SINGLE BUBBLE GROWTH AT DIFFERENT GRAVITY AND THE EFFECTS OF MICROGRAVITY ON MARANGONI CONVECTION

摘要

In this paper, based on the previous experiment and the VOF (Volume of Fluid) multiphase model, the growth characteristics of a single bubble was numerically investigated in a rectangular pool boiling channel (10 mm × 10 mm × 25 mm) under micro-gravity. The transportation of mass and energy during the phase change was established by adding source term to the mass and energy equations with User Defined Function (UDF). The results showed that under microgravity, the streamline and the temperature field distribution around the bubble were significantly changed compared with the normal gravity, and the flow field and the temperature are no longer a symmetrical distribution. The bubble between microgravity and normal gravity was different from the detachment, and it does not departure from the heating wall directly under the microgravity conditions because of surface tension. But the surface tension gradient caused Marangoni effects are more significant at the smaller microgravity. The bubble growth is more complicated under the conditions of microgravity, and it is connected with the degree of the microgravity: smaller microgravity will result higher bubble growth rate. Moreover, the bubble diameter was changed more fantasticality, under microgravity and the heat transfer coefficient fluctuated more heavily with the increasing of microgravity.