Fundamental study for application of swirling flow generated downstream of a multi-elbow layout to divertor cooling

In this study, heat transfer performance downstream of three-dimensionally-connected multi elbows, where a strong swirling flow appear due to the elbow layout, was experimentally studied and compared to that of a swirl tube supposed to be used in the ITER divertor. Dual and triple elbow layouts were tested, and local and averaged Nusselt numbers in the circumferential direction were evaluated from the experiment. The averaged Nusselt numbers of the triple elbow layout were slightly larger than those of the dual one. Although a comparably weak swirling flow was generated in the experiment, the heat transfer rate becomes 0.8 times as large as that of the swirl tube under the condition of single phase flow. (author)