Analysis on heat transfer and pressure drop of fin-and-oval-tube heat exchangers with tear-drop delta vortex generators

作者：Lu, Gaofeng; Zhai, Xiaoqiang^*

来源：International Journal of Heat and Mass Transfer, 2018, 127: 1054-1063.

DOI：10.1016/j.ijheatmasstransfer.2018.07.148

• Tear-drop
• Vortex generator
• Heat transfer enhancement
• Field synergy principle
• Secondary flow

Numerical simulations are performed to examine the thermal and flow characteristics of tear-drop delta vortex generators (VGs) on the fin surfaces of fin-and-oval-tube heat exchangers. The VGs deployed in a "common flow up" configuration behind tubes can induce longitudinal vortices and reduce the area of wake region, which results in significant heat transfer enhancement and negligible augmentation of pressure drop compared with plain fins without VGs. The heat transfer performance and pressure loss are analyzed using the dimensionless parameters j/j(o), f/f(o). and R = (j/j(0))/(j/f(0))(1/3) with ReDC ranging from 255 to 1533. The results indicate that the tear-drop delta VGs have a better thermal-hydraulic performance than plane delta VGs and the value of R reaches as high as 1.06-1.23 at the ratio of division for chord length (l(1)/l(2)) being 2/3. Further parameters study reveals that when the height of VGs is 0.6 times of fin pitch, the lateral length is 0.3 times of fin pitch, and the chord length is 1.2-1.4 times of fin pitch, the optimal overall performance can be obtained. The mechanism of heat transfer enhancement is investigated by intensity of secondary flow and field synergy principle. It suggests that for the case with higher Nusselt number, the corresponding secondary flow intensity is higher and the synergy angle is smaller. In addition, for each case, where the Nusselt number is higher, the secondary flow intensity is higher and the synergy angle is smaller.

• 出版日期2018-12
• 单位上海交通大学