Wall Friction Factor and Void Fraction in Vertical Pipes under Flooding Conditions

We measured counter-current flow limitation (CCFL), pressure gradient dP/dz, and void fraction αG in a 40 mm diameter vertical pipe with the rounded top bottom ends working fluids of air water under flooding conditions, we obtained wall interface friction factors, fw fi. compared CCFL, αG, fi those from our previous experiments pipes sharp-edged ends, ends. As result, shape upper end affected characteristics conditions stronger than lower did. was expressed by correlation for single-phase flows region large liquid Reynolds number ReL, but much larger that low ReL. Therefore, ReL as function or Kutateladze KL*, evaluated uncertainty volume αL = 1－αG when dP/dz data.