Estudo da ventilação mecânica e natural numa torre de arrefecimento

Na presente dissertação analisam-se as potencialidades da ventilação natural e forçada numa torre de arrefecimento de uma central termoelétrica. Para tal, recorreu-se a um modelo analítico simplificado para o estudo da ventilação, já utilizado em trabalhos anteriores, e aqui adaptado para estudo da ventilação natural e forçada na torre de arrefecimento. O caso de estudo é caracterizado pela documentação técnica da torre de arrefecimento que a partir da mesma e através da sua modelação deu origem ao Caso 0, caso esse capaz de ser estudado e validado no modelo. Numa primeira fase e após a definição do Caso 0, foram realizados casos variantes do mesmo para serem estudados e comparados do ponto de vista da ventilação natural, onde se fez variar, dimensões estruturais e a velocidade do vento exterior. Numa segunda fase, é validada a modelação dos ventiladores, utilizados nas simulações com ventilação forçada para o Caso 0, e são simulados todos os casos de ventilação forçada e natural propostos para estudo de resultados e comparações. Por fim, são discutidos os resultados onde se verificou a importância da impulsão térmica, efeito chaminé, velocidade do vento exterior e o efeito de curto circuito, todos estes relevantes para o estudo da ventilação natural

Development of methods for thermo-hydraulic simulation of nuclear reactors and similar systems in normal working conditions and in transient processes

The goal of this report is to present the final project conducted in order to fulfill the requirements of the M.Sc. degree at the Department of Mechanical Engineering, Ben-Gurion University (BGU) of the Negev. The project comprises theoretical research investigating natural convection compressible flow with high temperature differences and with complex geometries. The research motivation comes from long-term research investigating and simulating the steady state and transient multiphase flow regimes existing in the reactor core, that was established by the Soreq Nuclear Center. The main objective of this project is to develop a comprehensive numerical methodology that is capable of theoretical modeling of natural convection compressible flow with high temperature differences and with complex geometries, using standard techniques of computational fluid dynamics (CFD) - pressure-based solution algorithms and immersed boundary methods. This report contains: - A comprehensive literature review surveying methods for the simulation of natural convection flow and immersed boundary methods. - An extended outline of the objectives of the performed research. - A comprehensive physical model, including the governing equations, definitions, constitutive laws, and dimensional analysis. - A verification study by favorable comparison with corresponding independent numerical data available in the literature for incompressible, and non-Bossinesq compressible flows, without complex geometry. - A comparison between results obtained in the present study and results from previous studies for configurations with low temperature difference and complex geometry. - A solution and analysis of the configurations with high temperature differences and complex geometry. - A summary, conclusions , and recommendations for possible future work

A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows

International audienceThe development of an improved new IBM method is proposed in the present article. This method roots in efficient proposals developed for the simulation of incompressible flows, and it is expanded for compressible configurations. The main feature of this model is the integration of a pressure-based correction of the IBM forcing which is analytically derived from the set of dynamic equations. The resulting IBM method has been integrated in various flow solvers available in the CFD platform OpenFOAM. A rigorous validation has been performed considering different test cases of increasing complexity. The results have been compared with a large number of references available in the literature of experimental and numerical nature. This analysis highlights numerous favorable characteristics of the IBM method, such as precision, flexibility and computational cost efficiency

Study on Compressible Low-Reynolds-Number Flow over a Sphere

Tohoku University野々村拓課