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A CFD based empirical model for assessing gas holdup in bubble columns
Author(s) -
Ebrahimi Mehdi,
McGillis Andrew,
Lewis Cameron,
Ting David S.K.,
Carriveau Rupp
Publication year - 2019
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.23355
Subject(s) - bubble , mechanics , computational fluid dynamics , coalescence (physics) , reynolds number , work (physics) , breakup , flow (mathematics) , range (aeronautics) , materials science , chemistry , thermodynamics , physics , turbulence , astrobiology , composite material
Bubble columns are widely used in many industrial applications. Gas holdup knowledge is an essential element in bubble column design and process optimization. Despite the simple structure of bubble columns, the behaviour of the bubbly flow is still not well understood owing to the complexity of gas–liquid interactions and coupling between the phases. Variation of gas density and initial liquid height are the most likely reasons for gas holdup changes in bubble columns. These parameters affect bubble breakup and coalescence as well as the rise velocity of small bubbles, which causes change to bubble size distribution that finally affect the gas holdup. In this work, through the application of computational fluid dynamics (CFD) and by investigating the effect of gas density and the initial liquid height on the bubbly flow condition, a new correlation for deducing the total gas holdup is developed. To achieve this, a wide range of bubbly flows are modelled, and gas holdup values are determined for different heights and operating pressures. Ranges of the normalized pressure (P/P 0 ), superficial Reynolds number (Re sup ), and the aspect ratio of the bubble column (H 0 /D) were 1 ≤ P/P 0 ≤ 15, 3000 ≤ Re sup ≤ 57000, and1.5 ≤ H 0 /D ≤ 8, respectively. The proposed correlation has been found to predict the experimental as well as CFD gas holdup data fairly well. The results of this research provide a fast and accurate method for predicting gas holdup in bubble columns that work either in atmospheric or high‐pressure conditions.