Tougher environmental legislations are a driving force for development of aftertreatment technologies for truck and car exhaust gases. In particular, the emission requirements are high on nitrogen oxides (NOx) and particulate matter. Focus of this thesis work is to develop a component in the exhaust system, a NOx level reduction system. The currently used technology with urea evaporator has problem with formation of urea crystals due to delayed urea evaporation. Crystalline urea causes reduced exhaust flow and thus build up a pressure in the system that has negative impact on the performance of the engine. Feasibility study was done to understand function, advantage and disadvantages of current design and the need for a new design. The main task of this project was to investigate and propose a new design of the helix-rotary evaporator and to present it in the form of parametric model. Material selection needed for urea injection arrangement, 3D printed model for visualization of the concept and integration of the model to next generation aftertreatment system (NGA) are examples of sub-tasks that was performed to reach the main objective. Several generations of selected concept were developed in 3D design which later was 3D printed to visualize the ideas. The parametric 3D model was designed so that it later serves as input model for a later phase in the development project, where computational fluid dynamics is utilized. Parametric modelling is used to provide wide range of possibility to generate different models for simulation and reduce pre-simulation works. Selected concept parametric model has six different parameters that can be analysed. Material selection carried out to injection manifold thought CES Edupack and consultancy of material engineers. Three different austenitic stainless steels were recommended.

Made available in DSpace on 2014-06-11T19:23:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-05-17Bitstream added on 2014-06-13T20:30:31Z : No. of bitstreams: 1 bueno_ss_me_ilha.pdf: 1064602 bytes, checksum: fd46f925f2d20ccedc49c80672da6280 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho, apresenta-se um modelo numérico distribuído para a simulação dos escoamentos do fluido refrigerante e do ar, no regime transiente, em evaporadores de expansão seca de serpentina com tubos aletados, comuns em sistemas de refrigeração e ar condicionado. No modelo proposto, o escoamento do fluido refrigerante no interior dos tubos é dividido em duas regiões: uma de escoamento bifásico líquido-vapor e uma de escoamento de vapor superaquecido. Considera-se a queda de pressão no interior dos tubos e a condensação do vapor d'água do ar que escoa em fluxo cruzado na parte externa dos tubos. O escoamento bifásico do fluido refrigerante é simplificado como um escoamento unidimensional, considerando o deslizamento entre as fases de líquido e de vapor. Para o escoamento do refrigerante, resolvem-se as equações de conservação da massa, da quantidade de movimento e de conservação da energia. Para o escoamento de ar, são resolvidas as equações de conservação da energia e de conservação da massa (umidade). Resolve-se, também, a equação da conservação da energia para a parede do tubo, para se obter a sua temperatura. O método de volumes finitos é utilizado na discretização das equações governantes e o método de Newton-Raphson é utilizado para a solução do sistema de equações resultante. Inicialmente, condições de regime permanente são assumidas e, posteriormente, para avaliar o comportamento transiente do evaporador, uma variação em degrau da vazão em massa de refrigerante é imposta em sua entrada. O modelo permite o cálculo da vazão de refrigerante, conhecidas as condições de operação e os parâmetros geométricos, usando-se o processo de estimativa de parâmetros, com o método de minimização de Levenberg-Marquardt. Além disso, o modelo permite a análise de algumas configurações de... . / This work presents a numerical model to simulate the unsteady refrigerant fluid flow and air flow in dry-expansion finned-tube coil evaporators, the kind widely used in air conditioning and refrigeration systems. The model considers the refrigerant flow inside the tubes divided in a region of two-phase flow and a single-phase region, where the refrigerant is in the superheated state. The refrigerant pressure drop and the moisture condensation on the air flow crossing the outside of the tubes are also taking into account. The refrigerant two-phase flow is taken as one-dimensional and the slip between the liquid and vapor phases is considered. For the refrigerant flow, mass, momentum and energy conservation equations are solved in order to evaluate the specific mass, velocity, and temperature of the refrigerant fluid, respectively. For the air flow, energy and mass (humidity) conservation equations are solved, to obtain, respectively, the temperature and absolute humidity of the air crossing the evaporator. Also, the solution of energy conservation equation for the tube wall is used to determine the wall temperature distribution. Finite Volume Method is used all over to discretize the governing equations and a Newton-Raphson Scheme is utilized for the solution of the resulting system of equations. To analyze the evaporator unsteady behavior, the steady conditions are obtained initially and later a step change in the mass flow rate is imposed at the tube inlet. Obtained results such as superheating degree along the coil and air temperature at the outlet are compared to experimental data available in the open literature. From the model the refrigerant mass flow rate can be determined, from a known operating conditions and geometry parameters, using the process of parameter estimation with the method of Levenberg-Marquardt... (Complete abstract click electronic address below).

Made available in DSpace on 2015-05-08T14:59:53Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1176098 bytes, checksum: f4af6c1315fb2c04cc38083433e1f89d (MD5) Previous issue date: 2003-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we analyze a heat exchanger type cylindrical evaporator usually employed on the domestic refrigerators. The internal flow occurs with a fluid in phase change process. Equations representing the problem under study are the equations of conservation of mass momentum and energy. The tool used to solve these differential equations is the generalized integral transform technique (GITT) produces hybrid solutions for both the hydrodynamic field as for the thermal field. The used model for the evaporator considers it as straight duct and with stratified flow where both phase liquid and vapor can flow with different too. To avoid mathematical complexity of modeling each phase separately is introduced the void fraction concept. The thermal and hydrodynamic fields are studied on the dimensional form and combine as a coupled problem. The thermal field is plotted against enthalpy. / Neste trabalho analisamos um trocador de calor do tipo evaporador cilíndrico, largamente utilizado em refrigeradores domésticos. O escoamento interno ocorre com um fluido em mudança de fase. As equações representativas do problema em estudo são as equações da conservação da massa, da quantidade de movimento e da energia. A ferramenta utilizada para solucionar estas equações diferenciais é a Técnica da Transformada Integral Generalizada (GITT), que produz soluções híbridas tanto para o campo hidrodinâmico como para o campo térmico. O modelo considera que este evaporador é um tubo reto, com escoamento estratificado, onde ambas as fases, líquida e gasosa, podem escoar com velocidades diferentes. Para evitar a complexidade de se modelar cada fase separadamente é introduzido o conceito de fração de vazio. Os campos de velocidade e térmico são estudados na forma adimensional e formam um problema acoplado. O campo térmico é representado em função da entalpia.

Orientador: André Luiz Seixlack / Banca: Marco Antonio Soares de Paiva / Banca: Sérgio Said Mansur / Resumo: Neste trabalho, apresenta-se um modelo numérico distribuído para a simulação dos escoamentos do fluido refrigerante e do ar, no regime transiente, em evaporadores de expansão seca de serpentina com tubos aletados, comuns em sistemas de refrigeração e ar condicionado. No modelo proposto, o escoamento do fluido refrigerante no interior dos tubos é dividido em duas regiões: uma de escoamento bifásico líquido-vapor e uma de escoamento de vapor superaquecido. Considera-se a queda de pressão no interior dos tubos e a condensação do vapor d'água do ar que escoa em fluxo cruzado na parte externa dos tubos. O escoamento bifásico do fluido refrigerante é simplificado como um escoamento unidimensional, considerando o deslizamento entre as fases de líquido e de vapor. Para o escoamento do refrigerante, resolvem-se as equações de conservação da massa, da quantidade de movimento e de conservação da energia. Para o escoamento de ar, são resolvidas as equações de conservação da energia e de conservação da massa (umidade). Resolve-se, também, a equação da conservação da energia para a parede do tubo, para se obter a sua temperatura. O método de volumes finitos é utilizado na discretização das equações governantes e o método de Newton-Raphson é utilizado para a solução do sistema de equações resultante. Inicialmente, condições de regime permanente são assumidas e, posteriormente, para avaliar o comportamento transiente do evaporador, uma variação em degrau da vazão em massa de refrigerante é imposta em sua entrada. O modelo permite o cálculo da vazão de refrigerante, conhecidas as condições de operação e os parâmetros geométricos, usando-se o processo de estimativa de parâmetros, com o método de minimização de Levenberg-Marquardt. Além disso, o modelo permite a análise de algumas configurações de... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: This work presents a numerical model to simulate the unsteady refrigerant fluid flow and air flow in dry-expansion finned-tube coil evaporators, the kind widely used in air conditioning and refrigeration systems. The model considers the refrigerant flow inside the tubes divided in a region of two-phase flow and a single-phase region, where the refrigerant is in the superheated state. The refrigerant pressure drop and the moisture condensation on the air flow crossing the outside of the tubes are also taking into account. The refrigerant two-phase flow is taken as one-dimensional and the slip between the liquid and vapor phases is considered. For the refrigerant flow, mass, momentum and energy conservation equations are solved in order to evaluate the specific mass, velocity, and temperature of the refrigerant fluid, respectively. For the air flow, energy and mass (humidity) conservation equations are solved, to obtain, respectively, the temperature and absolute humidity of the air crossing the evaporator. Also, the solution of energy conservation equation for the tube wall is used to determine the wall temperature distribution. Finite Volume Method is used all over to discretize the governing equations and a Newton-Raphson Scheme is utilized for the solution of the resulting system of equations. To analyze the evaporator unsteady behavior, the steady conditions are obtained initially and later a step change in the mass flow rate is imposed at the tube inlet. Obtained results such as superheating degree along the coil and air temperature at the outlet are compared to experimental data available in the open literature. From the model the refrigerant mass flow rate can be determined, from a known operating conditions and geometry parameters, using the process of parameter estimation with the method of Levenberg-Marquardt... (Complete abstract click electronic address below). / Mestre

Orientadores: Bárbara Janet Teruel Mederos, Luiz Antônio Rossi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-24T04:54:48Z (GMT). No. of bitstreams: 1 Silva_JosedeCastro_D.pdf: 5569608 bytes, checksum: dc461643869a258550aa80e69569b426 (MD5) Previous issue date: 2013 / Resumo: Este trabalho teve como objetivo propor uma nova configuração para melhorar a distribuição do ar no interior de câmaras refrigeradas (frigoríficas), a fim de minimizar zonas de diferentes temperaturas. Com esse intuito, um instrumento de CFD foi usado (OpenFOAM), a fim de simular duas configurações de distribuição de ar no interior de câmaras de refrigeração. Dois protótipos experimentais foram montados com a finalidade de analisar a distribuição da temperatura do ar com as configurações propostas. Os resultados destas medidas foram comparadas através do software escolhido. As principais variáveis monitoradas foram a diferença de temperatura, o consumo de energia e o coeficiente de desempenho (COP) . Os resultados das simulações numérica e experimental mostraram que, a fim de melhorar a circulação de ar no interior de câmaras de refrigeração, minimizando as zonas com diferentes temperaturas, a utilização de um evaporador modelo cassete, atualmente utilizado em condicionadores de ar split, com o fluxo de ar em quatro direções, seria uma alternativa bastante viável para a redução de zonas com diferentes temperaturas em câmaras frigoríficas / Abstract: This work aimed to propose a new configuration to improve the air distribution inside refrigerated chambers, in order to minimize zones of different temperatures. For this, a CFD tool was used (OpenFOAM), in order to simulate two configurations of air distribution inside refrigerated chambers. Two experimental prototypes were assembled, in order to analyze the air temperature distribution with the proposed settings. The results of these measurements were compared using the chosen CFD software. The main variables monitored were temperature difference, power consumption and the coefficient of performance (COP). Results of numerical and experimental simulation showed that, in order to improve the air circulation inside refrigerated chambers, minimizing zones with different temperatures, the use of an evaporator model cassette, currently used in split air conditioners, with air flow in four directions, would be a very viable alternative for the reduction of zones with different temperatures in refrigerated chambers / Doutorado / Maquinas Agricolas / Doutor em Engenharia Agrícola

Master thesis is focused on design of ground heat pump with direct evaporation. First part is dedicated to description of heat pump technology, cooling circulation and sources of low-potential heat. Heat pump ground-water, its main components, classification of refridgerant and systems of direct evaporation are all described in the second part. The last part consists of design of each individual component of heat pump and solution of ground heat exchanger for direct evaporation of refridgerant.

The study involves development of a methodology to simulate a fin-tube evaporator under icing conditions using CFD in Ansys® Academic Fluent 2021R1. It aims to build on previous studies performed on heat pumps. It was performed by Abhay M. Hervatte in collaboration with Bosch Thermoteknik AB, Tranås, SE during the spring term of the year 2021. The thesis is published by Linköping University. Initially, experiments were conducted to measure the ice growth on the fins of the evaporator as a function of time. A CAD model of the evaporator was then generated. The evaporator geometry was scaled down and simplified to reduce the simulation time. Due to restrictions in the software, the simulations were split into two parts - one for the flow of the refrigerant through the evaporator pipes and another for flow of air over the fins. The internal flow simulation was a steady state simulation consisting of the phase-change of the refrigerant after absorbing heat from the ambient. through the pipes and a transient simulation for the external flow over the fins. The internal flow consisted of multi-phase simulation of the evaporation of the refrigerant - propane - after absorbing heat through the pipe walls. The external flow involved the multi-phase simulation of ice being deposited from humid air on the surface of the fins. The inner surface of the evaporator pipes was used as a bridge, and surface profiles from the internal simulation would be used to transfer the boundary conditions to the other simulation. Results of the ice-film thickness over the fins were obtained and compared to the experimental value and found to be in reasonable agreement with each other, with scope for improvement in the future.

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Wood consists not only of cellulose, lignin and hemicellulose but also of so called extractives which includes fats and acids and these components are separated in the mill from the black liquor. These extractives are in the mill denoted as tall oil soap. Tall oil has a large field of applications like chemicals and fuel and as it is produced to the atmosphere if it can replace oil and thus reduce the oil consumption. Tall oil soap is separated from the black liquor in a skimmer and the focus of this thesis was to examine the effect of air injection and the soap layer thickness on the soap separation efficiency in a skimmer. The work was focused on in analyzing the soap content of the inlet and outlet black liquor flow of the skimmer and to detect if an enhancement has been achieved with the two mentioned methods. The reason for the pulp mill to improve the soap separation efficiency was to decrease the risk of foaming and fouling in the evaporator but also to be able to increase the production of tall oil. The air injection gave a 41% improvement of the soap separation efficiency and further improvements are probably possible to achieve. The air injection flow was about 7 l air /m3 liquor in the black liquor feed. The airflow lowers the density of soap, creating a greater difference in density between soap and black liquor and this improves the separation efficiency. A thicker soap layer could increase the likelihood for soap drops to raise and reach the soap-liquor interface, because the soap drops have the tendency to bind with each other and will be separated from the liquor instead of following with the skimmed liquor outlet (fig. i.2). However, this study shows no indication of improvement with thicknesses that exceeds 0,75- 3,5 m which also endanger the skimmer due to overflow from the skimmer or create a short circuit between the in- and the outlet black liquor flow.