Review Heat Exchanger: Research Development of Self-rotating Inserts in Heat Exchanger Tubes

Heat exchangers are widely used in power engineering and industrial applications. Many techniques such as coiled tube, surface tension devices, rough surfaces and extended surfaces have been investigated to enhancethermal performance and minimize the cost and size of the heat exchanger equipment. One of the most important techniques is tube insert. In general,tube inserts can be classified into two broad categories: stationary inserts and self-rotating inserts.Compared with stationary inserts, the self-rotating inserts can rotate in the tube by fluid and the comprehensive performance of selfrotating inserts is improved significantly.This paper mainly focuses on reviewing the large number of experimental and numerical works taken by researchers on self-rotating inserts such as twisted tapes,miniature hydraulic turbine,turbine-type swirl generators, etc. To improve the thermal efficiency of heat exchanger and serviceable to designers implemention of passive enhancement techniques in heat exchanger are required. The authors found that self-rotating inserts can streng then the heat transfer efficiency, meanwhile achieve on-line automatic anti-scaling and descaling effect. When the fluid velocity is more than 0.2m/s, most of self-rotating inserts can be applied.The heat transfer performance and frictional loss have been discussed to get the optimal configuration of self-rotating inserts. The convective heat transfer correlations have also been discussed. Determining how to find the optimal self-rotating insert is the main objective of this paper.