AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER AND FLOW CHARACTERISTICS OF LAMINAR FLOW IN A CIRCULAR TUBE WITH WEDGE-SHAPED WAVY-TAPE INSERTS

摘要

In this study, a new type of tube inserts, named wedge-shaped wavy-tape insert, which is designed from bionics based on the movement of cuttlefish, is reported. The numerical simulation was carried out to investigate the effects of wedge-shaped wavy-tape insert arrangements on the heat transfer and flow characteristics of laminar flow in a circular tube under constant heat flux conditions. Details of the flow structures in the circular tube with wedge-shaped wavy-tape inserts which are arranged in same phase (S-type wavy tape) and different phase (D-type wavy tape) were presented and analyzed respectively. Then stereoscopic particle image velocimetry (Stereo-PIV) measurements on the flow structures were conducted to verify the numerical results. The flow structures obtained through simulations and PIV measurements agree well. It was observed that the arrangements of wedge-shaped wavy-tape inserts have a significant influence on the thermo-hydraulic performance. The average friction factor enhancement ratio f/f_0 of D-type wavy tape were about 14%-20% lower than S-type wavy tape, but average heat transfer enhancement ratio Nu/Nu_0 of D-type wavy tape were about 7%-14% higher than S-type wavy tape. The best performance evaluation criterion of D-type wavy tape could be improved to 3.02. The result shown the wedge-shaped wavy-tape insert is a promising technique for laminar convective heat transfer enhancement.