Wettability effect on the flow pattern of air-water two-phase flows in a vertical circular pipe

摘要

The flow pattern of air water two-phase flows in a vertical, circular pipe was experimentally investigated. The wettability of the pipe was changed by surface treatment. The original acrylic pipe had a contact angleθ{sub}c of 77°, while twopipes after the surface treatment hadθ{sub}c of 36° and 104°, respectively. The flow patterns in the pipes havingθ{sub}c of 36° and 77° were the same and agreed favourably with previously published results for pipes of good wettability(θ{sub}c<90°). On the other hand, different types of bubbly and slug flows appeared in the pipe ofθ{sub}c= 104°, being caused by attachment of bubbles and slugs to the wall of the pipe. The bubbly flows forθ{sub}c of 104° were classified into twocategories and slog flows for the same contact angle were classified into three categories. The boundary between the bubbly and slug flows, however, was hardly dependent on the wettability of the pipe.