Fração de vazio e gradiente de pressão nos escoamentos estratificados e anulares horizontais

Resumo: Neste trabalho, foram desenvolvidos dois modelos para predição de fração de vazio e gradiente de pressão em escoamentos horizontais com misturas bifásicas, nos padrões estratificado e anular. Um modelo considera o escoamento do filme líquido no regime laminar e o outro o considera turbulento. Os modelos desenvolvidos utilizam a idéia de tratamento diferencial para o filme líquido, como sugerido por Cheremisinoff & Davis [1979] e as equações constitutivas para fator de atrito interfacial e fração do perímetro molhado, propostos por Hart et alli. [1987]. Foi introduzido o conceito de "Número de Froude da Interface", para explicar a distribuição circunferencial do filme. As transições entre padrões de fluxo foram consideradas graduais. Os resultados dos modelos foram comparados com dados experimentais . próprios, realizados no laboratório do CENPES, e resultados publicados na literaturaAbstract: The prediction of void fraction and pressure gradient in a horizontal two-phase separated flow is the main goal in this work. The flow regimes covered were the stratified-smooth, the stratified-wavy and the annular flow. A differential approach was adopted to solve the flow in the liquid film, with a velocity profile resulting from the imposed boundary conditions. Two models were developed, considering the film beeing either in the laminar or turbulent flow condition. The liquid film distribution in the circunferential direction was considered and the correlation proposed by Hart et alii [1987] was adopted to calculate the wetted perimeter. Thus, the liquid was considered to be flowing in a channel of constant height. The gas flow was solved by means of an integral approach. Experimental void fraction and pressure drop data were taken in a set-up built in the Multiphase Flow Testing Plant site, at CENPES/PETROBRAS. The predictions of the theory are in satisfactory agreement wjth experimental data. Results from models published in the literature, as well as other experimental data were also used for, comparison. It is shown that the interfacial Froude number, based on the interfadal shear stress establishes the application range for the model, with errors less than ?mais ou menos? 5