating compressor can be considered as the most used in the industrial refrigeration, from lowers capacities to up to 300 kW. Also the reciprocating compressor has some advantages, where its cylinders can be disabled for capacity control purposes. One can perform field maintenance of almost every part for this compressor. The word reliability means the probability of some equipment can not perform its requested function for an established time period, under defined operation conditions.. One of the tools to allow actions to improve the reliability is the failure mode and effect analysis (FMEA). This tool is based on the analyzed function and sub function systems definitions seeking faults that affect each function and all fault modes that lead to every fault. For each fault mode, the effects are analyzed and the need of actions to decrease the occurrence of this event is defined, excluding or control this undesirable events. This work objective is to study the most important faults, fault modes of reciprocating semi-hermetic compressors, its occurrences and its behavior during the guarantee period under reliability point of view.

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KATTA, KRANTHI KUMAR, and Ifeanyi William Okogwu. "REFRIGERATOR COMPRESSOR TREATMENT AND RECYCLING." Thesis, Högskolan i Halmstad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-43388.

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Social demands of recycle is becoming strong. In modern production systems, largenumber of one model of product is manufactured at a time and the way ofproduction operations are well specified. In recycling systems, on the contrary, it isusual that operation of disassemble for each works differs. Because of this,achieving high efficiency in recycling systems have been difficult. Quality FunctionDeployment (QFD) was implemented in the project to obtain clear understandingof the problem being dealt with. Being a case study in the recycling of end-of-liferefrigerators means there are several stakeholders which must be satisfied includinggovernment regulations, workforce, and the business organisation. At the same timeproductivity is maximised while cost and time is diminished. Designing withfunction, brainstorming and patent searches were used to generate new ideas.Building morphology was also used to generate ideas as well as document them.The results of the project are different concepts that can be applied individually anda comprehensive concept that will entail exhaustive change in the entire system.The recycling of compressors for material recovery is discussed.
http://www.diva-portal.se/smash/get/diva2:1326957/FULLTEXT02.pdf

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Rigola, Serrano Joaquim. "Numerical simulation and experimental validation of hermetic reciprocating compressors. Integration in vapour compression refrigerating systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2002. http://hdl.handle.net/10803/6684.

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The numerical simulation model presented is based on the integration of the fluid conservation equations (continuity, momentum and energy) in the whole compressor domain (compression chamber, valves, manifolds, mufflers, connecting tubes, parallel paths, etc.) using instantaneous local mean values for the different variables. It is interesting to remark how momentum equation has been taken into account in all compressor parts and the possibility to solve parallel paths, resonators, etc. Effective flow areas are evaluated considering multidimensional models based on modal analysis of fluid interaction in the valve. Then, second and third order vibration models of valve are also considered. The possibility to use compound bound has been also implemented.

The force balances in the crankshaft connecting rod mechanical system are simultaneously solved at each time-step considered in the thermal and fluid dynamic compressor model. It allows to evaluate the instantaneous compression chamber volume and the different forces in the crankshaft connecting rod mechanical system. Mechanical system forces allows to know important information to predict possible
over-stresses in piston, piston pin, crankshaft, connecting rod, etc.

The thermal analysis of the solid elements is based on global energy balances at each macro volume considered (shell, muffler, tubes, cylinder head, crankcase, motor, etc.). Some improvements can be implemented (shell conduction, heat transfer coefficient evaluation, etc.).

The resulting governing equations (fluid flow, valve dynamics, conduction heat transfer in solids, etc.) are discretized by means of a fully implicit control volume formulation. The complete set of algebraic equations are coupled using the segregated he complete set of algebraic equations are coupled using the segregated pressure based algorithm Semi-Implicit Method for Pressure-Linked Equations(SIMPLEC) extended to compressible flow. Second and third time order schemes have been implemented for the transient terms.

An extensive hermetic reciprocating compressor experimental validation has been presented and the experimental know-how acquired has been highlighted. Furthermore, two commercial hermetic reciprocating compressor have been instrumented in detail to obtain the thermal temperatures map and the pressure fluid evolutions along compressor for different working conditions. It is interesting to remark as a novelty, the use of very small absolute pressure transducers, instead of the standard relative transducers. They allow to know instantaneous absolute pressure inside compressor chamber, without the necessity of measurement an absolute pressure outside the compression chamber (as is usual in this kind of experimental works).

The global comparative results have allowed to check the possibilities of the numerical simulation presented above and its accuracy compared with experimental data. After that, this work show the capabilities offered by the simulation presented and its final objective, a better understanding of the thermal and fluid dynamic compressor behaviour to improve the design of these equipments.

Then, the objective has been to review and present different physically meaningful parameters that characterize the reciprocating compressor behaviour (volumetric efficiency, isentropic efficiency, heat transfer efficiency, mechanical, electrical and heat losses, Coefficient of Performance, etc.), their influence detachment and evolution under different working conditions, with the idea to predict the performance of hermetic reciprocating compressors under different working conditions using the above mentioned non-dimensional parameters.

Finally, a parametric study of hermetic reciprocating compressors behaviour has been carried out. Results presented show the influence of different aspects (geometry, valves, motor, working conditions, etc.) in the compressor behaviour.

The parametric studies and compressor characterization detachment allows also a better implementation of simplest models of the compressors in the thermal and fluid dynamic numerical simulation of vapour compressor cycles together with the rest of elements.

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Grando, Fernando Paulo. "Two-Phase Lubrication Model for Refrigeration Reciprocating Compressors." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486397.

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The study of fluid film lubrication in mechanical components is fundamental to the analysis of their dynamic behaviour as well as determining friction losses between moving parts. In several cases, gases present in the system can interact with the oil changing lubrication characteristics - by their dissolution and release from the oil, forming bubbles or even producing foam. Additionally, in low pressure regions the lubricant loses the capacity to flow as a continuous film, and cavitation occurs. Generally cavitation is treated in numerical models via boundary conditions for the pressure equation, which is then used to solve the pr<;>blem only in the full film region instead of the whole solution domain. Several criteria are available, and the results are often sensitive to the chosen conditions. The present work proposes the study of cavitation considering the changes suffered by the lubricant as it flows through the lubricated component, considering the release of gas from the liquid and the existence of a two-phase flow. The numerical model treats the liquid-gas mixture as a homogeneous fluid, whose properties are calculated as weighted averages of the properties from the constituent phases. The model then solves the lubrication equation numerically using the finite volume methodology, considering variable fluid properties and without using any intermediate boundary conditions. The lubricant is considered a mixture of oil and refrigerant, widely studied due to its importance in lubrication and heat transfer problems in refrigeration systems. To advance in the understanding of the two-phase flow model, it was initially applied to simplified geometries, such as that of a partial journal bearing, and gradually the geometrical assumptions were relaxed, applying the model to a full journal bearing, where a . discussion against experimental results was possible. Finally, the problem of the reciprocating motion of the piston in a refrigeration compressor was considered. From the results, it is shown that the model can automatically predict three regions for the lubricated component,the positive pressure region, cavitation and pressure recovery. When the model is compared to solutions considering Reynolds boundary conditions, good agreement is observed for moderate and heavy loads. Studying the main operational parameters and the mixture behaviour, the discussion focuses on the fluid properties, which affect particularly density and as a result the cavitation region - or even the full bearing if bubbles are considered in all the bearing extent. Finally, in the light of the two-phase solution for piston lubrication, existing cavitation criteria for the problem seem inappropriate.

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MARTINEZ, LUIS CARLOS CASTILLO. "OPTIMIZATION THE CIRCUITING REFRIGERATION OF THE HEAT EXCHANGERS IN VAPOR COMPRESSION REFRIGERATION SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31763@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Em sistemas de refrigeração por compressão de vapor, o projeto adequado dos circuitos para o refrigerante nos trocadores de calor pode ter um impacto significativo no seu coeficiente de performance (COP). O projeto otimizado dos circuitos de refrigerante em sistemas de refrigeração com trocadores de calor do tipo tubo-aletado não é trivial, devido à complexidade de sua representação assim como o elevado número de possíveis combinações, mesmo quando metodologias inteligentes de otimização são empregadas. No presente trabalho propõe-se uma nova metodologia para a otimização simultânea (condensador e evaporador) dos circuitos do refrigerante em sistemas de refrigeração com trocadores de calor de tipo tubo-aletado. Esta metodologia, aqui denominada como GAFIS (Genetic algorithms applied in filtered spaces), mostra-se mais eficiente que as metodologias até então descritas na literatura. Foi aplicado o método GAFIS, em conjunto com um simulador completo para o sistema de refrigeração, Genesym, na otimização de unidades comerciais de condicionamento de ar de alto desempenho. Estudaram-se casos onde o sistema atingiu aumentos de até 15,3 por cento no coeficiente de performance. Em outros estudos, obtiveram-se casos onde o custo de produção foi reduzido em 3,85 por cento (do custo total da unidade), mantendo-se um similar desempenho (capacidade e COP). Testes de otimização, considerando-se diferentes diâmetros dos tubos, na construção dos trocadores de calor, e sistemas com distribuição não uniforme de velocidade de ar, também foram realizados com o GAFIS. Igualmente foram estudados condensadores de microcanais, devido ao interesse atual da indústria com estes trocadores de calor. A otimização do circuito para o refrigerante, neste caso, é relativamente simples, devido ao baixo custo computacional das simulações. Entretanto, modelos de simulação adequados para estes tipos de trocadores de calor só recentemente começaram a surgir, e não têm sido explorados de maneira adequada até a presente data. Explorou-se no presente trabalho, a influência, no desempenho térmico do condensador, dos parâmetros que definem o circuito do refrigerante. Para tal efeito, desenvolveu-se um modelo de simulação baseado em análise local, validado com dados experimentais disponíveis, de condensadores de microcanais de uso automotivo com diâmetro hidráulico (lado do refrigerante) de 0,9 e 1,0mm, para refrigerantes R-134a, Fluid-H e R-1234yf. Foram encontradas relações diretas entre os parâmetros geométricos que definem os circuitos de refrigerante no condensador e seu desempenho térmico. Tal fato pode ser utilizado como orientação expedita para o projeto do circuito ótimo do condensador.
Refrigerant circuiting in condensers and evaporators has a significant effect in the performance of refrigeration systems. The optimized project of the refrigerant circuits in refrigeration systems with plate-fin heat exchangers is not trivial, due to the complexity of their representation as well as the high number of possible combinations, even when methodologies of intelligent optimization are used. The present work proposes a new methodology for the simultaneous optimization of refrigerant circuiting in air-air refrigeration systems with plate-fin heat exchangers. This new methodology, here defined as GAFIS (Genetic algorithms applied in filtered spaces), has proven to be more efficient than traditional methods. The GAFIS method was applied, in conjunction with a full refrigeration system simulator, Genesym, for the optimization of high performance commercial air-conditioning units. Typical cases were studied and a coefficient of performance improvement of up to 15.3 percent has been observed. In other studies, there were cases where the manufacturer s predicted cost was reduced in 3,85 percent (of total cost of the unit), while a similar thermal performance (capacity and COP) was maintained. Optimization tests, considering different diameters of tube, for the construction of heat exchangers, as well as systems with non-uniform air velocity distribution, were also performed with the GAFIS method. Microchannel condensers were also studied, given the current interest of industry on this kind of heat exchanger. The optimization of the refrigerant circuiting, in this case, would not be a major problem, due to the low computational cost of its simulation. However, simulation models appropriate for these types of heat exchangers have only been recently in use, and, to date, have not been adequately explored. In the present work, the influence on condenser performance of parameters that define the refrigerant circuiting has been investigated. For this purpose, a simulation model, based on local analysis, was developed. It was validated against experimental data, available from automotive microchannel condenser tests, with hydraulic diameters (refrigerantside) of 0.9 and 1.0mm for refrigerants R-134a, Fluid-H and R-1234yf. A direct relation was found between the geometric parameters that define the condenser refrigerant circuiting and its thermal performance. This fact can be appropriately used as guidance for expeditious design practices of the optimal refrigerant circuit of the condenser.

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Wu, Shenyi. "Investigation of ejector re-compression absorption refrigeration cycle." Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/10369/.

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This thesis describes a theoretical and experimental investigation of the ejector re-compression lithium bromide absorption refrigeration cycle. In this novel cycle, a steam ejector is used to enhance the concentration process by compressing the vapour to a state that it can be used to re-heat the solution from where it was evolved. Since this cycle recovers the heat otherwise wasted in a conventional absorption cycle, the energy performance of the cycle is improved. The theoretical study shows that the improvement of the efficiency is proportional to the performance of the steam ejector. A COP of 1.013 was achieved from the experiment in this investigation. The novel cycle does not only improve the energy efficiency but also avoids the corrosion that will happen when high temperature heat sources are used to drive a lithium bromide absorption refrigerator. The steam ejector in the novel cycle acts as an efficient temperature converter in acceptance of different temperature heat sources, which reduces the energy loss when the temperature difference between the solution and the heat source is big. Therefore, the solution temperature can be set to a low level while the heat source temperature is high. This is significant to avoid the corrosion of lithium bromide solution at high temperature. Furthermore, the construction of the machine based on the novel cycle is simpler than that based on the conventional double-effect cycle. This refrigerator will be more reliable and have a lower initial capital cost. The cycle was investigated comprehensively in this thesis. In the theoretical study, a mathematical model for this novel cycle was established. The theoretical study reveals the operation characteristics and the factors that affect the energy efficiency of the cycle as well as how to design a refrigerator based on the novel cycle. In the experimental study, a concept-approved refrigerator was manufactured and tested. The part-load performance of the novel cycle was investigated from the experiment. The theoretical results had a good agreement with the experimental ones. NB. This ethesis has been created by scanning the typescript original and contains some inaccuracies. In case of difficulty, please refer to the original text.

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Leandro, Eduardo [UNESP]. "Um novo sistema de refrigeração com controle de temperatura, compressor aberto, máquina de indução trifásica com velocidade variável e correção ativa do fator de potência do estágio de entrada." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/87222.

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Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-09-25Bitstream added on 2014-06-13T19:26:47Z : No. of bitstreams: 1 leandro_e_me_ilha.pdf: 1745578 bytes, checksum: 2db70f1465f9f7258fdbcda3cdebf72c (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho apresenta uma nova proposta para sistema de refrigeração com controle dinâmico de temperatura, operando com estrutura de compressor aberto, acionado por motor de indução trifásico com velocidade variável, e estágio de entrada retificador com correção ativa do fator de potência. O estágio de entrada é composto por um retificador Boost monofásico com elevado fator de potência, com duas células entrelaçadas, operando no modo de condução crítica, empregando técnica de comutação não dissipativa e controlado por dispositivo FPGA, associado a um estágio de saída inversor de dois níveis convencional trifásico à IGBT, o qual é controlado por um Processador Digital de Sinais (DSP - Digital Signal Processor). A técnica de comutação não dissipativa para o estágio de entrada é baseada em células ZCS (Zero-current-switching). As principais características do retificador incluem a redução da ondulação da corrente de entrada, redução da ondulação da tensão de saída retificada, utilização de componentes com reduzidos esforços, reduzido volume do filtro de entrada para Interferências Eletromagnéticas (EMI - Electromagnetic Interference), elevado Fator de Potência (FP) e reduzida Distorção Harmônica Total (DHT) da corrente de entrada, atendendo os limites da norma IEC61000-3-2. O controle digital para o estágio de saída inversor foi desenvolvido usando duas diferentes técnicas, incluindo a técnica convencional controle escalar Volts/Hertz (V/Hz) e o controle Vetorial com Orientação pelo Fluxo do estator, com o propósito de verificar a aplicabilidade e a performance dos controles digitais propostos, para o controle contínuo da temperatura, aplicados a um protótipo de sistema de refrigeração.
This work presents a new proposal for refrigeration systems with dynamic control of temperature, working with structure of open compressor, driving a three-phase induction motor with variable speed, and input rectifier with active power factor correction. The proposed system is composed of a single-phase high-power-factor boost rectifier, with two cells in interleaved connection, operating in critical conduction mode, and employing a softswitching technique, controlled by a Field Programmable Gate Array (FPGA), associated with a conventional three-phase IGBT bridge inverter (VSI - Voltage Source Inverter), controlled by a Digital Signal Processor (DSP). The soft-switching technique for the input stage is based on zero-current-switching (ZCS) cells. The rectifier s features include reduction in input current ripple, reduction in output voltage ripple, use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller for the output stage inverter has been developed using two different techniques, the conventional Voltage-Frequency control (scalar V/Hz control), and a simplified stator oriented vector control, in order to verify the feasibility and performance of the proposed digital controls, for continuous temperature control, applied at a refrigerator prototype.

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Leandro, Eduardo. "Um novo sistema de refrigeração com controle de temperatura, compressor aberto, máquina de indução trifásica com velocidade variável e correção ativa do fator de potência do estágio de entrada /." Ilha Solteira : [s.n.], 2006. http://hdl.handle.net/11449/87222.

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Resumo: Este trabalho apresenta uma nova proposta para sistema de refrigeração com controle dinâmico de temperatura, operando com estrutura de compressor aberto, acionado por motor de indução trifásico com velocidade variável, e estágio de entrada retificador com correção ativa do fator de potência. O estágio de entrada é composto por um retificador Boost monofásico com elevado fator de potência, com duas células entrelaçadas, operando no modo de condução crítica, empregando técnica de comutação não dissipativa e controlado por dispositivo FPGA, associado a um estágio de saída inversor de dois níveis convencional trifásico à IGBT, o qual é controlado por um Processador Digital de Sinais (DSP - Digital Signal Processor). A técnica de comutação não dissipativa para o estágio de entrada é baseada em células ZCS (Zero-current-switching). As principais características do retificador incluem a redução da ondulação da corrente de entrada, redução da ondulação da tensão de saída retificada, utilização de componentes com reduzidos esforços, reduzido volume do filtro de entrada para Interferências Eletromagnéticas (EMI - Electromagnetic Interference), elevado Fator de Potência (FP) e reduzida Distorção Harmônica Total (DHT) da corrente de entrada, atendendo os limites da norma IEC61000-3-2. O controle digital para o estágio de saída inversor foi desenvolvido usando duas diferentes técnicas, incluindo a técnica convencional controle escalar Volts/Hertz (V/Hz) e o controle Vetorial com Orientação pelo Fluxo do estator, com o propósito de verificar a aplicabilidade e a performance dos controles digitais propostos, para o controle contínuo da temperatura, aplicados a um protótipo de sistema de refrigeração.
Abstract: This work presents a new proposal for refrigeration systems with dynamic control of temperature, working with structure of open compressor, driving a three-phase induction motor with variable speed, and input rectifier with active power factor correction. The proposed system is composed of a single-phase high-power-factor boost rectifier, with two cells in interleaved connection, operating in critical conduction mode, and employing a softswitching technique, controlled by a Field Programmable Gate Array (FPGA), associated with a conventional three-phase IGBT bridge inverter (VSI - Voltage Source Inverter), controlled by a Digital Signal Processor (DSP). The soft-switching technique for the input stage is based on zero-current-switching (ZCS) cells. The rectifiers features include reduction in input current ripple, reduction in output voltage ripple, use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller for the output stage inverter has been developed using two different techniques, the conventional Voltage-Frequency control (scalar V/Hz control), and a simplified stator oriented vector control, in order to verify the feasibility and performance of the proposed digital controls, for continuous temperature control, applied at a refrigerator prototype.
Orientador: Carlos Alberto Canesin
Coorientador: Flávio Alessandro Serrão Gonçalves
Banca: Fabio Toshiaki Wakabayashi
Banca: João Onofre Pereira Pinto
Mestre

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Roberti, Giovanni. "Steady-state Modelling of a Vapor Compression Refrigeration Cycle." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19438/.

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In this work a steady-state model of a simple vapor compression refrigeration cycle is presented. All the fundamental components of this system are modeled separately in order to consider them as black boxes that take inputs and convert them into output variables. The heat exchangers are treated as a set of multiple zones, identified by the refrigerant's state, connected in series, in which the heat transfer coefficient (HTC) is constant. A non-linear system of equations is obtained applying the energy balances and the ε-NTU method for each zone in the heat exchangers. A study on the HTC correlations used to connect the length of the zones with the value of the respective HTC is developed. The compressor is modeled using a polynomial function. Some iterative methods for the resolution in Matlab of the models of the components and the machine are presented, focusing on the strategy to decrease the execution time and to increase the accuracy of the results. Finally, all the models are validated through a set of experimental data and the global model is used to make some considerations about the efficiency and the exergy destruction in the plant.

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30

Cornejo, Ma Elena Rueda. "Fault detection and diagnosis in vapour compression refrigeration systems." Thesis, Brunel University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439801.

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31

Naghashzadegan, Mohammad. "Steady state and dynamic behaviour of vapour compression refrigeration systems." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284386.

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32

Grace, Iain Nicholas. "Modelling the performance and dynamics of vapour compression refrigeration systems." Thesis, Brunel University, 2000. http://bura.brunel.ac.uk/handle/2438/5265.

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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.

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33

Ibrahim, G. A. "An investigation into liquid film absorbers for refrigeration systems." Thesis, King's College London (University of London), 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245436.

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34

Holmgren, Robin, and Dante Hallenberg. "Driftoptimering av kyl- och frysanläggning : En analys av en kaskadprocess med partiell förångning." Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-52367.

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Studien är utförd åt Freezing Food Småland Öland AB. Syftet med undersökningen var att ge förslag på åtgärder som minskar anläggningens energibehov samt att beräkna återbetalningstid för åtgärder. Genom användningen av simuleringsprogramvara tillsammans med data från praktiska mätningar så testades olika förändringar i anläggningen. Studien resulterade i förslag på en höjning av frysrumstemperaturen och temperaturen i LTB1. Dessa åtgärder höjer anläggningens köldfaktor och minskar energibehovet. Förslag för att få bukt på istillväxten är att isolera av komponenter så som rör och ventiler. Isolering ger en energibesparing och en minskad risk för korrosion. Genom belastningstester framkom det att kompressorerna arbetar ofördelaktigt så förslag på lämpliga driftområden togs fram för att öka verkningsgraden och minska underhållskostnaderna och energibehovet. Anläggningen visade sig vara väl dimensionerad mot transmissionsförluster men att golvvärmen står för en oproportionerligt stor del av förlusterna i förhållande till dess yta.
The study is conducted for Freezing Food Småland Öland AB. The purpose of the study was to propose measures to decrease the facility’s energy demand and to calculate the payback time for these suggestions. By means of using simulation software along with data from practical measurements different configurations in the facility were tested. The study resulted in suggestions consisting of an increase of the temperature in the freezing room and the temperature in LTB1.Those suggestions increases the facilities COP and decreases the energy consumption. Proposals to curb the ice growth are the insulation of components such as pipes and valves. Insulation results in a small decrease in energy demand but greatly increases the accessibility and also decreases the risk of corrosion. Through load tests conducted on the compressors it showed that the compressors were not driven in the optimal load range, suggestions were made for operation in a more favourable load range. Thus increasing the efficiency and cutting the maintenance costs. From the results it is shown that the facility is well built and dimensioned against thermal transmission. Though it turned out that the floor heating accounts for a disproportionate amount of the thermal transmission.

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35

Coggins, Charles Lee. "Single- and Multiple-Stage Cascaded Vapor Compression Refrigeration for Electronics Cooling." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16283.

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The International Technology Roadmap for Semiconductors (ITRS) predicts that microprocessor power consumption will continue to increase in the foreseeable future. It is also well known that microprocessor performance can be improved by lowering the junction temperature: recent analytical studies show that for a power limited chip, there is a non-linear scaling effect that offers a 4.3x performance enhancement at -100 °C, compared to 85 °C operation. Vapor Compression Refrigeration (VCR) is a sufficiently compact, low cost, and power efficient technology for reducing the junction temperature of microprocessors below ambient, while removing very high heat fluxes via phase change. The current study includes a scaling analysis of single- and multiple-stage VCR systems for electronics cooling and an experimental investigation of small-scale, two-stage cascaded VCR systems. In the scaling analysis, a method for estimating the size of single- and multiple-stage VCR systems is described, and the resulting trends are presented. The compressor and air-cooled condenser are shown to be by far the largest components of the system, dwarfing the evaporator, expansion device, and inter-stage heat exchanger. For systems utilizing off-the-shelf components and removing up to 200 W at evaporator temperatures as low as 173 K, compressor size dominates the system and scales with the compressor s motor. The air-cooled condenser is the second largest component, and its size is constrained by the air-side heat transfer coefficient. In the experimental work, a two-stage cascaded VCR system with a total volume of 60000 cm3 is demonstrated that can remove 40 W at -61 °C.

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36

Tuomas, Roger. "Properties of oil and refrigerant mixtures : lubrication of ball bearings in refrigeration compressors /." Luleå : Division of Machine Elements, Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1544/2006/70/.

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37

Miller, Eric S. "Dynamic Modeling of Vapor Compression Cycle Systems." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337715881.

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38

Sabir, Hisham. "Heat and mass transfer processes in absorption systems." Thesis, King's College London (University of London), 1993. https://kclpure.kcl.ac.uk/portal/en/theses/heat-and-mass-transfer-processes-in-absorption-systems(ab68d065-c159-4292-ad39-b7a820ac0054).html.

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39

Gessler, Paul D. "A one-dimensional model of a closed-loop refrigeration test block for centrifugal compressors." Thesis, Marquette University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1554659.

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The management of Sclerotinia stem rot of soybean caused by [Sclerotinia sclerotiorum (Lib) de Bary] integrates several tactics that may include biological control. However, the successful incorporation of biocontrol agents into the management program might be hindered by agrochemical application. To determine the compatibility of potential biocontrol agents with agrochemicals, growth of Trichoderma asperellum, T. gamsii and Coniothyrium minitans was tested with selected chemicals on agar plates. Effects of selected agrochemicals on C. minitans growth and biocontrol activity were also tested in soil and in water. On amended agar media, Trichoderma spp. and C. minitans were insensitive to the herbicide lactofen and were inhibited to varying degrees by some of the tested fungicides. The survival and the biocontrol activity of C. minitans in the soil was not impaired by propamocarb HCl, tetraconazole or lactofen treatments. When mixed in a water suspension, none of the selected the herbicides or a biofertilizer affected C. minitans population in the suspension over a 4 h period, suggesting that they can be applied in a tank mix. Under field conditions, Trichoderma spp. and C. minitans reduced the disease severity and viable sclerotial population of S. sclerotiorum, but their efficacy varied across years and location. Co-application with lactofen enhanced the efficacy of disease suppression and yield in some cases but reduced the efficacy in others. The effect of the biological control agents or chemicals evaluated on yield during three years of trials was inconsistent.

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40

Zhang, Quansheng. "Modeling, Energy Optimization and Control of Vapor Compression Refrigeration Systems for Automotive Applications." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406121484.

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41

Smith, Benjamin D. "Sweeping gas membrane evaporative cooling for the enhanced performance of vapour compression refrigeration." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28809.

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A sweeping gas membrane evaporative (SGME) cooling system was developed to remove heat from the condenser of a vapour compression chiller. The chiller was designed for hot environments and could only achieve a coefficient of performance (COP) of 1.0 using an air-cooled condenser. In this work, the condenser was modified to have circulating water absorb heat, which was then cooled in membrane modules by evaporation across a hydrophobic membrane into an air stream. Steady-state operation of the chiller was achieved with the SGME system. Increasing either air flow or water circulation rate increased the COP of the chiller, which reached a value of 1.83 with an optimal heat load of 435 W. The SGME system was then compared to cooling towers, a conventional method of evaporative heat removal. It was found that the SGME system provided more heat removal per unit volume and per unit of air flow than any investigated cooling tower. 89% of the heat removal was attributed to evaporation, and only 1.5% of the water entering the module was lost to evaporation, making the system more compact and efficient than towers. The sweeping gas membrane evaporation system was superior to both air-cooled condensers and to cooling towers.

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42

Harraghy, P. G. "An assessment of refrigeration system performance with a particular emphasis on the effects of frosting and defrosting." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234842.

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43

Nikolaidis, Christos. "A computer study of multi-stage vapour compression refrigeration cycles by the Exergy Method." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264886.

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44

Hussen, Muaz Bedru. "STUDY OF A SMALL-SCALE COOLING SYSTEM BASED ON AN ICE-STORAGE AND A DC-POWERED VAPOUR COMPRESSION REFRIGERATION UNIT TO IMPLEMENT SOLAR ENERGY IN REMOTE AREAS." Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670597.

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La refrigeració manté la qualitat sensorial del productes i minimitza la pèrdua en les cadenes de valor del fred. Les àrees remotes dels països en desenvolupament es caracteritzen principalment pels baixos nivells de tecnologia, accés limitat a la xarxa elèctrica i el predomini de les petites explotacions agrícoles com un desafiament. El principal objectiu d'aquesta tesi és desenvolupar i caracteritzar un sistema de refrigeració modular multipropòsit basat en l'emmagatzematge de gel per a aplicacions de petita escala. El sistema d'emmagatzematge de gel va utilitzar un equip de refrigeració amb un compressor de corrent continu i velocitat variable. La càrrega de refrigerant i les dimensions de l'tub capil·lar es van optimitzar experimentalment per maximitzar el rendiment i evitar la caiguda de temperatura de la línia de succió. A més, es va avaluar experimentalment el rendiment de sistema sota diversos paràmetres. Els usos de l'emmagatzematge de gel per a refrigeració de llet i aplicacions de càmeres frigorífiques també es van investigar experimentalment. Es van utilitzar deposits de llet convencionals en un bany de refredament aïllat, i en una cambra frigorífica dotada d'una unitat de fancoil amb els seus respectius sistemes experimentals. En general, el treball de recerca realitzat en aquesta tesi aporta més coneixements sobre el desenvolupament de tecnologies de refrigeració baixes en carboni adequades per a països en desenvolupament.
La refrigeración mantiene la calidad sensorial del producto y minimiza la pérdida en las cadenas de valor del frío. Las áreas remotas de los países en desarrollo se caracterizaron principalmente por bajos niveles de tecnología, acceso limitado a la red eléctrica y el predominio de las pequeñas explotaciones agrícolas como un desafío. El principal objetivo de esta tesis es desarrollar y caracterizar un sistema de refrigeración modular multipropósito basado en el almacenamiento de hielo para aplicaciones de pequeña escala. El sistema de almacenamiento de hielo utilizó un equipo de refrigeración con un compresor de corriente continua y velocidad variable. La carga de refrigerante y las dimensiones del tubo capilar se optimizaron experimentalmente para maximizar el rendimiento y evitar la caída de temperatura de la línea de succión. Además, se evaluó experimentalmente el rendimiento del sistema bajo diversos parámetros. Los usos del almacenamiento de hielo para refrigeración de leche y aplicaciones de cámaras frigoríficas también se investigaron experimentalmente. Se utilizaron cantaras de leche convencionales en un baño de enfriamiento aislado, y en una cámara frigorífica dotada de una unidad de fancoil con sus respectivos sistemas experimentales. En general, el trabajo de investigación realizado en esta tesis aporta más conocimientos sobre el desarrollo de tecnologías de refrigeración bajas en carbono adecuadas para países en desarrollo.
Refrigeration and cooling maintains the sensory quality of the product and minimizes the loss in cold value chains. Remote areas of the developing countries were mainly characterized by low levels of technology, limited access to modern energy and dominance of small-holder farms as a challenge. Hence, the main objective of this thesis is to develop and characterize a modular-multipurpose cooling system based on an ice-storage for small-scale applications. As part of the experimental system, the ice storage with a variable speed DC-compressor was developed and fabricated. The refrigerant charge and the capillary tube dimensions were experimentally optimized to maximize performance and avoid suction line temperature drop. Moreover, performance of the system under varying parameters was evaluated. Uses of the ice storage for milk cooling and cold room applications were also experimentally investigated. Conventional milk-cans with insulated box and a heat simulated room with a FCU were utilized as respective experimental systems. Chilled water recirculation rates, ice-storage energy density, and air flow rate across FCU were varied as main experimental parameters. Improvement of the ice production technique and corresponding performance data obtained were among main contributions of this research. In general, the research work performed in this thesis contributes more knowledge on development of low-carbon cooling technologies suitable for developing countries. Therefore, piloting and field testing of the technology are among major recommendations for future work.

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Montanez, Morantes Maria Vanessa. "Operational optimisation of low-temperature energy systems." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/operational-optimisation-of-lowtemperature-energy-systems(a22bd339-1473-4401-bbc5-2e1280e57756).html.

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Low-temperature energy systems are processes that operate below ambient temperatures and make use of refrigeration cycles, where the main energy consumption is due to the shaft work required to drive the compressors. Very-low-temperature energy systems, also known as cryogenic processes, operate at around -150°C and below. Due to increasing demand of products from cryogenic processes and tighter environmental regulations, existing plants need to be revamped to increase their energy efficiency or adapt to new processing capacities. So, accurate models of the performance of cryogenic processes are needed in order to optimise their operation. The present work proposes a new approach for optimising the operating conditions of existing refrigeration cycles in cryogenic processes, using pure refrigerants, for different plant operating conditions. In this work, the process conditions are considered as given and not considered as variables during the optimisation. The operational optimisation is achieved by integrating models for the part-load performance of centrifugal compressors and models for the simulation of plate-fin heat exchangers (PFHEs), into a single optimisation approach. An optimisation approach similar to the one proposed in this work was not found in the open literature. The optimisation approach varies the refrigerant evaporation temperatures, flow rates and cooling duties, minimum temperature difference in PFHEs, and rotational speed of compressors. The objective function seeks to minimise shaft work demand and the constraints consider the operational limitations of centrifugal compressors (minimum and maximum flow rates) and PFHEs (no temperature crosses and meeting the target temperatures of the process streams). In order to explore the solution space that is generated by the complex interactions between the variables and find an approximation to a global optimum, a multistart optimisation algorithm is implemented. The part-load centrifugal compressor model implemented in this work uses regressed data from their performance curves together with the fan laws. The proposed simulation model of PFHEs represents these units as a ‘fictitious’ heat exchanger network of two-stream matches. The simulation model accounts for single and two-phase streams and for the temperature-dependent physical properties of pure refrigerants (e.g. viscosity, heat capacity, etc.). In addition to the simulation model, design and rating models for PFHEs with single and two-phase streams are also proposed. The examples presented in this work for the design, simulation and rating of single and two-phase streams in PFHEs show that the models proposed can find feasible designs, and can predict the outlet temperature of the process streams within ±3°C for different inlet conditions. The example presented in this work for the operational optimisation of refrigeration cycles shows that savings of around 3% in shaft work consumption (up to £0.86 million per year), for different process throughput, can be achieved using the proposed methodology.

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46

Schoenfeld, Jonathan Michael. "Integration of a thermoelectric subcooler into a carbon dioxide transcritical vapor compression cycle refrigeration system." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8726.

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Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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47

Breistein, Hallvard. "Fixed Speed Electric Motor Drives for LNG Refrigeration Compressors. : Back-to-Back Starting Methods and Grid Consequences." Thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9877.

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Experimental studies as well as simulations have been performed on the Back-to-Back starting schemes low frequency-, partial frequency-, and soft -start-up. A Back-to-Back configuration of two synchronous machines has been established in the laboratory, upon which parameter estimation and start-up experiments have been performed. Extensive parameter estimation was conducted in order to replicate the laboratory machines in the simulation model as accurately as possible. This was done in order to verify the validity of the simulation model. Studies into the effects of inductance interconnecting the machines were made in the laboratory and in the simulation model. Effects of resistance and inertia were studied in the simulation model. It is concluded that the simulation model appears to be as reliable as is its input parameters. Discrepancies were found in line voltages, due to faulty implementation of field current replication. Full scale simulations using Motorformer parameters were performed in the simulation model, featuring low frequency- and soft -staring. The effects of an interconnecting cable were studied. It is concluded that low frequency starting appears to be most reliable and least violent starting method. However, it might be limited by the availability of a turbine. This is not the case for soft starting, which has a lower starting capability and is more violent to the motor damper- and field windings. Low frequency startig is the recommended starting method of the ones studied. Dynamic short circuit simulations were done on a fixed speed LNG-facility. The fixed speed alternative appears to be more stable when responding to a short circuit. This is because the motors contribute to upholding the voltage during a fault by delivering reactive power to the short circuit, and because the motors do not loose all torque as is the case for LCI drives when the voltage dip exceeds 20$%$. Further work is needed in up-scaling the experiments. A sophisticated simulation model should be established and its validity tested on the up-scaled experiments. Preliminary custom design of machines should be initiated depending on what starting scheme is chosen. Custom machine parameters should then be used in full scale simulation using the more sophisticated model.

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48

Richardson, David Hallam. "An object oriented simulation framework for steady-state analysis of vapor compression refrigeration systems and components." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3753.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.
Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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49

Wadell, Robert Paul. "Experimental Investigation of Compact Evaporators for Ultra Low Temperature Refrigeration of Microprocessors." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7198.

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It is well known that microprocessor performance can be improved by lowering the junction temperature. Two stage cascaded vapor compression refrigeration (VCR) is a mature, inexpensive, and reliable cooling technology that can offer chip temperatures down to ?? C. Recent studies have shown that for a power limited computer chip, there is a non-linear scaling effect that offers a 4.3X performance enhancement at ?? C. The heat transfer performance of a compact evaporator is often the bottleneck in sub-ambient heat removal. For this reason, the design of a deep sub-ambient compact evaporator is critical to the cooling system performance and has not been addressed in the literature. Four compact evaporator designs were investigated as feasible designs - a baseline case with no enhancement structures, micro channels, inline pin fin arrays, and alternating pin fin arrays. A parametric experimental investigation of four compact evaporator designs has been performed aiming at enhancing heat transfer. Each evaporator consists of oxygen free copper and has a footprint of 20 mm x 36 mm, with a total thickness of 3.1 mm. The micro channel evaporator contains 13 channels that are 400 um wide by 1.2 mm deep, and the pin fin evaporators contain approximately 80 pin fins that are 400 um wide by 1.2 mm tall with a pitch of 800 um. Two phase convective boiling of R508b refrigerant was investigated in each evaporator at flow rates of 50 - 70 g/min and saturation temperatures of ??to ??C. Pressure drop and local heat transfer measurements are reported and used to explain the performance of the various evaporator geometries. The results are compared to predictions from popular macro- and micro-channel heat transfer and pressure drop correlations. The challenges of implementing a two stage cascade VCR systems for microprocessor refrigeration are also discussed.

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Mongey, Brian. "The experimental evaluation of a ternary mixture as an alternative to R22 in the vapour compression refrigeration cycle." Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241758.

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Dissertations / Theses on the topic 'Refrigeration compressor'

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