Improved flow and heat transfer characteristics for heat exchanger by using a new humped wavy fin

A novel humped wavy fin is presented in this paper. The flow and heat transfer characteristics for humped wavy fins with different humped radii (R = 0.3, 0.5, 0.7 and 0.9 mm) and Reynolds numbers (500 ≤ Re ≤ 5000) are studied numerically and experimentally. Results show that the overall thermal-hydraulic characteristics for humped fin patterns with different R are better than that of triangular fin. The recirculation Phenomena in the valley regions completely disappear for either laminar or turbulent flows by using the humped fin. The areas of separation zones near the suction side are smaller and more uniformly, and the core flow encounters a smaller resistance along the flow direction. The directions of the secondary flows in left half and right half regions are clockwise and anticlockwise respectively in both fin patterns at low Re, but the secondary flow disappears at a relatively high Re. Besides, the humped fin pattern can easily get into the turbulence state at a low Re. The JF factor first increases and later decreases while R increases from 0.3 mm to 0.9 mm, and when R = 0.5 mm, the duct has the highest JF. Using the filed synergy principle we can see the average field synergy angle first decreases and later increases with the increasing of R.