Annular Gap Bubble Column: Experimental Investigation and Computational Fluid Dynamics Modeling

Abstract

This paper investigates the countercurrent gas-liquid flow in an annular gap bubble column with a 0.24 m inner diameter by using experimental and numerical investigations. The two-phase flow is studied experimentally using flow visualizations, gas holdup measurements, and double fiber optical probes in the following range of operating conditions: superficial air velocities up to 0.23 m/s and superficial water velocities up to À0.11 m/s, corresponding to gas holdups up to 29%. The flow visualizations were used to observe the flow patterns and to obtain the bubble size distribution (BSD). The gas holdup measurements were used for investigating the flow regime transitions, and the double fiber optical probes were used to study the local flow phenomena. A computational fluid dynamics (CFD) Eulerian two-fluid modeling of the column operating in the bubbly flow regime is proposed using the commercial software ANSYS FLUENT. The three-dimensional (3D) transient simulations have been performed considering a set of nondrag forces and polydispersity. It is shown that the errors in the global holdup and in the local properties are below 7% and 16%, respectively, in the range considered.

Two-Phase Bubble Columns: A Comprehensive Review

“…Extensive studies on the influence of the liquid velocity in the counter-current mode were performed by Besagni et al [28,34,46,[51][52][53][54], who found that the counter-current mode destabilized the homogeneous regime in all of the different configurations studied (viz. the pipe sparger in the annular gap and in the open tube configuration [34] and the spider sparger [46] [28,34,46,[51][52][53][54]. Recently, Trivedi et al [55] performed a detailed study on the hydrodynamics of counter-current bubble columns and found results in agreement with Besagni and co-authors.…”

“…Similar trends were found by Otake et al [49], as already discussed when considering the flow regime transition. Besagni et al [34,46,[51][52][53][54] found that when increasing the liquid flowrate, a faster increase in the hold-up is observed at low U G , and the transition point also moves toward lower superficial gas velocities (Figures 16-18). This change was explained by the effect of the liquid flow, which slows down the rise of the bubbles, leading to higher hold-up-a more compact arrangement of bubbles leads to an earlier flow regime transition.…”

“…This change in the distribution of bubble size has been justified by increased coalescence [242] or break-up [244]. Besagni and Inzoli [46,52,53,229] described the BSDs in a polydispersed homogeneous flow regime in the batch and counter-current modes. The changes in the BSD (from bimodal to unimodal) in the counter-current mode were based on the force pushing the small bubbles toward the center of the pipe.…”

“…Different methods have been presented over the last few decades, as discussed by Shaikh and Al-Dahhan [102], Nedeltchev and Shaikh [26] and Nedeltchev [27]. The most common methods employed are statistical methods (by interpretation of the ε G -U G curve), the swarm velocity [7,11,34,46,[51][52][53]75,76,89,91,229,315,316] and the drift flux [7,11,34,38,46,51,53,75,76,229,[316][317][318] approaches. These methods are based on the analysis of ε G data.…”

A critical review of flow maps for gas-liquid flows in vertical pipes and annuli

“…Besagni, et al [83] experimentally investigated the influence of two inner pipes on counter-current flow in a bubble column, however this study is not directly relevant to the focus of this review paper due to the difference in geometry. The majority of the available experimental investigations of counter-current flows in vertical pipes focus on identifying the onset of flooding or counter-current flow limitation (CCFL).…”