Influence of a Flow Obstacle on Boiling Two-Phase Flow

In the view of the safety operation and the designing of boiling two-phase flow equipments, boiling two-phase flow characteristics, especially the critical heat flux is very important. In addition, the flow obstacle in a boiling channel, such as the spacer of boiling water reactor, influences the boiling heat transfer and flow characteristics. In this study, the experimental investigation was conducted by using a SUS304 tube (I.D. = 8 mm, LT =810, 840 and 900 mm) in which a rod-type flow obstacle (O.D. = 3.6 mm L = 20 mm) was equipped. Two kinds of detecting points of CHF, i.e. at the upstream of the flow obstacle and at the exit of the test section were observed. The difference of the detecting location of the CHF has been explained well by using the film flow model. On the basis of these results the influence length of the turbulent effect by the flow obstacle and the magnitude of the entrainment caused by the boiling were estimated.