Two-phase flow patterns and void fractions in downward flow Part I: Steady-state flow patterns

Observations of void fractions and flow patterns have been made during steady-state, co-current, downward flow of liquid refrigerant 113 and its vapor. The new data on flow pattern transitions, plus the available downward flow data in the literature, have been compared with available predictions. It was found that the flow pattern map previously developed for horizontal and upward flow can be extended to downward flow with only minor modifications. Part II of this paper will report on the void fraction measurements and the observations of flow pattern transitions during flow transients.