Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 11, 2020 - November 13, 2020
For the promotion of heat transfer, various measures have been taken to induce stirring flow until now. It was confirmed that the dimple can restrain the pressure loss to the same level as the bare tube and obtain the heat transfer effect equal to or more than that of the fin(1). However, it is hardly mentioned what sort of flow style was formed by the dimples and so what influence was brought out on the main flow. In addition to this question, many studies have dealt with typical circular dimples and arrangements of multiple dimples to adapt to the actual machine(2)(3), so the performance in the cases of other shape and single dimple have not been clarified yet. The purpose of this study is expose the mixing flow characteristics generated by simplex dimple of different shape was evaluated. In this paper, it described the external mean flow around the dimples, which is circular, elliptical and teardrop shape, in the three-dimensional flow field by PIV measurement(4). As a result, with respect to the Reynolds stresses u’v’, the circular and elliptical dimples had distributed from the center of dimple to the backward. The teardrop-shaped dimple had a generated region extending backward from the trailing edge near the sidewall. The Second invariant of velocity gradient Q value was distributed along the trailing edge of the dimple. In the elliptical, it was also confirmed at the leading edge.
