Abstract
Phase transition, and more specifically bubble formation, plays an important role in many industrial applications, where bubbles are formed as a consequence of reaction such as in electrolytic processes or fermentation. Predictive tools, such as numerical models, are thus required to study, design or optimize these processes. This paper aims at providing a meso-scale modelling description of gas–liquid bubbly flows including heterogeneous bubble nucleation using a Discrete Bubble Model (DBM), which tracks each bubble individually and which has been extended to include phase transition. The model is able to initialize gas pockets (as spherical bubbles) representing randomly generated conical nucleation sites, which can host, grow and detach a bubble. To demonstrate its capabilities, the model was used to study the formation of bubbles on a surface as a result of supersaturation. A higher supersaturation results in a faster rate of nucleation, which means more bubbles in the column. A clear depletion effect could be observed during the initial growth of the bubbles, due to insufficient mixing.
Highlights
Bubble columns, and in general bubbly flows, represent an often encountered class of unit operations in industrial processes where contact between a gas and a liquid takes place, often in presence of chemical reaction and heat/mass transport between the phases
The use of Computational Fluid Dynamics (CFD) to model and study these systems is becoming more and more widespread resulting from large improvements in computational power
Relevant industrial applications are in electrolytic processes where gas bubbles are formed on the electrodes [4,5], carbonated beverages [6], molten polymers [7] and even bubbles in oil reservoirs [8]
Summary
In general bubbly flows, represent an often encountered class of unit operations in industrial processes where contact between a gas and a liquid takes place, often in presence of chemical reaction and heat/mass transport between the phases. Despite the widespread applications of these systems, detailed understanding of the complex interactions between hydrodynamics and mass/heat transport is still insufficient, especially concerning dense flows (heterogeneous regime) and their effect on the large-scale performance of bubble column reactors [1,2]. A well known example is opening a bottle of soda: the sudden change in pressure creates a local supersaturation and bubbles form on the surface of the bottle. Another mechanism to obtain local supersaturation is when a reaction produces gas in excess. Relevant industrial applications are in electrolytic processes where gas (such as H2 in the electrolysis of brine) bubbles are formed on the electrodes [4,5], carbonated beverages [6], molten polymers [7] and even bubbles in oil reservoirs [8]
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