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Abstract(s)
O presente trabalho apresenta um estudo experimental e numérico de um escoamento bifásico, gás-líquido, no padrão slug flow. Este padrão é caracterizado por uma sucessão de bolhas alongadas seguidas de pistões de líquido que não ocorrem com tamanhos e periodicidade definidos devido à interação entre as fases que se comportam de maneira intermitente.
Neste trabalho, estudou-se mais precisamente a fração de vazio ou retenção de gás no sistema ar-água em regime Slug Flow e em modo co-corrente ascendente e vertical. O estudo experimental foi realizado por dois métodos: fecho síncrono de válvulas e relação de Zuber/Nicklin. A tubagem de acrílico utilizada possui um diâmetro interno de 0,032𝑚 e um comprimento de 3,56𝑚. Realizaram-se 30 testes experimentais e numéricos, à temperatura ambiente de 19,5ºC, correspondentes a 6 velocidades superficiais de líquido variando entre 2,1×10−2 e 55×10−2 𝑚/𝑠 e 5 velocidades superficiais de gás variando entre 25×10−2 e 43×10−2 𝑚/𝑠. Realizou-se também o projeto de adaptação e montagem de um mecanismo na instalação experimental para obter a fração de vazio através do fecho rápido e síncrono de válvulas.
O modelo numérico usado é baseado no modelo de mistura e foi implementado no software Matlab, tendo-se efetuado as simulações com as mesmas condições experimentais, para comparar os resultados. Nas condições ensaiadas obtiveram-se frações de vazio a variar entre 23,55% e 62,68%. A comparação entre os resultados numéricos e experimentais da fração de vazio apresentou uma incerteza inferior a 15% para os métodos do fecho síncrono de válvulas e a relação de Zuber/Nicklin, sendo a incerteza média de 6,69% para o fecho síncrono de válvulas e de 3,68% para a relação de Zuber/Nicklin. Os resultados obtidos mostram que o modelo de mistura é adequado na previsão da fração de vazio. São apresentadas curvas de densidade de probabilidade para as distribuições da fração de vazio pelo método do fecho síncrono das válvulas, mostrando a variabilidade na retenção de gás para as diferentes velocidades superficiais de gás e liquido.
The being work show an experimental and numerical study of a two-phase flow, gas-liquid, in the slug flow pattern. This pattern is characterized by a succession of elongated bubbles followed by liquid that don’t occur with defined sizes and periodicity due to the interaction between the phases that behave intermittently. In this work, it was studied more precisely the void fraction or gas retention in the air-water system in the Slug Flow regime in an upward and vertical co-current mode. The experimental study was carried out by two methods: quick-closing valves method and Zuber/Nicklin relation. The acrylic pipe used has an inner diameter of 0.032𝑚 and a length of 3,56𝑚. 30 experimental and numerical tests were carried out, at room temperature of 19.5 °C, with 6 superficial liquid velocities from 2,1×10−2 to 55×10−2 𝑚/𝑠 with 5 superficial gas velocities ranging from 25×10−2 to 43×10−2 𝑚/𝑠. A project was also carried out to adapt and assemble a mechanism in the experimental installation to obtain the void fraction through quick-closing valves method. The numerical model that is based on the mixture model, implement in Matlab software, were carried out simulations for the same experimental conditions to compare the results. Under the conditions tested, voids fractions between 23.55% and 62.68% were obtained. The comparison between the numerical and experimental results of the void fraction showed an uncertainty of less than 15% for both experimental methods, with an average uncertainty of 6.69% for the quick-closing valves method and 3.68% Zuber/Nicklin relation. The results obtained showed that the mixture model is adequate to predict the void fraction. Probability density curves are presented for the void fraction distributions by the quick-closing valves method, showing the variability in gas retention for the different superficial velocities of gas and liquid.
The being work show an experimental and numerical study of a two-phase flow, gas-liquid, in the slug flow pattern. This pattern is characterized by a succession of elongated bubbles followed by liquid that don’t occur with defined sizes and periodicity due to the interaction between the phases that behave intermittently. In this work, it was studied more precisely the void fraction or gas retention in the air-water system in the Slug Flow regime in an upward and vertical co-current mode. The experimental study was carried out by two methods: quick-closing valves method and Zuber/Nicklin relation. The acrylic pipe used has an inner diameter of 0.032𝑚 and a length of 3,56𝑚. 30 experimental and numerical tests were carried out, at room temperature of 19.5 °C, with 6 superficial liquid velocities from 2,1×10−2 to 55×10−2 𝑚/𝑠 with 5 superficial gas velocities ranging from 25×10−2 to 43×10−2 𝑚/𝑠. A project was also carried out to adapt and assemble a mechanism in the experimental installation to obtain the void fraction through quick-closing valves method. The numerical model that is based on the mixture model, implement in Matlab software, were carried out simulations for the same experimental conditions to compare the results. Under the conditions tested, voids fractions between 23.55% and 62.68% were obtained. The comparison between the numerical and experimental results of the void fraction showed an uncertainty of less than 15% for both experimental methods, with an average uncertainty of 6.69% for the quick-closing valves method and 3.68% Zuber/Nicklin relation. The results obtained showed that the mixture model is adequate to predict the void fraction. Probability density curves are presented for the void fraction distributions by the quick-closing valves method, showing the variability in gas retention for the different superficial velocities of gas and liquid.
Description
Mestrado de dupla diplomação com o CEFET/RJ- Angra dos Reis
Keywords
Escoamento bifásico ar-água Slug flow Fração de vazio Modelo de mistura Mecanismo de fecho síncrono de válvulas