Steam volume fraction of two phase flow

The steam volume fraction of two phase mixture flowing upward under atmospheric pressure in the two vertical circular pipes of which inner diameters are 13.8 mm and 21.0 mm was measured, taking into consideration the flow patterns, with a capacitance type void meter. The steam volume fraction and slip ratio vary with steam weight fraction (steam quality) x in different fashions for different flow patterns. For example, the slip ratio increases with increasing the steam quality, but its slope decreases as the bubble flow (x < 0.1%) changes into slug flow (0.1% < x < 0.5∼1%) and the slug flow into annular flow (x > 0.5∼1%). The effect of superficial velocity V₀ on slip ratio S is most significant in the region of annular flow, and S decreases as V₀ increases from 30 cm/s to 100 cm/s. For bubble flow, taking account of the effect of wake of bubbles, a theoretical equation to predict its slip ratio and steam volume fraction was derived. This equation satisfies not only the present experimental results but also the experimental data under high pressure obtained by several investigators. For slug flow, the present experimental results were compared with Moissis, et al.'s experiments which discussed the development of slug. (author)