Hydrodynamics and gas holdup in a cocurrent air-water-fiber bubble column

Gas‐liquid‐fiber flow in a cocurrent bubble column

“…For example, at C ϭ 1.0%, the entrained gas fraction is estimated to be ϳ25% of the total gas holdup when U g ϭ 0.52 cm/s and U l ϭ 10 cm/s, and ϳ8% when U g ϭ 5.1 cm/s and U l ϭ 10 cm/s. Data at other fiber mass fractions 31 reveal the separation distance between neighboring U g / vs. U g curves varies nonuniformly with C, suggesting that the intercept B 0 in Eq. 3 is a nonlinear function of C.…”

“…Data have also been acquired at C ϭ 2.0%, but are not presented here because the gas holdup does not follow the general trend due to significant gas entrainment in the fiber suspension; significant gas entrainment is not observed at any other fiber mass fraction. 31 When C Յ 0.2%, the influence of fiber mass fraction on gas holdup is insignificant. This is because at C ϭ 0.1% and 0.2%, fiber flocculation does not occur and bubble movement in the fiber suspension is similar to that of water.…”

Similitude Analysis for Gas-Liquid-Fiber Flows in Cocurrent Bubble Columns

“…where Ap; = PL,i -PH,i is the pressure difference between the lower (PL,i) and higher (PH,;) ends of column section i (i =1, 2, 3, 4); Apo,; is the corresponding pressure difference when the column is filled only with the specified water-fiber suspension flowing at the same U 1 • Equation (11) accounts for the effects of wall shear stress but neglects the effect of liquid acceleration due to void changes that may influence gas holdup in cocurrent bubble columns [72,73]; however, these effects are estimated to be negligible for the conditions of this study [71,74]. The overall column gas holdup is defined ass= (s 1 + E2 + e 3 )/3, the average gas holdup in the three lower sections.…”

“…The gas holdup in the top section is not included in the overall gas holdup because of measurement error due to the void caused by large bubbles escaping the column top, which is significant during some experimental conditions [21]. Measurement uncertainties are estimated following the method provided by Figliola and Beasley [75] and details are presented by Tang [71]. The typical uncertainties associated with superficial velocities are ±2-4% for Ug and ±1.5-5% for Uh respectively.…”

“…The experimental procedures used in this study have been described in detail by Tang [71] and will be briefly reviewed here. The experiments for this study are conducted in a cylindrical cocurrent bubble column, which consists of four 0.914 m tall acrylic tubes with 15.24 em internal diameter.…”