Gas–liquid two-phase flow patterns and pressure drop in a horizontal micro-rod bundle

Two-phase flow patterns and frictional pressure drop in a horizontal micro-rod bundle were experimentally studied, using air and water. The rod bundle was 23 cm long and consisted of seven 3.17-mm diameter rods arranged in a rectangular pattern with 3.71-mm pitch. The rod bundle hydraulic diameter was 1.29 mm. The liquid and gas superficial velocities in the rod bundle center covered the 0.03–5.0 and 0.02–4.0 m/s ranges, respectively. Six distinct flow patterns were observed: bubbly, plug/slug, froth, stratified–intermittent, annular–intermittent and annular. Complete stratification, bundle-wide or in individual subchannels, did not occur. The frictional pressure drops were strongly flow pattern-dependent.