Experimental study on the dryout point and post-dryout heat transfer in square channel

Abstract

Blanket is one of the most important safety components for heat transfer in fusion reactor. Under accident conditions, two-phase fluid boiling flow in square channel of blanket is extremely efficient for cooling of fusion reactor core. The second kind of heat transfer deterioration usually occurs when the quality is high such as annular flow in the boiling process. The liquid film is depleted for the entrainment of liquid droplets and the evaporation, and no longer covers the wall. The heat transfer between the fluid and the channel wall deteriorates, leading to the boiling crisis called dryout (DO) and a rapid rise in wall temperature when the wall heat flux reaches critical heat flux (CHF), which could damage the channel wall. Therefore, accurate prediction of dryout occurrence and the post-dryout heat transfer are crucial to the optimized design and safety operation of fusion reactor. For square channel in blanket, the experimental study of dryout has been conducted. Experimental results show that the dryout heat flux increases with the increase of mass velocity and with the decrease of inlet vapor quality. Furthermore, with the increase of heat flux, the location of dryout point move to inlet of test section and the wall temperature in dryout point increases gradually. Based on the obtained experimental data, the correlation for prediction of critical vapor quality (XDO) in the square channels is proposed, which is compared with the predictions obtained by other correlations.