Characteristics of flow fields in the gas–liquid mini‐bubble columns with particle image velocimetry measurements

Abstract

As a new type of gas-liquid microreactors, the gas-liquid mini-bubble column has potential applications. However, few studies on the flow fields in the mini-bubble column can be found at present. In this work, particle image velocimetry (PIV) was used to visually study the velocity fields, vorticity fields and bubble dynamics in the gas-liquid mini-bubble columns with column inner diameters of 1-3 mm and minibubble diameters ranged from 0.7 to 1.3 mm. It is found that with the increase of superficial liquid velocity, bubbles rose from almost straight line to Z-shaped or S-shaped trajectory, and the bubble trajectory changed from one-dimension to three-dimension; when the bubble velocity changed, the bubble size and gas holdup decreased; bubble terminal velocity was controlled by bubble buoyancy and flow resistance, and increased slightly with bubble coalescence. These findings may provide basic reference for the design and scale-up of such a mini-bubble column reactor.

Multibubble Behavior and Solid Circulation Rate in a Gas–Liquid–Solid Circulating Microfluidized Bed

“…With an increase in superficial liquid velocity, the shear stress exerted by the liquid on the bubbles intensifies. This leads to an increase in bubble spacing and the number of smaller bubbles. , Increasing the superficial gas velocity can enhance the frequency of bubble generation in the riser, which promotes coalescence of the bubbles and increases d 32 .…”

“…This leads to an increase in bubble spacing and the number of smaller bubbles. 15,38 Increasing the superficial gas velocity can enhance the frequency of bubble generation in the riser, which promotes coalescence of the bubbles and increases d 32 .…”

Polydisperse particle inline image method and its application onto gas–liquid flow in a stirred tank

“…19 Insufficient resolution of the techniques can lead to inaccuracies in the characterization of bubble hydrodynamics, for example, the loading regime is determined based on the empirical formula, while numerous small bubbles exist beneath the impeller in reality. 20 The laser based techniques, that is, laser Doppler velocimetry (LDV) 21 and particle image velocimetry (PIV) 22,23 are widely used to investigate the gas/liquid velocity profiles. However, owing to the characteristics of individual bubbles not distinguished, the gas velocity is computed by averaging bubbles of all sizes contained in the research/interrogation area, that is with a manner of simple arithmetic average.…”

“…The laser based techniques, that is, laser Doppler velocimetry (LDV) 21 and particle image velocimetry (PIV) 22,23 are widely used to investigate the gas/liquid velocity profiles. However, owing to the characteristics of individual bubbles not distinguished, the gas velocity is computed by averaging bubbles of all sizes contained in the research/interrogation area, that is with a manner of simple arithmetic average.…”