A STUDY ON VOID FRACTION IN VERTICAL COCURRENT UPWARD AND DOWNWARD 2-PHASE GAS-LIQUID FLOW .1. EXPERIMENTAL RESULTS

An experimental study on void fraction in a small diameter tube (9.525 mm) for vertical upward and downward, gas-liquid, two-phase flow was carried out. Void fraction measurements in water-air were taken for bo th upward and downward flow using a single beam gamma densitometer. Th e gamma densitometer was calibrated against the reading from a quick-c losing valve system. The experimental results indicate that for V(SL) greater-than-or-equal-to a 1.7 m/s, the void fraction in both upward a nd downward flow is almost independent of the liquid flow rate. For do wnward flow and V(SL) less-than-or-equal-to 0.1 m/s, the void fraction is independent of the gas flow rate. This corresponds to the flow in the falling film region. In general the void fractions in downward flo w were slightly higher than those with upward flow. The experimental d ata were compared with some correlations and data in the literature. F airly good agreements (overall relative R.M.S. deviation of 18%) were obtained.