Numerical studies on heat transfer and flow characteristics for laminar flow in a tube with multiple regularly spaced twisted tapes

The principle of heat transfer enhancement in the core flow of tube has been proposed to improve the temperature uniformity and reduce flow resistance, which is different from that of heat transfer enhancement in the boundary flow of tube. This article presents a simulation of multi-longitudinal vortices in a tube induced by triple and quadruple twisted tapes insertion. The simulation is conducted in order to gain an understanding of physical behavior of the thermal and fluid flow in the tube fitted with triple and quadruple twisted tapes for the Reynolds number from 300 to 1800. The obtained results show that, a maximum increase of 171% and 182% are observed in the Nusselt number by using triple and quadruple twisted tapes. And the friction factors of the tube fitted with triple and quadruple twisted tapes are around 4.06–7.02 times as that of the plain tube. The PEC of the tubes varies from 1.64 to 2.46. And the results verify the theory of the core flow heat transfer enhancement. Physical quantity synergy analysis is performed to investigate the mechanism of heat transfer enhancement. The synergy angles β and θ, are calculated, and the numerical results verify the synergy regulation among physical quantities of fluid particle in the flow field of convective heat transfer, which can guide us to get the optimum design. ► A tube with multiple regularly spaced twisted tapes is numerically studied. ► Effect of number of twisted tapes on performance of the enhanced tube. ► Effect of clearance ratio on performance of the enhanced tube. ► Heat transfer enhancement mechanism in the core flow. ► Heat transfer enhancement mechanism based on the field synergy principle.