Loading...
4 results
Search Results
Now showing 1 - 4 of 4
- Mass transfer models for oxygen-water co-current flow in vertical bubble columnsPublication . Garcia, Valdemar; Sobrinho Teixeira, João AlbertoThe present work reports a theoretical and experimental study of mass transfer for oxygen-water co-current flow in vertical bubble columns. The axial dispersion of liquid phase was also studied. Experiments were carried out in a 32 mm internal diameter and 5.35 and 5.37 m height columns. The superficial liquid velocity ranged from 0.3 to 0.8 m/s and volumetric flow rate ratio of gas to liquid ranged from 0.015 to 0.25. Mathematical models were developed to predict concentration of gas dissolved in the liquid as function of different physical and dynamic variables for two-phase cocurrent downflow and upflow. We obtained for the ratio of the liquid side mass transfer coefficient to initial bubbles radius, kL/r0=0.12 s-1.
- Oxigenação de águas em colunas de borbulhamento a operar em escoamento co-corrente descendentePublication . Sobrinho Teixeira, João Alberto; Balsa, Carlos; Garcia, ValdemarApresenta-se um estudo teórico e experimental sobre transferência de massa num escoamento co-corrente descendente de oxigénio-água em colunas de borbulhamento verticais. As experiências foram efectuadas num tubo de 32 mm de diâmetro interno e 5.37 m de altura. A velocidade superficial do líquido variou entre 0.3 e 0.8 m/s e a razão de caudais volumétricos gás/líquido entre 0.015 e 0.30. Desenvolve-se um modelo teórico de transferência de massa para este tipo de escoamento. Obteve-se para a razão entre o coeficiente de transferência de massa e o raio inicial das bolhas, kL/r0=0.12 s-1.
- Oxigenação de águas em colunas de borbulhamento inclinadas com um sistema de anteparos perfuradosPublication . Garcia, Valdemar; Sobrinho Teixeira, João AlbertoApresenta-se um estudo teórico e experimental sobre transferência de oxigénio para água em colunas de borbulhamento inclinadas. Para permitir a absorção, instalou-se ao longo da coluna um sistema de anteparos perfurados igualmente espaçados. A inclinação variou entre 0º (vertical) e 60º. Desenvolve-se um modelo simples de transferência de massa considerando a coluna como uma série de “tanques” perfeitamente agitados e uma metodologia de análise que permite prever o perfil de concentrações numa coluna com qualquer número de anteparos, a partir dos valores de KLA (coeficiente de transferência de massa vezes a área interfacial) obtidos numa coluna idêntica com reduzido número de anteparos.
- Gas-liquid flow dispersion in a vertical pipePublication . Garcia, Valdemar; Sobrinho Teixeira, João AlbertoThe main purpose of this work was to analyse the transport f a solute dissolved in a flowing liquid in upward direction at low velocity along a vertical column, in the bottom of which slugs are injected. These experiments were carried out in a column with an internal diameter of 19 mm and height of 344.2 cm. Liquid flowrates of 1.0, 2.5 and 5.5 cm3/s were utilized, and an enlarged variety of gas flowrates were injected; in these conditions the slugs were normally formed at a frequency between 0.78 and 88.1 s-1. The scientific techniques used in this study based on the measurement, at the top of the column, of a tracer solution injected in its bottom. A simplified physical model was developed to explain the results obtained, which was based on two hypotheses: (i) the flow of the liquid between two slugs is laminar, being the respective profile of velocity approximate to the Poiseuille law; (ii) the stirring action provoked by each slug in the liquid is limited to a small region, the wake of slug, which can be taken as a “perfectly mixed tank”. One of the most relevant conclusions derived from this work and which at first analysis would appear paradoxical, is that, it is possible to proceed in such a way that the bubbling of gas through a liquid will provoke less dispersion in the residence time of liquid than which would be obtained in the absence of the introduction of gas.