BUBBLE FORMATION IN FLOWING LIQUID UNDER REDUCED GRAVITY

A great deal of research has been done regarding bubble formation from submerged orifices in liquids under the force of gravity for the desi gn of gas-liquid or gas-liquid-solid contacting equipment. On the othe r hand, little research has been done concerning bubble formation unde r reduced gravity conditions. For the basic design of the chemical pro cess systems or life-support systems in space stations and on other pl anets, it is important to clarify the effects of various factors on th e volume and shape of bubbles formed at submerged orifices or nozzles under reduced gravity conditions. In order to disperse adequately bubb les in liquids for mass transfer or chemical reaction processes at rel atively low gas flow rates under reduced gravity, it is necessary to f orce bubbles to become detached from nozzles by external forces. In th is study, the liquid flow was used as the external force on bubble for mation. The aim of this study is to clarify the behavior of bubble for mation in flowing liquids under reduced gravity conditions. We experim entally investigated the effects of gas flow rate, liquid flow velocit y, and liquid flow direction (cocurrent, countercurrent or cross-curre nt flow) on bubble formation for a period of 1.2 s under reduced gravi ty conditions that were produced in the 10 m drop tower at the Hokkaid o National Industrial Research Institute at Sapporo in Hokkaido. In or der to describe theoretically the bubble formation in flowing liquids under reduced gravity conditions, a revised non-spherical bubble forma tion model was proposed and the calculated results of the bubble volum e were compared with the experimental ones. (C) 1997 Elsevier Science Ltd.