Numerical and experimental study on an isolated bubble in the swirling separator

Abstract

In the online fission gas removal system applied for thorium molten salt reactor, the vane-type gas-liquid separator was developed to separate the dilute dispersed bubbles from the reactor coolant. For the efficient separation, it’s essential to quantitatively describe the bubble trajectory and the separation length of bubble that for the design of the separator. The separation trajectory of sized spherical bubble ranging from 0.22 mm to 1.05 mm produced by the customized isolated bubble generator were preliminary investigated numerically and experimentally in surrogate molten salt of five concentrations of CaCl2 aqueous solution up to 32.91 wt% covering initial inlet velocity of the separator from 0.842 m/s to 2.526 m/s. A promising numerical simulation method was used to effectively and fast predict the isolate bubble motion in the swirling flow, which combines bubble mechanical model with analytical expressions of liquid velocity field. The visualization experiments using high-speed camera and image processing were implemented to record the bubble trajectory during separation under the same conditions. Both numerical and experimental results indicate that the bubble has a convergent spiral movement during separation before captured by the air core. The separation length Ls increases as the bubble diameter decreases or the initial inlet velocity and the concentration of CaCl2 solution increase. The comparison between numerical and experimental data of Ls shows good agreement and the relative errors of Ls between them are bounded to ±10%.