To examine the heat transfer performance of compound enhancement with helical fins and vortex generators for the shell of double-pipe heat exchangers at different curvatures

helical fins and delta-winglet-pair vortex generators are installed on the shell side with different middle diameters at the same pitch.Heat transfer and pressure drop characteristics on the shell side are investigated experimentally and numerically at Re=680—16000 with air as working fluid.The comprehensive performance on the shell side is enhanced and the enhancement mechanism is analyzed.The results show that larger curvature of the shell leads higher heat transfer coefficient and friction factor.For curvatures of 0.131

0.321 and 0.440

heat transfer coefficient is increased by 31.52%

20.83% and 18.33%

respectively

with vortex generators. Vortex generators can change the fluid flow structure and improve the synergy of velocity field and temperature field

so the heat transfer on the shell side is improved.