Identification of Various Transition Velocities in a Bubble Column Based on Kolmogorov Entropy

Abstract

AbstractThe Kolmogorov entropy (KE) algorithm was applied successfully to gas holdup fluctuations measured in a 0.102 m I.D. stainless steel bubble column equipped with a perforated plate distributor (19 holes ∅︁ 1 mm). Nitrogen was used as the gas, while both 1‐butanol and gasoline were used as liquids. 1‐Butanol was aerated at pressures, P = 0.1 and 0.5 MPa, whereas gasoline was aerated at P = 0.1 and 0.2 MPa. Based on the peaks in the KE values under the pressures examined in both liquids, the boundaries of the following five regimes were identified: bubbly flow, first transition, second transition, coalesced bubble (4‐region flow) and coalesced bubble (3‐region flow). As the pressure increases to P = 0.5 MPa in 1‐butanol, all four transition velocities shift to higher superficial gas velocity, uG. In addition, in gasoline at P = 0.2 MPa and uG ≤ 0.017 m s–1, the existence of a chain bubbling regime was detected, whereas in 1‐butanol at P = 0.5 MPa and uG ≤ 0.02 m s–1, both laminar and turbulent chain bubbling subregimes were identified. It was found that in 1‐butanol under ambient pressure, the second and fourth transition velocities occur earlier than in gasoline.