Summary and evaluation on single-phase heat transfer enhancement techniques of liquid laminar and turbulent pipe flow

A comprehensive literature survey on the thermal-hydraulic performance of liquid flow and heat transfer in pipes with internal integral-fins, twisted tape inserts, corrugations, dimples, and compound enhancement techniques is conducted in this paper. The results of recent published papers with the developments of each technology are also included. It is found that for turbulent heat transfer the enhancement ratio of experimental Nusselt number over Dittus-Boelter equation for internal integral-finned tube is generally in the range of 2-4; twisted tape insert is 1.5-6; corrugated tube is 1.5-4 and dimpled tube is 1.5-4, including the compound enhancement techniques. The ratio of experimental friction factor over Fanning equation is mostly in the range of 1-4 for tubes with internal integral-fins, 2-13 for inserted twisted tape, 2-6 for corrugated tube and 3-5 for dimpled tube. The internally-finned tubes yield the best thermal-hydraulic performance compared with the other three types of tube, whose heat transfer rate augmentation over plain tube is more than the increase of friction factor at the same flow rate. For most of the corrugated and dimpled tubes, the heat transfer enhancement ratios are larger than the increment of pressure drop penalties. For the twisted tape inserts, the pressure drop is remarkably increased at the turbulent flow, and most of data have lower efficiency than the other three types of tube, while it is found to be effective in laminar and transition flow and higher viscosity fluid.