Experimental studies on two-phase flow patterns aboard the Mir space station

A series of experiments on two-phase gas–liquid flow patterns in a test tube with a length of 356 mm and an inside diameter of 10 mm were performed aboard the Mir Space Station in August 1999. Carbogal and air were used as the liquid and the gas phase, respectively. In the present paper, the experimental results at the background microgravity environment of the Mir Space Station (no more than 10−5g) were reported. Five kinds of flow patterns, namely dispersed bubble flow, bubble flow, slug flow, slug–annular transitional flow, and annular flow, were observed in the space experiment. Due to the small length-to-diameter ratio of the test tube used in the present study, the observed flow patterns should be considered to be developing ones. The experimental results were compared with the model proposed previously which accounts for the entrance effects on the flow pattern transitions. A good agreement between the predictions and the experimental data was obtained. Some widely used models developed based on the analysis of fully developed two-phase flow at microgravity were also compared with the present data in order to make evaluations of these models and to have some insights on the flow evolution.