关键词: 防垢, 强化传热, 旋流, 旋转扭带

Abstract: The question of the low efficiency and fouling deposit for heat exchangers is a worldwide difficult problem all the time. The technology of a self-rotating cleaning twisted tape is dveloped, which has double functions of heat transfer enhancement and online cleaning fouling. Some heat transfer enhancement mechanisms of the rotating twisted tape are proposed, it can be attributed to the following four effects: ① The reduction of the equivalent diameter. ② The velocity increase near the tube wall due to the blockage of the twisted tape. ③ The velocity increase due to the helical flow following the twisted tape. ④ The velocity increase due to the second flow. Based on the theory analysis of the four heat transfer enhancement mechanisms, the prediction correlations of the heat transfer Nusselt number are put forward respectively. The results show that, for y≥10, the reduction effect of the equivalent diameter and the velocity increase effect near the tube wall area are the main contributing factor of heat transfer enhancement, for y＜10，the helical flow effect is the main contributing factor of heat transfer enhancement. The contribution to heat transfer enhancement of the second flow motion is smaller than other three ones, only for y≤1, it becomes the main contributing factor. The prediction results of the heat transfer Nusselt number for the tube with a self-rotating twisted tape insert are compared with the experimental results. They show reasonably good agreement.

Key words: Heat transfer mechanism, Preventing fouling, Rotating twisted tape, Swirl flow