Characteristics and mechanism of bubble breakup in a bubble generator developed for a small TMSR

In present study, a new bubble generator was designed for TMSR and tested in an experimental loop using water and air as the working fluids. With the help of a high speed camera, the distribution and detailed breakup process of bubbles in the generator were recorded, and accordingly, the mechanism of bubble breakup was tried to be illustrated combined with a numerical simulation by the software of FLUENT. The experimental results showed that the generated small bubbles by the generator had an average diameter about 0.5-0.6 mm and were uniformly dispersed in the main stream when the void fraction covered the range of 0.2%-0.3%, meeting the requirement of xenon removal for a small molten-salt breeder reactor. On the other hand, the numerical results indicated that the sudden deceleration of the bubbles in the diverging part of the generator led to a sharp velocity gradient in the vicinity of the bubble. This resulted in larger shear stress than the surface tension on the bubble surface, which played a dominant role in bubble breakup in the generator. (C) 2017 Elsevier Ltd. All rights reserved.